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  • Mapping many-to-many association table with extra column(s)

    - by user635524
    My database contains 3 tables: User and Service entities have many-to-many relationship and are joined with the SERVICE_USER table as follows: USERS - SERVICE_USER - SERVICES SERVICE_USER table contains additional BLOCKED column. What is the best way to perform such a mapping? These are my Entity classes @Entity @Table(name = "USERS") public class User implements java.io.Serializable { private String userid; private String email; @Id @Column(name = "USERID", unique = true, nullable = false,) public String getUserid() { return this.userid; } .... some get/set methods } @Entity @Table(name = "SERVICES") public class CmsService implements java.io.Serializable { private String serviceCode; @Id @Column(name = "SERVICE_CODE", unique = true, nullable = false, length = 100) public String getServiceCode() { return this.serviceCode; } .... some additional fields and get/set methods } I followed this example http://giannigar.wordpress.com/2009/09/04/m ... using-jpa/ Here is some test code: User user = new User(); user.setEmail("e2"); user.setUserid("ui2"); user.setPassword("p2"); CmsService service= new CmsService("cd2","name2"); List<UserService> userServiceList = new ArrayList<UserService>(); UserService userService = new UserService(); userService.setService(service); userService.setUser(user); userService.setBlocked(true); service.getUserServices().add(userService); userDAO.save(user); The problem is that hibernate persists User object and UserService one. No success with the CmsService object I tried to use EAGER fetch - no progress Is it possible to achieve the behaviour I'm expecting with the mapping provided above? Maybe there is some more elegant way of mapping many to many join table with additional column?

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  • Textbox extends outside of the grid cell in .Net 4.0 (but not in 3.5)

    - by Bryant
    There seems to be a change in behaviour between .Net 3.5 and .Net 4.0. If I define a window as: <Window x:Class="WpfApplication1.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="MainWindow" Height="350" Width="500" > <Grid> <Grid.ColumnDefinitions> <ColumnDefinition MinWidth="300" /> <ColumnDefinition /> </Grid.ColumnDefinitions> <TextBox Grid.Column="1" ScrollViewer.CanContentScroll="True" ScrollViewer.HorizontalScrollBarVisibility="Auto" Text="abc abc abc abc abc abc abc abc abcabc abc abcabc abc abc abc abc abc" /> </Grid> </Window> In .Net 3.5 the textbox correctly contains itself within the grid cell but in .Net 4.0 it extends beyond the cell and so gets clipped. This only happens if the MinWidth of the first column is greater than 50% of the overall width. Does anyone know how to get 4.0 to exhibit the same behavior as 3.5?

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  • How do I make a lock that allows only ONE thread to read from the resource ?

    - by mare
    I have a file that holds an integer ID value. Currently reading the file is protected with ReaderWriterLockSlim as such: public int GetId() { _fileLock.EnterUpgradeableReadLock(); int id = 0; try { if(!File.Exists(_filePath)) CreateIdentityFile(); FileStream readStream = new FileStream(_filePath, FileMode.Open, FileAccess.Read); StreamReader sr = new StreamReader(readStream); string line = sr.ReadLine(); sr.Close(); readStream.Close(); id = int.Parse(line); return int.Parse(line); } finally { SaveNextId(id); // increment the id _fileLock.ExitUpgradeableReadLock(); } } The problem is that subsequent actions after GetId() might fail. As you can see the GetId() method increments the ID every single time, disregarding what happens after it has issued an ID. The issued ID might be left hanging (as said, exceptions might occur). As the ID is incremented, some IDs might be left unused. So I was thinking of moving the SaveNextId(id) out, remove it (the SaveNextId() actually uses the lock too, except that it's EnterWriteLock). And call it manually from outside after all the required methods have executed. That brings out another problem - multiple threads might enter the GetId() method before the SaveNextId() gets executed and they might all receive the same ID. I don't want any solutions where I have to alter the IDs after the operation, correcting them in any way because that's not nice and might lead to more problems. I need a solution where I can somehow callback into the FileIdentityManager (that's the class that handles these IDs) and let the manager know that it can perform the saving of the next ID and then release the read lock on the file containing the ID. Essentialy I want to replicate the relational databases autoincrement behaviour - if anything goes wrong during row insertion, the ID is not used, it is still available for use but it also never happens that the same ID is issued. Hopefully the question is understandable enough for you to provide some solutions..

