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  • Is there a term for this concept, and does it exist in a static-typed language?

    - by Strilanc
    Recently I started noticing a repetition in some of my code. Of course, once you notice a repetition, it becomes grating. Which is why I'm asking this question. The idea is this: sometimes you write different versions of the same class: a raw version, a locked version, a read-only facade version, etc. These are common things to do to a class, but the translations are highly mechanical. Surround all the methods with lock acquires/releases, etc. In a dynamic language, you could write a function which did this to an instance of a class (eg. iterate over all the functions, replacing them with a version which acquires/releases a lock.). I think a good term for what I mean is 'reflected class'. You create a transformation which takes a class, and returns a modified-in-a-desired-way class. Synchronization is the easiest case, but there are others: make a class immutable [wrap methods so they clone, mutate the clone, and include it in the result], make a class readonly [assuming you can identify mutating methods], make a class appear to work with type A instead of type B, etc. The important part is that, in theory, these transformations make sense at compile-time. Even though an ActorModel<T> has methods which change depending on T, they depend on T in a specific way knowable at compile-time (ActorModel<T> methods would return a future of the original result type). I'm just wondering if this has been implemented in a language, and what it's called.

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  • Problem logging in and changing permissions in Facebook

    - by kujawk
    Hi everybody, I've got a piece of code that logs into Facebook, gets a session, sets status_update and offline_access permission if they are not set, and gets a new session with the newly set permissions. This code used to work fine but now I'm getting error 100 "One of the parameters specified was missing or invalid" as a response to the second call to get session and I can't figure out why. Here's the sequence in detail: CREATE TOKEN restserver.php?method=auth.createToken&api_key=[our key]&v=1.0&format=JSON&sig=[sig created with our secret] response: new token LOGIN m.facebook.com/login.php?api_key=[our key]&v=1.0&auth_token=[token created above] login screen loads and user successfully logs in with their username/password. GET SESSION restserver.php?method=auth.getSession&api_key=[our key]&v=1.0&format=JSON&auth_token=token created above&sig=[sig created with our secret] response: session key with expiration date and a secret CHECK/AUTHORIZE PERMISSIONS restserver.php?method=users.hasAppPermission&api_key=[our key]&v=1.0&format=JSON&ext_perm=status_update&call_id=[proper id]&session_key=[key returned above]&sig=[sig created with secret returned for get session] response: 0 m.facebook.com/authorize.php?api_key=[our key]&v=1.0&ext_perm=status_update authorization screen loads and user authorizes Same steps for status_update CREATE NEW TOKEN Same steps as done to create the first token LOGIN m.facebook.com/login.php?api_key=[our key]&v=1.0&auth_token=[new token] user is already logged in, redirected to their homepage GET NEW SESSION restserver.php?method=auth.getSession&api_key=[our key]&format=JSON&auth_token=[new token]&sig=[sig created with our secret] response: error 100 - missing or invalid parameter. Of course it doesn't tell me which one. Anybody have any ideas what I'm doing wrong here? I tried skipping the second login and going right to creating the new session and that didn't work. The only thing that seems to work is logging out the user after they've authorized the permissions and having them log back in again. I'd like to avoid this if possible. Can you have two outstanding sessions at one time? This code used to work but I'm thinking maybe something changed on Facebook's end that I'm not aware of. Thanks, kris

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  • MySQL LIMIT 1 but query 15 rows?

