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  • Anything wrong with this function for comparing floats?

    - by Michael Borgwardt
    When my Floating-Point Guide was yesterday published on slashdot, I got a lot of flak for my suggested comparison function, which was indeed inadequate. So I finally did the sensible thing and wrote a test suite to see whether I could get them all to pass. Here is my result so far. And I wonder if this is really as good as one can get with a generic (i.e. not application specific) float comparison function, or whether I still missed some edge cases. import static org.junit.Assert.assertFalse; import static org.junit.Assert.assertTrue; import org.junit.Test; public class NearlyEqualsTest { public static boolean nearlyEqual(float a, float b) { final float epsilon = 0.000001f; final float absA = Math.abs(a); final float absB = Math.abs(b); final float diff = Math.abs(a-b); if (a*b==0) { // a or b or both are zero // relative error is not meaningful here return diff < Float.MIN_VALUE / epsilon; } else { // use relative error return diff / (absA+absB) < epsilon; } } /** Regular large numbers - generally not problematic */ @Test public void big() { assertTrue(nearlyEqual(1000000f, 1000001f)); assertTrue(nearlyEqual(1000001f, 1000000f)); assertFalse(nearlyEqual(10000f, 10001f)); assertFalse(nearlyEqual(10001f, 10000f)); } /** Negative large numbers */ @Test public void bigNeg() { assertTrue(nearlyEqual(-1000000f, -1000001f)); assertTrue(nearlyEqual(-1000001f, -1000000f)); assertFalse(nearlyEqual(-10000f, -10001f)); assertFalse(nearlyEqual(-10001f, -10000f)); } /** Numbers around 1 */ @Test public void mid() { assertTrue(nearlyEqual(1.0000001f, 1.0000002f)); assertTrue(nearlyEqual(1.0000002f, 1.0000001f)); assertFalse(nearlyEqual(1.0002f, 1.0001f)); assertFalse(nearlyEqual(1.0001f, 1.0002f)); } /** Numbers around -1 */ @Test public void midNeg() { assertTrue(nearlyEqual(-1.000001f, -1.000002f)); assertTrue(nearlyEqual(-1.000002f, -1.000001f)); assertFalse(nearlyEqual(-1.0001f, -1.0002f)); assertFalse(nearlyEqual(-1.0002f, -1.0001f)); } /** Numbers between 1 and 0 */ @Test public void small() { assertTrue(nearlyEqual(0.000000001000001f, 0.000000001000002f)); assertTrue(nearlyEqual(0.000000001000002f, 0.000000001000001f)); assertFalse(nearlyEqual(0.000000000001002f, 0.000000000001001f)); assertFalse(nearlyEqual(0.000000000001001f, 0.000000000001002f)); } /** Numbers between -1 and 0 */ @Test public void smallNeg() { assertTrue(nearlyEqual(-0.000000001000001f, -0.000000001000002f)); assertTrue(nearlyEqual(-0.000000001000002f, -0.000000001000001f)); assertFalse(nearlyEqual(-0.000000000001002f, -0.000000000001001f)); assertFalse(nearlyEqual(-0.000000000001001f, -0.000000000001002f)); } /** Comparisons involving zero */ @Test public void zero() { assertTrue(nearlyEqual(0.0f, 0.0f)); assertFalse(nearlyEqual(0.00000001f, 0.0f)); assertFalse(nearlyEqual(0.0f, 0.00000001f)); } /** Comparisons of numbers on opposite sides of 0 */ @Test public void opposite() { assertFalse(nearlyEqual(1.000000001f, -1.0f)); assertFalse(nearlyEqual(-1.0f, 1.000000001f)); assertFalse(nearlyEqual(-1.000000001f, 1.0f)); assertFalse(nearlyEqual(1.0f, -1.000000001f)); assertTrue(nearlyEqual(10000f*Float.MIN_VALUE, -10000f*Float.MIN_VALUE)); } /** * The really tricky part - comparisons of numbers * very close to zero. */ @Test public void ulp() { assertTrue(nearlyEqual(Float.MIN_VALUE, -Float.MIN_VALUE)); assertTrue(nearlyEqual(-Float.MIN_VALUE, Float.MIN_VALUE)); assertTrue(nearlyEqual(Float.MIN_VALUE, 0)); assertTrue(nearlyEqual(0, Float.MIN_VALUE)); assertTrue(nearlyEqual(-Float.MIN_VALUE, 0)); assertTrue(nearlyEqual(0, -Float.MIN_VALUE)); assertFalse(nearlyEqual(0.000000001f, -Float.MIN_VALUE)); assertFalse(nearlyEqual(0.000000001f, Float.MIN_VALUE)); assertFalse(nearlyEqual(Float.MIN_VALUE, 0.000000001f)); assertFalse(nearlyEqual(-Float.MIN_VALUE, 0.000000001f)); assertFalse(nearlyEqual(1e20f*Float.MIN_VALUE, 0.0f)); assertFalse(nearlyEqual(0.0f, 1e20f*Float.MIN_VALUE)); assertFalse(nearlyEqual(1e20f*Float.MIN_VALUE, -1e20f*Float.MIN_VALUE)); } }