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  • C#: Thread.CurrentThread.CurrentUICulture not working consistently

    - by xTRUMANx
    I've been working on a pet project on the weekends to learn more about C# and have encountered an odd problem when working with localization. To be more specific, the problem I have is with System.Threading.Thread.CurrentThread.CurrentUICulture. I've set up my app so that the user can quickly change the language of the app by clicking a menu item. The menu item in turn, saves the two-letter code for the language (e.g. "en", "fr", etc.) in a user setting called 'Language' and then restarts the application. Properties.Settings.Default.Language = "en"; Properties.Settings.Default.Save(); Application.Restart(); When the application is started up, the first line of code in the Form's constructor (even before InitializeComponent()) fetches the Language string from the settings and sets the CurrentUICulture like so: public Form1() { Thread.CurrentThread.CurrentUICulture = new CultureInfo(Properties.Settings.Default.Language); InitializeComponent(); } The thing is, this doesn't work consistently. Sometimes, all works well and the application loads the correct language based on the string saved in the settings file. Other times, it doesn't, and the language remains the same after the application is restarted. At first I thought that I didn't save the language before restarting the application but that is definitely not the case. When the correct language fails to load, if I were to close the application and run it again, the correct language would come up correctly. So this implies that the Language string has been saved but the CurrentUICulture assignment in my form constructor is having no effect sometimes. Any help? Is there something I'm missing of how threading works in C#? This could be machine-specific, so if it makes any difference I'm using Pentium Dual-Core CPU.

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  • Grep without storing search to the "/ register in Vim

    - by Phro
    In my .vimrc I have a mapping that makes a line of text 'title capitalized': noremap <Leader>at :s/\v<(.)(\w{2,})/\u\1\L\2/g<CR> However, whenever I run this function, it highlights every word that is at least three characters long in my entire document. Of course I could get this behaviour to stop simply by appending :nohlsearch<CR> to the end of the mapping, but this is more of an awkward hack that still avoids a bigger problem: The last search has been replaced by \v<(.)(\w{2,}). Is there any way to use the search commands in Vim without storing the last search in the "/ register; a 'silent' search of sorts? That way, after running this title-making command, I can still use my previous search to navigate the document using n, N, etc. Edit Using @brettanomyces' answer, I found that simply setting the mapping: noremap <Leader>at :call setline(line('.'),substitute(getline('.'), '\v<(.)(\w{2,})', '\u\1\L\2', 'g'))<CR> will successfully perform the substitution without storing the searched text into the / register.

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  • MVC JsonResult with the [Authorize] attribute going to Logon but not displaying the view

    - by likestoski
    I am seeing odd behavior with MVC 3 methods that return a JsonResult when used with the Authorize attribute. What looks like happens is the Authorize is correctly evaluated when I am not logged in but instead of redirecting to the logon form the Json response is the logon form. Is there an addition attribute that directs the response to not return a value but instead redirect the user to the logon form, preferebly with the correct returnUrl value? What I did as a demo was to setup a new MVC3 site and added AspNetMembership to my DB using the aspnet_regsql.exe command. All that is setup and logging me in correctly. The behavior of the JsonResult doesn't seem right and I'm hoping I have just missed an attribute to make it work properly. Any help is greatly appreciated, thanks in advance. Here is the Account Controller (leaving out the Post action which is not part of this question). public class AccountController : Controller { public ActionResult LogOn() { return View(); } [Authorize] public JsonResult AuthorizedAction() { return Json("Only returns if I am authorized"); } } Here is the Html markup: <script src="@Url.Content("~/Scripts/jquery-ui-1.8.11.min.js")" type="text/javascript"></script> <script type="text/javascript"> $(document).ready(function () { $("#btnTest").click(function () { $.ajax({ type: "POST", url: "Account/AuthorizedAction", data: {}, success: function (result) { $("#testMe").html(result); }, error: function (result) { $("#testMe").html('Something broke in the ajax request'); } }); }); }); </script> <input type="button" id="btnTest" value="Test me" /> <div id="testMe">I have initial text</div> The Result: 1) When logged in I get 'Only returns if I am authorized' in my test div 2) When not logged and I have a break point in my Logon() method I see this value Request["returnUrl"] "/Account/AuthorizedAction" The test div I have displays the logon form :) this seems like I'm just not handling this properly.