    - by Ian
    Basically what I'm trying to do is compare the ID's of rows against 15 results in MySQL, eliminating all but 1 (using NOT IN) and then pull that result. Now normally this would be fine by itself, however the order of the 15 rows I'm doing the SQL query for are constantly changing based on a ranking, so there is a possibility that between the time the ranking updates, and the ajax request (which I submit the ID's for NOT IN) more than just one ID has changed, which would of course bring back more than one row which I do not want. So in short, is there a way in which I can query 15 rows, but only return one? Without having to run two separate queries. Any help is appreciated, thank you. EXAMPLE: Say I have 7 items in my database, and I'm displaying 5 on the page to the user. These are what are being displayed to the user: Apple Orange Kiwi Banana Grape But in the database I also have Peach Blackberry Now what I want to do is if the user deletes an item from their list, it will add another item (based on a ranking they have) Now the issue is, in order to know what they have on their list at the moment I send the remaining items to the database (say they deleted Kiwi, I would send Apple, Orange, Banana, and Grape) So now I select the highest ranked 5 items from are remaining six items, make sure they are not the ones already displayed on the page, and then add the new one to list (either Peach or Blackberry) All good and well, except that if both peach and blackberry now outrank grape, then I will be returning two results instead of just one. Because it would've searched... Apple Orange Banana Peach Blackberry and excluded... Apple Orange Banana Grape Which leaves us with both Peach and Blackberry, instead of just Peach or Blackberry

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  • Deploying a Rails app on an Ubuntu server using Git

    - by NudeCanalTroll
    I'm completely new to Linux, but today I find myself setting up a server (Ubuntu 10.04 LTS lucid) from scratch to host a Rails application. Anyway, I managed to get a Rails app up and running on the server itself, but I had to scrap that because I want to use Git. So I setup a git repository on the server, then pushed all the code from my local machine to the repository. Buuuut, of course Git doesn't actually store the files themselves in the repository -- all the code for my Rails app is now only on my local machine. How am I supposed to tell the server to host that? Right now my solution is to have the server use git to pull the code from its own repository. That's the code I'll host for all the world to see. In order to update the code, I guess I'll have to do something like this: Update the code on my local machine. Do some git adds, git commits, and a git push. On the server, do a git pull to update the code. So my question is, am I doing this the right way? enter code here

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  • In-order tree traversal

    - by Chris S
    I have the following text from an academic course I took a while ago about in-order traversal (they also call it pancaking) of a binary tree (not BST): In-order tree traversal Draw a line around the outside of the tree. Start to the left of the root, and go around the outside of the tree, to end up to the right of the root. Stay as close to the tree as possible, but do not cross the tree. (Think of the tree — its branches and nodes — as a solid barrier.) The order of the nodes is the order in which this line passes underneath them. If you are unsure as to when you go “underneath” a node, remember that a node “to the left” always comes first. Here's the example used (slightly different tree from below) However when I do a search on google, I get a conflicting definition. For example the wikipedia example: Inorder traversal sequence: A, B, C, D, E, F, G, H, I (leftchild,rootnode,right node) But according to (my understanding of) definition #1, this should be A, B, D, C, E, F, G, I, H Can anyone clarify which definition is correct? They might be both describing different traversal methods, but happen to be using the same name. I'm having trouble believing the peer-reviewed academic text is wrong, but can't be certain.

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  • Modifying File while in use using Java

    - by Marquinio
    Hi all, I have this recurrent Java JAR program tasks that tries to modify a file every 60seconds. Problem is that if user is viewing the file than Java program will not be able to modify the file. I get the typical IOException. Anyone knows if there is a way in Java to modify a file currently in use? Or anyone knows what would be the best way to solve this problem? I was thinking of using the File canRead(), canWrite() methods to check if file is in use. If file is in use then I'm thinking of making a backup copy of data that could not be written. Then after 60 seconds add some logic to check if backup file is empty or not. If backup file is not empty then add its contents to main file. If empty then just add new data to main file. Of course, the first thing I will always do is check if file is in use. Thanks for all your ideas.

