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• General Web Programming/designing Question: ?

  - by Prasad

  hi, I have been in web programming for 2 years (Self taught - a biology researcher by profession). I designed a small wiki with needed functionalities and a scientific RTE - ofcourse lot is expected. I used mootools framework and AJAX extensively. I was always curious when ever I saw the query strings passed from URL. Long encrypted query string directly getting passed to the server. Especially Google's design is such. I think this is the start of providing a Web Service to a client - I guess. Now, my question is : is this a special, highly professional, efficient / advanced web design technique to communicate queries via the URL ? I always felt that direct URL based communication is faster. I tried my bit and could send a query through the URL directly. here is the link: http://sgwiki.sdsc.edu/getSGMPage.php?8 By this , the client can directly link to the desired page instead of searching and / or can automate. There are many possibilities. The next request: Can I be pointed to such technique of web programming? oops: I am sorry, If I have not been able to convey my request clearly. Prasad.

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• Help needed implementing a web based file management system with a file hierarchy system, help neede

  - by molleman

  Hello i am trying to create a web application that will allow users to upload files online, i am using gwt while using hibernate for database communication, i am able to upload file to a server , and store them on the server. but what i want is to associate the files with a user. i want the user to be able to create folders and store a file in sub folders. my logic was to use the composite pattern to store folders and fileLocations with a user but i am am finding it difficult to implement this so i can show the files and folders within a gwt tree. what would be the best way to implement a hierarchy of folders and information of the location of a file so it could be displayed in a gwt tree? what i did have was a User would hold a reference to a root folder and then each sub folder could hold folders or fileLocations. i used the composite pattern to implement the file hierarchy, but when i want to display a the contents of a folder i need a for loop for each list. so i could a folder within a folder within a folder that would need 3 for loops to show the contents of my folders. What is the best way to implement this file management system. so what do you guys think?

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• Java RMI timeout in callback

  - by sakra

  We are using Java RMI for communication. An RMI client passes a processing request and an object with a callback method to an RMI server. The server invokes the callback when it is done with processing. The setup is similar to the one described in RMI Callbacks. Occasionally we are getting a "read time out" exception in the server upon invoking the callback method. The callback thread stalls for about a minute before the exception is raised. java.rmi.ConnectIOException: error during JRMP connection establishment; nested exception is: java.net.SocketTimeoutException: Read timed out at sun.rmi.transport.tcp.TCPChannel.createConnection(TCPChannel.java:286) at sun.rmi.transport.tcp.TCPChannel.newConnection(TCPChannel.java:184) at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:110) at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(RemoteObjectInvocationHandler.java:178) at java.rmi.server.RemoteObjectInvocationHandler.invoke(RemoteObjectInvocationHandler.java:132) at $Proxy2.finished(Unknown Source) at com.unrisk.db.grid.GridTask.invokeCallback(com.unrisk.db.grid.GridTask:1292) at com.unrisk.db.grid.GridTask.invokeCallbacks(com.unrisk.db.grid.GridTask:1304) at com.unrisk.db.service.tasks.EquityMDTask.afterRun(com.unrisk.db.service.tasks.EquityMDTask:276) at com.unrisk.db.grid.GridTask.run(com.unrisk.db.grid.GridTask:720) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:619) Caused by: java.net.SocketTimeoutException: Read timed out at java.net.SocketInputStream.socketRead0(Native Method) at java.net.SocketInputStream.read(SocketInputStream.java:129) at java.io.BufferedInputStream.fill(BufferedInputStream.java:218) at java.io.BufferedInputStream.read(BufferedInputStream.java:237) at java.io.DataInputStream.readByte(DataInputStream.java:248) at sun.rmi.transport.tcp.TCPChannel.createConnection(TCPChannel.java:228) ... 12 more We are using Sun Java JDK 1.6.0_18 under Windows Server 2003 32-bit. Is it possible to work around the connection problems by tuning RMI related system properties?

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• Load Balance WCF and Share a Remote MSMQ for High Throughput

  - by BarDev

  After a ton of reading in books and on the web, I have noticed hints of information that WCF and MSMQ can be used in achieving high throughput. The information I have seen mentions using multiple WCF services in a farm that reads from a single MSMQ queue. The problem is that I have found paragraphs here and there that mentions that high throughput can be done, but I cannot seem to find a document of how to implement it. The following is an excerpt from a MSDN article. The following paragraph is from Best Practices for Queued Communication http://msdn.microsoft.com/en-us/library/ms731093.aspx To achieve higher throughput and availability, use a farm of WCF services that read from the queue. This requires that all of these services expose the same contract on the same endpoint. The farm approach works best for applications that have high production rates of messages because it enables a number of services to all read from the same queue. This is what I'm trying to solve. I have an intranet application where a client sends a request to a WCF service. But I want the ability to load balance the WCF services on multiple servers in a farm. I also want these WCF services in the farm to do transactional reads from a remote MSMQ when an item is available in the Queue. If this is possible, an issue I have is that I do not understand the activation process of WCF to retrieve messages from a remote queue. If this is possible, does anyone know of any articles or Webcasts that would explain it in detail? BarDev

