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• Threading in Android

  - by virsir

  I am currently developing Android app, it needs download content from internet. I use thread to do that and then call runOnUiThread method to update GUI. I placed a refresh menu on it, if user tried to refresh the content, the download thread will be created and started. The problem is that how can I control the thread order, I need to accept the latest request's response and abandon previous thread requests if there were some other requests still running because the request parameters may have been changed by user. Currently I was using a threadId to do this thing, when a thread finished, it will check its threadId, if it was the latest recored one, it then takes control and render the response. My question is that is there any other proper better solution for this? Do I need to stop threads when user exit the app? I remember that some book said that do not try stop thread manually and wait itself finish is a good practice, is that true? Should I stop them by calling "stop" or "interrupt" method? I read some documents around threading in Android and found the class HandlerThread, what is it? In what kind of situation I need to use it?

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• Stop Rewrite htaccess create random pages

  - by Vistol

  Recently I saw in my Webmaster tools that some random sites are linking to my site. Actually this is not an big issue. The issue comes when the pages that are linked are not real pages because of my httaccess file. This is the htaccess code that Im running: <pre> #Options +FollowSymLinks RewriteEngine on RewriteRule ^([^/\.]+)/?$ index.php?id=$1 [L] RewriteRule ^([0-9]+)/(.*)$ index.php?id=$1 [L] </pre> So the real URLs would be: mysite.com/folder/999/TITLE-OR-NAME But cecause I only check the 1st folder ($1) which is an I numberD, this htaccess file is allowing hackers linking to my site with random URLs like: mysite.com/folder/999/TITLE-OR-NAME1 mysite.com/folder/999/TITLE-OR-NAME2 mysite.com/folder/999/TITLE-OR-NAME3 mysite.com/folder/999/TITLE-OR-NAME4 mysite.com/folder/999/TITLE-OR-NAME5 The worst part comes when google tells me that I am duplicating content!!! Actually I am not duplicating content, the htaccess is duplicating it for me. And yes I know, Im a bad newbie programmer but Id really appreciate your help with this cause Im struggling to find a solution but it never. Thank you very much for all your support to this newbie :)

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• j_security_check to SSO in different module under Oracle App Server?

  - by thebearinboulder

  I have an existing j2ee application running on Oracle App Server. It is targeted towards paying customers so the content is secured and a SSO module properly intercepts all requests for secured content. Now the company is adding a unbranded public-facing module with a number of unsecured pages. At one point the user is expected to register for a free account and log in to proceed further. Think doctors adding a public-facing site with information for potential patients, or lawyers adding a public-facing site with information for potential clients. There's some information on the session and the usual approach would be to authenticate the user, persist the session information using the now-known user id, invalidate the existing session (to prevent certain types of attacks), the reload the session information before returning to the user. I can't just persist it under the session id since that's about to change. The glitch is that the existing application already has an SSO module and I get a 404 error every time I try to direct to j_security_check. I've tried that, /sso/j_security_check, even http://localhost/sso/j_security_check, all without success. I noticed that an earlier question said that tomcat requires access to a secured page before j_security_check is even visible. I don't know if that's the case with Oracle AS. Ideas? Or is the best approach to continue arguing that we have a different user base so it would be better to handle authentication in our own module anyway?

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• how can i replace an image (inside a div) through jquery and ajax.

  - by oo

  I am trying to click on an image and change it to another image through jquery. When i step through the below code, on the serverside, the controller action fires and on the client side, i can see the correct html return in firebug watch window but the image doesn't change at all. any idea why this div is not updating? original div: <div class="inlineDiv" toggle="off" id="22"><img src="../../images/vote-favorite-off1.png" border="0"></div> jquery code: $(document).ready(function() { $('div.inlineDiv').live('click', function() { var id = $(this).attr("id"); var toggle = $(this).attr("toggle"); var url = '/Tracker/Update?id=' + id + '&toggle=' + toggle; $.get(url, function(data) { $(this).html(data); }); }); }); controller action: public ActionResult Update(int id, string toggle) { if (toggle == "off") { return Content("<img src='../../images/vote-favorite-on1.png' border=0'>"); } return Content("<img src='../../images/vote-favorite-off1.png' border=0'>"); }

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• Cloning ID3DXMesh with declration that has 12 floats breaks?