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  • writing a meta refresh method for rails

    - by aaronstacy
    I want a method in app/controllers/application.rb that can prepend/append text to whatever template gets rendered. Of course I can't call render twice w/o getting a double render error, so is this possible? I want to redirect after a delay using a meta refresh. Here's what I've got: app/controllers/application_controller.rb: def redirect_after_delay (url, delay) @redirect_delay = delay @redirect_url = url render end app/views/layouts/application.html.erb <!DOCTYPE html> <html lang="en"> <head> <%= yield :refresh_tag %> </head> <body> <%= yield %> </body> </html> So then if I want to add a redirect-after-delay, I add the following to 1) my controller and 2) the action's view: app/controllers/my_controller.rb def my_action redirect_after_delay 'http://www.google.com', 3 if some_condition end app/views/my_controller/my_action.html.erb <% content_for :refresh_tag do %> <meta http-equiv='refresh' content='<%=@redirect_delay%>;url=<%=@redirect_url%>'> <% end %> <h1>Please wait while you are redirected...</h1> Since the content_for block never changes, is it possible to do this in some generic way so that I don't have to put <%= yield :refresh_tag %> in each template? (e.g. could redirect_after_delay add it into whatever template is going to be rendered?)

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  • Developing on a windows machine that interacts with a linux system

    - by Jamie
    Sorry for the bad title (couldn't think of a better way to describe it) I have a windows machine which I do development on. However, I have a new project which needs to interact with a linux system (executing linux commands etc.). So, obviously I can't do development on my windows machine..and I don't wish to code on the dev machine, svn commit and then svn update it on the linux machine. Is there a way where any changes I make on my dev machine will be quickly mirrored to the linux machine? SVN is not a very quick alternative and of course some changes will be very minor. Any ideas? A network share I guess....but that's not very pretty (bit slow too). As fellow developers I would like to know if you've been in a similar situation and how you've resolved it. On a furthernote, I can't just install Ubuntu as my development machine and mirror the commands, applications etc. from the linux machine because it's a cluster 'master' machine and so therefore it has quite a special configuration. Thanks guys! EDIT: I've also thought about having web services on the linux machine and then just calling them from code thus seperating platform development dependency. What do you think about that too? thanks

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  • C++ Implicit Conversion Operators

    - by Imbue
    I'm trying to find a nice inheritance solution in C++. I have a Rectangle class and a Square class. The Square class can't publicly inherit from Rectangle, because it cannot completely fulfill the rectangle's requirements. For example, a Rectangle can have it's width and height each set separately, and this of course is impossible with a Square. So, my dilemma. Square obviously will share a lot of code with Rectangle; they are quite similar. For examlpe, if I have a function like: bool IsPointInRectangle(const Rectangle& rect); it should work for a square too. In fact, I have a ton of such functions. So in making my Square class, I figured I would use private inheritance with a publicly accessible Rectangle conversion operator. So my square class looks like: class Square : private Rectangle { public: operator const Rectangle&() const; }; However, when I try to pass a Square to the IsPointInRectangle function, my compiler just complains that "Rectangle is an inaccessible base" in that context. I expect it to notice the Rectangle operator and use that instead. Is what I'm trying to do even possible? If this can't work I'm probably going to refactor part of Rectangle into MutableRectangle class. Thanks.

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  • Pump Messages During Long Operations + C#

    - by Newbie
    Hi I have a web service that is doing huge computation and is taking more than a minute. I have generated the proxy file of the web service and then from my client end I am using the dll(of course I generated the proxy dll). My client side code is TimeSeries3D t = new TimeSeries3D(); int portfolioId = 4387919; string[] str = new string[2]; str[0] = "MKT_CAP"; DateRange dr = new DateRange(); dr.mStartDate = DateTime.Today; dr.mEndDate = DateTime.Today; Service1 sc = new Service1(); t = sc.GetAttributesForPortfolio(portfolioId, true, str, dr); But since it is taking to much time for the server to compute, after 1 minute I am receiving an error message The CLR has been unable to transition from COM context 0x33caf30 to COM context 0x33cb0a0 for 60 seconds. The thread that owns the destination context/apartment is most likely either doing a non pumping wait or processing a very long running operation without pumping Windows messages. This situation generally has a negative performance impact and may even lead to the application becoming non responsive or memory usage accumulating continually over time. To avoid this problem, all single threaded apartment (STA) threads should use pumping wait primitives (such as CoWaitForMultipleHandles) and routinely pump messages during long running operations. Kindly guide me what to do? Thanks

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  • Django: Serving a Download in a Generic View

