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  • How to organize and manage multiple database credentials in application?

    - by Polaris878
    Okay, so I'm designing a stand-alone web service (using RestLET as my framework). My application is divided in to 3 layers: Data Layer (just above the database, provides APIs for connecting to/querying database, and a database object) Object layer (responsible for serialization from the data layer... provides objects which the client layer can use without worrying about database) Client layer (This layer is the RestLET web service... basically just creates objects from the object layer and fulfills webservice request) Now, for each object I create in the object layer, I want to use different credentials (so I can sandbox each object...). The object layer should not know the exact credentials (IE the login/pw/DB URL etc). What would be the best way to manage this? I'm thinking that I should have a super class Database object in my data layer... and each subclass will contain the required log-in information... this way my object layer can just go Database db = new SubDatabase(); and then continue using that database. On the client level, they would just be able to go ItemCollection items = new ItemCollection(); and have no idea/control over the database that gets connected. I'm asking this because I am trying to make my platform extensible, so that others can easily create services off of my platform. If anyone has any experience with these architectural problems or how to manage this sort of thing I'd appreciate any insight or advice... Feel free to ask questions if this is confusing. Thanks! My platform is Java, the REST framework I'm using is RestLET, my database is MySQL.

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  • Truly declarative language?

    - by gjvdkamp
    Hi all, Does anyone know of a truly declarative language? The behaviour I'm looking for is kind of what Excel does, where I can define variables and formulas, and have the formula's result change when the input changes (without having set the answer again myself) The behaviour I'm looking for is best shown with this pseudo code: X = 10 // define and assign two variables Y = 20; Z = X + Y // declare a formula that uses these two variables X = 50 // change one of the input variables ?Z // asking for Z should now give 70 (50 + 20) I've tried this in a lot of languages like F#, python, matlab etc, but every time i try this they come up with 30 instead of 70. Wich is correct from an imperative point of view, but i'm looking for a more declerative behaviour if you know what i mean. And this is just a very simple calculation. When things get more difficult it should handle stuff like recursion and memoization automagically. The code below would obviously work in C# but it's just so much code for the job, i'm looking for something a bit more to the point without all that 'technical noise' class BlaBla{ public int X {get;set;} // this used to be even worse before 3.0 public int Y {get;set;} public int Z {get{return X + Y;}} } static void main(){ BlaBla bla = new BlaBla(); bla.X = 10; bla.Y = 20; // can't define anything here bla.X = 50; // bit pointless here but I'll do it anyway. Console.Writeline(bla.Z);// 70, hurray! } This just seems like so much code, curly braces and semicolons that add nothing. Is there a language/ application (apart from Exel) that does this? Maybe I'm no doing it right in the mentioned langauges, or I've completely missed an app that does just this. I prototyped a language/ application that does this (along with some other stuff) and am thinking of productizing it. I just can't believe it's not there yet. Don't want to waste my time. Thanks in advance, Gert-Jan

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  • How to properly set relationships in Core Data when using setValue and data already exists

    - by ern
    Let's say I have two objects: Articles and Categories. For the sake of this example all relevant categories have already been added to the data store. When looping through data that holds edits for articles, there is category relationship information that needs to be saved. I was planning on using the -setValue method in the Article class in order to set the relationships like so: - (void)setValue:(id)value forUndefinedKey:(NSString *)key { if([key isEqualToString:@"categories"]){ NSLog(@"trying to set categories..."); } } The problem is that value isn't a Category, it is just a string (or array of strings) holding the title of a category. I could certainly do a lookup within this method for each category and assign it, but that seems inefficient when processing a whole bunch of articles at once. Another option is to populate an array of all possible categories and just filter, but my question is where to store that array? Should it be a class method on Article? Is there a way to pass in additional data to the -setValue method? Is there another, better option for setting the relationship I'm not thinking of? Thanks for your help.

