Search Results

Search found 47130 results on 1886 pages for 'oracle java me embedded'.

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

Page 630/1886 | < Previous Page | 626 627 628 629 630 631 632 633 634 635 636 637  | Next Page >

  • Google Drive SDK: Writing your First App in Java

    Google Drive SDK: Writing your First App in Java During this session we'll show how to build a complete Java application that uses the Google Drive API to upload a file into the user's Drive account. If you follow along with the presentation, you can have a working Drive command-line application running by the end of the session. From: GoogleDevelopers Views: 0 0 ratings Time: 00:00 More in Science & Technology

    Read the article

  • Présentation de Zkoss, un framework RIA pure Java qui demande à être connu

    Zkoss, un framework RIA pure Java qui demande à être connu 1.Introduction Ce mini-article a pour intention de vous faire découvrir un framework RIA encore peu connu mais si puissant..Zkoss est un framework pur java permettant de faire des applications RIA comparables à Silverlight, Flex, IcesFaces, RichFaces, OpenFaces... Vous allez sûrement me dire qu'il s'agit d'un framework parmi tant d'autres... Cet exact, mais celui-ci apporte de gros avantages par rapport à ceux précités...Vous pouvez découvrir cette démo en ligne ici. 2.Avantages 2.1 Rapidité de conception La rapidité de prise ...

    Read the article

  • Qt : Nokia proposera démos et conférence lors du rts EMBEDDED SYSTEMS de Paris du 30 au 31 Mars proc

    Nokia proposera des démos de Qt lors du rts EMBEDDED SYSTEMS Du 30 au 31 Mars à la Porte de Versailles Nokia sera présent lors du rts EMBEDDED SYSTEMS, 18ème édition du salon des Solutions informatiques temps-réel et systèmes embarqués. Sur son stand (#A20) le constructeur proposera des démos de Qt et le mercredi 31 mars, à 13h, Thierry Bastian, Software Engineer, tiendra une conférence pour présenter le framework multi-plateformes. La manifestation se tiendra à la Porte de Versailles à Paris. Plus d'informations et les modalités pour s'inscrire sur cette page....

    Read the article

  • Qt : Nokia proposera démos et conférence lors du rts EMBEDDED SYSTEMS de Paris du 30 au 31 Mars proc

    Nokia proposera des démos de Qt lors du rts EMBEDDED SYSTEMS Du 30 au 31 Mars à la Porte de Versailles Nokia sera présent lors du rts EMBEDDED SYSTEMS, 18ème édition du salon des Solutions informatiques temps-réel et systèmes embarqués. Sur son stand (#A20) le constructeur proposera des démos de Qt et le mercredi 31 mars, à 13h, Thierry Bastian, Software Engineer, tiendra une conférence pour présenter le framework multi-plateformes. La manifestation se tiendra à la Porte de Versailles à Paris. Plus d'informations et les modalités pour s'inscrire sur cette page....

    Read the article

  • how to call web method in java application?.

    - by user12344
    Hi, I have created java web application(Web Service). I want to call the setName() method in java application(GUI). how is call web method in application?. package sv; import javax.jws.WebMethod; import javax.jws.WebParam; import javax.jws.WebService; @WebService() public class MyService { @WebMethod(operationName = "setName") public String setName(@WebParam(name = "name") String name) { return "my string is "+ name; } }

    Read the article

  • Accenture recrute des experts Java/J2EE à Paris, Nantes et Toulouse

    Accenture recrute des experts Java/J2EE A Paris, Nantes et Toulouse Que vous soyez stagiaire, jeune diplômé ou expert, Accenture recrute des développeurs, des ingénieurs d'études ava/J2EE pour sa filiale Accenture Technology Solutions. Les profils recherchés, fonctionnels ou techniques, concernent particulièrement les expertises SAP, Java/J2EE, Test, Oracle, BI Business Intelligence et AMOA. Citation: Rejoignez un groupe international de plus de 240 000...

