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  • How Stuff Works: Fiber Optic Cables [Science]

    - by Jason Fitzpatrick
    Most people are familiar with the general concept of fiber optic cables–light as a method of data transmission–but how do they really work? Find out in this informative video. Bill Hammack, of Engineer Guy Videos, shows us how fiber optic cables work using–of all things–a bucket and a laser. Check out the above video for a glimpse inside how fiber optic cables work and how your analog voice can go to from your phone’s handset to a digital stream and then back to analog sound for the benefit of your friend on the end of the fiber optic transmission cable. Fiber Optic Cables: How They Work and How Engineers Use Them to Send Messages [YouTube] What is a Histogram, and How Can I Use it to Improve My Photos?How To Easily Access Your Home Network From Anywhere With DDNSHow To Recover After Your Email Password Is Compromised

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  • Cocos2d copied actions not responding?

    - by Stephen
    I am running an animation on 2 sprites like so: -(void) startFootballAnimation { CCAnimation* footballAnim = [CCAnimation animationWithFrame:@"Football" frameCount:60 delay:0.005f]; spiral = [CCAnimate actionWithAnimation:footballAnim]; CCRepeatForever* repeat = [CCRepeatForever actionWithAction:spiral]; [self runAction:repeat]; [secondFootball runAction:[[repeat copy] autorelease]]; } The problem I am having is I call this method: - (void) slowAnimation { [spiral setDuration:[spiral duration] + 0.01]; } and it only slows down the first sprites animation and not the second one. Do I need to do something different with copied actions to get them to react to the slowing of the animation?

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  • Lending epub files for limited time to users

    - by JP Hellemons
    I am looking for components to build a digital library who lends people epub (ebooks) for about a week. It's like a digital version of the offline old public library. Now I have found several flash (pdf) file streaming solutions. But that would require an active internet link. And like the public library, you are able to take your books to the beach or pool on holiday abroad where you have no connection. So streaming is no option. The other file restriction method I have found was DRM, but that would require a really expensive license of Adobe Content Server 4 which is not suitable for my little hobby project. But it seems that adobe content server and Adobe Digital Editions is the only option at the moment. Or are there open source alternatives?

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  • Use adapter pattern for coupled classes

    - by kaiseroskilo
    I need (for unit testing purposes) to create adapters for external library classes.ExchangeService and ContactsFolder are Microsoft's implementations in its' EWS library. So I created my adapters that implement my interfaces, but it seems that contactsFolder has a dependency for ExchangeService in its' constructor. The problem is that I cannot instantiate ContactsFolderAdapter without somehow accessing the actual ExchangeService instance (I see only ExchangeServiceAdapter in scope). Is there a better pattern for this that retains the adapter classes? Or should I "infect" ExchangeServiceAdapter with some kind of GetActualObject method?

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  • How to safely shutdown Guest OS in VirtualBox using command line

    - by Bakhtiyor
    I have Ubuntu 10.10 and using VirtualBox 3.2. As a Guest OS I have another Ubuntu in the VirtualBox. I am starting Guest Ubuntu automatically using following command once my Host Ubuntu boots: VBoxHeadless -startvm Ubuntu --vrdp on Then I can access to it with ssh or tsclient. Now I need to shutdown automatically Guest Ubuntu once I shutdown my Host Ubuntu. Does anybody know any safe method to automatically shutdown Guest Ubuntu with a command line? I have found out two ways one can shutdown Guest OS but I am not sure whether they are safe or not. Here are they: VBoxManage controlvm Ubuntu acpipowerbutton or VBoxManage controlvm Ubuntu poweroff

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  • How to open a MIB file in tkmib?

    - by l0b0
    I've tried to open several MIB files in tkmib without success. For example: $ sudo apt-get install tkmib $ wget http://www.mibsearch.com/vendors/Compaq/download/CPQHLTH-MIB $ tkmib CPQHLTH-MIB Click "walk", then you should get an error message like this: setting opts getaddrinfo: CPQHLTH-MIB No address associated with hostname error:snmp_new_session: Couldn't open SNMP session at /usr/lib/perl5/SNMP.pm line 475. unable to create session at /usr/lib/perl5/SNMP.pm line 547. Tk::Error: Can't call method "getnext" on unblessed reference at /usr/bin/tkmib line 506. main::snmpwalk at /usr/bin/tkmib line 506 Tk callback for .frame5.button2 Tk::__ANON__ at /usr/lib/perl5/Tk.pm line 250 Tk::Button::butUp at /usr/lib/perl5/Tk/Button.pm line 175 <ButtonRelease-1> (command bound to event) As I'm completely new to SNMP and MIB files, and man tkmib is sparse to say the least, what do I actually need to do to be able to work with this file?