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  • NHibernate complex order query

    - by manu08
    Here's my simplified domain public class Notification { public Guid ID { get; set; } public string Name { get; set; } public IEnumerable<Location> Locations { get; set; } } public class Location { public Guid Id { get; set; } public string Name { get; set; } public decimal Longitude { get; set; } public decimal Latitude { get; set; } } Notifications and Locations have a many-to-many relationship (defined in table LocationsOnNotification). What I'd like to do is query for the nearest 10 Notifications from a given longitude and latitude. I've been trying to use ICriteria, but I'm not sure how to specify the ordering correctly: return Session.CreateCriteria<Notification>() .SetFirstResult(firstIndex) .SetMaxResults(maxResults) .AddOrder(Order.Asc( WHAT GOES HERE! )) .List<Notification>(); What I've been thinking of so far is adding a formula property to the Location mapping; something like this: <property name='Distance' formula='lots of geometry'/> But I'm not sure if that can take in parameters (since I'd need to pass in the user's location to calculate the distance), plus I'm not sure how to specify it in the Order.Asc clause given that it's a property on a many-to-many association class. Any ideas? Or perhaps I should take a different approach altogether. Thanks in advance!

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  • Moving information between databases

    - by williamjones
    I'm on Postgres, and have two databases on the same machine, and I'd like to move some data from database Source to database Dest. Database Source: Table User has a primary key Table Comments has a primary key Table UserComments is a join table with two foreign keys for User and Comments Dest looks just like Source in structure, but already has information in User and Comments tables that needs to be retained. I'm thinking I'll probably have to do this in a few steps. Step 1, I would dump Source using the Postgres Copy command. Step 2, In Dest I would add a temporary second_key column to both User and Comments, and a new SecondUserComments join table. Step 3, I would import the dumped file into Dest using Copy again, with the keys input into the second_key columns. Step 4, I would add rows to UserComments in Dest based on the contents of SecondUserComments, only using the real primary keys this time. Could this be done with a SQL command or would I need a script? Step 5, delete the SecondUserComments table and remove the second_key columns. Does this sound like the best way to do this, or is there a better way I'm overlooking?

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  • Is there any reason to use C instead of C++ for embedded development?

    - by Piotr Czapla
    Question I have two compilers on my hardware C++ and C89 I'm thinking about using C++ with classes but without polymorphism (to avoid vtables). The main reasons I’d like to use C++ are: I prefer to use “inline” functions instead of macro definitions. I’d like to use namespaces as I prefixes clutter the code. I see C++ a bit type safer mainly because of templates, and verbose casting. I really like overloaded functions and constructors (used for automatic casting). Do you see any reason to stick with C89 when developing for very limited hardware (4kb of RAM)? Conclusion Thank you for your answers, they were really helpful! I though the subject through and I will stick with C mainly because: It is easier to predict actual code in C and this is really important if you have only 4kb of ram. My team consists of C developers mainly so advance features of C++ won't be frequently used. I've found a way to inline functions in my C compiler (C89). It is hard to accept one answer as you provided so many good answers. Unfortunately I can't create a wiki and accept it so I will choose one answer that made me think most.

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  • Rails uploaded file blank

    - by Ceilingfish
    Hi chaps, I'm trying to upload a file to the server using a HTTP multipart form in rails, and for some reason it's turning up blank at the other end. I can see it being received in the rails log thusly: Processing Admin::HeadlinesController#update (for 127.0.0.1 at 2010-03-08 12:26:13) [PUT] Parameters: {"commit"=>"Save changes", "action"=>"update", "_method"=>"put", "authenticity_token"=>"mK70XRk5gOPUwXOcNboT/4K8PD9RBM7GqCOlEUKZwcA=", "headline"=>{"position"=>"1", "location"=>"primary", "attachment_id"=>"13", "headline_content"=>"questionnaires", "article_id"=>"3", "image"=>#<File:/tmp/RackMultipart20100308-63211-1vym9nj-0>}, "id"=>"140", "controller"=>"admin/headlines"} But if I have a look in /tmp/RackMultipart20100308-63211-1vym9nj-0 the file is blank. Am I right in thinking that this should be the file that I uploaded? I'm running Phusion Passenger 2.2.7 on Apache 2.2.13, with ruby 1.8.7 and rails 2.3.5, on OSX 10.6.2

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  • Reading in bytes produced by PHP script in Java to create a bitmap