  - by meds

  I have the following vertex declration: struct MESHVERTInstanced { float x, y, z; // Position float nx, ny, nz; // Normal float tu, tv; // Texcoord float idx; // index of the vertex! float tanx, tany, tanz; // The tangent const static D3DVERTEXELEMENT9 Decl[6]; static IDirect3DVertexDeclaration9* meshvertinstdecl; }; And I declare it as such: const D3DVERTEXELEMENT9 MESHVERTInstanced::Decl[] = { { 0, 0, D3DDECLTYPE_FLOAT3, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_POSITION, 0 }, { 0, 12, D3DDECLTYPE_FLOAT3, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_NORMAL, 0 }, { 0, 24, D3DDECLTYPE_FLOAT2, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_TEXCOORD, 0 }, { 0, 32, D3DDECLTYPE_FLOAT1, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_TEXCOORD, 1 }, { 0, 36, D3DDECLTYPE_FLOAT3, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_TANGENT, 0 }, D3DDECL_END() }; What I try to do next is copy an ID3DXMesh into another one with the new vertex declaration as such: model->CloneMesh( model->GetOptions(), MESHVERTInstanced::Decl, gd3dDevice, &pTempMesh ); When I try to get the FVF size of pTempMesh (D3DXGetFVFVertexSize(pTempMesh-GetFVF())) I get '0' though the size should be 48. The whole thing is fine if I don't have the last declaration, '{ 0, 36, D3DDECLTYPE_FLOAT3, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_TANGENT, 0 },' in it and the CloneMesh function does not return a FAIL. I've also tried using different declarations such as D3DDECLUSAGE_TEXCOORD and that has worked fine, returning a size of 48. Is there something specific about D3DDECLUSAGE_TANGENT I don't know? I'm at a complete loss as to why this isn't working...

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• C# and Objects/Classes

  - by user1192890

  I have tried to compile code from Deitel's C# 2010 for programmers. I copied it exactly out of the book, but it still can't find main, even though I declared it in one of the classes. Here is a look at the two classes: For GradeBookTest: // Fig. 4.2: GradeBookTest.cs // Create a GradeBook object and call its DisplayMessage method. public class GradeBookTest { // Main method begins program execution public static void Main(string[] args) { // create a GradeBook object and assign it to myGradeBook GradeBook myGradeBook = new GradeBook(); // call myGradeBook's DisplayMessage method myGradeBook.DisplayMessage(); } // end Main } // end class GradeBookTest Now for the GradeBook class: // Fig. 4.1: GradeBook.cs // Class declaration with one method. using System; public class GradeBook { // display a welcome message to the GradeBook user public void DisplayMessage() { Console.WriteLine( "Welcome to the Grade Book!" ); } // end method DisplayMessage } // end class GradeBook That is how I copied them. Here is how they appeared in the book: 1 // Fig. 4.2: GradeBookTest.cs 2 // Create a GradeBook object and call its DisplayMessage method. 3 public class GradeBookTest 4 { 5 // Main method begins program execution 6 public static void Main( string[] args ) 7 { 8 // create a GradeBook object and assign it to myGradeBook 9 GradeBook myGradeBook = new GradeBook(); 10 11 // call myGradeBook's DisplayMessage method 12 myGradeBook.DisplayMessage(); 13 } // end Main 14 } // end class GradeBookTest and // Fig. 4.1: GradeBook.cs // Class declaration with one method. using System; public class GradeBook { // display a welcome message to the GradeBook user public void DisplayMessage() { Console.WriteLine( "Welcome to the Grade Book!" ); } // end method DisplayMessage } // end class GradeBook I don't see why they are not working. Right now I am using Visual Studio Pro 2010. Any Thoughts?