    Read the article

  • Obtaining the correct Client IP address when a Physical Load Balancer and a Web Server Configured With Proxy Plug-in Are Between The Client And Weblogic

    - by adejuanc
    Some Load Balancers like Big-IP have build in interoperability with Weblogic Cluster, this means they know how Weblogic understand a header named 'WL-Proxy-Client-IP' to identify the original client ip.The problem comes when you have a Web Server configured with weblogic plug-in between the Load Balancer and the back-end weblogic servers - WL-Proxy-Client-IP this is not designed to go to Web server proxy plug-in. The plug-in will not use a WL-Proxy-Client-IP header that came in from the previous hop (which is this case is the Physical Load Balancer but could be anything), in order to prevent IP spoofing, therefore the plug-in won't pass on what Load Balancer has set for it.So unfortunately under this Architecture the header will be useless. To get the client IP from Weblogic you need to configure extended log format and create a custom field that gets the appropriate header containing the IP of the client.On WLS versions prior to 10.3.3 use these instructions:You can also create user-defined fields for inclusion in an HTTP access log file that uses the extended log format. To create a custom field you identify the field in the ELF log file using the Fields directive and then you create a matching Java class that generates the desired output. You can create a separate Java class for each field, or the Java class can output multiple fields. For a sample of the Java source for such a class, seeJava Class for Creating a Custom ELF Field to import weblogic.servlet.logging.CustomELFLogger;import weblogic.servlet.logging.FormatStringBuffer;import weblogic.servlet.logging.HttpAccountingInfo;/* This example outputs the X-Forwarded-For field into a custom field called MyOriginalClientIPField */public class MyOriginalClientIPField implements CustomELFLogger{ public void logField(HttpAccountingInfo metrics,  FormatStringBuffer buff) {   buff.appendValueOrDash(metrics.getHeader("X-Forwarded-For");  }}In this case we are using 'X-Forwarded-For' but it could be changed for the header that contains the data you need to use.Compile the class, jar it, and prepend it to the classpath.In order to compile and package the class: 1. Navigate to <WLS_HOME>/user_projects/domains/<SOME_DOMAIN>/bin2. Set up an environment by executing: $ . ./setDomainEnv.sh This will include weblogic.jar into classpath, in order to use any of the libraries included under package weblogic.*3. Compile the class by copying the content of the code above and naming the file as:MyOriginalClientIPField.java4. Run javac to compile the class.$javac MyOriginalClientIPField.java5. Package the compiled class into a jar file by executing:$jar cvf0 MyOriginalClientIPField.jar MyOriginalClientIPField.classExpected output is:added manifestadding: MyOriginalClientIPField.class(in = 711) (out= 711)(stored 0%)6. This will produce a file called:MyOriginalClientIPField.jar This way you will be able to get the real client IP when the request is passing through a Load Balancer and a Web server before reaching WLS. Since 10.3.3 it is possible to configure a specific header that WLS will check when getRemoteAddr is called. That can be set on the WebServer Mbean. In this case, set that to be X-Forwarded-For header coming from Load Balancer as well.

    Read the article

  • Windows Embedded Standard 8 : la CTP 2 disponible, 6.000 développeurs utiliseraient déjà l'OS embarqué dérivé de Windows 8

    Windows Embedded Standard 8 : la deuxième CTP disponible Plus de 6 000 développeurs utilisent déjà l'OS embarqué dérivé de Windows 8 Mise à jour du 07/06/12 Hier, au salon Computex de Taïwan, Steven Guggenheimer, vice-président du service OEM de Microsoft, est monté sur scène pour présenter les dernières technologies de Microsoft sur les « systèmes intelligents » (appareils qui embarquent un OS et qui permettent de se connecter à des terminaux spécialisés ou à des services en ligne comme des serveurs distants ou des bases de données). Il en a profité pour annoncer la disponibilité de la deuxième community technology preview (CTP) de Windows Embedded Standard 8...

    Read the article

  • Windows Embedded 8 sortira en mars 2013, Microsoft publie la Roadmap et une préversion de son OS embarqué, fondé sur Windows 8

    Windows Embedded Standard 8 : la deuxième CTP disponible Plus de 6 000 développeurs utilisent déjà l'OS embarqué dérivé de Windows 8 Mise à jour du 07/06/12 Hier, au salon Computex de Taïwan, Steven Guggenheimer, vice-président du service OEM de Microsoft, est monté sur scène pour présenter les dernières technologies de Microsoft sur les « systèmes intelligents » (appareils qui embarquent un OS et qui permettent de se connecter à des terminaux spécialisés ou à des services en ligne comme des serveurs distants ou des bases de données). Il en a profité pour annoncer la disponibilité de la deuxième community technology preview (CTP) de Windows Embedded Standard 8...