    - by TheLizardKing
    So I want to serve a couple of mp3s from a folder in /home/username/music. I didn't think this would be such a big deal but I am a bit confused on how to do it using generic views and my own url. urls.py url(r'^song/(?P<song_id>\d+)/download/$', song_download, name='song_download'), The example I am following is found in the generic view section of the Django documentations: http://docs.djangoproject.com/en/dev/topics/generic-views/ (It's all the way at the bottom) I am not 100% sure on how to tailor this to my needs. Here is my views.py def song_download(request, song_id): song = Song.objects.get(id=song_id) response = object_detail( request, object_id = song_id, mimetype = "audio/mpeg", ) response['Content-Disposition'= "attachment; filename=%s - %s.mp3" % (song.artist, song.title) return response I am actually at a loss of how to convey that I want it to spit out my mp3 instead of what it does now which is to output a .mp3 with all of the current pages html contained. Should my template be my mp3? Do I need to setup apache to serve the files or is Django able to retrieve the mp3 from the filesystem(proper permissions of course) and serve that? If it do need to configure Apache how do I tell Django that? Thanks in advanced. These files are all on the HD so I don't need to "generate" anything on the spot and I'd like to prevent revealing the location of these files if at all possible. A simple /song/1234/download would be fantastic.

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  • What's the best way to only output a tag if it exists in XSL?

    - by Morinar
    I'm working on an interface with a 3rd party app that basically needs to take XML that was spat out by the app and convert it into XML our system can deal with. It's basically just applying a stylesheet to the original XML to make it looks like "our" XML. I've noticed that in other stylesheets we have, there are constructs like this: <xsl:for-each select="State"> <StateAbbreviation> <xsl:value-of select="."/> </StateAbbreviation> </xsl:for-each> Basically, the "in" XML has a State tag that I need to output as our recognized StateAbbreviation tag. However, I want to ONLY output the StateAbbreviation tag if the "in" XML contains the State tag. The block above accomplishes this just fine, but is not very intuitive (at least it wasn't to me), as every time I see a for-each I assume there is more than one, whereas in these cases there is 0 or 1. My question: is that a standard-ish construct? If not, is there a more preferred way to do it? I could obviously check the string length (which is also being done in other stylesheets), but would like to do it the same, "best" way everywhere (assuming of course that a "best" way exists. Advice? Suggestions?

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  • Subversion commands not being run by Ubuntu rc.local

    - by talentedmrjones
    Here is my rc.local for an autoscaling amazon ec2 instance based on ubuntu: (Note that user names, domains, and paths have been changed for security purposes) logger "Begin rc.local startup script:" logger "svn checkout" sudo -u nonRootUser /usr/bin/svn co svn+ssh://[email protected]/path/to/repo /var/www/html | logger logger "chown writeable folder" chown www-data /var/www/html/writeableFolder logger "restart apache" /etc/init.d/apache2 restart | logger exit 0 And here is the output of sudo tail -n 40 /var/log/syslog Mar 10 22:05:20 ubuntu logger: Begin rc.local startup script: Mar 10 22:05:20 ubuntu logger: svn checkout Mar 10 22:05:20 ubuntu logger: chown writeable folder Of course its not getting to apache2 restart because it error'd on the chown. I did find however that if I do a checkout beforehand, and set the rc.local svn command to an svn update, that it still does not run the svn command but does output apache2 restart successfully. These same svn commands work perfectly when I run them manually, tho it's strange that within rc.local they do not produce any output whatsoever to logger yet apache2 restart does. I've also tried running the svn co and svn update both with sudo -u and without. How do I get the svn command to run? Either a full checkout or an update. At this point either would be better than nothing!

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  • Best Practice: Access form elements by HTML id or name attribute?