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• How to properly assign a value to the member of a struct that has a class data type?

  - by sasayins

  Hi, Please kindly see below for the codes. Its compiling successfully but the expected result is not working. Im very confused because my initialization of the array is valid, //cbar.h class CBar { public: class CFoo { public: CFoo( int v ) : m_val = v {} int GetVal() { return m_val; } private: int m_val; }; public: static const CFoo foo1; static const CFoo foo2; public: CBar( CFoo foo ) m_barval( foo.GetVal() ){} int GetFooVal() { return m_barval; } private: int m_barval; }; //cbar.cpp const CBar::CFoo foo1 = CBar::CFoo(2); const CBar::CFoo foo2 = CBar::CFoo(3); //main.cpp struct St { CBar::CFoo foo; }; St st[] = { CBar::foo1, CBar::foo2 }; for( int i=0; i<sizeof(st)/sizeof(St); i++ ) { CBar cbar( st[i].foo ); std::cout << cbar.GetFooVal() << std::endl; } But then when I change the St::foo to a pointer. And like assign the address of CBar::foo1 or CBar::foo2, its working, like this, //main.cpp struct St { const CBar::CFoo *foo; }; St st[] = { &CBar::foo1, &CBar::foo2 }; for( int i=0; i<sizeof(st)/sizeof(St); i++ ) { CBar cbar( *st[i].foo ); std::cout << cbar.GetFooVal() << std::endl; } The real problem is. The app should output 2 3 Please advice. Many thanks.

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• Is possible : javascript extract value from c:forEach tag ?

  - by EswaraMoorthyNEC

  Hi, i have populate some values using c:forEach tag. I want to get those values in my javascript. If I click GetCtag value button, then i want to read from (c:forEach) values in javascript. Is any other-way to retrieve the c:forEach tag value <%@page contentType="text/html" pageEncoding="UTF-8"%> <%@ taglib uri="http://java.sun.com/jsf/html" prefix="h" %> <%@ taglib uri="http://java.sun.com/jsf/core" prefix="f" %> <%@ taglib uri="http://richfaces.org/a4j" prefix="a4j"%> <%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <f:view> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <script type="text/javascript"> function getCTagValue(ctagObject) { alert("CFor Each Tag Object Value: " + ctagObject); // Here i want write code for retrieve the c:forEach tag value } </script> </head> <body> <h:form id="cTagForm" > <c:forEach items="${cTagBean.tagList}" var="ctag"> <c:out value="${ctag.name} : "/> <c:out value="${ctag.age}"/></br> </c:forEach> <a4j:commandButton id="GetCtagId" value="GetCtag" oncomplete="getCTagValue('#{cTagBean.tagList}')"/> </h:form> </body> </html> Help me. Thanks in advance.

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• Dynamic change .click value Jquery IE issue.

  - by user326100

  Hello guys.. it's i first time i'm asking here. Sorry if the answer is available already. I have a very small jQuery script that canges the paramether for onclick attr on a DIV. IT works like as right and left arrows for some content in the middle. BAsically i set the onclick="foo(1)" then when get clicked sld change the value 1 to 2, and keep changing everytime i click. on jQuery functio i'm using: $("#v_arrow_r").attr('onclick','').unbind().click(newclick_next); it works like a charm on FF and Chrome, but does not work on IE !!!! Argh... here the the code: if (start == 24) { var a = 0; var b = 0; } else { var a = start-6; var b = start+6; } next = "home_featured_videos(" + b + ");"; newclick_next = eval("(function(){"+next+"});"); prev = "home_featured_videos(" + a + ");"; newclick_prev = eval("(function(){"+prev+"});"); $('#video-module').css('background',''); $('#video-module').html(response); $("#v_arrow_l").attr('onclick','').unbind().click(newclick_prev); $("#v_arrow_r").attr('onclick','').unbind().click(newclick_next); The html: //CONTENT So like i said.. i define the attr onclick when page open. It work well on IE. but when i click the arrow and call the function the oncli is set to null and i add the function to .click. IE stop working. the click is dead. If anybody have idea why this is happening. Thanx in advance. Kind Regards Varois

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• Custom ADO.NET provider to intercept and modify sql queries.