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  • How to draw textures on a model

    - by marc wellman
    The following code is a complete XNA 3.1 program almost unaltered to that code skeleton Visual Studio is creating when creating a new project. The only things I have changed are imported a .x model to the content folder of the VS solution. (the model is a simple square with a texture spanning over it - made in Google Sketchup and exported with several .x exporters) in the Load() method I am loading the .x model into the game. The Draw() method uses a BasicEffect to render the model. Except these three things I haven't added any code. Why does the model does not show the texture ? What can I do to make the texture visible ? This is the texture file (a standard SketchUp texture from the palette): And this is what my program looks like - as you can see: No texture! Find below the complete source code of the program AND the complete .x file: namespace WindowsGame1 { /// <summary> /// This is the main type for your game /// </summary> public class Game1 : Microsoft.Xna.Framework.Game { GraphicsDeviceManager graphics; SpriteBatch spriteBatch; public Game1() { graphics = new GraphicsDeviceManager(this); Content.RootDirectory = "Content"; } /// <summary> /// Allows the game to perform any initialization it needs to before starting to run. /// This is where it can query for any required services and load any non-graphic /// related content. Calling base.Initialize will enumerate through any components /// and initialize them as well. /// </summary> protected override void Initialize() { // TODO: Add your initialization logic here base.Initialize(); } Model newModel; /// <summary> /// LoadContent will be called once per game and is the place to load /// all of your content. /// </summary> protected override void LoadContent() { // Create a new SpriteBatch, which can be used to draw textures. spriteBatch = new SpriteBatch(GraphicsDevice); // TODO: usse this.Content to load your game content here newModel = Content.Load<Model>(@"aau3d"); foreach (ModelMesh mesh in newModel.Meshes) { foreach (ModelMeshPart meshPart in mesh.MeshParts) { meshPart.Effect = new BasicEffect(this.GraphicsDevice, null); } } } /// <summary> /// UnloadContent will be called once per game and is the place to unload /// all content. /// </summary> protected override void UnloadContent() { // TODO: Unload any non ContentManager content here } /// <summary> /// Allows the game to run logic such as updating the world, /// checking for collisions, gathering input, and playing audio. /// </summary> /// <param name="gameTime">Provides a snapshot of timing values.</param> protected override void Update(GameTime gameTime) { // Allows the game to exit if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed) this.Exit(); // TODO: Add your update logic here base.Update(gameTime); } /// <summary> /// This is called when the game should draw itself. /// </summary> /// <param name="gameTime">Provides a snapshot of timing values.</param> protected override void Draw(GameTime gameTime) { if (newModel != null) { GraphicsDevice.Clear(Color.CornflowerBlue); Matrix[] transforms = new Matrix[newModel.Bones.Count]; newModel.CopyAbsoluteBoneTransformsTo(transforms); foreach (ModelMesh mesh in newModel.Meshes) { foreach (BasicEffect effect in mesh.Effects) { effect.EnableDefaultLighting(); effect.TextureEnabled = true; effect.World = transforms[mesh.ParentBone.Index] * Matrix.CreateRotationY(0) * Matrix.CreateTranslation(new Vector3(0, 0, 0)); effect.View = Matrix.CreateLookAt(new Vector3(200, 1000, 200), Vector3.Zero, Vector3.Up); effect.Projection = Matrix.CreatePerspectiveFieldOfView(MathHelper.ToRadians(45.0f), 0.75f, 1.0f, 10000.0f); } mesh.Draw(); } } base.Draw(gameTime); } } } This is the model I am using (.x): xof 0303txt 0032 // SketchUp 6 -> DirectX (c)2008 edecadoudal, supports: faces, normals and textures Material Default_Material{ 1.0;1.0;1.0;1.0;; 3.2; 0.000000;0.000000;0.000000;; 0.000000;0.000000;0.000000;; } Material _Groundcover_RiverRock_4inch_{ 0.568627450980392;0.494117647058824;0.427450980392157;1.0;; 3.2; 0.000000;0.000000;0.000000;; 0.000000;0.000000;0.000000;; TextureFilename { "aau3d.xGroundcover_RiverRock_4inch.jpg"; } } Mesh mesh_0{ 4; -81.6535;0.0000;74.8031;, -0.0000;0.0000;0.0000;, -81.6535;0.0000;0.0000;, -0.0000;0.0000;74.8031;; 2; 3;0,1,2, 3;1,0,3;; MeshMaterialList { 2; 2; 1, 1; { Default_Material } { _Groundcover_RiverRock_4inch_ } } MeshTextureCoords { 4; -2.1168,-3.4022; 1.0000,-0.0000; 1.0000,-3.4022; -2.1168,-0.0000;; } MeshNormals { 4; 0.0000;1.0000;-0.0000; 0.0000;1.0000;-0.0000; 0.0000;1.0000;-0.0000; 0.0000;1.0000;-0.0000;; 2; 3;0,1,2; 3;1,0,3;; } }