    - by Kareem
    I'm having trouble getting the compressed jpeg image (stored as a blob in my database). here is the snippet of code I use to output the image that I have in my database: if($row = mysql_fetch_array($sql)) { $size = $row['image_size']; $image = $row['image']; if($image == null){ echo "no image!"; } else { header('Content-Type: content/data'); header("Content-length: $size"); echo $image; } } here is the code that I use to read in from the server: URL sizeUrl = new URL(MYURL); URLConnection sizeConn = sizeUrl.openConnection(); // Get The Response BufferedReader sizeRd = new BufferedReader(new InputStreamReader(sizeConn.getInputStream())); String line = ""; while(line.equals("")){ line = sizeRd.readLine(); } int image_size = Integer.parseInt(line); if(image_size == 0){ return null; } URL imageUrl = new URL(MYIMAGEURL); URLConnection imageConn = imageUrl.openConnection(); // Get The Response InputStream imageRd = imageConn.getInputStream(); byte[] bytedata = new byte[image_size]; int read = imageRd.read(bytedata, 0, image_size); Log.e("IMAGEDOWNLOADER", "read "+ read + " amount of bytes"); Log.e("IMAGEDOWNLOADER", "byte data has length " + bytedata.length); Bitmap theImage = BitmapFactory.decodeByteArray(bytedata, 0, image_size); if(theImage == null){ Log.e("IMAGEDOWNLOADER", "the bitmap is null"); } return theImage; My logging shows that everything has the right length, yet theImage is always null. I'm thinking it has to do with my content type. Or maybe the way I'm uploading?

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  • trouble setting up anonymous login in ejabberd

    - by sofia
    Hi, In ejabberd.cfg I have the following {host_config, "thisislove-MacBook-2.local", [{auth_method, [internal, anonymous]}, {allow_multiple_connections, false}, {anonymous_protocol, both}]}. but when using speeqe javascript client (speeqe.com) to connect, I see it sends <body rid='1366284187' xmlns='http://jabber.org/protocol/httpbind' to='thisislove-macbook-2.local' xml:lang='en' wait='60' hold='1' window='5' content='text/xml; charset=utf-8' ver='1.6' xmpp:version='1.0' xmlns:xmpp='urn:xmpp:xbosh'/> and the server responds with <body xmlns='http://jabber.org/protocol/httpbind' sid='f89bf034b02fa6b884bb0c55be3f1f69e45e3866' wait='60' requests='2' inactivity='30' maxpause='120' polling='2' ver='1.8' from='thisislove-macbook-2.local' secure='true' authid='353072658' xmlns:xmpp='urn:xmpp:xbosh' xmlns:stream='http://etherx.jabber.org/streams' xmpp:version='1.0'><stream:features xmlns:stream='http://etherx.jabber.org/streams'><mechanisms xmlns='urn:ietf:params:xml:ns:xmpp-sasl'><mechanism>DIGEST-MD5</mechanism><mechanism>PLAIN</mechanism></mechanisms><register xmlns='http://jabber.org/features/iq-register'/></stream:features></body> Notice the mechanisms, DIGEST-MD5 & PLAIN. If I'm not mistaken it should have ANONYMOUS as a mechanism as well. So what happens is that speeqe simply terminates the connection. As such I'm thinking i must be missing something in the anonymous configuration or the muc config. In the mod_muc configg, I have {mod_muc, [ %%{host, "conference.@HOST@"}, {access, muc}, {access_create, muc}, {access_persistent, muc}, {access_admin, muc_admin}, {max_room_name, 190}, {max_room_desc, 190}, {max_users, 500} ]} So what am I missing? Thanks

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  • Editing a remote file on-the-fly with PHP

    - by user275074
    Hi, I have a requirement to edit a remote text file on-the-fly, the content of which currently stands at ~1Mb. I have tried a couple of approaches and both seem to be clunky or hog memory which I can't rely on. Thinking out logically what I'm trying to achieve is: FTP to a remote server. Download a copy of the file for backup purposes and store it somewhere locally. Open the remote file and add the necessary lines required. Remove lines from the remote file as per an array of un-required data generated from the local server. Is this possible? I've managed to code steps 1 and 2 but I'm having difficult with 3 and 4. The way I'm doing it now is to use fgets and return the whole string. Really, I don't want to do this as it involves manipulating and re-generating the whole string (and it's large) and then re-inserting it in between two markers in the remote file. Is there no way of manipulating the lines of text in the file on-the-fly?

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  • Which languages and techniques can I use to improve my coding practices?