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  • Visual C++ function suddenly 170 ms slower (4x longer)

    - by Mikael
    For the past few months I've been working on a Visual C++ project to take images from cameras and process them. Up until today this has taken about 65 ms to update the data but now it has suddenly increased significantly. What happens is: I launch my program and for the first 30 or so iterations it performs as expected, then suddenly the loop time increases from 65 ms to 250 ms. The odd thing is, after timing each function I found out that the part of the code which is causing the slowdown is fairly basic and has not been modified in over a month. The data which goes into it is unchanged and identical every iteration but the execution time which is initially less than 1 ms suddenly increases to 170 ms while the rest of the code is still performing as expected (time-wise). Basically, I am calling the same function over and over, for the first 30 calls it performs as it should, after that it slows down for no apparent reason. It might also be worth noting that it is a sudden change in execution time, not a gradual increase. What could be causing this? The code is leaking some memory (~50 kb/s) but not nearly enough to warrant a sudden 4x slowdown. If anyone has any ideas I'd love to hear them!

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  • Common methods/implementation across multiple WCF Services

    - by Rob
    I'm looking at implementing some WCF Services as part of an API for 3rd parties to access data within a product I work on. There are currently a set of services exposed as "classic" .net Web Services and I need to emulate the behaviour of these, at least in part. The existing services all have an AcquireAuthenticationToken method that takes a set of parameters (username, password, etc) and return a session token (represented as a GUID), which is then passed in on calls to any other method (There's also a ReleaseAuthenticationToken method, no guesses needed as to what that does!). What I want to do is implement multiple WCF services, such as: ProductData UserData and have both of these services share a common implementation of Acquire/Release. From the base project that is created by VS2k8, it would appear I will start with, per service: public class ServiceName : IServiceName { } public interface IServiceName { } Therefore my questions would be: Will WCF tolerate me adding a base class to this, public class ServiceName : ServiceBase, IServiceName, or does the fact that there's an interface involved mean that won't work? If "No it won't work" to Question 1, could I change IServiceName so it extends another interface, IServiceBase, thus forcing the presence of Acquire/Release methods, but then having to supply the implementation in each service. Are 1 and 2 both really bad ideas and there's actually a much better solution that, knowing next to nothing about WCF, I just haven't thought of?

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  • Calculations on the iteration count in for loop in Ruby 1.8.7

    - by user1805035
    I was playing around with Ruby and Latex to create a color coding set. I'm more than a novice with C++, but haven't looked at Ruby until now. So, still learning a lot of coding. I have the following block of code below. When attempting to run this, band1 = 1e+02. I've tried band1 = (BigDecimal(i) * 100).to_f thinking maybe there was some odd floating point issue. This is just me trying anything though as an integer multiplied by an integer should create an integer, if I'm still thinking correctly. I've tried a variety of other things as well (things that I can do in C++, but this ain't C++), but to no avail. (1..9).each do |i| #Band 1 (0..9).each do |j| #Band 2 (0..11).each do |k| #Band 3 #Band 3 Start #these are the colors of the resistor bands b1 = $c_band12[i] b2 = $c_band12[j] b3 = $c_band3[k] b4 = "Gold" oms = ((i*100) + (j*10)) * $mult[k] band1 = i*100 band2 = j band3 = $mult[k] end end end Not sure what I'm missing. Should I be using .each_with_index through these iterations? I've tried this: (1..9).each_with_index {|i, indexi| #Band 1 (0..9).each_with_index {|j, indexj| #Band 2 (0..11).each_with_index {|k, indexk| #Band 3 #Band 3 Start #these are the colors of the resistor bands b1 = $c_band12[i] b2 = $c_band12[j] b3 = $c_band3[k] b4 = "Gold" oms = ((i*100) + (j*10)) * $mult[k] band1 = indexk * 100 and I get the same answer. I can't see why 1*100 should equate to such a large number? Thank you, AT

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  • Weird Rails database errors