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  • [News] Repenser les IDE avec l'interface Code Bubbles

    Andrew Bragdon, ?tudiant surdou? d'une universit? am?ricaine, a repens? les interfaces graphiques des IDE pour remplacer les fen?tres par des bulles communicantes. Une id?e farfelue ? Pas du tout, la d?mo (ou plut?t la vid?o) est bluffante : "A bubble is a fully editable and interactive view of a fragment such as a method or collection of member variables. Bubbles, in contrast to windows, have minimal border decoration, avoid clipping their contents by using automatic code reflow and elision, and do not overlap but instead push each other out of the way". A d?couvrir absolument, c'est un concept d'avenir...

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  • Checking is sides of cubes are solid

    - by Christian Frantz
    In relation to this question: http://gamedev.stackexchange.com/a/28524/31664 And a question I asked earlier: Creating a DrawableGameComponent And also because my internet is too slow to get on chat. I'm wondering how to check if the sides of a cube are solid. I've created 12 methods, each one creating indices and vertices for sides of a cube. Now when I use these methods, the cube creates how it should. All 6 sides show up and its like I didnt change a thing. How can use if statements to check if the side of a cube is solid? The pseudocode from the question above shows this: if(!isSolidAt(x+1,y,z)) verticesToDraw += AddXPlusFace(x,y,z) But in my case is would be: if(!sideIsSolid) SetUpFrontFaceIndices(); My method simply takes these index and vertex values and adds them to a list indicesToDraw and verticesToDraw, as shown in the answer above

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  • Stop map from scrolling but let player still move?

    - by ChocoMan
    I have a basic method of scrolling around on a map (moving the map instead of the player), but at when the player gets to a certain proximity to the edge, how do you stop the map from scrolling, but still allow the player to move around until it is away from that proximity? I'm not looking for any code. Just a suggestion so that I can implement it myself. I can see it visually (creating 4 boxed intersecting boundaries for the player to enter), but not sure how to come about stopping and resuming the scrolling of the map.

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  • A rather long question about installation/uninstall

    - by user2364312
    Ok so here's the deal guys, last week I decided I want to install Ubunutu again because I really missed it. (Last time I had an ubunutu was 7.somehting) I downloaded 12.04 and isntalled it via bootable usb device. Knowing how dual boots works I cleared up some space on my hard disc before hand using the windows 7 built in disc manager. During Ubunutu's installation I thought that by choosing "Install Ubuntu alongside Windows 7" will automatically just use the space I cleared before, but apperentaly it did not since that partition is still 100% free space. On what partition is Ubunutu installed when using that method? And how can I uninstall it to re-install it back on the space I cleared up for it? Thank you very your time reading and helping!

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  • kubuntu - what's the best smplayer configuration for best quality in hd movies (mkv)

    - by Frank
    I have ubuntu x64 13.04 with kde 4.11 and smplayer v0.8.6 and the last mplayer version from ppa. I have ATI video card HD6870 MSI with fglrx driver v13.4. My kde settings are: Composition mode: Opengl 3.1 graphic system qt: Raster scaling mode: precise Vsync: auto So what's the best configuration for quality over performace in smplayer according to my system specs? For example what do I have to set for the following options? enable postprocessing by default and postprocessing quality output driver Deinterlacing method software equalizer direct rendering double buffering draw video using slices threads for decoding (MPEG-1/2 and H.264 only loop filter use CoreAVC Thanks

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  • design pattern for unit testing? [duplicate]

    - by Maddy.Shik
    This question already has an answer here: Unit testing best practices for a unit testing newbie 4 answers I am beginner in developing test cases, and want to follow good patterns for developing test cases rather than following some person or company's specific ideas. Some people don't make test cases and just develop the way their senior have done in their projects. I am facing lot problems like object dependencies (when want to test method which persist A object i have to first persist B object since A is child of B). Please suggest some good books or sites preferably for learning design pattern for unit test cases. Or reference to some good source code or some discussion for Dos and Donts will do wonder. So that i can avoid doing mistakes be learning from experience of others.