    - by Danjah
    I've been offered the opportunity upskill through study, while at work which is great. My background I am mostly self-taught, but have worked with many excellent people over the years - both self-taught and fully educated, and on many decent projects. I have mild experience in Actionscript, I'm getting better every day with my Javascript, and my CSS is angled at best practice, but needs a bit of modernising. I'm a traditional interface developer, I'm not stupid and I like a challenge. My goal I need to start seeing ways of applying better logic, optimising code, refactoring, different styles of development (agile, others?), and.. well I need to try and start thinking like.. a more solid programmer. Its hard to describe, I have good solutions and I'm efficient - but I KNOW that there's a bunch I am missing. I am already employed with a solid career, but I feel the need to fill gaps. My question/s Are there a set of guiding principles you can recommend I focus on to improve the points above? Are there particular programming languages which I might focus on to get a broader overview? Do you think I should avoid particular styles of development, or even languages, while solidifying what might end up being part 'the basics' but hopefully 'advanced programming'? -- Sorry if this appears off topic or something but I figure you're probably some of the best people to ask.

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  • Modeling complex hierarchies

    - by jdn
    To gain some experience, I am trying to make an expert system that can answer queries about the animal kingdom. However, I have run into a problem modeling the domain. I originally considered the animal kingdom hierarchy to be drawn like -animal -bird -carnivore -hawk -herbivore -bluejay -mammals -carnivores -herbivores This I figured would allow me to make queries easily like "give me all birds", but would be much more expensive to say "give me all carnivores", so I rewrote the hierarchy to look like: -animal -carnivore -birds -hawk -mammals -xyz -herbivores -birds -bluejay -mammals But now it will be much slower to query "give me all birds." This is of course a simple example, but it got me thinking that I don't really know how to model complex relationships that are not so strictly hierarchical in nature in the context of writing an expert system to answer queries as stated above. A directed, cyclic graph seems like it could mathematically solve the problem, but storing this in a relational database and maintaining it (updates) would seem like a nightmare to me. I would like to know how people typically model such things. Explanations or pointers to resources to read further would be acceptable and appreciated.

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  • php - usort or array_multisort?

    - by Simpson88Keys
    Trying to sort the array below by memnum in ascending order, and I'm a bit confused which is better to use... usort or array_multisort? I was thinking usort because it's multidimensional? Does anyone have an example of this? Array ( [0] => Array ( [memnum] => 3236467423 [mid] => 1104881300 [fname] => JOHN [lname] => DOE [add1] => OMITTED [add2] => [city] => CHESTERFIELD [state] => MI [zip] => 48051 [age] => 50 ) [1] => Array ( [memnum] => 3258467922 [mid] => 1105121457 [fname] => JANE [lname] => DOE [add1] => OMITTED [add2] => [city] => CHESTERFIELD [state] => MI [zip] => 48051 [age] => 50 ) [2] => Array ( [memnum] => 3237769108 [mid] => 1104489312 [fname] => BOB [lname] => DOE [add1] => OMITTED [add2] => [city] => CHESTERFIELD [state] => MI [zip] => 48051 [age] => 50 ) )

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  • Set a callback function to a new window in javascript

    - by SztupY
    Is there an easy way to set a "callback" function to a new window that is opened in javascript? I'd like to run a function of the parent from the new window, but I want the parent to be able to set the name of this particular function (so it shouldn't be hardcoded in the new windows page). For example in the parent I have: function DoSomething { alert('Something'); } ... <input type="button" onClick="OpenNewWindow(linktonewwindow,DoSomething);" /> And in the child window I want to: <input type="button" onClick="RunCallbackFunction();" /> The question is how to create this OpenNewWindow and RunCallbackFunction functions. I though about sending the function's name as a query parameter to the new window (where the server side script generates the appropriate function calls in the generated child's HTML), which works, but I was thinking whether there is another, or better way to accomplish this, maybe something that doesn't even require server side tinkering. Pure javascript, server side solutions and jQuery (or other frameworks) are all welcomed.

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  • What Do You Need To Write Your Own Blog Engine?