    Read the article

  • Android Out of memory regarding png image

    - by turtleboy
    I have a jpg image in my app that shows correctly. In my listview i'd like to make the image more transparent so it is easier to see the text. I changed the image to a png format and altered it's opacity in GIMP. Now that the new image is in the app drawable folder. Im getting the following error. why? 09-28 09:24:07.560: I/global(20140): call socket shutdown, tmpsocket=Socket[address=/178.250.50.40,port=80,localPort=35172] 09-28 09:24:07.570: I/global(20140): call socket shutdown, tmpsocket=Socket[address=/212.169.27.217,port=84,localPort=55656] 09-28 09:24:07.690: D/dalvikvm(20140): GC_FOR_ALLOC freed 113K, 4% free 38592K/39907K, paused 32ms 09-28 09:24:07.690: I/dalvikvm-heap(20140): Forcing collection of SoftReferences for 28072816-byte allocation 09-28 09:24:07.740: D/dalvikvm(20140): GC_BEFORE_OOM freed 9K, 4% free 38582K/39907K, paused 43ms 09-28 09:24:07.740: E/dalvikvm-heap(20140): Out of memory on a 28072816-byte allocation. 09-28 09:24:07.740: I/dalvikvm(20140): "main" prio=5 tid=1 RUNNABLE 09-28 09:24:07.740: I/dalvikvm(20140): | group="main" sCount=0 dsCount=0 obj=0x40a57490 self=0x1b6e9a8 09-28 09:24:07.740: I/dalvikvm(20140): | sysTid=20140 nice=0 sched=0/0 cgrp=default handle=1074361640 09-28 09:24:07.740: I/dalvikvm(20140): | schedstat=( 2289118000 760844000 2121 ) utm=195 stm=33 core=1 09-28 09:24:07.740: I/dalvikvm(20140): at android.graphics.BitmapFactory.nativeDecodeAsset(Native Method) 09-28 09:24:07.740: I/dalvikvm(20140): at android.graphics.BitmapFactory.decodeResourceStream(BitmapFactory.java:486) 09-28 09:24:07.740: I/dalvikvm(20140): at android.graphics.drawable.Drawable.createFromResourceStream(Drawable.java:773) 09-28 09:24:07.740: I/dalvikvm(20140): at android.content.res.Resources.loadDrawable(Resources.java:2042) 09-28 09:24:07.740: I/dalvikvm(20140): at android.content.res.TypedArray.getDrawable(TypedArray.java:601) 09-28 09:24:07.740: I/dalvikvm(20140): at android.view.View.<init>(View.java:2812) 09-28 09:24:07.740: I/dalvikvm(20140): at android.view.ViewGroup.<init>(ViewGroup.java:410) 09-28 09:24:07.740: I/dalvikvm(20140): at android.widget.LinearLayout.<init>(LinearLayout.java:174) 09-28 09:24:07.740: I/dalvikvm(20140): at android.widget.LinearLayout.<init>(LinearLayout.java:170) 09-28 09:24:07.740: I/dalvikvm(20140): at java.lang.reflect.Constructor.constructNative(Native Method) 09-28 09:24:07.740: I/dalvikvm(20140): at java.lang.reflect.Constructor.newInstance(Constructor.java:417) 09-28 09:24:07.740: I/dalvikvm(20140): at android.view.LayoutInflater.createView(LayoutInflater.java:586) 09-28 09:24:07.740: I/dalvikvm(20140): at com.android.internal.policy.impl.PhoneLayoutInflater.onCreateView(PhoneLayoutInflater.java:56) 09-28 09:24:07.740: I/dalvikvm(20140): at android.view.LayoutInflater.onCreateView(LayoutInflater.java:653) 09-28 09:24:07.740: I/dalvikvm(20140): at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:678) 09-28 09:24:07.740: I/dalvikvm(20140): at android.view.LayoutInflater.inflate(LayoutInflater.java:466) 09-28 09:24:07.740: I/dalvikvm(20140): at android.view.LayoutInflater.inflate(LayoutInflater.java:396) 09-28 09:24:07.740: I/dalvikvm(20140): at android.view.LayoutInflater.inflate(LayoutInflater.java:352) 09-28 09:24:07.740: I/dalvikvm(20140): at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:278) 09-28 09:24:07.740: I/dalvikvm(20140): at android.app.Activity.setContentView(Activity.java:1897) 09-28 09:24:07.740: I/dalvikvm(20140): at com.carefreegroup.ShowMoreDetails.onCreate(ShowMoreDetails.java:26) 09-28 09:24:07.740: I/dalvikvm(20140): at android.app.Activity.performCreate(Activity.java:4543) 09-28 09:24:07.740: I/dalvikvm(20140): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1071) 09-28 09:24:07.740: I/dalvikvm(20140): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2181) 09-28 09:24:07.740: I/dalvikvm(20140): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2260) 09-28 09:24:07.740: I/dalvikvm(20140): at android.app.ActivityThread.access$600(ActivityThread.java:139) 09-28 09:24:07.740: I/dalvikvm(20140): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1277) 09-28 09:24:07.740: I/dalvikvm(20140): at android.os.Handler.dispatchMessage(Handler.java:99) 09-28 09:24:07.740: I/dalvikvm(20140): at android.os.Looper.loop(Looper.java:156) 09-28 09:24:07.740: I/dalvikvm(20140): at android.app.ActivityThread.main(ActivityThread.java:5045) 09-28 09:24:07.740: I/dalvikvm(20140): at java.lang.reflect.Method.invokeNative(Native Method) 09-28 09:24:07.740: I/dalvikvm(20140): at java.lang.reflect.Method.invoke(Method.java:511) 09-28 09:24:07.740: I/dalvikvm(20140): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 09-28 09:24:07.740: I/dalvikvm(20140): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 09-28 09:24:07.740: I/dalvikvm(20140): at dalvik.system.NativeStart.main(Native Method) 09-28 09:24:07.740: E/dalvikvm(20140): Out of memory: Heap Size=46115KB, Allocated=38582KB, Limit=65536KB 09-28 09:24:07.740: E/dalvikvm(20140): Extra info: Footprint=39907KB, Allowed Footprint=46115KB, Trimmed=892KB 09-28 09:24:07.740: E/Bitmap_JNI(20140): Create Bitmap Failed. 09-28 09:24:07.740: A/libc(20140): Fatal signal 11 (SIGSEGV) at 0x00000004 (code=1) 09-28 09:24:09.750: I/dalvikvm(20367): Turning on JNI app bug workarounds for target SDK version 10... 09-28 09:24:09.940: D/dalvikvm(20367): GC_CONCURRENT freed 864K, 21% free 3797K/4771K, paused 2ms+2ms thanks. [update] @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.showmoredetailslayout); actualCallTime = (TextView)findViewById(R.id.actualcalltime); doubleUp = (TextView)findViewById(R.id.doubleupcallid); needName = (TextView)findViewById(R.id.needname); needNameLabel = (TextView)findViewById(R.id.neednamelabel); getRotaDetails = (Button)findViewById(R.id.buttongetrotadetails); intent = this.getIntent(); String actualTimeIn = intent.getStringExtra("actTimeIn"); String actualTimeOut = intent.getStringExtra("actTimeOut"); String doubleUpValue = intent.getStringExtra("doubleUpValue"); String needNameWithCommas = intent.getStringExtra("needNameWithCommas"); callID = intent.getStringExtra("callID"); String[] needs = needNameWithCommas.split(","); actualCallTime.setText("This call was completed at " + actualTimeIn + " -" + actualTimeOut); if( ! doubleUpValue.equalsIgnoreCase("") || doubleUpValue.equalsIgnoreCase("]")){ doubleUp.setText("This call was not a double up "); }else{ doubleUp.setText("This call was a double up " + doubleUpValue); } needNameLabel.setText("Purpose of Call: "); for (int i = 0; i < needs.length; i++){ needName.append( needs[i] + "\n"); } getRotaDetails.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { Intent intent = new Intent(ShowMoreDetails.this, GetRotaDetails.class); intent.putExtra("callIDExtra", callID); startActivity(intent); } }); } }