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  • NHibernate and hbm2dll update attribute

    - by michael lucas
    Hi, i'm using NHibernate with Sdf database. In my hibernate.cfg.xml file i've set: <property name="hbm2ddl.auto" value="update"/> But this does not seem to work at all. "Update" attribute should make NHibernate generate missing tables and columns during application launch, but it does not happen. If i want missing tables geenrated I have to set hbm2dll.auto property to "create" which is not an option for me since it drops existing db content beforehand. I experienced the same problem with PostgreSql problem. Am I missing something?

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  • PHP Strange error "0:". Possible Object syntax problem?

    - by Michael Stone
    I'm trying to transfer a site from one hosting company to another. I was using 000webhost until the client had hosting and a domain. Now that the client has their domain and hosting, using FatCow.com, I can not for the life of me, debug my PHP code. I'm not getting any errors. I have a successful DB connection. If you procedurally display data, it works, but when I try to use my original objects, something is breaking and just returns "0:". I have all errors on. On old server where the site worked: PHP Version 5.2.11 MySQL Version: 5.0.81 On new server where I get the "0:": PHP Version 5.2.12 MySQL Version 5.0.32 I've setup a test page to test just the output of the variables with the DB connection. Below is my code: <?php error_reporting(E_ALL); ini_set('display_errors', '1'); try { $link = mysql_connect('connectionstring', 'username', 'password'); if (!$link) { die('Could not connect: ' . mysql_error()); } else{ $db = mysql_select_db('a8210422_lit'); } if($db){ include_once('admin/classes/clsPOW.php'); include_once('admin/classes/clsProviders.php'); $pow = new POW(); $prov = new Providers(); $new = $pow->getNew(); $newAr = $new->val(); $get = $prov->getAll($newAr['providerId']); $getAr = $get->val(); $img = $getAr['image']; $name = $getAr['provider']; $desc = $getAr['description']; $zip = $getAr['zip']; $web = $getAr['link']; if($zip==0){ $zip = "Unavailable"; } print $img; print $name; print $desc; print $zip; print $web; } else{ print 'fail!'; } } //catch exception catch(Exception $e) { echo 'Message: ' .$e->getMessage(); } ?>

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  • Error copying file from app bundle