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• Deploying software on compromised machines

  - by Martin

  I've been involved in a discussion about how to build internet voting software for a general election. We've reached a general consensus that there exist plenty of secure methods for two way authentication and communication. However, someone came along and pointed out that in a general election some of the machines being used are almost certainly going to be compromised. To quote: Let me be an evil electoral fraudster. I want to sample peoples votes as they vote and hope I get something scandalous. I hire a bot-net from some really shady dudes who control 1000 compromised machines in the UK just for election day. I capture the voting habits of 1000 voters on election day. I notice 5 of them have voted BNP. I look these users up and check out their machines, I look through their documents on their machine and find out their names and addresses. I find out one of them is the wife of a tory MP. I leak 'wife of tory mp is a fascist!' to some blogger I know. It hits the internet and goes viral, swings an election. That's a serious problem! So, what are the best techniques for running software where user interactions with the software must be kept secret, on a machine which is possibly compromised?

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• WCF for a shared data access

  - by Audrius

  Hi all, I have a little experience with WCF and would like to get your opinion/suggestion on how the following problem can be solved: A web service needs to be accessible from multiple clients simultaneously and service needs to return a result from a shared data set. The concrete project I'm working on has to store a list of IP addresses/ranges. This list will be queried by a bunch of web servers for a validation purposes and we speak of a couple of thousand or more queries per minute. My initial draft approach was to use Windows service as a WCF host with service contract implementing class that is decorated with ServiceBehavior(InstanceContextMode = InstanceContextMode.Single, ConcurrencyMode = ConcurrencyMode.Multiple) that has a list object and a custom locking for accessing it. So basically I have a WCF service singleton with a list = shared data - multiple clients. What I do not like about it is that data and communication layers are merged into one and performance wise this doesn't feel "right". What I really really (- want is Windows service running an instance of IP list holding container class object, a second service running WCF service contract implementation and a way the latter querying the former in a nice way with a minimal blocking. Using another WCF channel would not really take me far away from the initial draft implementation or would it? What approach would you take? Project is still in a very early stage so complete design re-do is not out of question. All ideas are appreciated. Thanks! UPDATE: The data set will be changed dynamically. Web service will have a separate method to add IP or IP range and on top of that there will be a scheduled task that will trigger data cleanup every 10-15 minutes according to some rules. UPDATE 2: a separate benchmark project will be kicked up that should use MSSQL as a data backend (instead on in-memory list).

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• wcf configuration for this code

  - by user208081

  I have the following code and would like to convert a lot of code into configuration settings for WCF. As you can see, the code is using wshttpbinding. I appreciate any help on this. try { // Provides a unique network address that a client uses to communicate with a service endpoint. EndpointAddress endpointAddress = new EndpointAddress(new Uri(FAXServiceSettings.Default.FAXReceiveServiceURL)); // Specify the protocols, transports, and message encoders used for communication between the client and the service. // WSHttpBinding represents an interoperable binding that supports distributed transactions and secure, reliable sessions. // Spefically, SOAP message security is enabled for secure transmission of the message content. WSHttpBinding clientBinding = new WSHttpBinding(SecurityMode.Message); clientBinding.OpenTimeout = TimeSpan.FromSeconds(FAXServiceSettings.Default.FAXReceiveServiceOpenTimeoutInSeconds); clientBinding.SendTimeout = TimeSpan.FromSeconds(FAXServiceSettings.Default.FAXReceiveServiceOpenTimeoutInSeconds); // Use the ChannelFactory to enable the creation of channels to the binding and endpoint. using (ChannelFactory<IReceiveFAX> channelFactory = new ChannelFactory<IReceiveFAX>(clientBinding, endpointAddress)) { // Creates a channel of a specified type to a specified endpoint address. IReceiveFAX channel = channelFactory.CreateChannel(); if (channel != null) { try { // Submit the FaxSchedule instance for routing. channel.SubmitFAXForRouting(CreateNewFaxScheduleContainerInstance()); // Explicitly close the channel using the IClientChannel interface. CloseChannel((channel as IClientChannel)); } finally { // Explicitly dispose of the channel using IDisposable interface. DisposeOfChannel((channel as IDisposable)); channel = null; } } // This method causes a CommunicationObject to gracefully transition from any state, other than the Closed state, into the Closed state. The Close method allows any // unfinished work to be completed before returning. For example, finish sending any buffered messages. channelFactory.Close(); } } catch { throw; } Pratik

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• Porting a select loop application to Android with NDK. Design question.