    Read the article

  • Performance Comparison of Shell Scripts vs high level interpreted langs (C#/Java/etc.)

    - by dferraro
    Hi all, First - This is not meant to be a 'which is better, ignorant nonionic war thread'... But rather, I generally need help in making an architecture decision / argument to put forward to my boss. Skipping the details - I simply just would love to know and find the results of anyone who has done some performance comparisons of Shell vs [Insert General Purpose Programming Language (interpreted) here), such as C# or Java... Surprisingly, I have spent some time on Google on searching here to not find any of this data. Has anyone ever done these comparisons, in different use-cases; hitting a database like in a XYX # of loops doing different types of SQL (Oracle pref, but MSSQL would do) queries such as any of the CRUD ops - and also not hitting database and just regular 50k loop type comparison doing different types of calculations, and things of that nature? In particular - for right now, I need to a comparison of hitting an Oracle DB from a shell script vs, lets say C# (again, any GPPL thats interpreted would be fine, even the higher level ones like Python). But I also need to know about standard programming calculations / instructions/etc... Before you ask 'why not just write a quick test yourself? The answer is: I've been a Windows developer my whole life/career and have very limited knowledge of Shell scripting - not to mention *nix as a whole.... So asking the question on here from the more experienced guys would be grealty beneficial, not to mention time saving as we are in near perputual deadline crunch as it is ;). Thanks so much in advance,

