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  • how get attribute relation from another entity class Java Persistance API and show to JSP through servlet?

    - by user1787209
    I have 2 entities are entities meeting and meetingAgenda. I write code entity class (EJB) from database like this. public class Meeting implements Serializable { ...... @XmlTransient public Collection<MeetingAgenda> getMeetingAgendaCollection() { return meetingAgendaCollection; } public void setMeetingAgendaCollection(Collection<MeetingAgenda> meetingAgendaCollection) { this.meetingAgendaCollection = meetingAgendaCollection; } ....... } and entity class meeting agenda like this. ..... public class MeetingAgenda implements Serializable { .... public String getAgenda() { return agenda; } public void setAgenda(String agenda) { this.agenda = agenda; } .... } method getMeetingAgendaCollection is a relation from meeting entity . then, in my controller servlet i call EJB like this. public class ControllerServlet extends HttpServlet { @EJB private RapatFacadeLocal rapatFacade; public void init() throws ServletException { // store category list in servlet context getServletContext().setAttribute("meetings", rapatFacade.findAll()); } ...... i want to show data from table entities meeting and meetingAgenda...but i can't.. please help.. i write code in JSP page.. like this.. <c:forEach var="meeting" items="${meetings}"> <td> MeetingCode : ${meeting.meetingCode} </td> <td> Meeting : ${meeting.meeting} </td> <td> Agenda : ${meeting.getMeetingAgendaCollection} </td> </c:forEach> how do I display data Agenda using getMeetingAgendaCollection ???? thanks for your help.

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  • Generating an identifier for objects so that they can be added to a hashtable I have created

    - by dukenukem
    I have a hashtable base class and I am creating different type of hashtable by deriving from it. I only allow it to accept objects that implement my IHashable interface.For example - class LinearProbingHashTable<T> : HashTableBase<T> where T: IHashable { ... ... ... } interface IHashable { /** * Every IHashable implementation should provide an indentfying value for use in generating a hash key. */ int getIdentifier(); } class Car : IHashable { public String Make { get; set; } public String Model { get; set; } public String Color { get; set; } public int Year { get; set; } public int getIdentifier() { /// ??? } } Can anyone suggest a good method for generating an identifier for the car that can be used by the hash function to place it in the hash table? I am actually really looking for a general purpose solution to generating an id for any given class. I would like to have a base class for all classes, HashableObject, that implements IHashable and its getIdentifier method. So then I could just derive from HashableObject which would automatically provide an identifier for any instances. Which means I wouldn't have to write a different getIdentifier method for every object I add to the hashtable. public class HashableObject : IHashable { public int getIdentifier() { // Looking for code here that would generate an id for any object... } } public class Dog : HashableObject { // Dont need to implement getIdentifier because the parent class does it for me }

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  • Create new folder for new sender name and move message into new folder

    - by Dave Jarvis
    Background I'd like to have Outlook 2010 automatically move e-mails into folders designated by the person's name. For example: Click Rules Click Manage Rules & Alerts Click New Rule Select "Move messages from someone to a folder" Click Next The following dialog is shown: Problem The next part usually looks as follows: Click people or public group Select the desired person Click specified Select the desired folder Question How would you automate those problematic manual tasks? Here's the logic for the new rule I'd like to create: Receive a new message. Extract the name of the sender. If it does not exist, create a new folder under Inbox Move the new message into the folder assigned to that person's name I think this will require a VBA macro. Related Links http://www.experts-exchange.com/Software/Office_Productivity/Groupware/Outlook/A_420-Extending-Outlook-Rules-via-Scripting.html http://msdn.microsoft.com/en-us/library/office/ee814735.aspx http://msdn.microsoft.com/en-us/library/office/ee814736.aspx http://stackoverflow.com/questions/11263483/how-do-i-trigger-a-macro-to-run-after-a-new-mail-is-received-in-outlook http://en.kioskea.net/faq/6174-outlook-a-macro-to-create-folders http://blogs.iis.net/robert_mcmurray/archive/2010/02/25/outlook-macros-part-1-moving-emails-into-personal-folders.aspx Update #1 The code might resemble something like: Public WithEvents myOlApp As Outlook.Application Sub Initialize_handler() Set myOlApp = CreateObject("Outlook.Application") End Sub Private Sub myOlApp_NewMail() Dim myInbox As Outlook.MAPIFolder Dim myItem As Outlook.MailItem Set myInbox = myOlApp.GetNamespace("MAPI").GetDefaultFolder(olFolderInbox) Set mySenderName = myItem.SenderName On Error GoTo ErrorHandler Set myDestinationFolder = myInbox.Folders.Add(mySenderName, olFolderInbox) Set myItems = myInbox.Items Set myItem = myItems.Find("[SenderName] = " & mySenderName) myItem.Move myDestinationFolder ErrorHandler: Resume Next End Sub Update #2 Split the code as follows: Sent a test message and nothing happened. The instructions for actually triggering a message when a new message arrives are a little light on details (for example, no mention is made regarding ThisOutlookSession and how to use it). Thank you.

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  • Windows 7 - Windows XP - sharing - why isn't working?

    - by durumdara
    Hi! This is seems to be "hardware" and not "software" / "programming" question, but I need to use this share in my programs, so it is "close to programming". We had an XP based wireless network. The server is XP Professional, the clients are XP Home (Notebooks). This was working well with folder sharing (with user rights, not simple share). Then we replaced the one of the notebook with Win7/X64 notebook. First time this can reach the server, and the another client too. Later I went to another sites, and connect to another servers, another networks. And then, when I return to this network, I saw that I cannot connect to this server. Nothing of resources I see, and when try to dbl click on this computer, I got login window, where I can write anything, never I can login... The interesting part, that: Another XP home can see the server, can login as quest, or with other user. The server can see the XP home notebook. The Win7 can see the notebook's shared folders, and XP home can see the Win7 shared folders. The server can see the Win7 folders, BUT: the Win7 cannot see the server folders. Cannot see the resources too... The Win7 is in "work networking group", the group name is not mshome. I tried everything on the server, I tried to remove MS client, restore it with simple sharing, set guest password, etc., but I lost the possibilities to access this server from Win7. Does anyone have any idea what I need to see, what I need to set to access these resource - to use them in my programs? Thanks for every info, link: dd

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  • Can not copy files from NTFS partition

    - by Ali
    I am experiencing a weird problem. I was running Xubuntu on my laptop until yesterday that I had to delete Xubuntu and install Windows. I had a NTFS partition on my Xubuntu that I kept some files on it. Today after installing windows I wanted to move all the files from that partition to an external HDD. I selected all files and folders and clicked on Copy, then I went to the HDD and clicked on paste but nothing happened. I can not do that. I do not know why. I copy the files, and wherever I click paste, nothing happens. If I try to copy the files and folders one by one, I can copy some of them, but some of them do not move. The other problem I have is that I can not open some files, in particular pdf files. When I click on pdf files I get this error: There was an error opening this document. This file cannot be found. Also, I cannot play some mp4 files. I can not open some jpg and txt files. I get this error The directory name is invalid. So in summary, after removing Xubuntu and installing windows 7 I have the following problems with one of the NTFS partitions on my internal drive: Can not copy or cut all folders and files from that partition to any other partition - I also do not get any errors. Can copy some folders and files Can not access some pdf, jpeg, txt and mp4 files and get the above errors. I should also mention I did not change anything for this partition during the installation or formatting the other partitions.

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  • List symlinks in specific relative directories

    - by Clinton Blackmore
    I have a server that shares out user home folders over the network. Each user has a Cache folder. Sometimes a symlink is used to redirect this folder to the hard drive of whichever machine they are using (and sometimes that doesn't work and they have a broken symlink [which is a matter for another day].) I'm trying to find out which users have symlinks and which don't. Within the shared folder, to get to the Cache folder you would substitute folders like so: $GRADE/$USERNAME/Library/Caches Right now I'm searching to see which users have symlinks and which do not. I've come up with: cd /path/to/shared/home/folders sudo find . -name "Caches" -exec ls -ld {} \; and get results like this: lrwxr-xr-x@ 1 name0 ES_Students 27 Jan 18 11:05 ./CES_Grade_03/name0/Library/Caches -> /tmp/name0/Library/Caches drwx------ 11 name1 ES_Students 374 Dec 8 15:44 ./CES_Grade_03/name1/Library/Caches lrwxr-xr-x@ 1 name2 ES_Students 27 Feb 23 14:27 ./CES_Grade_03/name2/Library/Caches -> /tmp/name2/Library/Caches drwx------ 17 name3 ES_Students 578 Jan 25 11:13 ./CES_Grade_03/name3/Library/Caches drwx------ 12 name4 ES_Students 408 Mar 22 13:09 ./CES_Grade_03/name4/Library/Caches but it nags at me that there must be a better way. Yes, it is good enough, and a one-off task, but I want to know how to do it right! Surely, I should be able to do something like: cd /path/to/shared/home/folders sudo ls -ld **/**/Library/Caches I'm afraid that I don't know the proper syntax or if there is a recursive folder-replacing wildcard format in bash, and my google-fu failed me. So, how do I properly formulate the search?