  - by plaisthos

  Hi, I have an network application which uses a select loop like this: bool shutdown=false; while (!shutdown) { [do something] select(...,timeout); } THe main loop cannot work like this in an Android application anymore since the application needs to receive Intents, need to handle GUI, etc. I think I have basically three possibilities: Move the main loop to the java part of the application. Let the loop run in its own thread and somehow communicate from/to java. Screw Android <= 2.3 and use a native activity and use AInputQueue/ALooper instead of select. The first possibility is not easy since java has no select which works on fds. Simply using the select and return after each loop to java is not an elegant possibility either since that requires setting the timeout to something like 20ms to have a good response time in the java part of the program. The second probability sound nicer but I have do some communication between java and the c++/c part of the program. Things that cold work: Using a socket, kind of ugly. using native calls in the "java gui thread" and callback from native in the "c thread". Both threads need to have thread safe implementations but this is managable. I have not explored the third possibility but I think that it is not the way to go. I think I can hack something together which will work but I asking what is the best path to chose.

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• using ghostscript in server mode to convert pdfs to pngs

  - by emh

  while i am able to convert a specific page of a PDF to a PNG like so: gs -dSAFER -dBATCH -dNOPAUSE -sDEVICE=png16m -dGraphicsAlphaBits=4 -sOutputFile=gymnastics-20.png -dFirstPage=20 -dLastPage=20 gymnastics.pdf i am wondering if i can somehow use ghostscript's JOBSERVER mode to process several conversions without having to incur the cost of starting up ghostscript each time. from: http://pages.cs.wisc.edu/~ghost/doc/svn/Use.htm -dJOBSERVER Define \004 (^D) to start a new encapsulated job used for compatibility with Adobe PS Interpreters that ordinarily run under a job server. The -dNOOUTERSAVE switch is ignored if -dJOBSERVER is specified since job servers always execute the input PostScript under a save level, although the exitserver operator can be used to escape from the encapsulated job and execute as if the -dNOOUTERSAVE was specified. This also requires that the input be from stdin, otherwise an error will result (Error: /invalidrestore in --restore--). Example usage is: gs ... -dJOBSERVER - < inputfile.ps -or- cat inputfile.ps | gs ... -dJOBSERVER - Note: The ^D does not result in an end-of-file action on stdin as it may on some PostScript printers that rely on TBCP (Tagged Binary Communication Protocol) to cause an out-of-band ^D to signal EOF in a stream input data. This means that direct file actions on stdin such as flushfile and closefile will affect processing of data beyond the ^D in the stream. the idea is to run ghostscript in-process. the script would receive a request for a particular page of a pdf and would use ghostscript to generate the specified image. i'd rather not start up a new ghostscript process every time.

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• C# serialPort speed

  - by MarekK

  Hi I am developing some monitoring tool for some kind of protocol based on serial communication. Serial BaudRate=187,5kb I use System.IO.Ports.SerialPort class. This protocol has 4 kinds of frames. They have 1Byte,3Bytes,6Bytes, 10-255Bytes. I can work with them but I receive them too late to respond. For the beginning I receive first packed after ex. 96ms (too late), and it contains about 1000B. This means 20-50 frames (too much, too late). Later its work more stable, 3-10Bytes but it is still too late because it contains 1-2 frames. Of Course 1 frame is OK, but 2 is too late. Can you point me how can I deal with it more reliable? I know it is possible. Revision1: I tried straight way: private void serialPort1_DataReceived(object sender, SerialDataReceivedEventArgs e) { if (!serialPort1.IsOpen) return; this.BeginInvoke(new EventHandler(this.DataReceived)); } And Backgroud worker: And ... new Tread(Read) and... always the same. Too late, too slow. Do I have to go back to WinApi and import some kernel32.dll functions? Revision 2: this is the part of code use in the Treading way: int c = serialPort1.BytesToRead; byte[] b = new byte[c]; serialPort1.Read(b, 0, c); I guess it is some problem with stream use inside SerialPort class. Or some synchronization problem. Revision 3: I do not use both at once!! I just tried different ways. Regards MarekK

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• PackageMaker install script for rxtx