    - by Michael Chen
    I used the FireFox add-on SQLite Manager, created a database, which saved to my desktop as "DB.sqlite". I copied the file into my supporting files for the project. But when I run the app, immediately I get the error "Assertion failure in -[AppDelegate copyDatabaseIfNeeded], /Users/Mac/Desktop/Note/Note/AppDelegate.m:32 2014-08-19 23:38:02.830 Note[28309:60b] Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Failed to create writable database file with message 'The operation couldn’t be completed. (Cocoa error 4.)'.' First throw call stack: "... Here is the App Delegate Code where the error takes place -(void) copyDatabaseIfNeeded { NSFileManager *fileManager = [NSFileManager defaultManager]; NSError *error; NSString *dbPath = [self getDBPath]; BOOL success = [fileManager fileExistsAtPath:dbPath]; if (!success) { NSString *defaultDBPath = [[ [NSBundle mainBundle ] resourcePath] stringByAppendingPathComponent:@"DB.sqlite"]; success = [fileManager copyItemAtPath:defaultDBPath toPath:dbPath error:&error]; if (!success) NSAssert1(0, @"Failed to create writable database file with message '%@'.", [error localizedDescription]); } } I am very new to Sqlite, so I maybe I didn't create a database correctly in the FireFox Sqlite manager, or maybe I didn't "properly" copy the .sqlite file in? (I did check the target membership in the sqlite and it correctly has my project selected. Also, the .sqlite file names all match up perfectly.)

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  • Changing <object> height and width works in Chrome but not Firefox or IE. Why?

    - by Michael Hopkins
    I am making a site with two Youtube videos. These videos use the raw embed code from Youtube. The site's design doesn't work with any of the default Youtube sizes, so I am writing code to automatically resize the video. Here is my code. There will never be more than these two tags on the page, otherwise I'd do a better job selecting the videos. <script language='JavaScript' type='text/javascript'> var x=document.getElementsByTagName('object'); x.[0].width='350'; x.[0].height='350'; x.[1].width='350'; x.[1].height='350'; </script> For reference, here's a sample default Youtube embed that the code might alter: <object width="480" height="385"> <param name="movie" value="http://www.youtube-nocookie.com/v/zSgiXGELjbc&hl=en_US&fs=1&rel=0"></param> <param name="allowFullScreen" value="true"></param> <param name="allowscriptaccess" value="always"></param> <embed src="http://www.youtube-nocookie.com/v/zSgiXGELjbc&hl=en_US&fs=1&rel=0" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed> </object> In Chrome, the video players sit perfectly in a 350x350 box. In IE and FF (latest versions), the videos are the unchanged, normal size. I cannot find anything in Google that explans why this won't work. I have tried using setattribute, for loops, adjusting both and , single-quotes and double-quotes, etc. Any ideas what is going wrong?

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  • Using beautifulsoup to extract text between line breaks (e.g. <br /> tags)

    - by Michael Altman
    I have the following HTML that is within a larger document <br /> Important Text 1 <br /> <br /> Not Important Text <br /> Important Text 2 <br /> Important Text 3 <br /> <br /> Non Important Text <br /> Important Text 4 <br /> I'm currently using BeautifulSoup to obtain other elements within the HTML, but I have not been able to find a way to get the important lines of text between <br /> tags. I can isolate and navigate to each of the <br /> elements, but can't find a way to get the text in between. Any help would be greatly appreciated. Thanks.

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  • Custom class object in Initialization list

    - by Michael
    I have a class Bar: class Bar { public: Bar(void); ~Bar(void); }; And a class Foo that gets a reference to Bar object as a constructor parameter and needs to save it in a private member bar_ : class Foo { private: Bar& bar_; public: Foo(Bar& bar) : bar_(bar) {} ~Foo(void) {} }; This doesn't compile : overloaded member function not found in 'Parser' missing type specifier - int assumed. Note: C++ does not support default-int Now i suspect couple of things that i need to assure, the second error is for Bar& bar_; declaration in Foo. Do i need to use an explicit constructor when declaring bar_ ? I am interested in learning how the compiler works regarding this matter, so a detailed explanation would be highly appreciated. Thanks.

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  • Including a NSUserDefault password test in 1st Tab.m to load a loginView gives eror?