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  • Windows 7 - Windwos XP - sharing - why isn't working?

    - by durumdara
    Hi! This is seems to be "hardware" and not "software" / "programming" question, but I need to use this share in my programs, so it is "close to programming". We had an XP based wireless network. The server is XP Professional, the clients are XP Home (Notebooks). This was working well with folder sharing (with user rights, not simple share). Then we replaced the one of the notebook with Win7/X64 notebook. First time this can reach the server, and the another client too. Later I went to another sites, and connect to another servers, another networks. And then, when I return to this network, I saw that I cannot connect to this server. Nothing of resources I see, and when try to dbl click on this computer, I got login window, where I can write anything, never I can login... The interesting part, that: Another XP home can see the server, can login as quest, or with other user. The server can see the XP home notebook. The Win7 can see the notebook's shared folders, and XP home can see the Win7 shared folders. The server can see the Win7 folders, BUT: the Win7 cannot see the server folders. Cannot see the resources too... The Win7 is in "work networking group", the group name is not mshome. I tried everything on the server, I tried to remove MS client, restore it with simple sharing, set guest password, etc., but I lost the possibilities to access this server from Win7. Does anyone have any idea what I need to see, what I need to set to access these resource - to use them in my programs? Thanks for every info, link: dd

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  • FTP FileWatcher

    - by Meiscooldude
    So, I am in this little predicament where I am stuck watching a few ftp folders to see if they have new files added to them. If they do, it needs to throw an event with the file name. Thereby telling something else to download that file. This is a pretty simple object to make, I was just curious if anyone knew how expensive this operation would be? I plan on using the command NLIST because I don't need file size information, and there will be no sub-directories in the folder. Each file in the folder will have exactly 25 characters in its name. There could be anywhere from 10 to 'maybe' a couple thousand (max around 2000) files per folder (usually on the lower end, 100-300, but currently growing). The files are anywhere from 250kb to a very VERY unlikely 10mb (usually within the 250kb to 4mb range). There possibly could be up to a few hundred folders (in which case I could change the watch frequency depending on number of folders), but currently there are only a few (6-10ish). There also would be multiple logins for the ftp server, different logins would have access to different folders. I am not asking for an implementation, just if anyone has some first or second hand knowledge about FTP, how could this affect my network. I am not opposed to putting in file retention times or change the frequency in which I check for new files.

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  • Guest can't access host windows network share

    - by Asteroza
    HI folks, I've recently run into a strange problem after upgrading to VMware player 3. Certain virtual machines (currently an XP and a VIsta VM) seem to have lost the ability to access the host (XP) network shared folders (SMB). Both VM machines are bridged networking, firewall is up. Host firewall is up. Host and guests use DHCP. All OS are workgroup connected. The Vista VM I am not completely sure, but the XP VM did have access to the host's network shared folders after the player upgrade. Then today it wouldn't work, network path can't be found. Now here's the wierd part. The host's network shared folders can be accessed properly by other PC's on the network (and as far as I know, no settings have been changed). The host is pingable from the guests, and name resolution works. The guests can access network shares on other PC's in the network, and access the internet. My Network Places shows the host PC, but double clicking on it takes a long time before it finally times out with an error. Doing a wireshark packet capture, the guest is sending out the protocol negotiation, and the host is sending a response, but after that the guest behaves like it didn't receive anything and is doing TCP retransmissions. Anybody have any idea what could be wrong? Yes I know I can drag and drop files or setup the special VMware shared folders, but I want to access the host just like any other network accessible shared folder. It just seems really odd when any other computer works, just not between the guest and host.

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  • Can not copy files after installing windows

    - by Ali
    I am experiencing a weird problem. I was running Xubuntu on my laptop until yesterday that I had to delete Xubuntu and install Windows. I had a NTFS partition on my Xubuntu that I kept some files on it. Today after installing windows I wanted to move all the files from that partition to an external HDD. I selected all files and folders and clicked on Copy, then I went to the HDD and clicked on paste but nothing happened. I can not do that. I do not know why. I copy the files, and wherever I click paste, nothing happens. If I try to copy the files and folders one by one, I can copy some of them, but some of them do not move. The other problem I have is that I can not open some files, in particular pdf files. When I click on pdf files I get this error: There was an error opening this document. This file cannot be found. Also, I cannot play some mp4 files. I can not open some jpg and txt files. I get this error The directory name is invalid. So in summary, after removing Xubuntu and installing windows 7 I have the following problems with one of the NTFS partitions on my internal drive: Can not copy or cut all folders and files from that partition to any other partition - I also do not get any errors. Can copy some folders and files Can not access some pdf, jpeg, txt and mp4 files and get the above errors. I should also mention I did not change anything for this partition during the installation or formatting the other partitions.

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  • IP addresses not listed for IIS website bindings

    - by Svinn
    Recently purchased a windows cloud server godaddy. Now i installed iis7 and all other required software. And i have 50.62.1.89 and 2 more public ips. Also i have a private ip 10.1.0.2. Now the problem is am unable to access any website through any public ip. All my public ips are opening default website only. also i cant see pubic ips for IIS website bindings. Only my private ip listed for IIS binding. And in my server also public opening only default website. But am able to open websites using private ip. But my public ip addresses pointed to my server correctly. am able to open my server using remote desktop using public ip. Also as i said already public ip opening default website from IIS without problem. Please help me. Am confused for last 2 days.

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  • User profile service fails

    - by s.r.a
    I have Windows 7 and 3 drives on my HDD. The second drive is D:\, and there are some files in that. I decided to install 8.1 Enterprise so I installed it in dual boot manner beside 7 and in D:\ drive which as I said was not empty and when installing 8.1, I didn't format the D:. I installed 8.1 successfully in D:\ and it was working fine. One time which I came up with 7, I thought I should arrange the 8.1 folders in D: to be separated from the other non-8.1 folders, so I created a new folder named it "Windows 8.1" and cut all 8.1 folders and pasted them into that new folder. Now my D: drive was arranged. When I restart the PC, I selected the 8.1 to start with, but it didn't come up like before and instead, it shows now a blue screen (not the blue screen of death!) and the time is shown in left-down corner of it. When I click the screen this message appears: The User Profile Service service Failed the sign-in. User Profile can not be loaded. I know two things: 1- The problem is to do with that cutting and pasting the 8.1 folders to be arranged. And 2- If I reinstall the 8.1, the problem will be solved (but if I don't do that cutting and pasting again!) Is there any simpler way to solve the issue and have the two OSs with each other?

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  • Java constructor using generic types

    - by user37903
    I'm having a hard time wrapping my head around Java generic types. Here's a simple piece of code that in my mind should work, but I'm obviously doing something wrong. Eclipse reports this error in BreweryList.java: The method initBreweryFromObject() is undefined for the type <T> The idea is to fill a Vector with instances of objects that are a subclass of the Brewery class, so the invocation would be something like: BreweryList breweryList = new BreweryList(BrewerySubClass.class, list); BreweryList.java package com.beerme.test; import java.util.Vector; public class BreweryList<T extends Brewery> extends Vector<T> { public BreweryList(Class<T> c, Object[] j) { super(); for (int i = 0; i < j.length; i++) { T item = c.newInstance(); // initBreweryFromObject() is an instance method // of Brewery, of which <T> is a subclass (right?) c.initBreweryFromObject(); // "The method initBreweryFromObject() is undefined // for the type <T>" } } } Brewery.java package com.beerme.test; public class Brewery { public Brewery() { super(); } protected void breweryMethod() { } } BrewerySubClass.java package com.beerme.test; public class BrewerySubClass extends Brewery { public BrewerySubClass() { super(); } public void androidMethod() { } } I'm sure this is a complete-generics-noob question, but I'm stuck. Thanks for any tips!

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  • Files showing in smbclient but not smbmount

    - by Staale
    I have a samba folder that I try and access through smbclient, and I can browse it just fine. However, mounting it through smbmount, all the folders under the share are empty. I can list the folders directly under the share fine, but they all appear empty. smbclient: # smbclient //server/share -U username -W workgroup password smbmount # sudo smbmount //server/share mntpoint -o user=username,workgroup=workgroup,password=password I have also tried with domain=workgroup instead of workgroup, both give the same result. No error messages, everything mounts fine, but all the folders under mntpoint are empty, despite the same folders being non-empty when using smbclient. Are these using different libraries? How can I debug the error? Additionally, if I try to mount //server/share/folder, doing an ls results in a segmentation fault. Using dmesg I find: kernel BUG at /build/buildd/linux-2.6.28/fs/cifs/cifs_dfs_ref.c:315! Full trace: http://pastebin.com/m70adc213 Using a credentials file, I first get empty dirs, then Resource temporarily unavailable. In my dmesg I see the following output: CIFS VFS: compose_mount_options: Failed to resolve server part of \\srv\share to IP: -11

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  • Microsoft Server 2003 Explorer shows duplicate local shares

    - by user52167
    Hi folks, I am new here and I could really use some advice please. I am having a problem with our file server. When I try to browse the shared folders using explorer, several of the shared folders all appear to have the same name. Whenever I attempt to rename one of the affected folders, all the affected folders name also change. Our File Server is Windows Server 2003 R2. I am logged on directly to the server using remote desktop. When I open the folder all is as it should be, the proper content is there and the address bar displays the correct folder name and path. The share names are correct, so everything that needs to access the shared folder/files can do so. Also when I browse to the folder using the command-line all it as it should be there too. The only issue seems to be the incorrect display name when browsing using explorer. Can anyone offer any advice or help as to how to resolve this issue please? It would be most appreciated. Thanks

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  • IPTables Reroute SSH based on Connection string?