  - by vinzenzweber

  I am using PackageMaker to create an installer for my application. During installation I need to run a bash script to properly install rxtx, a JNI library for serial port communication. This library needs to have the directory /var/lock in place with user "root" and group "uucp". The installation script also needs to add the current user to the group "uucp" for the lib to be able to write to /var/lock. Now when I run my application installer the preinstall script is run as root. Therefore "whoami" returns root instead of the user who is actually running the installer. The result is that rxtx is not able to create lock files in /var/lock because the actual user was not added as a member to "uucp". How can I get the user while my script is run by the installer. Or is it better to set the permissions for /var/lock to a different group maybe? Any suggestions are welcome! !/bin/sh curruser=whoami logger "Setting permissions for /var/lock for user $curruser!" if [ ! -d /var/lock ] then logger "Creating /var/lock!" sudo mkdir /var/lock fi sudo chgrp uucp /var/lock sudo chmod 775 /var/lock MacOSX 10.5 and later use dscl if [ sudo dscl . -read /Groups/uucp GroupMembership | grep $curruser | wc -l = "0" ] then logger "Add user $curruser to /Groups/uucp!" sudo dscl . -append /Groups/uucp GroupMembership $curruser # to revert use: # sudo dscl . -delete /Groups/uucp GroupMembership $curruser else logger "GroupMembership of /var/lock not changed!" fi

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• Java exception handling in non sequential tasks (pattern/good practice)

  - by Hernán Eche

  There are some task that should't be done in parallel, (for example opening a file, reading, writing, and closing, there is an order on that...) But... Some task are more like a shoping list, I mean they could have a desirable order but it's not a must..example in communication or loading independient drivers etc.. For that kind of tasks, I would like to know a java best practice or pattern for manage exceptions.. The java simple way is: getUFO { try { loadSoundDriver(); loadUsbDriver(); loadAlienDetectorDriver(); loadKeyboardDriver(); } catch (loadSoundDriverFailed) { doSomethingA; } catch (loadUsbDriverFailed) { doSomethingB; } catch (loadAlienDetectorDriverFailed) { doSomethingC; } catch (loadKeyboardDriverFailed) { doSomethingD; } } But what about having an exception in one of the actions but wanting to try with the next ones?? I've thought this approach, but don't seem to be a good use for exceptions I don't know if it works, doesn't matter, it's really awful!! getUFO { Exception ex=null; try { try{ loadSoundDriver(); }catch (Exception e) { ex=e; } try{ loadUsbDriver(); }catch (Exception e) { ex=e; } try{ loadAlienDetectorDriver(); }catch (Exception e) { ex=e; } try{ loadKeyboardDriver() }catch (Exception e) { ex=e; } close the file; if(ex!=null) { throw ex; } } catch (loadSoundDriverFailed) { doSomethingA; } catch (loadUsbDriverFailed) { doSomethingB; } catch (loadAlienDetectorDriverFailed) { doSomethingC; } catch (loadKeyboardDriverFailed) { doSomethingD; } } seems not complicated to find a better practice for doing that.. I still didn't thanks for any advice

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• Debugging Key-Value-Observing overflow.

  - by Paperflyer

  I wrote an audio player. Recently I started refactored some of the communication flow to make it fully MVC-compliant. Now it crashes, which in itself is not surprising. However, it crashes after a few seconds inside the Cocoa key-value-observing routines with a HUGE stack trace of recursive calls to NSKeyValueNotifyObserver. Obviously, it is recursively observing a value and thus overflowing the NSArray that holds pending notifications. According to the stack trace, the program loops from observeValueForKeyPath to setMyValue and back. Here is the according code: - (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { if ([keyPath isEqual:@"myValue"] && object == myModel && [self myValue] != [myModel myValue]) { [self setMyValue:[myModel myValue]; } } and - (void)setMyValue:(float)value { myValue = value; [myModel setMyValue:value]; } myModel changes myValue every 0.05 seconds and if I log the calls to these two functions, they get called only every 0.05 seconds just as they should be, so this is working properly. The stack trace looks like this: -[MyDocument observeValueForKeyPath:ofObject:change:context:] NSKeyValueNotifyObserver NSKeyValueDidChange -[NSObject(NSKeyValueObserverNotification) didChangeValueForKey:] -[MyDocument setMyValue:] _NSSetFloatValueAndNotify …repeated some ~8k times until crash Do you have any idea why I could still be spamming the KVO queue?

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• What is the best way to send structs containing enum values via sockets in C.