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  • Handling Players, enemies and attacks in HTML5

    - by Chris Morris
    I'm building a simple (currently) game with free roaming player and monsters on a map built by a 2D grid. I've been looking at the methods for implementing characters and enemies onto the screen and I've seen two seperate methods for doing this online. Drawing the player onto the screen canvas directly and refreshing the entire screen every FPS tick. Having a separate canvas to handle the player and moving the player canvas on top of the screen canvas via absolute positioning. I can see some pros and cons of both methods but what is generally the best method for doing this? I assume the second due to not having to drain resources by refreshing the map when the user is not moving, but the type of game will generally have constant movement.

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  • How to manage and improve web application with 50 customers?

    - by Muhammet Göktürk Ayan
    First of all, sorry for my English. We've developed a Web Application using ASP.NET and Sql Server. We've started selling it and of course are still continually improving and developing it. The question is, how do we go about updating each client's version of the site? We have, maybe, 50 customers. 50 different folders and 50 different db's sounds like a bad idea. Is there any known method for solving this kind of scenario? For Explain: We are developing a Crm, for 50 companies. They will have 10 users maybe. It makes 500 users and their customers and products.

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  • Why write clean, refactored code?

    - by Shamal Karunarathne
    Hi programming lovers, This is a question I've been asking myself for a long time. Thought of throwing out it to you. From my experience of working on several Java based projects, I've seen tons of codes which we call 'dirty'. The unconventional class/method/field naming, wrong way of handling of exceptions, unnecessarily heavy loops and recursion etc. But the code gives the intended results. Though I hate to see dirty code, it's time taking to clean them up and eventually comes the question of "is it worth? it's giving the desired results so what's the point of cleaning?" In team projects, should there be someone specifically to refactor and check for clean code? Or are there situations where the 'dirty' codes fail to give intended results or make the customers unhappy? Do feel free to comment and reply. And tell me if I'm missing something here. Thanks.

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  • Stupid Geek Tricks: Disable Windows 7 Aero Peek in Two Clicks

    - by The Geek
    Most of you probably already know how to do this, but earlier today I was showing somebody how to turn Aero Peek off, and they were surprised at just how simple it is—you only have to use two mouse clicks to disable it. This method only disables the setting in the lower-right. If you’d like to disable the taskbar thumbnail version of Aero Peek, you’ll need to read our article on the subject. Or if you’d like to disable the delay, you can do that too.What is a Histogram, and How Can I Use it to Improve My Photos?How To Easily Access Your Home Network From Anywhere With DDNSHow To Recover After Your Email Password Is Compromised

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  • How to handle shoot instructions, in a multiplayer TD

    - by Martin Elvar Jensen
    I'm currently working on a Multiplayer Tower Defense game, using ImpactJS & Node. I seek some clarification about how to handle projectiles from towers, let me explain. So the server is running the master game, and the clients just follow the instruction from the server. Lets say there is about 20 towers on the stage, all needs instructions for which creeps to shoot at. Now lets say each towers fires twice in a second, that's 40 shots each second, (worst case scenario) which is 40 request per second to each client, would't this casue alot of stress to the server, saying that we have 50 games running the same time. So what i am really asking, is this method inefficient, and is there a smarter way to handle all these instructions. Thank you.

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  • PhP Login/Register system [migrated]