    - by senrabdet
    We are using a cloud server (Debian Squeeze) where public ports on a public IP route traffic to internal servers. We are looking for a way to use IPTables and ssh where based on some part of the ssh connection string (or something along these lines) iptables will reroute the ssh connection to the "right" internal server. This would allow us to use one common public port, and then re-route ssh connections to individual servers. So, for example we hope to do something like the following: user issues ssh connection (public key encryption) such as ssh -X -v -p xxx [email protected] but maybe adds something into the string for iptables to use iptables uses some part of that string or some means to re-route the connection to an internal server using something like iptables -t nat -A PREROUTING ! -s xxx.xxx.xxx.0/24 -m tcp -p tcp --dport $EXTPORT -j DNAT --to-destination $HOST:$INTPORT ....where $HOST is the internal ip of a server, $EXTPORT is the common public facing port and $INTPORT is the internal server port. It appears that the "string" aspect of iptables does not do what we want. We can currently route based on the IP table syntax we're using, but rely on having a separate public port for each server and are hoping to use one common public port and then re-route to specific internal servers based on some part of the ssh connection string or some other means. Any suggestions? Thanks!

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  • Sending Messages to SignalR Hubs from the Outside

    - by Ricardo Peres
    Introduction You are by now probably familiarized with SignalR, Microsoft’s API for real-time web functionality. This is, in my opinion, one of the greatest products Microsoft has released in recent time. Usually, people login to a site and enter some page which is connected to a SignalR hub. Then they can send and receive messages – not just text messages, mind you – to other users in the same hub. Also, the server can also take the initiative to send messages to all or a specified subset of users on its own, this is known as server push. The normal flow is pretty straightforward, Microsoft has done a great job with the API, it’s clean and quite simple to use. And for the latter – the server taking the initiative – it’s also quite simple, just involves a little more work. The Problem The API for sending messages can be achieved from inside a hub – an instance of the Hub class – which is something that we don’t have if we are the server and we want to send a message to some user or group of users: the Hub instance is only instantiated in response to a client message. The Solution It is possible to acquire a hub’s context from outside of an actual Hub instance, by calling GlobalHost.ConnectionManager.GetHubContext<T>(). This API allows us to: Broadcast messages to all connected clients (possibly excluding some); Send messages to a specific client; Send messages to a group of clients. So, we have groups and clients, each is identified by a string. Client strings are called connection ids and group names are free-form, given by us. The problem with client strings is, we do not know how these map to actual users. One way to achieve this mapping is by overriding the Hub’s OnConnected and OnDisconnected methods and managing the association there. Here’s an example: 1: public class MyHub : Hub 2: { 3: private static readonly IDictionary<String, ISet<String>> users = new ConcurrentDictionary<String, ISet<String>>(); 4:  5: public static IEnumerable<String> GetUserConnections(String username) 6: { 7: ISet<String> connections; 8:  9: users.TryGetValue(username, out connections); 10:  11: return (connections ?? Enumerable.Empty<String>()); 12: } 13:  14: private static void AddUser(String username, String connectionId) 15: { 16: ISet<String> connections; 17:  18: if (users.TryGetValue(username, out connections) == false) 19: { 20: connections = users[username] = new HashSet<String>(); 21: } 22:  23: connections.Add(connectionId); 24: } 25:  26: private static void RemoveUser(String username, String connectionId) 27: { 28: users[username].Remove(connectionId); 29: } 30:  31: public override Task OnConnected() 32: { 33: AddUser(this.Context.Request.User.Identity.Name, this.Context.ConnectionId); 34: return (base.OnConnected()); 35: } 36:  37: public override Task OnDisconnected() 38: { 39: RemoveUser(this.Context.Request.User.Identity.Name, this.Context.ConnectionId); 40: return (base.OnDisconnected()); 41: } 42: } As you can see, I am using a static field to store the mapping between a user and its possibly many connections – for example, multiple open browser tabs or even multiple browsers accessing the same page with the same login credentials. The user identity, as is normal in .NET, is obtained from the IPrincipal which in SignalR hubs case is stored in Context.Request.User. Of course, this property will only have a meaningful value if we enforce authentication. Another way to go is by creating a group for each user that connects: 1: public class MyHub : Hub 2: { 3: public override Task OnConnected() 4: { 5: this.Groups.Add(this.Context.ConnectionId, this.Context.Request.User.Identity.Name); 6: return (base.OnConnected()); 7: } 8:  9: public override Task OnDisconnected() 10: { 11: this.Groups.Remove(this.Context.ConnectionId, this.Context.Request.User.Identity.Name); 12: return (base.OnDisconnected()); 13: } 14: } In this case, we will have a one-to-one equivalence between users and groups. All connections belonging to the same user will fall in the same group. So, if we want to send messages to a user from outside an instance of the Hub class, we can do something like this, for the first option – user mappings stored in a static field: 1: public void SendUserMessage(String username, String message) 2: { 3: var context = GlobalHost.ConnectionManager.GetHubContext<MyHub>(); 4: 5: foreach (String connectionId in HelloHub.GetUserConnections(username)) 6: { 7: context.Clients.Client(connectionId).sendUserMessage(message); 8: } 9: } And for using groups, its even simpler: 1: public void SendUserMessage(String username, String message) 2: { 3: var context = GlobalHost.ConnectionManager.GetHubContext<MyHub>(); 4:  5: context.Clients.Group(username).sendUserMessage(message); 6: } Using groups has the advantage that the IHubContext interface returned from GetHubContext has direct support for groups, no need to send messages to individual connections. Of course, you can wrap both mapping options in a common API, perhaps exposed through IoC. One example of its interface might be: 1: public interface IUserToConnectionMappingService 2: { 3: //associate and dissociate connections to users 4:  5: void AddUserConnection(String username, String connectionId); 6:  7: void RemoveUserConnection(String username, String connectionId); 8: } SignalR has built-in dependency resolution, by means of the static GlobalHost.DependencyResolver property: 1: //for using groups (in the Global class) 2: GlobalHost.DependencyResolver.Register(typeof(IUserToConnectionMappingService), () => new GroupsMappingService()); 3:  4: //for using a static field (in the Global class) 5: GlobalHost.DependencyResolver.Register(typeof(IUserToConnectionMappingService), () => new StaticMappingService()); 6:  7: //retrieving the current service (in the Hub class) 8: var mapping = GlobalHost.DependencyResolver.Resolve<IUserToConnectionMappingService>(); Now all you have to do is implement GroupsMappingService and StaticMappingService with the code I shown here and change SendUserMessage method to rely in the dependency resolver for the actual implementation. Stay tuned for more SignalR posts!