  - by Faisal

  Our client has an application that stores blobs in database which has now grown enough to impact the performance of SQL Server. To overcome this issue, we are planning to offload all blobs to file system and leave the path of file in a new column in user table. Like if user has a table docs with columns id, name and content (blob); we would ask him to add a new column 'filepath' in this table. Our client is willing to make this change in this database. But when it comes to changing the sql queries to read and write into this table, they are not ready to accep this. Actually, they don't want any change that results in recompilation and deployment. Now we are planning to write a custom ADO.NET provider that will intercept the select queries add a column 'filepath' at the end of the select statement retieve the result set and modify the 'content' column value based on 'filepath' value Is there any use case that you think will certainly fail with this approach? I know this sounds dirty but do we have a better way?

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• CI + Joomla 1.5

  - by DMin

  Hi, This is something that I just cooked up with Joomla and CodeIgniter(CI). I Wrote my database intensive application in CodeIgniter and frontend is Joomla. I'm using Jumi(Joomla Extention) so I can include the CI files inside joomla to basically insert the content generated by CI into Joomla articles. Problem is, you can't include CI files directly using JUMI from joomla because CI tends to route the pages so instead of seeing your joomla page with the CI content, you be redirected to the CI page itself. I did a little work around for this : Made an additional page that just basically does cURL to the CI page - gets the data and echos it out. From jumi, I include this cURL page instead. Couple of questions: I've seen at least a few posts that CI + Joomla is difficult to do(link). 1) Do you see any glaring security issues or possible performance issues? 2) Do you know of a better way to implement this? 3) What do you think of this? Do you think this is a good way to do this? There is one component out there that plugs CI with Joomla but it requires you to have a fresh CI install. It allows only one controller & the download link is down as well.

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• A Null Reference Exception

  - by Alex

  "Object reference not set to an instance of an object." using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Content; using Microsoft.Xna.Framework.Graphics; namespace XNAdev { class Sprite { //The size of the Sprite public Rectangle Size; //Used to size the Sprite up or down from the original image public float Scale = 1.0f; //The current position of the Sprite public Vector2 Position = new Vector2(115, 0); //The texture object used when drawing the sprite private Texture2D mSpriteTexture; //Load the texture for the sprite using the Content Pipeline public void LoadContent(ContentManager theContentManager, string theAssetName) { mSpriteTexture = theContentManager.Load<Texture2D>(theAssetName); Size = new Rectangle(0, 0, (int)(mSpriteTexture.Width * Scale), (int)(mSpriteTexture.Height * Scale)); } //Draw the sprite to the screen public void Draw(SpriteBatch theSpriteBatch) { theSpriteBatch.Draw(mSpriteTexture, Position, new Rectangle(0, 0, mSpriteTexture.Width, mSpriteTexture.Height), Color.White, 0.0f, Vector2.Zero, Scale, SpriteEffects.None, 0); } } } I am very new at this C# so any help would be great. I have no idea what my error is.