  - by Axel

  I've lots of different structs containing enum members that I have to transmit via TCP/IP. While the communication endpoints are on different operating systems (Windows XP and Linux) meaning different compilers (gcc 4.x.x and MSVC 2008) both program parts share the same header files with type declarations. For performance reasons, the structures should be transmitted directly (see code sample below) without expensively serializing or streaming the members inside. So the question is how to ensure that both compilers use the same internal memory representation for the enumeration members (i.e. both use 32-bit unsigned integers). Or if there is a better way to solve this problem... //type and enum declaration typedef enum { A = 1, B = 2, C = 3 } eParameter; typedef enum { READY = 400, RUNNING = 401, BLOCKED = 402 FINISHED = 403 } eState; #pragma pack(push,1) typedef struct { eParameter mParameter; eState mState; int32_t miSomeValue; uint8_t miAnotherValue; ... } tStateMessage; #pragma pack(pop) //... send via socket tStateMessage msg; send(iSocketFD,(void*)(&msg),sizeof(tStateMessage)); //... receive message on the other side tStateMessage msg_received; recv(iSocketFD,(void*)(&msg_received),sizeof(tStateMessage)); Additionally... Since both endpoints are little endian maschines, endianess is not a problem here. And the pack #pragma solves alignment issues satisfactorily. Thx for your answers, Axel

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• Browser Based Streaming Video/Audio (not progressive download)

  - by Josh

  Hello, I am trying to understand conceptually the best way to deliver real streaming audio and video content. I would want it to be consumed with a web browser, utilizing the least amount of proprietary technology. I wouldn't be serving static files and using progressive download, this would be real audio streams being captured live. How does one broadcast a stream that will be reasonably in sync with the source? What kind of protocol is suitable? Edit: In research I've found that there are a few protocols: RTSP, HTTP Streaming, RTMP, and RTP. HTTP streaming is somewhat unsuitable if you are streaming a live performance/communication of some kind because it relies on TCP (as its HTTP based) and you don't lose packets. In a low bandwidth situation, the client can get significantly behind in playback. ref RTMP is a proprietary technology, requiring flash media server. Crap on that. The reason I looked at flash is because they are extremely flexible as far as user experience goes. SoundManager2 provides an excellent javascript interface for playing media with flash. This is what I would look for in a client application. RTSP/RTP is what Microsoft switched to using, deprecating their MMS protocol. RTSP is the control protocol. Its similar to HTTP with a few distinct difference -- server can also talk to the client, and there are additional commands, like PAUSE. Its also a stateful protocol, which is maintained with a session id. RTP is the protocol for delivering the payload (encoded audio or video). There are a few open sourced projects, one of them being supported by apple here. It seems like this might do what I want it to, and it looks like quite a few players support it. It sounds like it would be suitable for a "live" broadcast from this page here. Thanks, Josh

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• Not able to use spring Beans outside container . Always picking up WebSphere Context

  - by Abhijit

  We have the a whole lot of spring bean defined in our project which we deploy in Websphere ^. One example being the following: oracle.jdbc.driver.OracleDriver jdbc:oracle:thin:@oracle:1521:OASIS oasis_owner o3ngin33r Now we have a service locator class like following private static ServiceLocator serviceLocator = new ServiceLocator(); private static ApplicationContext beanFactory = new ClassPathXmlApplicationContext(APPLICATION_CONTEXT_LOCATION); protected ServiceLocator() { } public ApplicationContext getBeanFactory() { return beanFactory; } public static ServiceLocator getInstance() { return serviceLocator; Now when I am trying to do this from my jUnit ServiceLocator.getInstance().getBean("oasJdbcData"; getting the following exception Caused by: javax.naming.ServiceUnavailableException: Could not obtain an initial context due to a communication failure. Since no provider URL was specified, the default provider URL of "corbaloc:iiop:[email protected]:2809/NameService" was used. Make sure that any bootstrap address information in the URL is correct and that the target name server is running. Possible causes other than an incorrect bootstrap address or unavailable name server include the network environment and workstation network configuration. [Root exception is org.omg.CORBA.TRANSIENT: java.net.ConnectException: Connection refused: connect:host=192.168.255.1,port=2809 vmcid: IBM minor code: E02 completed: No] at com.ibm.ws.naming.util.WsnInitCtxFactory.mapInitialReferenceFailure(WsnInitCtxFactory.java:1968) at com.ibm.ws.naming.util.WsnInitCtxFactory.mergeWsnNSProperties(WsnInitCtxFactory.java:1172) at com.ibm.ws.naming.util.WsnInitCtxFactory.getRootContextFromServer(WsnInitCtxFactory.java:720) at com.ibm.ws.naming.util.WsnInitCtxFactory.getRootJndiContext(WsnInitCtxFactory.java:643) at com.ibm.ws.naming.util.WsnInitCtxFactory.getInitialContextInternal(WsnInitCtxFactory.java:489) at com.ibm.ws.naming.util.WsnInitCtx.getContext(WsnInitCtx.java:113) at com.ibm.ws.naming.util.WsnInitCtx.getContextIfNull(WsnInitCtx.java:428) at com.ibm.ws.naming.util.WsnInitCtx.lookup(WsnInitCtx.java:144) at javax.naming.InitialContext.lookup(InitialContext.java:361) at org.springframework.jndi.JndiTemplate$1.doInContext(JndiTemplate.java:155) at org.springframework.jndi.JndiTemplate.execute(JndiTemplate.java:88) at org.springframework.jndi.JndiTemplate.lookup(JndiTemplate.java:153) at org.springframework.jndi.JndiTemplate.lookup(JndiTemplate.java:178) at org.springframework.jndi.JndiLocatorSupport.lookup(JndiLocatorSupport.java:104) at org.springframework.jndi.JndiObjectLocator.lookup(JndiObjectLocator.java:105) at org.springframework.jndi.JndiObjectFactoryBean.lookupWithFallback(JndiObjectFactoryBean.java:200) at org.springframework.jndi.JndiObjectFactoryBean.afterPropertiesSet(JndiObjectFactoryBean.java:186) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1368) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1334) ... 33 more which clearly shows it is looking for IntialContext of Websphere which I dont want Any body can tell me what I am doing wrong?