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  • Using Unity – Part 2

    - by nmarun
    In the first part of this series, we created a simple project and learned how to implement IoC pattern using Unity. In this one, I’ll show how you can instantiate other types that implement our IProduct interface. One place where this one would want to use this feature is to create mock types for testing purposes. Alright, let’s dig in. I added another class – Product2.cs  to the ProductModel project. 1: public class Product2 : IProduct 2: { 3: public string Name { get; set;} 4: public Category Category { get; set; } 5: public DateTime MfgDate { get;set; } 6:  7: public Product2() 8: { 9: Name = "Canon Digital Rebel XTi"; 10: Category = new Category {Name = "Electronics", SubCategoryName = "Digital Cameras"}; 11: MfgDate = DateTime.Now; 12: } 13:  14: public string WriteProductDetails() 15: { 16: return string.Format("Name: {0}<br/>Category: {1}<br/>Mfg Date: {2}", 17: Name, Category, MfgDate.ToShortDateString()); 18: } 19: } Highlights of this class are that it implements IProduct interface and it has some different properties than the Product class. The Category class looks like below: 1: public class Category 2: { 3: public string Name { get; set; } 4: public string SubCategoryName { get; set; } 5:  6: public override string ToString() 7: { 8: return string.Format("{0} - {1}", Name, SubCategoryName); 9: } 10: } We’ll go to our web.config file to add the configuration information about this new class – Product2 that we created. Let’s first add a typeAlias element. 1: <typeAlias alias="Product2" type="ProductModel.Product2, ProductModel"/> That’s all that is needed for us to get an instance of Product2 in our application. I have a new button added to the .aspx page and the click event of this button is where all the magic happens: 1: private IUnityContainer unityContainer; 2: protected void Page_Load(object sender, EventArgs e) 3: { 4: unityContainer = Application["UnityContainer"] as IUnityContainer; 5: 6: if (unityContainer == null) 7: { 8: productDetailsLabel.Text = "ERROR: Unity Container not populated in Global.asax.<p />"; 9: } 10: else 11: { 12: if (!IsPostBack) 13: { 14: IProduct productInstance = unityContainer.Resolve<IProduct>(); 15: productDetailsLabel.Text = productInstance.WriteProductDetails(); 16: } 17: } 18: } 19:  20: protected void Product2Button_Click(object sender, EventArgs e) 21: { 22: unityContainer.RegisterType<IProduct, Product2>(); 23: IProduct product2Instance = unityContainer.Resolve<IProduct>(); 24: productDetailsLabel.Text = product2Instance.WriteProductDetails(); 25: } The unityContainer instance is set in the Page_Load event. Line 22 in the click event of the Product2Button registers a type mapping in the container. In English, this means that when unityContainer tries to resolve for IProduct, it gets an instance of Product2. Once this code runs, following output is rendered: There’s another way of doing this. You can resolve an instance of the requested type with a name from the container. We’ll have to update the container element of our web.config file to include the following: 1: <container name="unityContainer"> 2: <types> 3: <type type="IProduct" mapTo="Product"/> 4: <!-- Named mapping for IProduct to Product --> 5: <type type="IProduct" mapTo="Product" name="LegacyProduct" /> 6: <!-- Named mapping for IProduct to Product2 --> 7: <type type="IProduct" mapTo="Product2" name="NewProduct" /> 8: </types> 9: </container> I’ve added a Dropdownlist and a button to the design page: 1: <asp:DropDownList ID="ModelTypesList" runat="server"> 2: <asp:ListItem Text="Legacy Product" Value="LegacyProduct" /> 3: <asp:ListItem Text="New Product" Value="NewProduct" /> 4: </asp:DropDownList> 5: <br /> 6: <asp:Button ID="SelectedModelButton" Text="Get Selected Instance" runat="server" 7: onclick="SelectedModelButton_Click" /> 1: protected void SelectedModelButton_Click(object sender, EventArgs e) 2: { 3: // get the selected value: LegacyProduct or NewProduct 4: string modelType = ModelTypesList.SelectedValue; 5: // pass the modelType to the Resolve method 6: IProduct customModel = unityContainer.Resolve<IProduct>(modelType); 7: productDetailsLabel.Text = customModel.WriteProductDetails(); 8: } Pretty straight forward right? The only thing to note here is that the values in the dropdownlist item need to match the name attribute of the type. Depending on what you select, you’ll get an instance of either the Product class or the Product2 class and the corresponding WriteProductDetails() method is called. Now you see, how either of these methods can be used to create mock objects your the test project. See the code here. I’ll continue to share more of Unity in the next blog.

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  • Interface contracts – forcing code contracts through interfaces

    - by DigiMortal
    Sometimes we need a way to make different implementations of same interface follow same rules. One option is to duplicate contracts to all implementation but this is not good option because we have duplicated code then. The other option is to force contracts to all implementations at interface level. In this posting I will show you how to do it using interface contracts and contracts class. Using code from previous example about unit testing code with code contracts I will go further and force contracts at interface level. Here is the code from previous example. Take a careful look at it because I will talk about some modifications to this code soon. public interface IRandomGenerator {     int Next(int min, int max); }   public class RandomGenerator : IRandomGenerator {     private Random _random = new Random();       public int Next(int min, int max)     {         return _random.Next(min, max);     } }    public class Randomizer {     private IRandomGenerator _generator;       private Randomizer()     {         _generator = new RandomGenerator();     }       public Randomizer(IRandomGenerator generator)     {         _generator = generator;     }       public int GetRandomFromRangeContracted(int min, int max)     {         Contract.Requires<ArgumentOutOfRangeException>(             min < max,             "Min must be less than max"         );           Contract.Ensures(             Contract.Result<int>() >= min &&             Contract.Result<int>() <= max,             "Return value is out of range"         );           return _generator.Next(min, max);     } } If we look at the GetRandomFromRangeContracted() method we can see that contracts set in this method are applicable to all implementations of IRandomGenerator interface. Although we can write new implementations as we want these implementations need exactly the same contracts. If we are using generators somewhere else then code contracts are not with them anymore. To solve the problem we will force code contracts at interface level. NB! To make the following code work you must enable Contract Reference Assembly building from project settings. Interface contracts and contracts class Interface contains no code – only definitions of members that implementing type must have. But code contracts must be defined in body of member they are part of. To get over this limitation, code contracts are defined in separate contracts class. Interface is bound to this class by special attribute and contracts class refers to interface through special attribute. Here is the IRandomGenerator with contracts and contracts class. Also I write simple fake so we can test contracts easily based only on interface mock. [ContractClass(typeof(RandomGeneratorContracts))] public interface IRandomGenerator {     int Next(int min, int max); }   [ContractClassFor(typeof(IRandomGenerator))] internal sealed class RandomGeneratorContracts : IRandomGenerator {     int IRandomGenerator.Next(int min, int max)     {         Contract.Requires<ArgumentOutOfRangeException>(                 min < max,                 "Min must be less than max"             );           Contract.Ensures(             Contract.Result<int>() >= min &&             Contract.Result<int>() <= max,             "Return value is out of range"         );           return default(int);     } }   public class RandomFake : IRandomGenerator {     private int _testValue;       public RandomGen(int testValue)     {         _testValue = testValue;     }       public int Next(int min, int max)     {         return _testValue;     } } To try out these changes use the following code. var gen = new RandomFake(3);   try {     gen.Next(10, 1); } catch(Exception ex) {     Debug.WriteLine(ex.Message); }   try {     gen.Next(5, 10); } catch(Exception ex) {     Debug.WriteLine(ex.Message); } Now we can force code contracts to all types that implement our IRandomGenerator interface and we must test only the interface to make sure that contracts are defined correctly.

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  • Routing Issue in ASP.NET MVC 3 RC 2

    - by imran_ku07
         Introduction:             Two weeks ago, ASP.NET MVC team shipped the ASP.NET MVC 3 RC 2 release. This release includes some new features and some performance optimization. This release also fixes most of the bugs but still some minor issues are present in this release. Some of these issues are already discussed by Scott Guthrie at Update on ASP.NET MVC 3 RC2 (and a workaround for a bug in it). In addition to these issues, I have found another issue in this release regarding routing. In this article, I will show you the issue regarding routing and a simple workaround for this issue.       Description:             The easiest way to understand an issue is to reproduce it in the application. So create a MVC 2 application and a MVC 3 RC 2 application. Then in both applications, just open global.asax file and update the default route as below,     routes.IgnoreRoute("{resource}.axd/{*pathInfo}"); routes.MapRoute( "Default", // Route name "{controller}/{action}/{id1}/{id2}", // URL with parameters new { controller = "Home", action = "Index", id1 = UrlParameter.Optional, id2 = UrlParameter.Optional } // Parameter defaults );              Then just open Index View and add the following lines,    <%@ Page Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage" %> <asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server"> Home Page </asp:Content> <asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server"> <% Html.RenderAction("About"); %> </asp:Content>             The above view will issue a child request to About action method. Now run both applications. ASP.NET MVC 2 application will run just fine. But ASP.NET MVC 3 RC 2 application will throw an exception as shown below,                  You may think that this is a routing issue but this is not the case here as both ASP.NET MVC 2 and ASP.NET MVC  3 RC 2 applications(created above) are built with .NET Framework 4.0 and both will use the same routing defined in System.Web. Something is wrong in ASP.NET MVC 3 RC 2. So after digging into ASP.NET MVC source code, I have found that the UrlParameter class in ASP.NET MVC 3 RC 2 overrides the ToString method which simply return an empty string.     public sealed class UrlParameter { public static readonly UrlParameter Optional = new UrlParameter(); private UrlParameter() { } public override string ToString() { return string.Empty; } }             In MVC 2 the ToString method was not overridden. So to quickly fix the above problem just replace UrlParameter.Optional default value with a different value other than null or empty(for example, a single white space) or replace UrlParameter.Optional default value with a new class object containing the same code as UrlParameter class have except the ToString method is not overridden (or with a overridden ToString method that return a string value other than null or empty). But by doing this you will loose the benefit of ASP.NET MVC 2 Optional URL Parameters. There may be many different ways to fix the above problem and not loose the benefit of optional parameters. Here I will create a new class MyUrlParameter with the same code as UrlParameter class have except the ToString method is not overridden. Then I will create a base controller class which contains a constructor to remove all MyUrlParameter route data parameters, same like ASP.NET MVC doing with UrlParameter route data parameters early in the request.     public class BaseController : Controller { public BaseController() { if (System.Web.HttpContext.Current.CurrentHandler is MvcHandler) { RouteValueDictionary rvd = ((MvcHandler)System.Web.HttpContext.Current.CurrentHandler).RequestContext.RouteData.Values; string[] matchingKeys = (from entry in rvd where entry.Value == MyUrlParameter.Optional select entry.Key).ToArray(); foreach (string key in matchingKeys) { rvd.Remove(key); } } } } public class HomeController : BaseController { public ActionResult Index(string id1) { ViewBag.Message = "Welcome to ASP.NET MVC!"; return View(); } public ActionResult About() { return Content("Child Request Contents"); } }     public sealed class MyUrlParameter { public static readonly MyUrlParameter Optional = new MyUrlParameter(); private MyUrlParameter() { } }     routes.IgnoreRoute("{resource}.axd/{*pathInfo}"); routes.MapRoute( "Default", // Route name "{controller}/{action}/{id1}/{id2}", // URL with parameters new { controller = "Home", action = "Index", id1 = MyUrlParameter.Optional, id2 = MyUrlParameter.Optional } // Parameter defaults );             MyUrlParameter class is a copy of UrlParameter class except that MyUrlParameter class not overrides the ToString method. Note that the default route is modified to use MyUrlParameter.Optional instead of UrlParameter.Optional. Also note that BaseController class constructor is removing MyUrlParameter parameters from the current request route data so that the model binder will not bind these parameters with action method parameters. Now just run the ASP.NET MVC 3 RC 2 application again, you will find that it runs just fine.             In case if you are curious to know that why ASP.NET MVC 3 RC 2 application throws an exception if UrlParameter class contains a ToString method which returns an empty string, then you need to know something about a feature of routing for url generation. During url generation, routing will call the ParsedRoute.Bind method internally. This method includes a logic to match the route and build the url. During building the url, ParsedRoute.Bind method will call the ToString method of the route values(in our case this will call the UrlParameter.ToString method) and then append the returned value into url. This method includes a logic after appending the returned value into url that if two continuous returned values are empty then don't match the current route otherwise an incorrect url will be generated. Here is the snippet from ParsedRoute.Bind method which will prove this statement.       if ((builder2.Length > 0) && (builder2[builder2.Length - 1] == '/')) { return null; } builder2.Append("/"); ........................................................... ........................................................... ........................................................... ........................................................... if (RoutePartsEqual(obj3, obj4)) { builder2.Append(UrlEncode(Convert.ToString(obj3, CultureInfo.InvariantCulture))); continue; }             In the above example, both id1 and id2 parameters default values are set to UrlParameter object and UrlParameter class include a ToString method that returns an empty string. That's why this route will not matched.            Summary:             In this article I showed you the issue regarding routing and also showed you how to workaround this problem. I explained this issue with an example by creating a ASP.NET MVC 2 and a ASP.NET MVC 3 RC 2 application. Finally I also explained the reason for this issue. Hopefully you will enjoy this article too.   SyntaxHighlighter.all()