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• How do I retrieve twitter xml for Flash site via php properly

  - by daidai

  Am I using TwitterScript to retrieve Twitter data for inside a Flash site. Due to Twitter's crossdomain policy, I need to setup a php proxy... Firstly I made a simple one <?php $url = $_GET['url']; readfile($url); ?> but I then get this error URL file-access is disabled in the server configuration which is only resolved by getting my host to turn fopen() on, which I don't want to do. Then I found this <?php function get_content($url) { $ch = curl_init(); curl_setopt ($ch, CURLOPT_URL, $url); curl_setopt ($ch, CURLOPT_HEADER, 0); ob_start(); curl_exec ($ch); curl_close ($ch); $string = ob_get_contents(); ob_end_clean(); return $string; } #usage: $url = $_GET['url']; $content = get_content ($url); var_dump ($content); ?> which solves that problem but the data now is the correct XML but looks like: string(39950) "<?xml version="1.0" encoding="UTF-8"?> <statuses type="array"> <status> ... </statuses>" How do I get the XML data out of that string?

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• What was your "aha moment" in understanding delegates?

  - by CM90

  Considering the use of delegates in C#, does anyone know if there is a performance advantage or if it is a convenience to the programmer? If we are creating an object that holds a method, it sounds as if that object would be a constant in memory to be called on, instead of loading the method every time it is called. For example, if we look at the following Unity3D-based code: public delegate H MixedTypeDelegate<G, H>(G g) public class MainParent : MonoBehaviour // Most Unity classes inherit from M.B. { public static Vector3 getPosition(GameObject g) { /* GameObject is a Unity class, and Vector3 is a struct from M.B. The "position" component of a GameObject is a Vector3. This method takes the GameObject I pass to it & returns its position. */ return g.transform.position; } public static MixedTypeDelegate<GameObject, Vector3> PositionOf; void Awake( ) // Awake is the first method called in Unity, always. { PositionOf = MixedTypeDelegate<GameObject, Vector3>(getPosition); } } public class GameScript : MainParent { GameObject g = new GameObject( ); Vector3 whereAmI; void Update( ) { // Now I can say: whereAmI = PositionOf(g); // Instead of: whereAmI = getPosition(g); } } . . . But that seems like an extra step - unless there's that extra little thing that it helps. I suppose the most succinct way to ask a second question would be to say: When you had your aha moment in understanding delegates, what was the context/scenario/source? Thank you!

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• jQuery UI Dialog Issue With IE

  - by Dan Appleyard

  I am using the new jQuery 1.3.2 and jQuery-ui-1.7 libraries along with the UI Dialog. I have a div tag with several form elements (textbox, checkbox, etc.) in it. Upon page load, jQuery shows the div as a dialog. This works absolutely fine in FF, but in IE, the height of the div is wrong. It is just showing the title bar a bit of the content. I explicitly set the height when creating the div. If I set the height option after opening the dialog, the height is corrected, but the content is blank (shows the top third of a textbox). If I allow the dialog to be resizable, if you resize it in IE it works fine, but I don't want to force IE users to resize just to see the contents. Any ideas? Here is the code I use to create the dialog: $('#dialogDiv').dialog({ bgiframe: true, height: 400, width: 620, modal: true, draggable: true, resizable: false, close: function(event, ui) { if($('#agree').val() != '1') location.href = 'somepage.html'; } });

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• Anything wrong with my cURL code (http status of 0)?

  - by Ilya

  Consistently getting a status of 0 even though if I copy and paste the url sent into my browser, I get a json object right back <?php $mainUrl = "https://api.xxxx.com/?"; $co = "xxxxx"; $pa = "xxxx"; $par = "xxxx"; $part= "xxxx"; $partn = "xxxx"; $us= "xxx"; $fields_string; $fields = array( 'co'=>urlencode($co), 'pa'=>urlencode($pa), 'par'=>urlencode($par), 'part'=>urlencode($part), 'partn'=>urlencode($partn), 'us'=>urlencode($us) ); foreach($fields as $key=>$value) { $fields_string .= $key . '=' . $value . '&' ;} $fields_string = rtrim($fields_string, "&"); $fields_string = "?" . $fields_string; $url = "https://api.xxxxx.com/" . $fields_string; $request = $url; $ch = curl_init(); curl_setopt($ch, CURLOPT_URL, $url); curl_setopt($ch, CURLOPT_RETURNTRANSFER,1); curl_setopt($ch, CURLOPT_TIMEOUT,'3'); $content = trim(curl_exec($ch)); $http_status = curl_getinfo($ch, CURLINFO_HTTP_CODE); curl_close($ch); print $url; print $http_status; print $content; ?>

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• How to retain the value of a text box?