    - by seth
    As any seasoned JavaScript developer knows, there are many (too many) ways to do the same thing. For example, say you have a text field as follows: <form name="myForm"> <input type="text" name="foo" id="foo" /> There are many way to access this in JavaScript: [1] document.forms[0].elements[0]; [2] document.myForm.foo; [3] document.getElementById('foo'); [4] document.getElementById('myForm').foo; ... and so on ... Methods [1] and [3] are well documented in the Mozilla Gecko documentation, but neither are ideal. [1] is just too general to be useful and [3] requires both an id and a name (assuming you will be posting the data to a server side language). Ideally, it would be best to have only an id attribute or a name attribute (having both is somewhat redundant, especially if the id isn't necessary for any css, and increases the likelihood of typos, etc). [2] seems to be the most intuitive and it seems to be widely used, but I haven't seen it referenced in the Gecko documentation and I'm worried about both forwards compatibility and cross browser compatiblity (and of course I want to be as standards compliant as possible). So what's best practice here? Can anyone point to something in the DOM documentation or W3C specification that could resolve this? Note I am specifically interested in a non-library solution (jQuery/Prototype).

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  • ASP.Net MVC - how can I easily serialize query results to a database?

    - by Mortanis
    I've been working on a little property search engine while I learn ASP.Net MVC. I've gotten the results from various property database tables and sorted them into a master generic property response. The search form is passed via Model Binding and works great. Now, I'd like to add pagination. I'm returning the chunk of properties for the current page with .Skip() and .Take(), and that's working great. I have a SearchResults model that has the paged result set and various other data like nextPage and prevPage. Except, I no longer have the original form of course to pass to /Results/2. Previously I'd have just hidden a copy of the form and done a POST each time, but it seems inelegant. I'd like to serialize the results to my MS SQL database and return a unique key for that results set - this also helps with a "Send this query to a friend!" link. Killing two birds with one stone. Is there an easy way to take an IQueryable result set that I have, serialize it, stick it into the DB, return a unique key and then reverse the process with said key? I'm using Linq to SQL currently on a MS SQL Express install, though in production it'll be on MS SQL 2008.

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  • Load PHP function with jQuery Ajax

    - by brandon14_99
    I have a file which is loaded at the top of my document, which is called Videos.php. Inside that file are several functions, such as getYoutubeVideos. On some pages, I need to call upon that function several times (up to 50), and it of course creates major lag on load times. So I have been trying to figure out how to call that function in, only when it is need (when someone clicks the show videos button). I have very little experience with jQuery's ajax abilities. I would like the ajax call to be made inside of something like this: jQuery('a[rel=VideoPreview1).click(function(){ jQuery ("a[rel=VideoPreview1]").hide(); jQuery ("a[rel=HideVideoPreview1]").show(); jQuery ("#VideoPreview1").show(); //AJAX STUFF HERE preventDefault(); }); Ok I have created this based on the responses, but it is still not working: jQuery Code: jQuery(document).ready(function(){ jQuery("a[rel=VideoPreview5]").click(function(){ jQuery("a[rel=VideoPreview5]").hide(); jQuery("a[rel=HideVideoPreview5]").show(); jQuery.post("/Classes/Video.php", {action: "getYoutubeVideos", artist: "Train", track: "Hey, Soul Sister"}, function(data){ jQuery("#VideoPreview5").html(data); }, 'json'); jQuery("#VideoPreview5").show(); preventDefault(); }); jQuery("a[rel=HideVideoPreview5]").click(function(){ jQuery("a[rel=VideoPreview5]").show(); jQuery("a[rel=HideVideoPreview5]").hide(); jQuery("#VideoPreview5").hide(); preventDefault(); }); }); And the PHP code: $Action = isset($_POST['action']); $Artist = isset($_POST['artist']); $Track = isset($_POST['track']); if($Action == 'getYoutubeVideos') { echo 'where are the videos'; echo json_encode(getYoutubeVideos($Artist.' '.$Track, 1, 5, 'relevance')); }

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  • ASP.NET server data persistence