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  • C#: Does an IDisposable in a Halted Iterator Dispose?

    - by James Michael Hare
    If that sounds confusing, let me give you an example. Let's say you expose a method to read a database of products, and instead of returning a List<Product> you return an IEnumerable<Product> in iterator form (yield return). This accomplishes several good things: The IDataReader is not passed out of the Data Access Layer which prevents abstraction leak and resource leak potentials. You don't need to construct a full List<Product> in memory (which could be very big) if you just want to forward iterate once. If you only want to consume up to a certain point in the list, you won't incur the database cost of looking up the other items. This could give us an example like: 1: // a sample data access object class to do standard CRUD operations. 2: public class ProductDao 3: { 4: private DbProviderFactory _factory = SqlClientFactory.Instance 5:  6: // a method that would retrieve all available products 7: public IEnumerable<Product> GetAvailableProducts() 8: { 9: // must create the connection 10: using (var con = _factory.CreateConnection()) 11: { 12: con.ConnectionString = _productsConnectionString; 13: con.Open(); 14:  15: // create the command 16: using (var cmd = _factory.CreateCommand()) 17: { 18: cmd.Connection = con; 19: cmd.CommandText = _getAllProductsStoredProc; 20: cmd.CommandType = CommandType.StoredProcedure; 21:  22: // get a reader and pass back all results 23: using (var reader = cmd.ExecuteReader()) 24: { 25: while(reader.Read()) 26: { 27: yield return new Product 28: { 29: Name = reader["product_name"].ToString(), 30: ... 31: }; 32: } 33: } 34: } 35: } 36: } 37: } The database details themselves are irrelevant. I will say, though, that I'm a big fan of using the System.Data.Common classes instead of your provider specific counterparts directly (SqlCommand, OracleCommand, etc). This lets you mock your data sources easily in unit testing and also allows you to swap out your provider in one line of code. In fact, one of the shared components I'm most proud of implementing was our group's DatabaseUtility library that simplifies all the database access above into one line of code in a thread-safe and provider-neutral way. I went with my own flavor instead of the EL due to the fact I didn't want to force internal company consumers to use the EL if they didn't want to, and it made it easy to allow them to mock their database for unit testing by providing a MockCommand, MockConnection, etc that followed the System.Data.Common model. One of these days I'll blog on that if anyone's interested. Regardless, you often have situations like the above where you are consuming and iterating through a resource that must be closed once you are finished iterating. For the reasons stated above, I didn't want to return IDataReader (that would force them to remember to Dispose it), and I didn't want to return List<Product> (that would force them to hold all products in memory) -- but the first time I wrote this, I was worried. What if you never consume the last item and exit the loop? Are the reader, command, and connection all disposed correctly? Of course, I was 99.999999% sure the creators of C# had already thought of this and taken care of it, but inspection in Reflector was difficult due to the nature of the state machines yield return generates, so I decided to try a quick example program to verify whether or not Dispose() will be called when an iterator is broken from outside the iterator itself -- i.e. before the iterator reports there are no more items. So I wrote a quick Sequencer class with a Dispose() method and an iterator for it. Yes, it is COMPLETELY contrived: 1: // A disposable sequence of int -- yes this is completely contrived... 2: internal class Sequencer : IDisposable 3: { 4: private int _i = 0; 5: private readonly object _mutex = new object(); 6:  7: // Constructs an int sequence. 8: public Sequencer(int start) 9: { 10: _i = start; 11: } 12:  13: // Gets the next integer 14: public int GetNext() 15: { 16: lock (_mutex) 17: { 18: return _i++; 19: } 20: } 21:  22: // Dispose the sequence of integers. 23: public void Dispose() 24: { 25: // force output immediately (flush the buffer) 26: Console.WriteLine("Disposed with last sequence number of {0}!", _i); 27: Console.Out.Flush(); 28: } 29: } And then I created a generator (infinite-loop iterator) that did the using block for auto-Disposal: 1: // simply defines an extension method off of an int to start a sequence 2: public static class SequencerExtensions 3: { 4: // generates an infinite sequence starting at the specified number 5: public static IEnumerable<int> GetSequence(this int starter) 6: { 7: // note the using here, will call Dispose() when block terminated. 8: using (var seq = new Sequencer(starter)) 9: { 10: // infinite loop on this generator, means must be bounded by caller! 11: while(true) 12: { 13: yield return seq.GetNext(); 14: } 15: } 16: } 17: } This is really the same conundrum as the database problem originally posed. Here we are using iteration (yield return) over a large collection (infinite sequence of integers). If we cut the sequence short by breaking iteration, will that using block exit and hence, Dispose be called? Well, let's see: 1: // The test program class 2: public class IteratorTest 3: { 4: // The main test method. 5: public static void Main() 6: { 7: Console.WriteLine("Going to consume 10 of infinite items"); 8: Console.Out.Flush(); 9:  10: foreach(var i in 0.GetSequence()) 11: { 12: // could use TakeWhile, but wanted to output right at break... 13: if(i >= 10) 14: { 15: Console.WriteLine("Breaking now!"); 16: Console.Out.Flush(); 17: break; 18: } 19:  20: Console.WriteLine(i); 21: Console.Out.Flush(); 22: } 23:  24: Console.WriteLine("Done with loop."); 25: Console.Out.Flush(); 26: } 27: } So, what do we see? Do we see the "Disposed" message from our dispose, or did the Dispose get skipped because from an "eyeball" perspective we should be locked in that infinite generator loop? Here's the results: 1: Going to consume 10 of infinite items 2: 0 3: 1 4: 2 5: 3 6: 4 7: 5 8: 6 9: 7 10: 8 11: 9 12: Breaking now! 13: Disposed with last sequence number of 11! 14: Done with loop. Yes indeed, when we break the loop, the state machine that C# generates for yield iterate exits the iteration through the using blocks and auto-disposes the IDisposable correctly. I must admit, though, the first time I wrote one, I began to wonder and that led to this test. If you've never seen iterators before (I wrote a previous entry here) the infinite loop may throw you, but you have to keep in mind it is not a linear piece of code, that every time you hit a "yield return" it cedes control back to the state machine generated for the iterator. And this state machine, I'm happy to say, is smart enough to clean up the using blocks correctly. I suspected those wily guys and gals at Microsoft engineered it well, and I wasn't disappointed. But, I've been bitten by assumptions before, so it's good to test and see. Yes, maybe you knew it would or figured it would, but isn't it nice to know? And as those campy 80s G.I. Joe cartoon public service reminders always taught us, "Knowing is half the battle...". Technorati Tags: C#,.NET

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  • C# Extension Methods - To Extend or Not To Extend...