  - by udaya

  This is the content on my view page and i want to replace the value from "0" when the monthfunc() is called...the monthfunc() is given below the view content <tr> <td> <input type="submit" name="monthplus" id="monthplus" onClick="return monthfunc('monthplus');" value=">>>>>>"> <input type="hidden" name="monthnum" id="monthnum" value="1"> <input type="text" name="monthname" id="monthname" value="0" value="<? echo $month;?>" > <input type="submit" name="monthminus" id="monthminus" onClick="return monthfunc('monthminus');" value="<<<<<<"> </td> </tr> My script is function monthfunc(mnth) { if(mnth == 'monthplus') { var yn = document.getElementById('monthnum').value; ynpo = parseInt(yn)+1; if(ynpo==13) { ynpo=1; } } else if(mnth == 'monthminus') { var yn = document.getElementById('monthnum').value; ynpo = parseInt(yn)-1; if(ynpo==0) { ynpo=12; } } if(ynpo ==1) { document.getElementById('monthname').value = 'january'; document.getElementById('monthnum').value = ynpo; return true; } else if(ynpo ==2) { document.getElementById('monthname').value = 'february'; document.getElementById('monthnum').value = ynpo; return true; } else if(ynpo ==3) { document.getElementById('monthname').value = 'March'; document.getElementById('monthnum').value = ynpo; return true; } return false; } How can i replace The value with the value like january february etc.. Actually i can change the values but cannot retain the values... i want to retain the values ,,,How to do that

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• Client side page call/scrape?

  - by Silvre

  Here is the problem: I have a web application - a frequently changing notification system - that runs on a series of local computers. The application refreshes every couple of seconds to display the new information. The computers only display info, and do not have keyboards or ANY input device. The issue is that if the connection to the server is lost (say updates are installed and a server must be rebooted), a page not found error is displayed). We must then either reboot all computers that are running this app, OR add a keyboard and refresh the browser, OR try to access each computer remotely and refresh the browser. None of these are good options and result in a lot of frustration. I cannot change the actual application OR server environment. So what I need is some way to test the call to the application, and if an error is returned or it times out, continue trying every minute or so until the connection is reestablished. My idea is to create a client-side page scraper, that makes a JS request to the application (which displays basic HTML), and can run locally on the machine, no server required. If the scrape returns the correct content, it displays it. If not it continues to request the page until the actual page content is returned. Is this possible? What is the best way to do it?

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• jQuery : how to determine that a div is scrolled down

  - by subtenante

  I have a div with defined height, and overflow:scroll;. Its content is too long so scrollbars appear. Now for the ichy part. Some of its inner HTML strangely appears all the time (to be precise, the footer of a table generated by the tableFilter plugin). I'd like to make this footer disappear when it is not needed (it actually appears out of the containing <div>'s border). I resolved to make it disappear but setting its z-index to -1000. But I want to make it appear when the containing <div> is totally scrolled down. How can I know the user has scrolled at the bottom ? Using the help from answers below, I used scrollTop attribute but the difference between scrollTop and innerHeight is the size of the scrollbar plus some unidentified delta. A scrollbar is 16 pixels high in most browsers under Windows, but I get a difference of 17 in Firefox and something like 20 in IE, where my <div> content's borders seems to be rendered bigger. A way (actually two ways...) to compute the scrollbar size has been given there.

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• How to save errors with the handleError in CakePHP 2.0?