    - by Wayne Werner
    Hi, I'm not really sure exactly how the question should be phrased, so please be patient if I ask the wrong thing. I'm writing an ASP.NET application using VB as the code behind language. I have a data access class that connects to the DB to run the query (parameterized, of course), and another class to perform the validation tasks - I access this class from my aspx page. What I would like is to be able to store the data server side and wait for the user to choose from a few options based on the validity of the data. But unless my understanding is completely off, having persistent data objects on the server will give problems when multiple users connect? My ultimate goal is that once the data has been validated the end user can't modify it. Currently I'm validating the data, but I still have to retrieve it from the web form AFTER the user says OK, which obviously leaves open the possibility of injecting bad data either accidentally (unlikely) or on purpose (also unlikely for the use, but I'd prefer not to take the chance). So am I completely off in my understanding? If so, can someone point me to a resource that provides some instructions on keeping persistent data on the server, or provide instruction? Thanks!

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  • Best practices for encrypting continuous/small UDP data

    - by temp
    Hello everyone, I am having an application where I have to send several small data per second through the network using UDP. The application need to send the data in real-time (no waiting). I want to encrypt these data and insure that what I am doing is as secure as possible. Since I am using UDP, there is no way to use SSL/TLS, so I have to encrypt each packet alone since the protocol is connectionless/unreliable/unregulated. Right now, I am using a 128-bit key derived from a passphrase from the user, and AES in CBC mode (PBE using AES-CBC). I decided to use a random salt with the passphrase to derive the 128-bit key (prevent dictionary attack on the passphrase), and of course use IVs (to prevent statistical analysis for packets). However I am concerned about few things: Each packet contains small amount of data (like a couple of integer values per packet) which will make the encrypted packets vulnerable to known-plaintext attacks (which will result in making it easier to crack the key). Also, since the encryption key is derived from a passphrase, this will make the key space way less (I know the salt will help, but I have to send the salt through the network once and anyone can get it). Given these two things, anyone can sniff and store the sent data, and try to crack the key. Although this process might take some time, once the key is cracked all the stored data will be decrypted, which will be a real problem for my application. So my question is, what is the best practices for sending/encrypting continuous small data using a connectionless protocol (UDP)? Is my way the best way to do it? ...flowed? ...Overkill? ... Please note that I am not asking for a 100% secure solution, as there is no such thing. Cheers

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  • JPA/Hibernate Parent/Child relationship

    - by NubieJ
    Hi I am quite new to JPA/Hibernate (Java in general) so my question is as follows (note, I have searched far and wide and have not come across an answer to this): I have two entities: Parent and Child (naming changed). Parent contains a list of Children and Children refers back to parent. e.g. @Entity public class Parent { @Id @Basic @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "PARENT_ID", insertable = false, updatable = false) private int id; /* ..... */ @OneToMany(cascade = { CascadeType.ALL }, fetch = FetchType.LAZY) @JoinColumn(name = "PARENT_ID", referencedColumnName = "PARENT_ID", nullable = true) private Set<child> children; /* ..... */ } @Entity public class Child { @Id @Basic @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "CHILD_ID", insertable = false, updatable = false) private int id; /* ..... */ @ManyToOne(cascade = { CascadeType.REFRESH }, fetch = FetchType.EAGER, optional = false) @JoinColumn(name = "PARENT_ID", referencedColumnName = "PARENT_ID") private Parent parent; /* ..... */ } I want to be able to do the following: Retrieve a Parent entity which would contain a list of all its children (List), however, when listing Parent (getting List, it of course should omit the children from the results, therefore setting FetchType.LAZY. Retrieve a Child entity which would contain an instance of the Parent entity. Using the code above (or similar) results in two exceptions: Retrieving Parent: A cycle is detected in the object graph. This will cause infinitely deep XML... Retrieving Child: org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: xxxxxxxxxxx, no session or session was closed When retrieving the Parent entity, I am using a named query (i.e. calling it specifically) @NamedQuery(name = "Parent.findByParentId", query = "SELECT p FROM Parent AS p LEFT JOIN FETCH p.children where p.id = :id") Code to get Parent (i.e. service layer): public Parent findByParentId(int parentId) { Query query = em.createNamedQuery("Parent.findByParentId"); query.setParameter("id", parentId); return (Parent) query.getSingleResult(); } Why am I getting a LazyInitializationException event though the List property on the Parent entity is set as Lazy (when retrieving the Child entity)?