    - by Jason Swett
    I've had some trouble getting my Rails app to connect to PostgreSQL so I decided to just say screw it and use SQLite for now. (I'm using the tutorial here: http://guides.rubyonrails.org/getting_started.html) I started a BRAND NEW, fresh Rails app from this tutorial. When I visit my app in the browser after deleting public/index.html, I get this the first time: Please install the pg adapter: `gem install activerecord-pg-adapter` (no such file to load -- active_record/connection_adapters/pg_adapter) That's odd to me because I'm not mentioning PostgreSQL anywhere. Here's my databases.yml: # SQLite version 3.x # gem install sqlite3-ruby (not necessary on OS X Leopard) development: adapter: sqlite3 database: db/development.sqlite3 pool: 5 timeout: 5000 # Warning: The database defined as "test" will be erased and # re-generated from your development database when you run "rake". # Do not set this db to the same as development or production. test: adapter: sqlite3 database: db/test.sqlite3 pool: 5 timeout: 5000 production: adapter: sqlite3 database: db/production.sqlite3 pool: 5 timeout: 5000 To make things more confusing, I only get that "pg adapter" error on the first load. For every subsequent page request, I get this error: ActiveRecord::ConnectionNotEstablished So even though I removed all mention of PostgreSQL, I'm still getting errors. What could be going on?

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  • How to prevent onclick statements from being executed?

    - by ryanli
    I want to use an event listener for preventing the onclick statement of a submit button, however, using event.preventDefault() doesn't work as intended. The code is like this: <?xml version="1.0" encoding="utf-8"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <script type="application/x-javascript"> function addListener() { document.getElementById("submit").addEventListener("click", function(ev) { alert("listener"); ev.preventDefault(); }, false); } </script> <title></title> </head> <body onload="addListener();"> <form id="form" method="post" target=""> <input type="submit" id="submit" onclick="alert('onclick')" value="test" /> </form> </body> </html> The expected behaviour is only "listener" will be alerted, but in practice (Firefox 3.7a5pre), "onclick" and "listener" are both alerted, in the given order. It seems that onclick is being executed before the listener, so event.preventDefault() doesn't work. Is there a way to prevent onclick from being executed?

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  • my web service works locally but, not when it is deployed

    - by rogdawg
    When I deploy my web service, I get the following error: There is no build provider registered for the extension '.svc'. You can register one in the section in machine.config or web.config. Make sure is has a BuildProviderAppliesToAttribute attribute which includes the value 'Web' or 'All'. I found one thread (http://forums.asp.net/t/1228638.aspx) that suggested a solution but, I can not get it to work. If I make the changes to my web config file as suggested in the thread, I then get a configuration error. One odd thing is that, if I check the machine.config file on my machine, located at C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\CONFIG\machine.config, I don't see any of the config settings described in the thread. As a matter of fact, there is no mention of "compilation" or "buildProviders" at all. The on-line documents I have found regarding BuildProviderAppliesToAttribute have not been of any help. Thanks in advance for any advice you can give. Here is my entire config file listing: <?xml version="1.0"?>

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  • PHP download page: file_exists() returns true, but browser returns 'page not found'

    - by Chris
    I'm using PHP for a file download page. Here's a snippet of the problem code: if (file_exists($attachment_location)) { header($_SERVER["SERVER_PROTOCOL"] . " 200 OK"); header("Cache-Control: public"); // needed for i.e. header("Content-Type: application/zip"); header("Content-Transfer-Encoding: Binary"); header("Content-Length:".filesize($attachment_location)); header("Content-Disposition: attachment; filename=file.zip"); readfile($attachment_location); die("Hooray"); } else { die("Error: File not found."); } This code works absolutely fine when testing locally, but after deploying to the live server the browser returns a 'Page not found' error. I thought it might be an .htaccess issue, but all .htaccess files on the live server are identical to their local counterparts. My next guess would be the live server's PHP configuration, but I have no idea what PHP setting might cause this behaviour. The file_exists() function always returns true - I've checked this on the live server and it's always correctly picking up the file, its size etc., so it does have a handle on the file. It just won't perform the download! The main site is a Wordpress site, but this code isn't part of a Wordpress page - it's in a standalone directory within the site root. UPDATE: is_file() and is_readable() are both returning true for the file, so that's not the problem. The specific line that is causing the problem is: readfile($attachment_location) Everything up until that point is super happy.

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  • Can anyone provide a good "idiot's guide" to creating an installer in VS2008 (C#) Pro?

    - by paxdiablo
    I have Visual C# 2008 Professional and have developed the first half of a C# application (console mode) with the second half in progress now (GUI). I'm looking for an easy path to creating an installer for it. What are the steps that need to be taken to produce a professional installer? There's a similar question here regarding the Express edition but I have Pro, and I would like as much as possible to stick with just the standard VS stuff (if you think you can convince me that a third party installer creator is much better than a VS-only solution, give it a shot, by all means). Keep in mind that I have no interest in upgrading to VS2010 yet, even if it's a hundred times easier to create an installer. That can come later, when the revenue starts rolling in :-) Also be aware that the GUI component of this application is a totally separate executable from the console part. The console part is a simple "open file 1, do some work on it, write file 2" type and the GUI is a fairly standard "open file, do some stuff" beast so there's no tricky or wildly undocumented behaviour happening. Basically, I'm looking for (at least) the following: professional looking installer. ability to specify where the application files go. changes to the registry to allow double-clicks on my file extension to open the GUI app with the file as an argument. needs to install everything required (my stuff, .Net if required, and so on).