  - by jags1988cr

  I have a big problem. Well, I'm trying to save the errors that happen in my web application. For example (only a example), if I make a division by zero, or happens an error in a query or something like that. So, I wanna catch that and save it in the database. But the handleError of CakePHP is static, so I can't use $this-MyModel-saveError(...). In my /app/Lib/AppError.php I have this: class AppError extends ErrorHandler { public $uses = array('Errors.Error'); public static function handleError($code, $description, $file = null, $line = null, $context = null) { //This print the error: echo "Code: ".$code." Description: ".$description." File: ".$file." Line: ".$line."<br>"; //I want to do this, (save to the database): $this->Error->saveError($code, $description, $file, $line); } } Without the $this-Error-saveError($code, $description, $file, $line); it works but I not only want to show the error. I think need an example or something like that. Please help me. Regards and thank you. Thanks... P.D.: Sorry for the English, I'm an english student...

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• How to avoid concurrent execution of a time-consuming task without blocking?

  - by Diego V

  I want to efficiently avoid concurrent execution of a time-consuming task in a heavily multi-threaded environment without making threads wait for a lock when another thread is already running the task. Instead, in that scenario, I want them to gracefully fail (i.e. skip its attempt to execute the task) as fast as possible. To illustrate the idea considerer this unsafe (has race condition!) code: private static boolean running = false; public void launchExpensiveTask() { if (running) return; // Do nothing running = true; try { runExpensiveTask(); } finally { running = false; } } I though about using a variation of Double-Checked Locking (consider that running is a primitive 32-bit field, hence atomic, it could work fine even for Java below 5 without the need of volatile). It could look like this: private static boolean running = false; public void launchExpensiveTask() { if (running) return; // Do nothing synchronized (ThisClass.class) { if (running) return; running = true; try { runExpensiveTask(); } finally { running = false; } } } Maybe I should also use a local copy of the field as well (not sure now, please tell me). But then I realized that anyway I will end with an inner synchronization block, that still could hold a thread with the right timing at monitor entrance until the original executor leaves the critical section (I know the odds usually are minimal but in this case we are thinking in several threads competing for this long-running resource). So, could you think in a better approach?

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• How to encrypt a RSAKey using another RSAKey?

  - by Tom Brito

  I know its not the usual thing to do. But the specification I'm implementing is discribed this way, and I cannot run out. I was trying to encrypt the modulus and exponent of the private key, but the following test code raises an exception because the byte array is 1 byte larger then the maximum allowed by RSA block: import java.security.KeyPair; import java.security.KeyPairGenerator; import java.security.NoSuchAlgorithmException; import java.security.NoSuchProviderException; import java.security.interfaces.RSAPrivateKey; import java.security.interfaces.RSAPublicKey; import javax.crypto.Cipher; import org.apache.commons.lang.ArrayUtils; public class TEST { public static KeyPair generateKeyPair() throws NoSuchAlgorithmException, NoSuchProviderException { KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA", "BC"); keyPairGenerator.initialize(1024); return keyPairGenerator.generateKeyPair(); } public static void main(String[] args) throws Exception { KeyPair keyPair = generateKeyPair(); RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate(); System.out.println("Priv modulus len = " + privateKey.getModulus().bitLength()); System.out.println("Priv exponent len = " + privateKey.getPrivateExponent().bitLength()); System.out.println("Priv modulus toByteArray len = " + privateKey.getModulus().toByteArray().length); byte[] byteArray = privateKey.getModulus().toByteArray(); // the byte at index 0 have no value (in every generation it is always zero) byteArray = ArrayUtils.subarray(byteArray, 1, byteArray.length); System.out.println("byteArray size: " + byteArray.length); RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic(); Cipher cipher = Cipher.getInstance("RSA", "BC"); cipher.init(Cipher.ENCRYPT_MODE, publicKey); byte[] encryptedBytes = cipher.doFinal(byteArray); System.out.println("Success!"); } } (obs. its just a test, i would never encrypt the private key with its pair public key) The byte array is 128 bytes, the exactly maximum allowed by a RSA block, so why the exception? And how to fix it?