    - by Marian
    I found this good tutorial on creating a login/register system using PhP and MySQL. The forum is around 5 years old (edited last year) but it can still be usefull. Beginner Simple Register-Login system There seems to be an issue with both login and register pages. <?php function register_form(){ $date = date('D, M, Y'); echo "<form action='?act=register' method='post'>" ."Username: <input type='text' name='username' size='30'><br>" ."Password: <input type='password' name='password' size='30'><br>" ."Confirm your password: <input type='password' name='password_conf' size='30'><br>" ."Email: <input type='text' name='email' size='30'><br>" ."<input type='hidden' name='date' value='$date'>" ."<input type='submit' value='Register'>" ."</form>"; } function register(){ $connect = mysql_connect("host", "username", "password"); if(!$connect){ die(mysql_error()); } $select_db = mysql_select_db("database", $connect); if(!$select_db){ die(mysql_error()); } $username = $_REQUEST['username']; $password = $_REQUEST['password']; $pass_conf = $_REQUEST['password_conf']; $email = $_REQUEST['email']; $date = $_REQUEST['date']; if(empty($username)){ die("Please enter your username!<br>"); } if(empty($password)){ die("Please enter your password!<br>"); } if(empty($pass_conf)){ die("Please confirm your password!<br>"); } if(empty($email)){ die("Please enter your email!"); } $user_check = mysql_query("SELECT username FROM users WHERE username='$username'"); $do_user_check = mysql_num_rows($user_check); $email_check = mysql_query("SELECT email FROM users WHERE email='$email'"); $do_email_check = mysql_num_rows($email_check); if($do_user_check > 0){ die("Username is already in use!<br>"); } if($do_email_check > 0){ die("Email is already in use!"); } if($password != $pass_conf){ die("Passwords don't match!"); } $insert = mysql_query("INSERT INTO users (username, password, email) VALUES ('$username', '$password', '$email')"); if(!$insert){ die("There's little problem: ".mysql_error()); } echo $username.", you are now registered. Thank you!<br><a href=login.php>Login</a> | <a href=index.php>Index</a>"; } switch($act){ default; register_form(); break; case "register"; register(); break; } ?> Once pressed the register button the page does nothing, fields are erased and no data is added inside the database or error given. I tought that the problem might be the switch($act){ part so I removed it and changed the page using a require require('connect.php'); where connect.php is <?php mysql_connect("localhost","host","password"); mysql_select_db("database"); ?> Removed the function register_form(){ and echo part turning it into an HTML code: <form action='register' method='post'> Username: <input type='text' name='username' size='30'><br> Password: <input type='password' name='password' size='30'><br> Confirm your password: <input type='password' name='password_conf' size='30'><br> Email: <input type='text' name='email' size='30'><br> <input type='hidden' name='date' value='$date'> <input type='submit' name="register" value='Register'> </form> And instead of having a function register(){ I replaced it with a if($register){ So when the Register button is pressed it runs the php code, but this edit doesn't seem to work either. So what can the problem be? If needed I can re-add this code on my Domain The login page has the same issue, nothing happens when the button is pressed beside emptying the fields.

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  • Opposite Force to Apply to a Collided Rigid Body?