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  • Faster or more memory-efficient solution in Python for this Codejam problem.

    - by jeroen.vangoey
    I tried my hand at this Google Codejam Africa problem (the contest is already finished, I just did it to improve my programming skills). The Problem: You are hosting a party with G guests and notice that there is an odd number of guests! When planning the party you deliberately invited only couples and gave each couple a unique number C on their invitation. You would like to single out whoever came alone by asking all of the guests for their invitation numbers. The Input: The first line of input gives the number of cases, N. N test cases follow. For each test case there will be: One line containing the value G the number of guests. One line containing a space-separated list of G integers. Each integer C indicates the invitation code of a guest. Output For each test case, output one line containing "Case #x: " followed by the number C of the guest who is alone. The Limits: 1 = N = 50 0 < C = 2147483647 Small dataset 3 = G < 100 Large dataset 3 = G < 1000 Sample Input: 3 3 1 2147483647 2147483647 5 3 4 7 4 3 5 2 10 2 10 5 Sample Output: Case #1: 1 Case #2: 7 Case #3: 5 This is the solution that I came up with: with open('A-large-practice.in') as f: lines = f.readlines() with open('A-large-practice.out', 'w') as output: N = int(lines[0]) for testcase, i in enumerate(range(1,2*N,2)): G = int(lines[i]) for guest in range(G): codes = map(int, lines[i+1].split(' ')) alone = (c for c in codes if codes.count(c)==1) output.write("Case #%d: %d\n" % (testcase+1, alone.next())) It runs in 12 seconds on my machine with the large input. Now, my question is, can this solution be improved in Python to run in a shorter time or use less memory? The analysis of the problem gives some pointers on how to do this in Java and C++ but I can't translate those solutions back to Python.

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  • "Permission denied" with Internet Explorer and jQuery

    - by rallex
    I try to do an AJAX call with jQuery and $.post in Internet Explorer, but all I get is an error saying "Permission denied". The problem is kinda weird since it occurs only when I access a page after I was on any other page. For instance I type the URL in the adress line and let IE load the page. Then I click on a button so the script should start loading JSON data. (The script providing the data lies on the same server and I access it with a relative URL, so using a different domain is not the problem here. Even tried to use a absolute URL with the same host part.) But when I refresh the page then and try it again it works! Same thing when I come to that page from another page. At first nothing works, but when I click "refresh" everything is fine. IE gives me the error message "Permission denied" while in every other browser I don't notice this behaviour. Since I have tried many things and still cannot imagine where the problem lies I'd like to ask you what you think the problem might be?

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  • HTML form with single text field + preventing postback in Internet Explorer

    - by SudheerKovalam
    I have noticed a rather strange behaviour in IE. I have a HTML form with a single input text field and a submit button On Submit click I need to execute a client side JavaScript function that does the necessary. Now when I want to prevent the postback in the text field (on enter key press) I have added a key press JavaScript function that looks like this: <input type=text onkeypress="return OnEnterKeyPress(event)" /> function OnEnterKeyPress(event) { var keyNum = 0; if (window.event) // IE { keyNum = event.keyCode; } else if (event.which) // Netscape/Firefox/Opera { keyNum = event.which; } else return true; if (keyNum == 13) // Enter Key pressed, then start search, else do nothing. { OnButtonClick(); return false; } else return true; } Strangly this doesn't work. But if I pass the text field to the function : <input type=text onkeypress="return OnEnterKeyPress(this,event);" /> function OnEnterKeyPress(thisForm,event) { var keyNum = 0; if (window.event) // IE { keyNum = event.keyCode; } else if (event.which) // Netscape/Firefox/Opera { keyNum = event.which; } else return true; if (keyNum == 13) // Enter Key pressed, then start search, else do nothing. { OnButtonClick(); return false; } else return true; } I am able to prevent the postback. Can anyone confirm what is exactly happening here?? the HTML form has just one text box and a submit button The resultant o/p of the JavaScript function executed on submit is displayed in a HTML text area in a separate div.