    - by James Michael Hare
    I've been thinking a lot about extension methods lately, and I must admit I both love them and hate them. They are a lot like sugar, they taste so nice and sweet, but they'll rot your teeth if you eat them too much.   I can't deny that they aren't useful and very handy. One of the major components of the Shared Component library where I work is a set of useful extension methods. But, I also can't deny that they tend to be overused and abused to willy-nilly extend every living type.   So what constitutes a good extension method? Obviously, you can write an extension method for nearly anything whether it is a good idea or not. Many times, in fact, an idea seems like a good extension method but in retrospect really doesn't fit.   So what's the litmus test? To me, an extension method should be like in the movies when a person runs into their twin, separated at birth. You just know you're related. Obviously, that's hard to quantify, so let's try to put a few rules-of-thumb around them.   A good extension method should:     Apply to any possible instance of the type it extends.     Simplify logic and improve readability/maintainability.     Apply to the most specific type or interface applicable.     Be isolated in a namespace so that it does not pollute IntelliSense.     So let's look at a few examples in relation to these rules.   The first rule, to me, is the most important of all. Once again, it bears repeating, a good extension method should apply to all possible instances of the type it extends. It should feel like the long lost relative that should have been included in the original class but somehow was missing from the family tree.    Take this nifty little int extension, I saw this once in a blog and at first I really thought it was pretty cool, but then I started noticing a code smell I couldn't quite put my finger on. So let's look:       public static class IntExtensinos     {         public static int Seconds(int num)         {             return num * 1000;         }           public static int Minutes(int num)         {             return num * 60000;         }     }     This is so you could do things like:       ...     Thread.Sleep(5.Seconds());     ...     proxy.Timeout = 1.Minutes();     ...     Awww, you say, that's cute! Well, that's the problem, it's kitschy and it doesn't always apply (and incidentally you could achieve the same thing with TimeStamp.FromSeconds(5)). It's syntactical candy that looks cool, but tends to rot and pollute the code. It would allow things like:       total += numberOfTodaysOrders.Seconds();     which makes no sense and should never be allowed. The problem is you're applying an extension method to a logical domain, not a type domain. That is, the extension method Seconds() doesn't really apply to ALL ints, it applies to ints that are representative of time that you want to convert to milliseconds.    Do you see what I mean? The two problems, in a nutshell, are that a) Seconds() called off a non-time value makes no sense and b) calling Seconds() off something to pass to something that does not take milliseconds will be off by a factor of 1000 or worse.   Thus, in my mind, you should only ever have an extension method that applies to the whole domain of that type.   For example, this is one of my personal favorites:       public static bool IsBetween<T>(this T value, T low, T high)         where T : IComparable<T>     {         return value.CompareTo(low) >= 0 && value.CompareTo(high) <= 0;     }   This allows you to check if any IComparable<T> is within an upper and lower bound. Think of how many times you type something like:       if (response.Employee.Address.YearsAt >= 2         && response.Employee.Address.YearsAt <= 10)     {     ...     }     Now, you can instead type:       if(response.Employee.Address.YearsAt.IsBetween(2, 10))     {     ...     }     Note that this applies to all IComparable<T> -- that's ints, chars, strings, DateTime, etc -- and does not depend on any logical domain. In addition, it satisfies the second point and actually makes the code more readable and maintainable.   Let's look at the third point. In it we said that an extension method should fit the most specific interface or type possible. Now, I'm not saying if you have something that applies to enumerables, you create an extension for List, Array, Dictionary, etc (though you may have reasons for doing so), but that you should beware of making things TOO general.   For example, let's say we had an extension method like this:       public static T ConvertTo<T>(this object value)     {         return (T)Convert.ChangeType(value, typeof(T));     }         This lets you do more fluent conversions like:       double d = "5.0".ConvertTo<double>();     However, if you dig into Reflector (LOVE that tool) you will see that if the type you are calling on does not implement IConvertible, what you convert to MUST be the exact type or it will throw an InvalidCastException. Now this may or may not be what you want in this situation, and I leave that up to you. Things like this would fail:       object value = new Employee();     ...     // class cast exception because typeof(IEmployee) != typeof(Employee)     IEmployee emp = value.ConvertTo<IEmployee>();       Yes, that's a downfall of working with Convertible in general, but if you wanted your fluent interface to be more type-safe so that ConvertTo were only callable on IConvertibles (and let casting be a manual task), you could easily make it:         public static T ConvertTo<T>(this IConvertible value)     {         return (T)Convert.ChangeType(value, typeof(T));     }         This is what I mean by choosing the best type to extend. Consider that if we used the previous (object) version, every time we typed a dot ('.') on an instance we'd pull up ConvertTo() whether it was applicable or not. By filtering our extension method down to only valid types (those that implement IConvertible) we greatly reduce our IntelliSense pollution and apply a good level of compile-time correctness.   Now my fourth rule is just my general rule-of-thumb. Obviously, you can make extension methods as in-your-face as you want. I included all mine in my work libraries in its own sub-namespace, something akin to:       namespace Shared.Core.Extensions { ... }     This is in a library called Shared.Core, so just referencing the Core library doesn't pollute your IntelliSense, you have to actually do a using on Shared.Core.Extensions to bring the methods in. This is very similar to the way Microsoft puts its extension methods in System.Linq. This way, if you want 'em, you use the appropriate namespace. If you don't want 'em, they won't pollute your namespace.   To really make this work, however, that namespace should only include extension methods and subordinate types those extensions themselves may use. If you plant other useful classes in those namespaces, once a user includes it, they get all the extensions too.   Also, just as a personal preference, extension methods that aren't simply syntactical shortcuts, I like to put in a static utility class and then have extension methods for syntactical candy. For instance, I think it imaginable that any object could be converted to XML:       namespace Shared.Core     {         // A collection of XML Utility classes         public static class XmlUtility         {             ...             // Serialize an object into an xml string             public static string ToXml(object input)             {                 var xs = new XmlSerializer(input.GetType());                   // use new UTF8Encoding here, not Encoding.UTF8. The later includes                 // the BOM which screws up subsequent reads, the former does not.                 using (var memoryStream = new MemoryStream())                 using (var xmlTextWriter = new XmlTextWriter(memoryStream, new UTF8Encoding()))                 {                     xs.Serialize(xmlTextWriter, input);                     return Encoding.UTF8.GetString(memoryStream.ToArray());                 }             }             ...         }     }   I also wanted to be able to call this from an object like:       value.ToXml();     But here's the problem, if i made this an extension method from the start with that one little keyword "this", it would pop into IntelliSense for all objects which could be very polluting. Instead, I put the logic into a utility class so that users have the choice of whether or not they want to use it as just a class and not pollute IntelliSense, then in my extensions namespace, I add the syntactical candy:       namespace Shared.Core.Extensions     {         public static class XmlExtensions         {             public static string ToXml(this object value)             {                 return XmlUtility.ToXml(value);             }         }     }   So now it's the best of both worlds. On one hand, they can use the utility class if they don't want to pollute IntelliSense, and on the other hand they can include the Extensions namespace and use as an extension if they want. The neat thing is it also adheres to the Single Responsibility Principle. The XmlUtility is responsible for converting objects to XML, and the XmlExtensions is responsible for extending object's interface for ToXml().

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  • ASP.NET MVC 3 Hosting :: Error Handling and CustomErrors in ASP.NET MVC 3 Framework