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  • How can I share an entity framework model across website users

    - by richardmoss
    Hello, Currently my website is based around MVC and the Entity Framework running against a SQL Server 2005 database. So far, it has all been running very smoothly, and I really enjoy MVC and its slimmer more concise code (and no huge viewstates or soul destroying postbacks ;)) Recently I was working on upgrading the site to use a simple forum system, and this is where I started running into problems. When I was testing the site using two different browsers, if I created or replied to a post in one browser, the other browser couldn't see the post. At the moment, each visitor to the site gets their own copy of the entity model, which I store in their session data. Obviously this is the problem as updates to one model aren't getting carried to the other. As a test, I tried storing a single copy of the model which all visitors would access by assigning the model to a static variable. This worked, and both browsers could see each others modifications. However, it had its side effects. For example, if I fired up both browsers at the same time and the model was initialized, one browser would crash, and the other would work fine, despite me using a locking object so in theory one of them should have been delayed until the model was ready (of course I could have implemented this wrong ;)). Also, originally this site did use one model for all visitors and when it was live, it frequently shut down - killing the IIS application pool while it did. Now I'm not sure if this was related, but I don't really want to reintroduce whatever bug I had that caused this shut down. So, my question is a simple one really - what is the best way of either using the same model for all website users so they all see updates, or if they do have separate copies (which I imagine will have a performance impact in time) how can the models detect changes in the database and update themselves according. Thanks in advance for any advice! Regards; Richard Moss

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  • Which is faster for large "for" loop: function call or inline coding?

    - by zaplec
    Hi, I have programmed an embedded software (using C of course) and now I'm considering ways to improve the running time of the system. The most important single module in my system is one very large nested for loop module. That module consists of two nested for loops that loops max 122500 times. That's not very much yet, but the problem is that inside that nested for loop I have a function call to a function that is in another source file. That specific function consists mostly of two another nested for loops which loops always 22500 times. So now I have to make a function call 122500 times. I have made that function that is to be called a lot lighter and shorter (yet still works as it should) and now I started to think that would it be faster to rip off that function call and write that process directly inside those first two for loops? The processor in that system is ARM7TDMI and its frequency is 55MHz. The system itself isn't very time critical so it doesn't have to be real time capable. However the faster it can process its duties the better. Also would it be also faster to use while loops instead of fors? And any piece of advice about how to improve the running time is appreciated. -zaplec

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  • JQuery: how to store records id for data from ajax query in dynamicly created html elements

    - by grapkulec
    Probably question title is rather cryptic but I will try to explain myself here so please bare with me :) Let's assume this configuration: server-side is PHP application responding for requests with data (list of items, single item details, etc.) in json format client-side is JQuery application sending ajax request to that PHP app and creating html content corresponding with received data So, for example: client requests "list of all animals with names staring with 'A'", gets the json response from server, and for every "animal" creates some html gizmo like div with animal description or something like that. It doesn't really matter what html element it will be but it has to point exactly to specific record by "containing" id of that record. And here is my dilemma: is it good solution to use "id" property for that? So it would be like: <div id="10" class="animal"> <p> This is animal of very mysterious kind... </p> </div> <div id="11" class="animal"> <p> And this one is very common to our country... </p> </div> where id="10" is of course indication that this is representation of record with id = 10. Or maybe I should store this record id in some custom made tag like <record_id>10</record_id> and leave an "id" strictly for what it was meant to be (css selector)? I need that record id for further stuff like updating database with some user input or deleting some of "animals" or creating new ones or anything that will be needed. All manipulations will be done with JQuery and ajax requests and responses will be visualized also with dynamic creation of html interface. I'm sure that somebody had to deal with that kind of stuff before so I would be grateful for some tips on that topic.

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  • Why doesn't the Java Collections API include a Graph implementation?