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  • How do I stop events from bubbling/multiple events with animated mouseovers?

    - by Kurucu
    I noticed a lot of JQuery answers on this, but I'm using MooTools... I have a Table of Contents which uses CSS Fixed positioning to keep it off to the left side, except for 20 pixels. The user hovers their cursor over the 20 pixels, which fires the DIV's mouseover event and the ToC slides fully into the page. When the cursor leaves, the ToC slides back to where it was. $('frameworkBreakdown').addEvents({ 'mouseover': function(event){ event = new Event(event); $('frameworkBreakdown').tween('left', 20); event.stop; }, 'mouseout': function(event){ event = new Event(event); $('frameworkBreakdown').tween('left', (10 - $('frameworkBreakdown').getStyle('width').toInt()) ); event.stop; } }); This works well (aside from unrelated issues) except that when I move the mouse on the DIV it starts to jitter, presumably because the contents of the DIV are also firing the event, or the event refires as the mouse tracks over the DIV. How can I stop this behaviour from occuring? Is there a standard method, or do I use some sort of nast global variable that determines whether effects are in action, and thus ignore the event?

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  • Disabled input text color

    - by Incidently
    Hi The simple HTML below displays differently in Firefox and WebKit-based browsers (I checked in Safari, Chrome and iPhone). In Firefox both border and text have the same color (#880000), but in Safari the text gets a bit lighter (as if it had some transparency applied to it). Can I somehow fix this (remove this transparency in Safari)? UPDATE: Thank you for your answers. I don't need this for my work anymore (instead of disabling, I'm replacing input elements with styled div elements), but I'm still curious why this happens and if there is any way to control this behaviour ... <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title></title> <style type="text/css"> input:disabled{ border:solid 1px #880000; background-color:#ffffff; color:#880000; } </style> </head> <body> <form action=""> <input type="text" value="disabled input box" disabled="disabled"/> </form> </body> </html>

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  • Why won't JPA delete owned entities when the owner entity loses the reference to them?

    - by Nick
    Hi! I've got a JPA entity "Request", that owns a List of Answers (also JPA entities). Here's how it's defined in Request.java: @OneToMany(cascade= CascadeType.ALL, mappedBy="request") private List<Answer> answerList; And in Answer.java: @JoinColumn(name = "request", referencedColumnName="id") @ManyToOne(optional = false) private Request request; In the course of program execution, the Request's List of Answers may have Answers added or removed from it, or the actual List object may be replaced. My problem is thus: when I merge a Request to the database, the Answer objects that used to be in the List are kept in the database -- that is, Answer objects that the Request no longer holds a reference to (indirectly, via a List) are not deleted. This is not the behaviour I desire, as if I merge a Request to the database, and then fetch it again, its Answers List may not be the same. Am I making some programming mistake? Is there an annotaion or setting that will ensure that the Answers in the database are exactly the Answers in the Request's List? A solution is to keep references to the original Answers List and then use the EntityManager to remove each old Answer before merging the Request, but it seems like there should be a cleaner way. Thank you!

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  • Java: multi-threaded maps: how do the implementations compare?

    - by user346629
    I'm looking for a good hash map implementation. Specifically, one that's good for creating a large number of maps, most of them small. So memory is an issue. It should be thread-safe (though losing the odd put might be an OK compromise in return for better performance), and fast for both get and put. And I'd also like the moon on a stick, please, with a side-order of justice. The options I know are: HashMap. Disastrously un-thread safe. ConcurrentHashMap. My first choice, but this has a hefty memory footprint - about 2k per instance. Collections.sychronizedMap(HashMap). That's working OK for me, but I'm sure there must be faster alternatives. Trove or Colt - I think neither of these are thread-safe, but perhaps the code could be adapted to be thread safe. Any others? Any advice on what beats what when? Any really good new hash map algorithms that Java could use an implementation of? Thanks in advance for your input!

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  • While in a transaction, how can reads to an affected row be prevented until the transaction is done?