    - by C. Miller
    So, what else is new in MVC 3? MVC 3 now has a GlobalFilterCollection that is automatically populated with a HandleErrorAttribute. This default FilterAttribute brings with it a new way of handling errors in your web applications. In short, you can now handle errors inside of the MVC pipeline. What does that mean? This gives you direct programmatic control over handling your 500 errors in the same way that ASP.NET and CustomErrors give you configurable control of handling your HTTP error codes. How does that work out? Think of it as a routing table specifically for your Exceptions, it's pretty sweet! Global Filters The new Global.asax file now has a RegisterGlobalFilters method that is used to add filters to the new GlobalFilterCollection, statically located at System.Web.Mvc.GlobalFilter.Filters. By default this method adds one filter, the HandleErrorAttribute. public class MvcApplication : System.Web.HttpApplication {     public static void RegisterGlobalFilters(GlobalFilterCollection filters)     {         filters.Add(new HandleErrorAttribute());     } HandleErrorAttributes The HandleErrorAttribute is pretty simple in concept: MVC has already adjusted us to using Filter attributes for our AcceptVerbs and RequiresAuthorization, now we are going to use them for (as the name implies) error handling, and we are going to do so on a (also as the name implies) global scale. The HandleErrorAttribute has properties for ExceptionType, View, and Master. The ExceptionType allows you to specify what exception that attribute should handle. The View allows you to specify which error view (page) you want it to redirect to. Last but not least, the Master allows you to control which master page (or as Razor refers to them, Layout) you want to render with, even if that means overriding the default layout specified in the view itself. public class MvcApplication : System.Web.HttpApplication {     public static void RegisterGlobalFilters(GlobalFilterCollection filters)     {         filters.Add(new HandleErrorAttribute         {             ExceptionType = typeof(DbException),             // DbError.cshtml is a view in the Shared folder.             View = "DbError",             Order = 2         });         filters.Add(new HandleErrorAttribute());     }Error Views All of your views still work like they did in the previous version of MVC (except of course that they can now use the Razor engine). However, a view that is used to render an error can not have a specified model! This is because they already have a model, and that is System.Web.Mvc.HandleErrorInfo @model System.Web.Mvc.HandleErrorInfo           @{     ViewBag.Title = "DbError"; } <h2>A Database Error Has Occurred</h2> @if (Model != null) {     <p>@Model.Exception.GetType().Name<br />     thrown in @Model.ControllerName @Model.ActionName</p> }Errors Outside of the MVC Pipeline The HandleErrorAttribute will only handle errors that happen inside of the MVC pipeline, better known as 500 errors. Errors outside of the MVC pipeline are still handled the way they have always been with ASP.NET. You turn on custom errors, specify error codes and paths to error pages, etc. It is important to remember that these will happen for anything and everything outside of what the HandleErrorAttribute handles. Also, these will happen whenever an error is not handled with the HandleErrorAttribute from inside of the pipeline. <system.web>  <customErrors mode="On" defaultRedirect="~/error">     <error statusCode="404" redirect="~/error/notfound"></error>  </customErrors>Sample Controllers public class ExampleController : Controller {     public ActionResult Exception()     {         throw new ArgumentNullException();     }     public ActionResult Db()     {         // Inherits from DbException         throw new MyDbException();     } } public class ErrorController : Controller {     public ActionResult Index()     {         return View();     }     public ActionResult NotFound()     {         return View();     } } Putting It All Together If we have all the code above included in our MVC 3 project, here is how the following scenario's will play out: 1.       A controller action throws an Exception. You will remain on the current page and the global HandleErrorAttributes will render the Error view. 2.       A controller action throws any type of DbException. You will remain on the current page and the global HandleErrorAttributes will render the DbError view. 3.       Go to a non-existent page. You will be redirect to the Error controller's NotFound action by the CustomErrors configuration for HTTP StatusCode 404. But don't take my word for it, download the sample project and try it yourself. Three Important Lessons Learned For the most part this is all pretty straight forward, but there are a few gotcha's that you should remember to watch out for: 1) Error views have models, but they must be of type HandleErrorInfo. It is confusing at first to think that you can't control the M in an MVC page, but it's for a good reason. Errors can come from any action in any controller, and no redirect is taking place, so the view engine is just going to render an error view with the only data it has: The HandleError Info model. Do not try to set the model on your error page or pass in a different object through a controller action, it will just blow up and cause a second exception after your first exception! 2) When the HandleErrorAttribute renders a page, it does not pass through a controller or an action. The standard web.config CustomErrors literally redirect a failed request to a new page. The HandleErrorAttribute is just rendering a view, so it is not going to pass through a controller action. But that's ok! Remember, a controller's job is to get the model for a view, but an error already has a model ready to give to the view, thus there is no need to pass through a controller. That being said, the normal ASP.NET custom errors still need to route through controllers. So if you want to share an error page between the HandleErrorAttribute and your web.config redirects, you will need to create a controller action and route for it. But then when you render that error view from your action, you can only use the HandlerErrorInfo model or ViewData dictionary to populate your page. 3) The HandleErrorAttribute obeys if CustomErrors are on or off, but does not use their redirects. If you turn CustomErrors off in your web.config, the HandleErrorAttributes will stop handling errors. However, that is the only configuration these two mechanisms share. The HandleErrorAttribute will not use your defaultRedirect property, or any other errors registered with customer errors. In Summary The HandleErrorAttribute is for displaying 500 errors that were caused by exceptions inside of the MVC pipeline. The custom errors are for redirecting from error pages caused by other HTTP codes.

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  • Reasoner Conversion Problems:

    - by Annalyne
    I have this code right here in Java and I wanted to translate it in C++, but I had some problems going: this is the java code: import java.io.*; import java.util.*; public class ClueReasoner { private int numPlayers; private int playerNum; private int numCards; private SATSolver solver; private String caseFile = "cf"; private String[] players = {"sc", "mu", "wh", "gr", "pe", "pl"}; private String[] suspects = {"mu", "pl", "gr", "pe", "sc", "wh"}; private String[] weapons = {"kn", "ca", "re", "ro", "pi", "wr"}; private String[] rooms = {"ha", "lo", "di", "ki", "ba", "co", "bi", "li", "st"}; private String[] cards; public ClueReasoner() { numPlayers = players.length; // Initialize card info cards = new String[suspects.length + weapons.length + rooms.length]; int i = 0; for (String card : suspects) cards[i++] = card; for (String card : weapons) cards[i++] = card; for (String card : rooms) cards[i++] = card; numCards = i; // Initialize solver solver = new SATSolver(); addInitialClauses(); } private int getPlayerNum(String player) { if (player.equals(caseFile)) return numPlayers; for (int i = 0; i < numPlayers; i++) if (player.equals(players[i])) return i; System.out.println("Illegal player: " + player); return -1; } private int getCardNum(String card) { for (int i = 0; i < numCards; i++) if (card.equals(cards[i])) return i; System.out.println("Illegal card: " + card); return -1; } private int getPairNum(String player, String card) { return getPairNum(getPlayerNum(player), getCardNum(card)); } private int getPairNum(int playerNum, int cardNum) { return playerNum * numCards + cardNum + 1; } public void addInitialClauses() { // TO BE IMPLEMENTED AS AN EXERCISE // Each card is in at least one place (including case file). for (int c = 0; c < numCards; c++) { int[] clause = new int[numPlayers + 1]; for (int p = 0; p <= numPlayers; p++) clause[p] = getPairNum(p, c); solver.addClause(clause); } // If a card is one place, it cannot be in another place. // At least one card of each category is in the case file. // No two cards in each category can both be in the case file. } public void hand(String player, String[] cards) { playerNum = getPlayerNum(player); // TO BE IMPLEMENTED AS AN EXERCISE } public void suggest(String suggester, String card1, String card2, String card3, String refuter, String cardShown) { // TO BE IMPLEMENTED AS AN EXERCISE } public void accuse(String accuser, String card1, String card2, String card3, boolean isCorrect) { // TO BE IMPLEMENTED AS AN EXERCISE } public int query(String player, String card) { return solver.testLiteral(getPairNum(player, card)); } public String queryString(int returnCode) { if (returnCode == SATSolver.TRUE) return "Y"; else if (returnCode == SATSolver.FALSE) return "n"; else return "-"; } public void printNotepad() { PrintStream out = System.out; for (String player : players) out.print("\t" + player); out.println("\t" + caseFile); for (String card : cards) { out.print(card + "\t"); for (String player : players) out.print(queryString(query(player, card)) + "\t"); out.println(queryString(query(caseFile, card))); } } public static void main(String[] args) { ClueReasoner cr = new ClueReasoner(); String[] myCards = {"wh", "li", "st"}; cr.hand("sc", myCards); cr.suggest("sc", "sc", "ro", "lo", "mu", "sc"); cr.suggest("mu", "pe", "pi", "di", "pe", null); cr.suggest("wh", "mu", "re", "ba", "pe", null); cr.suggest("gr", "wh", "kn", "ba", "pl", null); cr.suggest("pe", "gr", "ca", "di", "wh", null); cr.suggest("pl", "wh", "wr", "st", "sc", "wh"); cr.suggest("sc", "pl", "ro", "co", "mu", "pl"); cr.suggest("mu", "pe", "ro", "ba", "wh", null); cr.suggest("wh", "mu", "ca", "st", "gr", null); cr.suggest("gr", "pe", "kn", "di", "pe", null); cr.suggest("pe", "mu", "pi", "di", "pl", null); cr.suggest("pl", "gr", "kn", "co", "wh", null); cr.suggest("sc", "pe", "kn", "lo", "mu", "lo"); cr.suggest("mu", "pe", "kn", "di", "wh", null); cr.suggest("wh", "pe", "wr", "ha", "gr", null); cr.suggest("gr", "wh", "pi", "co", "pl", null); cr.suggest("pe", "sc", "pi", "ha", "mu", null); cr.suggest("pl", "pe", "pi", "ba", null, null); cr.suggest("sc", "wh", "pi", "ha", "pe", "ha"); cr.suggest("wh", "pe", "pi", "ha", "pe", null); cr.suggest("pe", "pe", "pi", "ha", null, null); cr.suggest("sc", "gr", "pi", "st", "wh", "gr"); cr.suggest("mu", "pe", "pi", "ba", "pl", null); cr.suggest("wh", "pe", "pi", "st", "sc", "st"); cr.suggest("gr", "wh", "pi", "st", "sc", "wh"); cr.suggest("pe", "wh", "pi", "st", "sc", "wh"); cr.suggest("pl", "pe", "pi", "ki", "gr", null); cr.printNotepad(); cr.accuse("sc", "pe", "pi", "bi", true); } } how can I convert this? there are too many errors I get. for my C++ code (as a commentor asked for) #include <iostream> #include <cstdlib> #include <string> using namespace std; void Scene_Reasoner() { int numPlayer; int playerNum; int cardNum; string filecase = "Case: "; string players [] = {"sc", "mu", "wh", "gr", "pe", "pl"}; string suspects [] = {"mu", "pl", "gr", "pe", "sc", "wh"}; string weapons [] = {"kn", "ca", "re", "ro", "pi", "wr"}; string rooms[] = {"ha", "lo", "di", "ki", "ba", "co", "bi", "li", "st"}; string cards [0]; }; void Scene_Reason_Base () { numPlayer = players.length; // Initialize card info cards = new String[suspects.length + weapons.length + rooms.length]; int i = 0; for (String card : suspects) cards[i++] = card; for (String card : weapons) cards[i++] = card; for (String card : rooms) cards[i++] = card; cardNum = i; }; private int getCardNum (string card) { for (int i = 0; i < numCards; i++) if (card.equals(cards[i])) return i; cout << "Illegal card: " + card <<endl; return -1; }; private int getPairNum(String player, String card) { return getPairNum(getPlayerNum(player), getCardNum(card)); }; private int getPairNum(int playerNum, int cardNum) { return playerNum * numCards + cardNum + 1; }; int main () { return 0; }