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• Java NIO (Netty): How does Encryption or GZIPping work in theory (with filters)

  - by Tom

  Hello Experts, i would be very thankfull if you can explain to me, how in theory the "Interceptor/Filter" Pattern in ByteStreams (over Sockets/Channels) work (in Asynchronous IO with netty) in regard to encryption or compression of data. Given I have a Filter that does GZIPPING. How is this internally implemented? Does the Filter "collect" so many bytes form the channel, that this is a usefull number of bytes that can then be en/decoded? What is in general the minimal "blocksize(data to encode/decode in a chunk)" of socket based gzipping? Does this "blocksize" have to be negotiated in advance between server and client? What happens if the client does not send enough data to "fill" the blocksize (due to a network conquestion) but does not close the connection. Does this mean the other side will simply wait until it gets enough bytes to decode or until a timeout occoures...How is the Filter pattern the applied? The compression filter will de/compress the blocksize of bytes and then store them again in the same buffer would (in the case of netty) i normally be using the ChannelHanlderContext to pass the de/encoded data to the next filter?... Any explanations/links/tutorials (for beginners;-) will be very much appreciated to help me understand how for example encryption/compressing are implemented in socket based communication with filters/interceptor pattern. thank you very much tom

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• Error generating Interface with svcutil.exe

  - by capdragon

  Can someone help me generate the Interface (c#) file for the following OGC schema? Schema files: Download Schema Files Link I need to create web services for the Ordering wsdl in the schema zip file above. I've been at it for days now with no luck generating the interface. I've tried: svcutil.exe thewsdl.wsdl /language:c# /out:ITheInterface.cs svcutil Order.wsdl /out:IOrder.cs svcutil Order.wsdl Order.xsd ..\ws-addressing\ws-addr.xsd /out:IOrder.cs svcutil Order.wsdl Order.xsd ws-addr.xsd /out:IOrder.cs and i get the following error: Microsoft (R) Service Model Metadata Tool [Microsoft (R) Windows (R) Communication Foundation, Version 4.0.30319.1] Copyright (c) Microsoft Corporation. All rights reserved. Error: Cannot read ws-addr.xsd. Cannot load file D:\Documents\DEV\SARPilot\Docs\eoschema\schema\OrderSchema\ws-addr.xsd as an Assembly. Check the FusionLogs f or more Information. Could not load file or assembly 'file:///D:\Documents\DEV\SARPilot\Docs\eoschema\schema\OrderSchema\ws-addr.xsd' or one of its dependencies. The module was expected to contain an assembly manifest.