    - by deworde
    I've been messing around with basic websites for a few years, using companies like www.Fasthosts.co.uk to do my web hosting. But I'd like to expand my skills from C++ and Java app programming into Web-based programming, and I think the best way to do that is with a project. I've chosen to go with a blog engine because it's a relative comprehensive yet non-complex project. I'm aware that you can just go to Blogger and bam! One blog. I've done that, so that I can at least have some content, and work out what I want to do with this blog. At the moment, I'm thinking I'll use it to chart my progress creating the blogging engine. But I have some questions. Do you need to be running your own server? Or is it more sensible in the short-term to use a hosting company? What types of language are worth considering? What's important to focus on from a design perspective? What unexpected problems might I encounter?

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  • How to efficiently convert String, integer, double, datetime to binary and vica versa?

    - by Ben
    Hi, I'm quite new to C# (I'm using .NET 4.0) so please bear with me. I need to save some object properties (their properties are int, double, String, boolean, datetime) to a file. But I want to encrypt the files using my own encryption, so I can't use FileStream to convert to binary. Also I don't want to use object serialization, because of performance issues. The idea is simple, first I need to somehow convert objects (their properties) to binary (array), then encrypt (some sort of xor) the array and append it to the end of the file. When reading first decrypt the array and then somehow convert the binary array back to object properties (from which I'll generate objects). I know (roughly =) ) how to convert these things by hand and I could code it, but it would be useless (too slow). I think the best way would be just to get properties' representation in memory and save that. But I don't know how to do it using C# (maybe using pointers?). Also I though about using MemoryStream but again I think it would be inefficient. I am thinking about class Converter, but it does not support toByte(datetime) (documentation says it always throws exception). For converting back I think the only options is class Converter. Note: I know the structure of objects and they will not change, also the maximum String length is also known. Thank you for all your ideas and time. EDIT: I will be storing only parts of objects, in some cases also parts of different objects (a couple of properties from one object type and a couple from another), thus I think that serialization is not an option for me.

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  • Generic callbacks

    - by bobobobo
    Extends So, I'm trying to learn template metaprogramming better and I figure this is a good exercise for it. I'm trying to write code that can callback a function with any number of arguments I like passed to it. // First function to call int add( int x, int y ) ; // Second function to call double square( double x ) ; // Third func to call void go() ; The callback creation code should look like: // Write a callback object that // will be executed after 42ms for "add" Callback<int, int, int> c1 ; c1.func = add ; c1.args.push_back( 2 ); // these are the 2 args c1.args.push_back( 5 ); // to pass to the "add" function // when it is called Callback<double, double> c2 ; c2.func = square ; c2.args.push_back( 52.2 ) ; What I'm thinking is, using template metaprogramming I want to be able to declare callbacks like, write a struct like this (please keep in mind this is VERY PSEUDOcode) <TEMPLATING ACTION <<ANY NUMBER OF TYPES GO HERE>> > struct Callback { double execTime ; // when to execute TYPE1 (*func)( TYPE2 a, TYPE3 b ) ; void* argList ; // a stored list of arguments // to plug in when it is time to call __func__ } ; So for when called with Callback<int, int, int> c1 ; You would automatically get constructed for you by < HARDCORE TEMPLATING ACTION > a struct like struct Callback { double execTime ; // when to execute int (*func)( int a, int b ) ; void* argList ; // this would still be void*, // but I somehow need to remember // the types of the args.. } ; Any pointers in the right direction to get started on writing this?

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  • Dealing with expired authentication for a partially filled form?

    - by aaronls
    I have a large webform, and would like to prompt the user to login if their session expires, or have them login when they submit the form. It seems that having them login when they submit the form creates alot of challenges because they get redirected to the login page and then the postback data for the original form submission is lost. So I'm thinking about how to prompt them to login asynchrounsly when the session expires. So that they stay on the original form page, have a panel appear telling them the session has expired and they need to login, it submits the login asynchronously, the login panel disapears, and the user is still on the original partially filled form and can submit it. Is this easily doable using the existing ASP.NET Membership controls? When they submit the form will I need to worry about the session key? I mean, I am wondering if the session key the form submits will be the original one from before the session expired which won't match the new one generated after logging in again asynchrounously(I still do not understand the details of how ASP.NET tracks authentication/session IDs). Edit: Yes I am actually concerned about authentication expiration. The user must be authenticated for the submitted data to be considered valid.