    - by Milo
    I'm working on the physics for my GTA2-like game so I can learn more about game physics. The collision detection and resolution are working great. I'm now just unsure how to compute the force to apply to a body after it collides with a wall. My rigid body looks like this: /our simulation object class RigidBody extends Entity { //linear private Vector2D velocity = new Vector2D(); private Vector2D forces = new Vector2D(); private float mass; private Vector2D v = new Vector2D(); //angular private float angularVelocity; private float torque; private float inertia; //graphical private Vector2D halfSize = new Vector2D(); private Bitmap image; private Matrix mat = new Matrix(); private float[] Vector2Ds = new float[2]; private Vector2D tangent = new Vector2D(); private static Vector2D worldRelVec = new Vector2D(); private static Vector2D relWorldVec = new Vector2D(); private static Vector2D pointVelVec = new Vector2D(); private static Vector2D acceleration = new Vector2D(); public RigidBody() { //set these defaults so we don't get divide by zeros mass = 1.0f; inertia = 1.0f; setLayer(LAYER_OBJECTS); } protected void rectChanged() { if(getWorld() != null) { getWorld().updateDynamic(this); } } //intialize out parameters public void initialize(Vector2D halfSize, float mass, Bitmap bitmap) { //store physical parameters this.halfSize = halfSize; this.mass = mass; image = bitmap; inertia = (1.0f / 20.0f) * (halfSize.x * halfSize.x) * (halfSize.y * halfSize.y) * mass; RectF rect = new RectF(); float scalar = 10.0f; rect.left = (int)-halfSize.x * scalar; rect.top = (int)-halfSize.y * scalar; rect.right = rect.left + (int)(halfSize.x * 2.0f * scalar); rect.bottom = rect.top + (int)(halfSize.y * 2.0f * scalar); setRect(rect); } public void setLocation(Vector2D position, float angle) { getRect().set(position.x,position.y, getWidth(), getHeight(), angle); rectChanged(); } public Vector2D getPosition() { return getRect().getCenter(); } @Override public void update(float timeStep) { doUpdate(timeStep); } public void doUpdate(float timeStep) { //integrate physics //linear acceleration.x = forces.x / mass; acceleration.y = forces.y / mass; velocity.x += (acceleration.x * timeStep); velocity.y += (acceleration.y * timeStep); //velocity = Vector2D.add(velocity, Vector2D.scalarMultiply(acceleration, timeStep)); Vector2D c = getRect().getCenter(); v.x = getRect().getCenter().getX() + (velocity.x * timeStep); v.y = getRect().getCenter().getY() + (velocity.y * timeStep); setCenter(v.x, v.y); forces.x = 0; //clear forces forces.y = 0; //angular float angAcc = torque / inertia; angularVelocity += angAcc * timeStep; setAngle(getAngle() + angularVelocity * timeStep); torque = 0; //clear torque } //take a relative Vector2D and make it a world Vector2D public Vector2D relativeToWorld(Vector2D relative) { mat.reset(); Vector2Ds[0] = relative.x; Vector2Ds[1] = relative.y; mat.postRotate(JMath.radToDeg(getAngle())); mat.mapVectors(Vector2Ds); relWorldVec.x = Vector2Ds[0]; relWorldVec.y = Vector2Ds[1]; return relWorldVec; } //take a world Vector2D and make it a relative Vector2D public Vector2D worldToRelative(Vector2D world) { mat.reset(); Vector2Ds[0] = world.x; Vector2Ds[1] = world.y; mat.postRotate(JMath.radToDeg(-getAngle())); mat.mapVectors(Vector2Ds); worldRelVec.x = Vector2Ds[0]; worldRelVec.y = Vector2Ds[1]; return worldRelVec; } //velocity of a point on body public Vector2D pointVelocity(Vector2D worldOffset) { tangent.x = -worldOffset.y; tangent.y = worldOffset.x; pointVelVec.x = (tangent.x * angularVelocity) + velocity.x; pointVelVec.y = (tangent.y * angularVelocity) + velocity.y; return pointVelVec; } public void applyForce(Vector2D worldForce, Vector2D worldOffset) { //add linear force forces.x += worldForce.x; forces.y += worldForce.y; //add associated torque torque += Vector2D.cross(worldOffset, worldForce); } @Override public void draw( GraphicsContext c) { c.drawRotatedScaledBitmap(image, getPosition().x, getPosition().y, getWidth(), getHeight(), getAngle()); } public Vector2D getVelocity() { return velocity; } public void setVelocity(Vector2D velocity) { this.velocity = velocity; } } The way it is given force is by the applyForce method, this method considers angular torque. I'm just not sure how to come up with the vectors in the case where: RigidBody hits static entity RigidBody hits other RigidBody that may or may not be in motion. Would anyone know a way (without too complex math) that I could figure out the opposite force I need to apply to the car? I know the normal it is colliding with and how deep it collided. My main goal is so that say I hit a building from the side, well the car should not just stay there, it should slowly rotate out of it if I'm more than 45 degrees. Right now when I hit a wall I only change the velocity directly which does not consider angular force. Thanks!

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  • Spring can commit Transaction in finally block with RunTimeException in try block [migrated]

    - by Chance Lai
    The project used Spring + Hibernate Sample code: public void method(){ try{ dao.saveA(entityA); throw RuntimeException; dao.saveB(entityB); }catch(RuntimeException e){ throw e; }finally{ dao.saveC(entityC) } } Finally, just entityC will be saved in database in test. I think saveA, saveB, saveC in the same transaction,they should not be committed. In this case, I want to know why entityC is committed. How does Spring do this in the finally block?

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  • Errors happen when using World.destroyBody( Body body )

    - by minami
    on Android application using libgdx, when I use World.destroyBody( Body body ) method, once in a while the application suddenly shuts down. Is there some setting I need to do with body collision or Box2DDebugRenderer before I destroy bodies? Below is the source I use for destroying bodies. private void deleteUnusedObject( ) { for( Iterator<Body> iter = mWorld.getBodies() ; iter.hasNext() ; ){ Body body = iter.next( ) ; if( body.getUserData( ) != null ) { Box2DUserData data = (Box2DUserData) body.getUserData( ) ; if( ! data.getActFlag() ) { if( body != null ) { mWorld.destroyBody( body ) ; } } } } } Thanks

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  • WebSocket API 1.1 released!