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• Diffie-Hellman in Silverlight

  - by cmaduro

  I am trying to devise a security scheme for encrypting the application level data between a silverlight client, and a php webservice that I created. Since I am dealing with a public website the information I am pulling from the service is public, but the information I'm submitting to the webservice is not public. There is also a back end to the website for administration, so naturally all application data being pushed and pulled from the webservice to the silverlight administration back end must also be encrypted. Silverlight does not support asymmetric encryption, which would work for the public website. Symmetric encryption would only work on the back end because users do not log in to the public website, so no password based keys could be derived. Still symmetric encryption would be great, but I cannot securely save the private key in the silverlight client. Because it would either have to be hardcoded or read from some kind of config file. None of that is considered secure. So... plan B. My final alternative would be then to implement the Diffie-Hellman algorithm, which supports symmetric encryption by means of key agreement. However Diffie-Hellman is vulnerable to man-in-the-middle attacks. In other words, there is no guarantee that either side is sure of each others identity, making it possible for communication to be intercepted and altered without the receiving party knowing about it. It is thus recommended to use a private shared key to encrypt the key agreement handshaking, so that the identity of either party is confirmed. This brings me back to my initial problem that resulted in me needing to use Diffie-Hellman, how can I use a private key in a silverlight client without hardcoding it either in the code or an xml file. I'm all out of love on this one... is there any answer to this?

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• Archive log transfer from Oracle 9i to Oracle 10g

  - by Jamie Love

  Hi all, I have a situation where I need to transfer Oracle 9i archive logs to an Oracle 10g database, from where they are to be mined by a log-miner and then used by an Oracle streams capture/apply processes. (Oracle 9 archive logs can be read by the Oracle 10 logminer - I can manually copy the archive logs across, manually register them and have them mined, captured then applied). The difficulty is that the way Oracle does archive log transfer changed quite a bit between 9i and 10g and setting up the 9i database to transfer to the remote machine like so: log_archive_dest_state_2 = enable log_archive_dest_2 = "service=OTHERMACHINE arch optional" no longer works. I get this in the 9i logs: *** 2009-05-22 04:03:44.149 RFS network connection lost at host 'OTHERMACHINE' Error 3113 attaching RFS server to standby instance at host 'OTHERMACHINE' Error 3113 attaching to destination LOG_ARCHIVE_DEST_2 standby host 'OTHERMACHINE' Heartbeat failed to connect to standby 'OTHERMACHINE'. Error is 3113. *** 2009-05-22 04:03:44.150 kcrrfail: dest:2 err:3113 force:0 ORA-03113: end-of-file on communication channel And in the 10g log I get: Fri May 22 04:07:42 2009 WARNING: inbound connection timed out (ORA-3136) My question is: Does anyone know how I could configure my 9i or 10g server such that the 10g server will accept the 9i connection in such a way that I can transfer the 9i archive logs to the 10g server. It would be a bonus if the archive logs would be automatically registered in the 10g server. Note I have not set up a full DataGuard configuration here and the 10g database is not a secondary server. Thanks for any suggestions. Edit Note that I can log on to the 10g server from the 9i server via sqlplus, so connectivity is not the problem Edit 2 After a large amount of time searching for a solution, I've finally decided that such a mechanism doesn't work, and that a non-Oracle method of transferring archive logs from 9i to 10g will need to be used (e.g. rsync).

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• WCF Double Hop questions about Security and Binding.

  - by Ken Maglio

  Background information: .Net Website which calls a service (aka external service) facade on an app server in the DMZ. This external service then calls the internal service which is on our internal app server. From there that internal service calls a stored procedure (Linq to SQL Classes), and passes the serialized data back though to the external service, and from there back to the website. We've done this so any communication goes through an external layer (our external app server) and allows interoperability; we access our data just like our clients consuming our services. We've gotten to the point in our development where we have completed the system and it all works, the double hop acts as it should. However now we are working on securing the entire process. We are looking at using TransportWithMessageCredentials. We want to have WS2007HttpBinding for the external for interoperability, but then netTCPBinding for the bridge through the firewall for security and speed. Questions: If we choose WS2007HttpBinding as the external services binding, and netTCPBinding for the internal service is this possible? I know WS-* supports this as does netTCP, however do they play nice when passing credential information like user/pass? If we go to Kerberos, will this impact anything? We may want to do impersonation in the future. If you can when you answer post any reference links about why you're answering the way you are, that would be very helpful to us. Thanks!

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• SQL Server CLR stored procedures in data processing tasks - good or evil?

  - by Gart

  In short - is it a good design solution to implement most of the business logic in CLR stored procedures? I have read much about them recently but I can't figure out when they should be used, what are the best practices, are they good enough or not. For example, my business application needs to parse a large fixed-length text file, extract some numbers from each line in the file, according to these numbers apply some complex business rules (involving regex matching, pattern matching against data from many tables in the database and such), and as a result of this calculation update records in the database. There is also a GUI for the user to select the file, view the results, etc. This application seems to be a good candidate to implement the classic 3-tier architecture: the Data Layer, the Logic Layer, and the GUI layer. The Data Layer would access the database The Logic Layer would run as a WCF service and implement the business rules, interacting with the Data Layer The GUI Layer would be a means of communication between the Logic Layer and the User. Now, thinking of this design, I can see that most of the business rules may be implemented in a SQL CLR and stored in SQL Server. I might store all my raw data in the database, run the processing there, and get the results. I see some advantages and disadvantages of this solution: Pros: The business logic runs close to the data, meaning less network traffic. Process all data at once, possibly utilizing parallelizm and optimal execution plan. Cons: Scattering of the business logic: some part is here, some part is there. Questionable design solution, may encounter unknown problems. Difficult to implement a progress indicator for the processing task. I would like to hear all your opinions about SQL CLR. Does anybody use it in production? Are there any problems with such design? Is it a good thing?