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  • SpringMvc java.lang.NullPointerException When Posting Form To Server [closed]

    - by dev_darin
    I have a form with a user name field on it when i tab out of the field i use a RESTFUL Web Service that makes a call to a handler method in the controller. The method makes a call to a DAO class that checks the database if the user name exists. This works fine, however when the form is posted to the server i call the same exact function i would call in the handler method however i get a java.lang.NullPointerException when it accesses the class that makes a call to the DAO object. So it does not even access the DAO object the second time. I have exception handlers around the calls in all my classes that makes calls. Any ideas as to whats happening here why i would get the java.lang.NullPointerException the second time the function is called.Does this have anything to do with Spring instantiating DAO classes using a Singleton method or something to that effect? What can be done to resolve this? This is what happens the First Time The Method is called using the Web Service(this is suppose to happen): 13011 [http-8084-2] INFO com.crimetrack.jdbc.JdbcOfficersDAO - Inside jdbcOfficersDAO 13031 [http-8084-2] DEBUG org.springframework.jdbc.core.JdbcTemplate - Executing prepared SQL query 13034 [http-8084-2] DEBUG org.springframework.jdbc.core.JdbcTemplate - Executing prepared SQL statement [SELECT userName FROM crimetrack.tblofficers WHERE userName = ?] 13071 [http-8084-2] DEBUG org.springframework.jdbc.datasource.DataSourceUtils - Fetching JDBC Connection from DataSource 13496 [http-8084-2] DEBUG org.springframework.jdbc.core.StatementCreatorUtils - Setting SQL statement parameter value: column index 1, parameter value [adminz], value class [java.lang.String], SQL type unknown 13534 [http-8084-2] DEBUG org.springframework.jdbc.datasource.DataSourceUtils - Returning JDBC Connection to DataSource 13537 [http-8084-2] INFO com.crimetrack.jdbc.JdbcOfficersDAO - No username was found in exception 13537 [http-8084-2] INFO com.crimetrack.service.ValidateUserNameManager - UserName :adminz does NOT exist The Second time When The Form Is 'Post' and a validation method handles the form and calls the same method the web service would call: 17199 [http-8084-2] INFO com.crimetrack.service.OfficerRegistrationValidation - UserName is not null so going to check if its valid for :adminz 17199 [http-8084-2] INFO com.crimetrack.service.OfficerRegistrationValidation - User Name in try.....catch block is adminz 17199 [http-8084-2] INFO com.crimetrack.service.ValidateUserNameManager - Inside Do UserNameExist about to validate with username : adminz 17199 [http-8084-2] INFO com.crimetrack.service.ValidateUserNameManager - UserName :adminz EXCEPTION OCCURED java.lang.NullPointerException ValidateUserNameManager.java public class ValidateUserNameManager implements ValidateUserNameIFace { private OfficersDAO officerDao; private final Logger logger = Logger.getLogger(getClass()); public boolean DoesUserNameExist(String userName) throws Exception { logger.info("Inside Do UserNameExist about to validate with username : " + userName); try{ if(officerDao.OfficerExist(userName) == true){ logger.info("UserName :" + userName + " does exist"); return true; }else{ logger.info("UserName :" + userName + " does NOT exist"); return false; } }catch(Exception e){ logger.info("UserName :" + userName + " EXCEPTION OCCURED " + e.toString()); return false; } } /** * @return the officerDao */ public OfficersDAO getOfficerDao() { return officerDao; } /** * @param officerdao the officerDao to set */ public void setOfficerDao(OfficersDAO officerDao) { this.officerDao = officerDao; } } JdbcOfficersDAO.java public boolean OfficerExist(String userName){ String dbUserName; try{ logger.info("Inside jdbcOfficersDAO"); String sql = "SELECT userName FROM crimetrack.tblofficers WHERE userName = ?"; try{ dbUserName = (String)getJdbcTemplate().queryForObject(sql, new Object[]{userName},String.class); logger.info("Just Returned from database"); }catch(Exception e){ logger.info("No username was found in exception"); return false; } if(dbUserName == null){ logger.info("Database did not find any matching records"); } logger.info("after JdbcTemplate"); if (dbUserName.equals(userName)) { logger.info("User Name Exists"); return true; }else{ logger.info("User Name Does NOT Exists"); return false; } }catch(Exception e){ logger.info("Exception Message in JdbcOfficersDAO is "+e.getMessage()); return false; } } OfficerRegistrationValidation.java public class OfficerRegistrationValidation implements Validator{ private final Logger logger = Logger.getLogger(getClass()); private ValidateUserNameManager validateUserNameManager; public boolean supports(Class<?> clazz) { return Officers.class.equals(clazz); } public void validate(Object target, Errors errors) { Officers officer = (Officers) target; if (officer.getUserName() == null){ errors.rejectValue("userName", "userName.required"); }else{ String userName = officer.getUserName(); logger.info("UserName is not null so going to check if its valid for :" + userName); try { logger.info("User Name in try.....catch block is " + userName); if (validateUserNameManager.DoesUserNameExist(userName)== true){ errors.rejectValue("userName", "userName.exist"); } } catch (Exception e) { logger.info("Error Occured When validating UserName"); errors.rejectValue("userName", "userName.error"); } } if(officer.getPassword()== null){ errors.rejectValue("password", "password.required"); } if(officer.getPassword2()== null){ errors.rejectValue("password2", "password2.required"); } if(officer.getfName() == null){ errors.rejectValue("fName","fName.required"); } if(officer.getlName() == null){ errors.rejectValue("lName", "lName.required"); } if (officer.getoName() == null){ errors.rejectValue("oName", "oName.required"); } if (officer.getEmailAdd() == null){ errors.rejectValue("emailAdd", "emailAdd.required"); } if (officer.getDob() == null){ errors.rejectValue("dob", "dob.required"); } if (officer.getGenderId().equals("A")){ errors.rejectValue("genderId","genderId.required"); } if(officer.getDivisionNo() == 1){ errors.rejectValue("divisionNo", "divisionNo.required"); } if(officer.getPositionId() == 1){ errors.rejectValue("positionId", "positionId.required"); } if (officer.getStartDate() == null){ errors.rejectValue("startDate","startDate.required"); } if(officer.getEndDate() == null){ errors.rejectValue("endDate","endDate.required"); } logger.info("The Gender ID is " + officer.getGenderId().toString()); if(officer.getPhoneNo() == null){ errors.rejectValue("phoneNo", "phoneNo.required"); } } /** * @return the validateUserNameManager */ public ValidateUserNameManager getValidateUserNameManager() { return validateUserNameManager; } /** * @param validateUserNameManager the validateUserNameManager to set */ public void setValidateUserNameManager( ValidateUserNameManager validateUserNameManager) { this.validateUserNameManager = validateUserNameManager; } } Update Error Log using Logger.Error("Message", e): 39024 [http-8084-2] INFO com.crimetrack.service.OfficerRegistrationValidation - UserName is not null so going to check if its valid for :adminz 39025 [http-8084-2] INFO com.crimetrack.service.OfficerRegistrationValidation - User Name in try.....catch block is adminz 39025 [http-8084-2] ERROR com.crimetrack.service.OfficerRegistrationValidation - Message java.lang.NullPointerException at com.crimetrack.service.OfficerRegistrationValidation.validate(OfficerRegistrationValidation.java:47) at org.springframework.validation.DataBinder.validate(DataBinder.java:725) at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.doBind(HandlerMethodInvoker.java:815) at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.resolveHandlerArguments(HandlerMethodInvoker.java:367) at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:171) at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:436) at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:424) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:923) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:852) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882) at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:789) at javax.servlet.http.HttpServlet.service(HttpServlet.java:637) at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) at java.lang.Thread.run(Unknown Source) 39025 [http-8084-2] INFO com.crimetrack.service.OfficerRegistrationValidation - Error Occured When validating UserName

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