    - by Pavel Bucek
    Its my please to announce that JSR 356 – Java API for WebSocket maintenance release ballot vote finished with majority of “yes” votes (actually, only one eligible voter did not vote, all other votes were “yeses”). New release is maintenance release and it addresses only one issue:  WEBSOCKET_SPEC-226. What changed in the 1.1? Version 1.1 is fully backwards compatible with version 1.0, there are only two methods added to javax.websocket.Session: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 /** * Register to handle to incoming messages in this conversation. A maximum of one message handler per * native websocket message type (text, binary, pong) may be added to each Session. I.e. a maximum * of one message handler to handle incoming text messages a maximum of one message handler for * handling incoming binary messages, and a maximum of one for handling incoming pong * messages. For further details of which message handlers handle which of the native websocket * message types please see {@link MessageHandler.Whole} and {@link MessageHandler.Partial}. * Adding more than one of any one type will result in a runtime exception. * * @param clazz   type of the message processed by message handler to be registered. * @param handler whole message handler to be added. * @throws IllegalStateException if there is already a MessageHandler registered for the same native *                               websocket message type as this handler. */ public void addMessageHandler(Class<T> clazz, MessageHandler.Whole<T> handler); /** * Register to handle to incoming messages in this conversation. A maximum of one message handler per * native websocket message type (text, binary, pong) may be added to each Session. I.e. a maximum * of one message handler to handle incoming text messages a maximum of one message handler for * handling incoming binary messages, and a maximum of one for handling incoming pong * messages. For further details of which message handlers handle which of the native websocket * message types please see {@link MessageHandler.Whole} and {@link MessageHandler.Partial}. * Adding more than one of any one type will result in a runtime exception. * * * @param clazz   type of the message processed by message handler to be registered. * @param handler partial message handler to be added. * @throws IllegalStateException if there is already a MessageHandler registered for the same native *                               websocket message type as this handler. */ public void addMessageHandler(Class<T> clazz, MessageHandler.Partial<T> handler); Why do we need to add those methods? Short and not precise version: to support Lambda expressions as MessageHandlers. Longer and slightly more precise explanation: old Session#addMessageHandler method (which is still there and works as it worked till now) does rely on getting the generic parameter during the runtime, which is not (always) possible. The unfortunate part is that it works for some common cases and the expert group did not catch this issue before 1.0 release because of that. The issue is really clearly visible when Lambdas are used as message handlers: 1 2 3 session.addMessageHandler(message -> { System.out.println("### Received: " + message); }); There is no way for the JSR 356 implementation to get the type of the used Lambda expression, thus this call will always result in an exception. Since all modern IDEs do recommend to use Lambda expressions when possible and MessageHandler interfaces are single method interfaces, it basically just scream “use Lambdas” all over the place but when you do that, the application will fail during runtime. Only solution we currently have is to explicitly provide the type of registered MessageHandler. (There might be another sometime in the future when generic type reification is introduced, but that is not going to happen soon enough). So the example above will then be: 1 2 3 session.addMessageHandler(String.class, message -> { System.out.println("### Received: " + message); }); and voila, it works. There are some limitations – you cannot do 1 List<String>.class , so you will need to encapsulate these types when you want to use them in MessageHandler implementation (something like “class MyType extends ArrayList<String>”). There is no better way how to solve this issue, because Java currently does not provide good way how to describe generic types. The api itself is available on maven central, look for javax.websocket:javax.websocket-api:1.1. The reference implementation is project Tyrus, which implements WebSocket API 1.1 from version 1.8.

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  • Where should i organize my matrices in a 3D Game engine?

    - by Need4Sleep
    I'm working with a group of people from around the world to create a game engine(and hopefully a game with it) within the next upcoming years. My first task was writing a camera class for the engine to use in order to add cameras to the scene, position and follow points in the scene. The problem i have is with using matrices for transformations in the class, should i keep matrices separate to each class? such as have the model matrix in the model class, camera matrix in the camera class, or have all matrices placed in one class/chuck? I could see pros and cons for each method, but i wanted to hear some input form a more professional standpoint.