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• Unit Testing a Java Chat Application

  - by Epitaph

  I have developed a basic Chat application in Java. It consists of a server and multiple client. The server continually monitors for incoming messages and broadcasts them to all the clients. The client is made up of a Swing GUI with a text area (for messages sent by the server and other clients), a text field (to send Text messages) and a button (SEND). The client also continually monitors for incoming messages from other clients (via the Server). This is achieved with Threads and Event Listeners and the application works as expected. But, how do I go about unit testing my chat application? As the methods involve establishing a connection with the server and sending/receiving messages from the server, I am not sure if these methods should be unit tested. As per my understanding, Unit Testing shouldn't be done for tasks like connecting to a database or network. The few test cases that I could come up with are: 1) The max limit of the text field 2) Client can connect to the Server 3) Server can connect to the Client 4) Client can send message 5) Client can receive message 6) Server can send message 7) Server can receive message 8) Server can accept connections from multiple clients But, since most of the above methods involve some kind of network communication, I cannot perform unit testing. How should I go about unit testing my chat application?

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• PJSIP Custom Registration Header (iOS)

  - by Daniel Redington

  I am attempting to setup SIP communication with an internal server (using the PJSIP library), however, this server requires a custom header field with a specified header value for the REGISTRATION call. For example's sake we'll call this required header "MyHeader". From what I've found, the pjsua_acc_add() function will add an account and register it to the server using a config struct. The parameter "reg_hdr_list" of the config struct has the description "The optional custom SIP headers to be put in the registration request." Which sounds like exactly what I need, however doesn't seem to have any effect on the call itself. Here's what I have so far: pjsua_acc_config cfg; pjsua_acc_config_default(&cfg); //...Some other config stuff related to the server... pjsip_hdr test; test.name = pj_str("MyHeader"); test.sname = pj_str("MyHdr"); test.type = PJSIP_H_OTHER; test.prev = cfg.reg_hdr_list.prev; test.next = cfg.reg_hdr_list.next; cfg.reg_hdr_list = test; pj_status_t status; status = pjsua_acc_add(&cfg, PJ_TRUE, &acc_id); From the server side, there are no extra header fields or anything. And the struct that is used to define the header (pjsua_hdr) has no "value" or equivalent field, so even if it did create the header, how does it set the value? Here's the refrence for the header list definition: Link And the reference for the header struct: Link Any help would be greatly appreciated!

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• What are alternatives to Win32 PulseEvent() function?

  - by Bill

  The documentation for the Win32 API PulseEvent() function (kernel32.dll) states that this function is “… unreliable and should not be used by new applications. Instead, use condition variables”. However, condition variables cannot be used across process boundaries like (named) events can. I have a scenario that is cross-process, cross-runtime (native and managed code) in which a single producer occasionally has something interesting to make known to zero or more consumers. Right now, a well-known named event is used (and set to signaled state) by the producer using this PulseEvent function when it needs to make something known. Zero or more consumers wait on that event (WaitForSingleObject()) and perform an action in response. There is no need for two-way communication in my scenario, and the producer does not need to know if the event has any listeners, nor does it need to know if the event was successfully acted upon. On the other hand, I do not want any consumers to ever miss any events. In other words, the system needs to be perfectly reliable – but the producer does not need to know if that is the case or not. The scenario can be thought of as a “clock ticker” – i.e., the producer provides a semi-regular signal for zero or more consumers to count. And all consumers must have the correct count over any given period of time. No polling by consumers is allowed (performance reasons). The ticker is just a few milliseconds (20 or so, but not perfectly regular). Raymen Chen (The Old New Thing) has a blog post pointing out the “fundamentally flawed” nature of the PulseEvent() function, but I do not see an alternative for my scenario from Chen or the posted comments. Can anyone please suggest one? Please keep in mind that the IPC signal must cross process boundries on the machine, not simply threads. And the solution needs to have high performance in that consumers must be able to act within 10ms of each event.

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