    - by dvanaria
    I’m currently learning the Java Collections API and feel I have a good understanding of the basics, but I’ve never understood why this standard API doesn’t include a Graph implementation. The three base classes are easily understandable (List, Set, and Map) and all their implementations in the API are mostly straightforward and consistent. Considering how often graphs come up as a potential way to model a given problem, this just doesn’t make sense to me (it’s possible it does exist in the API and I’m not looking in the right place of course). Steve Yegge suggests in one of his blog posts that a programmer should consider graphs first when attacking a problem, and if the problem domain doesn’t fit naturally into this data structure, only then consider the alternative structures. My first guess is that there is no universal way to represent graphs, or that their interfaces may not be generic enough for an API implementation to be useful? But if you strip down a graph to its basic components (vertices and a set of edges that connect some or all of the vertices) and consider the ways that graphs are commonly constructed (methods like addVertex(v) and insertEdge(v1, v2)) it seems that a generic Graph implementation would be possible and useful. Thanks for helping me understand this better.

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  • Are there any downsides in using C++ for network daemons?

    - by badcat
    Hey guys! I've been writing a number of network daemons in different languages over the past years, and now I'm about to start a new project which requires a new custom implementation of a properitary network protocol. The said protocol is pretty simple - some basic JSON formatted messages which are transmitted in some basic frame wrapping to have clients know that a message arrived completely and is ready to be parsed. The daemon will need to handle a number of connections (about 200 at the same time) and do some management of them and pass messages along, like in a chat room. In the past I've been using mostly C++ to write my daemons. Often with the Qt4 framework (the network parts, not the GUI parts!), because that's what I also used for the rest of the projects and it was simple to do and very portable. This usually worked just fine, and I didn't have much trouble. Being a Linux administrator for a good while now, I noticed that most of the network daemons in the wild are written in plain C (of course some are written in other languages, too, but I get the feeling that 80% of the daemons are written in plain C). Now I wonder why that is. Is this due to a pure historic UNIX background (like KISS) or for plain portability or reduction of bloat? What are the reasons to not use C++ or any "higher level" languages for things like daemons? Thanks in advance! Update 1: For me using C++ usually is more convenient because of the fact that I have objects which have getter and setter methods and such. Plain C's "context" objects can be a real pain at some point - especially when you are used to object oriented programming. Yes, I'm aware that C++ is a superset of C, and that C code is basically C++. But that's not the point. ;)

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  • The Current State Of Serving a PHP 5.x App on the Apache, LightTPD & Nginx Web Servers?

    - by Gregory Kornblum
    Being stuck in a MS stack architecture/development position for the last year and a half has prevented me from staying on top of the world of open source stack based web servers recent evolution more than I would have liked to. However I am now building an open source stack based application/system architecture and sadly I do not have the time to give each of the above mentioned web servers a thorough test of my own to decide. So I figured I'd get input from the best development community site and more specifically the people who make it so. This is a site that is a resource for information regarding a specific domain and target audience with features to help users not only find the information but to also interact with one another in various ways for various reasons. I chose the open source stack for the wealth of resources it has along with much better offers than the MS stack (i.e. WordPress vs BlogEngine.NET). I feel Java is more in the middle of these stacks in this regard although I am not ruling out the possibility of using it in certain areas unrelated to the actual web app itself such as background processes. I have already come to the conclusion of using PHP (using CodeIgniter framework & APC), MySQL (InnoDB) and Memcached on CentOS. I am definitely serving static content on Nginx. However the 3 servers mentioned have no consensus on which is best for dynamic content in regards to performance. It seems LightTPD still has the leak issue which rules it out if it does, Nginx seems it is still not mature enough for this aspect and of course Apache tries to be everything for everybody. I am still going to compile the one chosen with as many performance tweaks as possible such as static linking and the likes. I believe I can get Apache to match the other 2 in regards to serving dynamic content through this process and not having it serve anything static. However during my research it seems the others are still worth considering. So with all things considered I would love to hear what everyone here has to say on the matter. Thanks!

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