    - by Michael Robinson
    I have a name and password in NSUserDefaults for login. I have this in my 1stTab View.m class to test for presence and load a login/signup loginView.xib modally if there is no password or name stored in the app. Here is the pulling of the defaults: -(void)refreshFields { NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults]; usernameLabel.text = [defaults objectForKey:kUsernameKey]; passwordLabel.text = [defaults objectForKey:kPasswordKey]; { Here is the Test: - (void)viewDidAppear:(BOOL)animated { [self refreshFields]; [super viewDidAppear:animated]; if ([usernameLabel.text length] == 0 || [passwordLabel.text length] == 0) { LoginViewController * vc = [[[LoginViewController alloc] initWithNibName:@"LoginView" bundle:nil] autorelease]; [self presentModalViewController:vc animated: false]; } else { [[self tableView ]reloadData]; } } Thanks in advance, I'm getting this error in the console: * Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[ setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key usernameLabel.'

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  • Visual studio feature - commenting code Ctrl K - Ctrl C

    - by Michael
    I commented on this answer some time ago regarding how visual studio comments out code with // or /* */. I was thinking to revise the answer (to include my findings) but I had to test it first, which kind of confused me. My finding is that depending on where your marker is when you press Ctrl - K, Ctrl - C you will get either // or /* */. So I tried it out on the following code: [1] [2]FD_ZERO(&mFSet); FD_SET(user->mSender, &mFSet); timeval zeroTime = { 0, 0 }; int sel = select(0, NULL, &mFSet, NULL, &zeroTime); [3] if (sel == SOCKET_ERROR){ [5]return false; [4] } if (sel == 0){ [6] return false; [7] } The [x] is markerpositions. All [1] positions give // for all marked lines. However Start position End Position: gives: [2] [3] : /* */ [2] [4] : // [2] [5] : /* */ [2] [more than 5] : // [5] [6] : /* */ [5] [7] : // I guess it has to do with forward indentation (not backwards), that whenever code is indented more than the starting line you get // except when you haven't selected any text on the indented line ([2] [5]). But why the distinction? Why not use /* */ for when you start at [2] and // when you start at [1]?

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  • PHP check http referer for form submitted by AJAX, secure?

    - by Michael Mao
    Hi all: This is the first time I am working for a front-end project that requires server-side authentication for AJAX requests. I've encountered problems like I cannot make a call of session_start as the beginning line of the "destination page", cuz that would get me a PHP Warning : Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at C:\xampp\htdocs\comic\app\ajaxInsert Book.php:1) in C:\xampp\htdocs\comic\app\common.php on line 10 I reckon this means I have to figure out a way other than checking PHP session variables to authenticate the "caller" of this PHP script, and this is my approach : I have a "protected" PHP page, which must be used as the "container" of my javascript that posts the form through jQuery $.ajax(); method In my "receiver" PHP script, what I've got is: <?php define(BOOKS_TABLE, "books"); define(APPROOT, "/comic/"); define(CORRECT_REFERER, "/protected/staff/addBook.php"); function isRefererCorrect() { // the following line evaluates the relative path for the referer uri, // Say, $_SERVER['HTTP_REFERER'] returns "http://localhost/comic/protected/staff/addBook.php" // Then the part we concern is just this "/protected/staff/addBook.php" $referer = substr($_SERVER['HTTP_REFERER'], 6 + strrpos($_SERVER['HTTP_REFERER'], APPROOT)); return (strnatcmp(CORRECT_REFERER, $referer) == 0) ? true : false; } //http://stackoverflow.com/questions/267546/correct-http-header-for-json-file header('Content-type: application/json charset=UTF-8'); header('Cache-Control: no-cache, must-revalidate'); echo json_encode(array ( "feedback"=>"ok", "info"=>isRefererCorrect() )); ?> My code works, but I wonder is there any security risks in this approach? Can someone manipulate the post request so that he can pretend that the caller javascript is from the "protected" page? Many thanks to any hints or suggestions.

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  • Systematically resolve conflicting styles in css

    - by Frank Michael Kraft
    I have some stylesheets from different sources in my web project. I want to harmonize them. Some styles I need from the one, some from the other. Is there a tool or method how to systematically resolve style conflicts? I tried IE8 developer tool, and yes, it is possible to view conflicts at the level of each element. But I have many elemens, so if I do it element by element I think this takes too long. Theoretically there could be a tool that shows conflicts of two css files at design time?!? I think this would save me a lot of time.