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• What's the deal with the hidden Throw when catching a ThreadAbortException?

  - by priehl

  I'm going through a book of general c# development, and I've come to the thread abort section. The book says something along the lines that when you call Thread.Abort() on another thread, that thread will throw a ThreadAbortException, and even if you tried to supress it it would automatically rethrow it, unless you did some bs that's generally frowned upon. Here's the simple example offered. using System; using System.Threading; public class EntryPoint { private static void ThreadFunc() { ulong counter = 0; while (true) { try { Console.WriteLine("{0}", counter++); } catch (ThreadAbortException) { // Attempt to swallow the exception and continue. Console.WriteLine("Abort!"); } } } static void Main() { try { Thread newThread = new Thread(new ThreadStart(EntryPoint.ThreadFunc)); newThread.Start(); Thread.Sleep(2000); // Abort the thread. newThread.Abort(); // Wait for thread to finish. newThread.Join(); } catch (Exception e) { Console.WriteLine(e.ToString()); } } } The book says: When your thread finishes processing the abort exception, the runtime implicitly rethrows it at the end of your exception handler. It’s the same as if you had rethrown the exception yourself. Therefore, any outer exception handlers or finally blocks will still execute normally. In the example, the call to Join won’t be waiting forever as initially expected. So i wrapped a try catch around the Thread.Abort() call and set a break point, expecting it to hit this, considering the text says "any outer exception handlers or finally blocks will still execute normally". BUT IT DOES NOT. I'm racking my brain to figure out why. Anyone have any thoughts on why this isn't the case? Is the book wrong? Thanks in advance.

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• VS2010 and CSS: What is the best way to position a single form control

  - by George

  OK, I have a ton of controls on my page that I need to individually place. I need to set a margin here, a padding there, etc. None of these particular styles that I want to apply will be applied to more than control. What is the bets practice for determining at which level the style is placed, etc? OK, my choices are 1) External CSS file 1A) Using ClientIdMode = Auto (the default) I could assign a unique CssClass value to the ASP.NET control and, in the external CSS file, create a class selector that would only be applied to that one control. 1B) User Client ID = Predicatable In the external CSS file, I could determine what the ID will be for the controls of interest and create an ID selector (#ControlID{Style} ). However, I fear maintenance issues due to including/removing parent containers that would cause the ID to change. 1C) User Client ID = Static. I could choose static IDs for the controls such that I minimize the likelihood of a clash with auto generated IDs (perhaps by prefixing the ID with "StaticID_" and use an external stylesheet with ID selectors. 2) I could place the style right on the control. The only disadvantage here, as I see it, is that style info is brought down each time instead of being cached , which is what I'd get using an external CSS. If a style isn't resused, I personally don't see much benefit to placing it in an external file, though please explain why if you disagree. Is there moire of a reason that "It's nice to have all the CSS in one place?"

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• Is this use of PreparedStatements in a Thread in JAVA correct?

  - by Gormcito

  I'm still an undergrad just working part time and so I'm always trying to be aware of better ways to do things. Recently I had to write a program for work where the main thread of the program would spawn "task" threads (for each db "task" record) which would perform some operations and then update the record to say that it has finished. Therefore I needed a database connection object and PreparedStatement objects in or available to the ThreadedTask objects. This is roughly what I ended up writing, is creating a PreparedStatement object per thread a waste? I thought static PreparedStatments could create race conditions... Thread A stmt.setInt(); Thread B stmt.setInt(); Thread A stmt.execute(); Thread B stmt.execute(); A´s version never gets execed.. Is this thread safe? Is creating and destroying PreparedStatement objects that are always the same not a huge waste? public class ThreadedTask implements runnable { private final PreparedStatement taskCompleteStmt; public ThreadedTask() { //... taskCompleteStmt = Main.db.prepareStatement(...); } public run() { //... taskCompleteStmt.executeUpdate(); } } public class Main { public static final db = DriverManager.getConnection(...); }

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