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  • Silverlight 4 ComboBox - Binding to Nullable data (tried TargetNullValue but not working as expected)

    - by Laurence
    (Please note - I am a Silverlight beginner and am looking for the simplest solution here, e.g. that doesn't involve writing/installing a replacement for the ComboBox control!) This is an issue with a Silverlight 4 application that uses the View Model (MVVM) approach. I have a simple form for editing a "Product" object. Product has a CategoryID property which is nullable (int?). A ComboBox is used to view and set the CategoryID - this is bound to an ObservableCollection of Categories. Product also has number of non-nullable properties bound to TextBoxes. I want the user to see "N/A" in the ComboBox for a product with no category, and to be use this "N/A" option to set CategoryID to null. So, I manually added a Category object with CategoryID=0 and CategoryName="N/A" to the collection; then I set TargetNullValue=0 in the SelectedValue Binding of the ComboBox. My thinking was - when the ComboBox SelectedValue was bound to a null CategoryID it would substitute zero, and therefore select the "N/A" option. When editing a Product with a non-null CategoryID, everything works. However when a null CategoryID is found, two problems occur: No option is selected in the ComboBox (its blank) The ComboBox binding seems broken from this point onwards - any Product I subsequently edit (incl. ones with a non-null CategoryID) have nothing selected in the ComboBox (its still populated with all categories - just no selected item). I've seen reports of problem #2 (here, here) but I was under the impression that #1 should have worked. What am I missing to get the "N/A" option to be selected? XAML for ComboBox: <ComboBox x:Name="cboCategory" ItemsSource="{Binding colCategories, Mode=OneWay}" SelectedValuePath="CategoryID" DisplayMemberPath="CategoryName" SelectedValue="{Binding CurrentProduct.CategoryID, Mode=TwoWay, TargetNullValue=0}" Height="24" Width="344"></ComboBox>

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  • Java - Calling all methods of a class

    - by Thomas Eschemann
    I'm currently working on an application that has to render several Freemarker templates. So far I have a Generator class that handles the rendering. The class looks more or less like this: public class Generator { public static void generate(…) { renderTemplate1(); renderTemplate2(); renderTemplate3(); } private static void render(…) { // renders the template } private static void renderTemplate1() { // Create config object for the rendering // and calls render(); }; private static void renderTemplate1() { // Create config object for the rendering // and calls render(); }; … } This works, but it doesn't really feel right. What I would like to do is create a class that holds all the renderTemplate...() methods and then call them dynamically from my Generator class. This would make it cleaner and easier to extend. I was thinking about using something like reflection, but it doesn't really feel like a good solution either. Any idea on how to implement this properly ?

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  • Dangers when deploying Flash/Flex UI test automation hooks to production?

    - by Merlyn Morgan-Graham
    I am interested in doing automated testing against a Flex based UI. I have found out that my best options for UI automation (due to being C# controllable, good licensing conditions, etc) all seem to require that I compile test hooks into my application. Because of this, I am thinking of recommending that these hooks be compiled into our build. I have found a few places on the net that recommend not deploying bits with this instrumentation enabled, and I'd like to know why. Is it a performance drain, or a security risk? If it is a security risk, can you explain how the attack surface is increased? I am not a Flash or Flex developer, though I have some experience with threat modeling. For reference, here's the tools I'm specifically considering: QTP Selenium-Flex API I am having problems finding all the warnings/suggestions I found last night, but here's an example that I can find: http://www.riatest.com/products/getting-started.html Warning! Automation enabled applications expose all properties of all GUI components. This makes them vulnerable to malicious use. Never make automation enabled application publicly available. Always restrict access to such applications and to RIATest Loader to trusted users only. Related question (how to do conditional compilation to insert/remove those hooks): Conditionally including Flex libraries (SWCs) in mxmlc/compc ant tasks

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  • Creating a [materialised]view from generic data in Oracle/Mysql