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  • Problems with my HTML/CSS

    - by Michael
    Note below is my CSS. This is a three column website. my main content is in the center. The problems that I am having is that my main content does not adjust correctly to IE. It is fine in FF but not in IE. .columns3headers2 #mainContent1 { margin: 0 22% 0 24%; width: 570px; background-color: #DDDDDD; height: 370px; padding: 0, 10, 0, 0; border: groove } .columns3headers2 #mainContent2 { margin: 0 22% 0 24%; width: 570px; background-color: #DDDDDD; height: 190px; border: groove } I do not have much in my main content. <div id="mainContent1"> <h1> Main Content </h1> <div id="cround"> <h3>Absolute Value</h3> <ul> <li>Test 1</li> <li>Test 2</li> <li>Test 3</li> <li>test 4</li> </ul> </p> </div>

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  • Problems with a from CSS

    - by Michael
    I am trying to create a fairly basic form with in my maincontent. I am sure I am coding things incorrectly and it is driving me crazy. Note my code. I get extremely wide vertical spacing in IE 7 and the bacground color between the field sets does not work correctly. All is good in FF. My CSS is: fieldset { margin: 1.5em 0 0 0; padding: 0; border-style: none; border-top: 1px solid #BFBAB0; background-color: #FFFFFF; } legend { margin-left: 1em; color: #000000; font-weight: bold; } fieldset ol { padding: 1em 1em 0 1em; list-style: none; } fieldset li { padding-bottom: 1em; } fieldset.submit { border-style: none; } { var w = document.myform.mylist.selectedIndex; var selected_text = document.myform.mylist.options[w].text; alert(selected_text); } label em { display: block; color: #900; font-size: 85%; font-style: normal; text-transform: uppercase; } This is my html code. <div id="mainContent1"> <form name="myform"> <label for="mylist"><strong>Select an Account Type:</strong></label> <select name="mylist"><option value="traditional">Traditional Account</option> <option value="paperless">Paperless Account</option> </select> </form> <br /><a> </a> <form action="example.php"> <fieldset> <legend>Contact Details</legend> <ol> <li> <label for="name">Name:</label> <input id="name" name="name" class="text" type="text" /> <label for="name"> <em>required</em> </label> </li> <li> <label for="email">Email address:</label> <input id="email" name="email" class="text" type="text" /> <label for="name"> <em>required</em> </li> <li> <label for="phone">Telephone:</label> <input id="phone" name="phone" class="text" type="text" /> <label for="name"> <em>required</em> <ol> <li> <input id="option1" name="option1" class="checkbox" type="checkbox" value="1" /> <label for="option1">Savings</label> </li> <li> <input id="option2" name="option2" class="checkbox" type="checkbox" value="1" /> <label for="option2">Checkings</label> </li> </ol> </fieldset> <fieldset> <legend>Delivery Address</legend> <ol> <li> <label for="address1">Address 1:</label> <input id="address1" name="address1" class="text" type="text" /> </li> <li> <label for="city">City:</label> <input id="city" name="city" class="text" type="text" /> </li> <li> <label for="postcode">Zip Code:</label> <input id="postcode" name="postcode" class="text textSmall" type="text" /> </li> <li> <label for="country">Country:</label> <input id="country" name="country" class="text" type="text" /> </li> </ol> </fieldset> <fieldset class="submit"> <input class="submit" type="submit" value="Submit" /> </fieldset> <fieldset class="clear"> <input class="clear" type="clear" value="Submit" /> </fieldset> </form>

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  • JS function returning another function

    - by Michael
    I want to understand about variables, that has been used in returning function. This is example code Prototype = {} Prototype.F = { bind: function() { var args = arguments, __method = args.shift(), object = args.shift(); return function() { return __method.apply(object, args.concat(arguments)); } } } function ObjectA() { ... this.addListener = Prototype.F.bind(this.eventSource.addListener, this.eventSource); ... } var a = ObjectA(); a.addListener(this); // assuming 'this' here will point to some window object As I understand the returning function in F() is not evaluated until it's called in the last line. It's ok to accept. So addListener will hold a function body containing 'apply'. But what I don't understand, when addListener is called, what kind of parameters it is going to have? particularly _method and args will always be uninitialized?