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  • .NET Security Part 4

    - by Simon Cooper
    Finally, in this series, I am going to cover some of the security issues that can trip you up when using sandboxed appdomains. DISCLAIMER: I am not a security expert, and this is by no means an exhaustive list. If you actually are writing security-critical code, then get a proper security audit of your code by a professional. The examples below are just illustrations of the sort of things that can go wrong. 1. AppDomainSetup.ApplicationBase The most obvious one is the issue covered in the MSDN documentation on creating a sandbox, in step 3 – the sandboxed appdomain has the same ApplicationBase as the controlling appdomain. So let’s explore what happens when they are the same, and an exception is thrown. In the sandboxed assembly, Sandboxed.dll (IPlugin is an interface in a partially-trusted assembly, with a single MethodToDoThings on it): public class UntrustedPlugin : MarshalByRefObject, IPlugin { // implements IPlugin.MethodToDoThings() public void MethodToDoThings() { throw new EvilException(); } } [Serializable] internal class EvilException : Exception { public override string ToString() { // show we have read access to C:\Windows // read the first 5 directories Console.WriteLine("Pwned! Mwuahahah!"); foreach (var d in Directory.EnumerateDirectories(@"C:\Windows").Take(5)) { Console.WriteLine(d.FullName); } return base.ToString(); } } And in the controlling assembly: // what can possibly go wrong? AppDomainSetup appDomainSetup = new AppDomainSetup { ApplicationBase = AppDomain.CurrentDomain.SetupInformation.ApplicationBase } // only grant permissions to execute // and to read the application base, nothing else PermissionSet restrictedPerms = new PermissionSet(PermissionState.None); restrictedPerms.AddPermission( new SecurityPermission(SecurityPermissionFlag.Execution)); restrictedPerms.AddPermission( new FileIOPermission(FileIOPermissionAccess.Read, appDomainSetup.ApplicationBase); restrictedPerms.AddPermission( new FileIOPermission(FileIOPermissionAccess.pathDiscovery, appDomainSetup.ApplicationBase); // create the sandbox AppDomain sandbox = AppDomain.CreateDomain("Sandbox", null, appDomainSetup, restrictedPerms); // execute UntrustedPlugin in the sandbox // don't crash the application if the sandbox throws an exception IPlugin o = (IPlugin)sandbox.CreateInstanceFromAndUnwrap("Sandboxed.dll", "UntrustedPlugin"); try { o.MethodToDoThings() } catch (Exception e) { Console.WriteLine(e.ToString()); } And the result? Oops. We’ve allowed a class that should be sandboxed to execute code with fully-trusted permissions! How did this happen? Well, the key is the exact meaning of the ApplicationBase property: The application base directory is where the assembly manager begins probing for assemblies. When EvilException is thrown, it propagates from the sandboxed appdomain into the controlling assembly’s appdomain (as it’s marked as Serializable). When the exception is deserialized, the CLR finds and loads the sandboxed dll into the fully-trusted appdomain. Since the controlling appdomain’s ApplicationBase directory contains the sandboxed assembly, the CLR finds and loads the assembly into a full-trust appdomain, and the evil code is executed. So the problem isn’t exactly that the sandboxed appdomain’s ApplicationBase is the same as the controlling appdomain’s, it’s that the sandboxed dll was in such a place that the controlling appdomain could find it as part of the standard assembly resolution mechanism. The sandbox then forced the assembly to load in the controlling appdomain by throwing a serializable exception that propagated outside the sandbox. The easiest fix for this is to keep the sandbox ApplicationBase well away from the ApplicationBase of the controlling appdomain, and don’t allow the sandbox permissions to access the controlling appdomain’s ApplicationBase directory. If you do this, then the sandboxed assembly can’t be accidentally loaded into the fully-trusted appdomain, and the code can’t be executed. If the plugin does try to induce the controlling appdomain to load an assembly it shouldn’t, a SerializationException will be thrown when it tries to load the assembly to deserialize the exception, and no damage will be done. 2. Loading the sandboxed dll into the application appdomain As an extension of the previous point, you shouldn’t directly reference types or methods in the sandboxed dll from your application code. That loads the assembly into the fully-trusted appdomain, and from there code in the assembly could be executed. Instead, pull out methods you want the sandboxed dll to have into an interface or class in a partially-trusted assembly you control, and execute methods via that instead (similar to the example above with the IPlugin interface). If you need to have a look at the assembly before executing it in the sandbox, either examine the assembly using reflection from within the sandbox, or load the assembly into the Reflection-only context in the application’s appdomain. The code in assemblies in the reflection-only context can’t be executed, it can only be reflected upon, thus protecting your appdomain from malicious code. 3. Incorrectly asserting permissions You should only assert permissions when you are absolutely sure they’re safe. For example, this method allows a caller read-access to any file they call this method with, including your documents, any network shares, the C:\Windows directory, etc: [SecuritySafeCritical] public static string GetFileText(string filePath) { new FileIOPermission(FileIOPermissionAccess.Read, filePath).Assert(); return File.ReadAllText(filePath); } Be careful when asserting permissions, and ensure you’re not providing a loophole sandboxed dlls can use to gain access to things they shouldn’t be able to. Conclusion Hopefully, that’s given you an idea of some of the ways it’s possible to get past the .NET security system. As I said before, this post is not exhaustive, and you certainly shouldn’t base any security-critical applications on the contents of this blog post. What this series should help with is understanding the possibilities of the security system, and what all the security attributes and classes mean and what they are used for, if you were to use the security system in the future.

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