    - by Mahn
    I'm fairly sure this has a simple solution, but I haven't been able to find it so far. Provided an InnoDB MySQL database with the isolation level set to SERIALIZABLE, and given the following operation: BEGIN WORK; SELECT * FROM users WHERE userID=1; UPDATE users SET credits=100 WHERE userID=1; COMMIT; I would like to make sure that as soon as the select inside the transaction is issued, the row corresponding to userID=1 is locked for reads until the transaction is done. As it stands now, UPDATEs to this row will wait for the transaction to be finished if it is in process, but SELECTs simply will read the previous value. I understand this is the expected behaviour in this case, but I wonder if there is a way to lock the row in such a way that SELECTs will also wait until the transaction is finished to return the values? The reason I'm looking for that is that at some point, and with enough concurrent users, it could happen that while the previous transaction is in process someone else reads the "credits" to calculate something else. Ideally the code run by that someone else should wait for the transaction to finish to use the new value, because otherwise it could lead to irreversible desync issues. Note that I don't want to lock the entire table for reads, just the specific row. Also, I could add a boolean "locked" field to the tables and set it to 1 every time I'm starting a transaction but I don't really feel this is the most elegant solution here, unless there is absolutely no other way to handle this through mysql directly.

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  • Android: stop activity appearing when an app is reopened?

    - by AP257
    Hi there In Android, I have some code to check whether the user has GPS switched on, and launch the Settings for them to turn it on if they don't. It looks like this: private void buildAlertMessageNoGps() { final AlertDialog.Builder builder = new AlertDialog.Builder(this); builder .setMessage( "Your GPS seems to be disabled - you need it to get a location fix. Turn it on now?") .setCancelable(false).setPositiveButton("Yes", new DialogInterface.OnClickListener() { public void onClick( @SuppressWarnings("unused") final DialogInterface dialog, @SuppressWarnings("unused") final int id) { Intent j = new Intent(); j.setAction("android.settings.LOCATION_SOURCE_SETTINGS"); startActivity(j); } }).setNegativeButton("No", new DialogInterface.OnClickListener() { public void onClick(final DialogInterface dialog, @SuppressWarnings("unused") final int id) { dialog.cancel(); } }); final AlertDialog alert = builder.create(); alert.show(); } However, I'm finding that if the user opens the Settings, turns GPS on, then carries on using the app as normal, there is an odd problem. Often, when the user reopens the app, the Settings are at the front. How can I set them so they don't keep reappearing? I wonder if I should be using the CLEAR_TOP flag or something similar... I've tried looking at the docs for the Activity flags but find them a bit confusing. Anyone know?

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  • Why is no encoding set in reponse by tomcat? How can I deal with it?

    - by Dishayloo
    I had recently a problem with encoding of websites generated by servlet, that occured if the servlets were deployed under tomcat, but not under jetty. I did a little bit of research about it and simplified the problem to the following servlet: public class TestServlet extends HttpServlet implements Servlet { @Override public void service(HttpServletRequest request, HttpServletResponse response) throws IOException { response.setContentType("text/plain"); Writer output = response.getWriter(); output.write("öäüÖÄÜß"); output.flush(); output.close(); } } If I deploy this under Jetty and direct the browser to it, it returns the expected result. The data is returned as ISO-8859-1 and if I take a look into the headers, then Jetty returns: Content-Type: text/plain; charset=iso-8859-1 The browser detects the encoding from this header. If I deploy the same servlet in a tomcat, the browser shows up strange characters. But Tomcat also returns the data as ISO-8859-1, the difference is, that no header tells about it. So the browser has to guess the encoding, and that goes wrong. My question is, is that behaviour of tomcat correct or a bug? And if it is correct, how can I avoid this problem? Sure, I can always add response.setCharacterEncoding("UTF-8"); to the servlet, but that means I set a fixed encoding, that the browser might or might not understand. The problem is more relevant, if no browser but another service accesses the servlet. So how I should deal with the problem in the most flexible way?

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  • C++ new memory allocation fragmentation

    - by tamulj
    I was trying to look at the behavior of the new allocator and why it doesn't place data contiguously. My code: struct ci { char c; int i; } template <typename T> void memTest() { T * pLast = new T(); for(int i = 0; i < 20; ++i) { T * pNew = new T(); cout << (pNew - pLast) << " "; pLast = pNew; } } So I ran this with char, int, ci. Most allocations were a fixed length from the last, sometimes there were odd jumps from one available block to another. sizeof(char) : 1 Average Jump: 64 bytes sizeof(int): 4 Average Jump: 16 sizeof(ci): 8 (int has to be placed on a 4 byte align) Average Jump: 9 Can anyone explain why the allocator is fragmenting memory like this? Also why is the jump for char so much larger then ints and a structure that contains both an int and char.

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