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  • Perl : how to interrupt/resume loop by user hitting a key?

    - by Michael Mao
    Hi all: This is for debugging purpose. I've got a for loop that generates some output to Cygwin bash's CLI. I know that I can redirect outputs to text files and use Perl or even just a normal text editor to inspect the values printed out for a particular iteration, just feel that a bit painful. What I am now thinking is, to place a special subroutine inside the for loop, so that it would be "interrupted" at the beginning of each iteration, and Perl script should only resume to run after user/programmer hits a key(the Enter Key from keyboard?) In this way I can directly inspect the values printed out during each iteration. Is there a simple way to do this, without using additional libraries/CPAN ? Many thanks to the hints/suggestions in advance.

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  • DataBind and Postback

    - by Michael La Voie
    This is a general how does DataBind work questions... I have a simple page with a GridView that is bound (in the aspx code) to an ObjectDataSource. I can look in the Select() function called by the ObjectDataSource to see that it is called on the initial load and on every post back. I have some logic that happens on post backs that will affect the GridView's data, and I want to call GridView.DataBind() later on in the post back, after I've made some changes. Is there a way to prevent the automatic rebinding that happens on each post back? Does this mean I can't use an ObjectDataSource for this control?

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  • Rendering another Action without changing URL?

    - by Michael Stum
    I have this code in my Rails 3 controller: def index now = Time.now.utc.strftime("%m%d") redirect_to :action => "show", :id => now end def show begin @date = Time.parse("12#{params[:id]}") dbdate = params[:id] rescue ArgumentError @date = Time.now.utc dbdate = @date.strftime("%m%d") end @date = @date.strftime("%B %d") @events = Event.events_for_date(dbdate) end So basically index is just a specialized version of show, hence I want it to execute show, render the show.html.erb view - but I do not want to change the URL like redirect_to does. I have tried this approach: def index now = Time.now.utc.strftime("%m%d") params[:id] = now show render :action => "show" end Now, this works, but it just smells badly. I'm new to Ruby and Rails, so I just wonder if there is something fundamentally wrong or if there is a better way to do this?

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  • How to access the relative directory of a ASP.NET website?

    - by Michael Schilling
    I need to access a folder that will contain various text files for my web site. I'm using Visual Web Developer 2010 Express. I made a web site using visual basic. Here is the failing code: Dim fileName As String fileName = CurDir.ToString + fileName.Text + ".txt" FileOpen(1, fileName, OpenMode.Output) FileClose(1) CurDir.ToString is giving me strange directory path that isn't anywhere near where my website files are located. I need to be able to access the files in a folder inside of the WebSite1 folder without using C:\Users\..., but I'm at a loss on how to do that. Can anyone help me out?

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  • How to access valuestack objects within struts iterator?

    - by Monika Michael
    I have following code - <s:iterator value="reviews"> <img src="<s:property value="#request.restaurant.portalImage.url" />" /> <s:property value="user.firstName" /> <s:property value="user.lastName" /> <s:property value="rating" /> <s:property value="review" /> </s:iterator> reviews is a list of review objects which contain details of a review, such as rating and name of user. My problem is that i'm not able to access any of the objects present on the valuestack within the loop. Outside the loop <s:property value="#request.restaurant.portalImage.url" /> works correctly. But within the loop it prints null. AFAIK an iterator pushes it's collection on the valuestack so that all ognl expressions resolve against it. But I've used # which means I'm explicitly specifying the root object for resolution. Why is it still not working?