    - by Andrew White
    I have a generic datamodel with 3 tables CREATE TABLE Properties ( propertyId int(11) NOT NULL AUTO_INCREMENT, name varchar(80) NOT NULL ) CREATE TABLE Customers ( customerId int(11) NOT NULL AUTO_INCREMENT, customerName varchar(80) NOT NULL ) CREATE TABLE PropertyValues ( propertyId int(11) NOT NULL, customerId int(11) NOT NULL, value varchar(80) NOT NULL ) INSERT INTO Properties VALUES (1, 'Age'); INSERT INTO Properties VALUES (2, 'Weight'); INSERT INTO Customers VALUES (1, 'Bob'); INSERT INTO Customers VALUES (2, 'Tom'); INSERT INTO PropertyValues VALUES (1, 1, '34'); INSERT INTO PropertyValues VALUES (2, 1, '80KG'); INSERT INTO PropertyValues VALUES (1, 2, '24'); INSERT INTO PropertyValues VALUES (2, 2, '53KG'); What I would like to do is create a view that has as columns all the ROWS in Properties and has as rows the entries in Customers. The column values are populated from PropertyValues. e.g. customerId Age Weight 1 34 80KG 2 24 53KG I'm thinking I need a stored procedure to do this and perhaps a materialised view (the entries in the table "Properties" change rarely). Any tips?

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  • What is the fastest way to find duplicates in multiple BIG txt files?

    - by user2950750
    I am really in deep water here and I need a lifeline. I have 10 txt files. Each file has up to 100.000.000 lines of data. Each line is simply a number representing something else. Numbers go up to 9 digits. I need to (somehow) scan these 10 files and find the numbers that appear in all 10 files. And here comes the tricky part. I have to do it in less than 2 seconds. I am not a developer, so I need an explanation for dummies. I have done enough research to learn that hash tables and map reduce might be something that I can make use of. But can it really be used to make it this fast, or do I need more advanced solutions? I have also been thinking about cutting up the files into smaller files. To that 1 file with 100.000.000 lines is transformed into 100 files with 1.000.000 lines. But I do not know what is best: 10 files with 100 million lines or 1000 files with 1 million lines? When I try to open the 100 million line file, it takes forever. So I think, maybe, it is just too big to be used. But I don't know if you can write code that will scan it without opening. Speed is the most important factor in this, and I need to know if it can be done as fast as I need it, or if I have to store my data in another way, for example, in a database like mysql or something. Thank you in advance to anybody that can give some good feedback.

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  • How to model has_many with polymorphism?

    - by Daniel Abrahamsson
    I've run into a situation that I am not quite sure how to model. Suppose I have a User class, and a user has many services. However, these services are quite different, for example a MailService and a BackupService, so single table inheritance won't do. Instead, I am thinking of using polymorphic associations together with an abstract base class: class User < ActiveRecord::Base has_many :services end class Service < ActiveRecord::Base validates_presence_of :user_id, :implementation_id, :implementation_type belongs_to :user belongs_to :implementation, :polymorphic = true delegate :common_service_method, :name, :to => :implementation end #Base class for service implementations class ServiceImplementation < ActiveRecord::Base validates_presence_of :user_id, :on => :create has_one :service, :as => :implementation has_one :user, :through => :service after_create :create_service_record #Tell Rails this class does not use a table. def self.abstract_class? true end #Default name implementation. def name self.class.name end protected #Sets up a service object def create_service_record service = Service.new(:user_id => user_id) service.implementation = self service.save! end end class MailService < ServiceImplementation #validations, etc... def common_service_method puts "MailService implementation of common service method" end end #Example usage MailService.create(..., :user_id => user.id) BackupService.create(...., :user_id => user.id) user.services.each do |s| puts "#{user.name} is using #{s.name}" end #Daniel is using MailService, Daniel is using BackupService So, is this the best solution? Or even a good one? How have you solved this kind of problem?

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  • Are women worse developers than men? [closed]

    - by Ekaterina
    Hi people, I am a software engineer and a woman. I constantly keep hearing all these jokes around me, about women in programming. They (they - stands for male colleagues) keep pointing out the differences in thinking between men and women. The truth is that when I started working as a developer, my colleagues gave a hard time only because I am a woman. They automatically assumed that I want to do only html and styling, and didn't even me giving me the chance to do something different. I am a .NET programmer and I really disliked (and still dislike) front-end developing. I do agree men and women think differently, but I don't agree that necessarily is a bad thing. Different approach of problems/goals brings more ideas and diversity. I really believe that there are good developer and bad developers despite the male/female factor. I am curious to hear overall opinion though. Would you not hire a woman developer only because is a woman? Cheers!

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