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  • NHibernate + Sql Compact + IoC - Connection Managment

    - by Michael
    When working with NHibernate and Sql Compact in a Windows Form application I am wondering what is the best practice for managing connections. With SQL CE I have read that you should keep your connection open vs closing it as one would typically do with standard SQL. If that is the case and your using a IoC, would you make your repositories lifetime be singletons so they exist forever or dispose of them after you perform a "Unit of Work". Also is there a way to determine the number of connections open to Sql CE?

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  • JPA Inheritance and Relations - Clarification question

    - by Michael
    Here the scenario: I have a unidirectional 1:N Relation from Person Entity to Address Entity. And a bidirectional 1:N Relation from User Entity to Vehicle Entity. Here is the Address class: @Entity public class Address implements Serializable { private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.AUTO) privat Long int ... The Vehicles Class: @Entity public class Vehicle implements Serializable { @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; @ManyToOne private User owner; ... @PreRemove protected void preRemove() { //this.owner.removeVehicle(this); } public Vehicle(User owner) { this.owner = owner; ... The Person Class: @Entity @Inheritance(strategy = InheritanceType.JOINED) @DiscriminatorColumn(name="PERSON_TYP") public class Person implements Serializable { @Id protected String username; @OneToMany(cascade = CascadeType.ALL, orphanRemoval=true) @JoinTable(name = "USER_ADDRESS", joinColumns = @JoinColumn(name = "USERNAME"), inverseJoinColumns = @JoinColumn(name = "ADDRESS_ID")) protected List<Address> addresses; ... @PreRemove protected void prePersonRemove(){ this.addresses = null; } ... The User Class which is inherited from the Person class: @Entity @Table(name = "Users") @DiscriminatorValue("USER") public class User extends Person { @OneToMany(mappedBy = "owner", cascade = {CascadeType.PERSIST, CascadeType.REMOVE}) private List<Vehicle> vehicles; ... When I try to delete a User who has an address I have to use orphanremoval=true on the corresponding relation (see above) and the preRemove function where the address List is set to null. Otherwise (no orphanremoval and adress list not set to null) a foreign key contraint fails. When i try to delete a user who has an vehicle a concurrent Acces Exception is thrown when do not uncomment the "this.owner.removeVehicle(this);" in the preRemove Function of the vehicle. The thing i do not understand is that before i used this inheritance there was only a User class which had all relations: @Entity @Table(name = "Users") public class User implements Serializable { @Id protected String username; @OneToMany(mappedBy = "owner", cascade = {CascadeType.PERSIST, CascadeType.REMOVE}) private List<Vehicle> vehicles; @OneToMany(cascade = CascadeType.ALL) @JoinTable(name = "USER_ADDRESS", joinColumns = @JoinColumn(name = "USERNAME") inverseJoinColumns = @JoinColumn(name = "ADDRESS_ID")) ptivate List<Address> addresses; ... No orphanremoval, and the vehicle class has used the uncommented statement above in its preRemove function. And - I could delte a user who has an address and i could delte a user who has a vehicle. So why doesn't everything work without changes when i use inheritance? I use JPA 2.0, EclipseLink 2.0.2, MySQL 5.1.x and Netbeans 6.8

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  • Why does instanceof seem to work in a static generic function sometimes?

    - by michael
    Greetings. This is my first post in this site. I thought that because of type erasure, one could not expect the following code to compile, and indeed, it did not compile on an earlier version of Eclipse. My understanding was that instanceof was a run-time operator and could not know about the generic type which would be, by run-time, compiled away: public static <E extends Comparable<? super E>> void SampleForQuestion(E e) { if ( !(e instanceof String) ) System.out.println("I am not a String"); else System.out.println("I am a String"); } However, I was surprised to see that one of your threads actually included some code like this in an answer, and my latest Eclipse (Galileo on Windows with JVM 1.6 rev 20) is perfectly happy with it -- and it works, too. (I did notice that someone said it worked on Eclipse but not in another IDE/JDK in that thread, but don't remember the specifics.) Can someone explain why it works, and more importantly, because I have to guide my students, whether it should be expected to work in the future. Thank you. (I hope the code formatting comes through correctly - it looks indented correctly from my perspective and there are no tabs.)

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