    Read the article

  • Windows 8 Embedded preview sera publié au premier trimestre 2012, la version finale disponible trois mois après la sortie de Windows 8

    Windows 8 Embedded : la préversion de l'OS sera publiée au premier trimestre 2012 La version finale sera disponible trois trimestres après la sortie de Windows 8 Microsoft prévoit de mettre à la disposition des développeurs une préversion de Windows 8 Embedded, son OS pour l'embarqué pendant le premier trimestre de l'année prochaine. La prochaine version du système sera développée suivant une approche plus agile, ciblée et moins monolithique. Elle a pour vocation d'étendre les solutions d'entreprises et les services Cloud aux appareils de la vie quotidienne, tels que les terminaux de points de service, les systèmes d'info loisirs automobiles, les équipements médicaux, les machines...

    Read the article

  • Javassist annoations problem

    - by Ali
    I'm trying to generate my Entity class using javassist. Everything went well until I added the GeneratedValue annotation to the Id field. The @Id annotation works fine but when I add @GeneeratedValue I get an exception. This is my code: ClassPool cp = ClassPool.getDefault(); CtClass ctClass = cp.makeClass("test.Snake"); ClassFile classFile = ctClass.getClassFile(); classFile.setVersionToJava5(); AnnotationsAttribute attribute = new AnnotationsAttribute(classFile.getConstPool(), AnnotationsAttribute.visibleTag); Annotation idAnnotation = new Annotation(classFile.getConstPool(), ClassPool.getDefault().get("javax.persistence.Id")); attribute.addAnnotation(idAnnotation); Annotation gvAnnotation = new Annotation(classFile.getConstPool(), ClassPool.getDefault().get("javax.persistence.GeneratedValue")); attribute.addAnnotation(gvAnnotation); CtField idField = new CtField(ClassPool.getDefault().get("java.lang.Long"), "id", ctClass); idField.getFieldInfo().addAttribute(attribute); ctClass.addField(idField); CtField nameField = new CtField(ClassPool.getDefault().get("java.lang.String"), "name", ctClass); ctClass.addField(nameField); AnnotationsAttribute attr = new AnnotationsAttribute(classFile.getConstPool(), AnnotationsAttribute.visibleTag); Annotation annotation = new Annotation(classFile.getConstPool(), ClassPool.getDefault().get("javax.persistence.Entity")); attr.addAnnotation(annotation); classFile.addAttribute(attr); snakeClass = ctClass.toClass(); newInstance = snakeClass.newInstance(); And this is the exception I get: java.lang.NullPointerException at javassist.bytecode.ConstPool.getUtf8Info(ConstPool.java:565) at javassist.bytecode.annotation.EnumMemberValue.getValue(EnumMemberValue.java:98) at javassist.bytecode.annotation.EnumMemberValue.write(EnumMemberValue.java:116) at javassist.bytecode.annotation.Annotation.write(Annotation.java:316) at javassist.bytecode.AnnotationsAttribute.setAnnotations(AnnotationsAttribute.java:246) at javassist.bytecode.AnnotationsAttribute.addAnnotation(AnnotationsAttribute.java:211) at ClassLoadingTest.javassitTest(ClassLoadingTest.java:56) It seems to be a problem with @GeneratedValue. When I use it alone whithout id I get this exception either. When I use eclipse debugger to watch variable values, I get get this com.sun.jdi.InvocationException occurred invoking method. instead of the annotation value. but for Id annotation it shows a javassist annotation object. I'm new to javassist. Can anyone help me?

    Read the article

  • BindException with INTERNET permission requested

    - by Mondain
    I have seen several questions regarding SocketException when using Android, but none of them cover the BindException that I get even with the INTERNET permission specified in my manifest. Here is part of my manifest: <uses-permission android:name="android.permission.INTERNET"></uses-permission> <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"></uses-permission> <uses-permission android:name="android.permission.ACCESS_WIFI_STATE"></uses-permission> <uses-permission android:name="android.permission.READ_OWNER_DATA"></uses-permission> <uses-permission android:name="android.permission.READ_PHONE_STATE"></uses-permission> <uses-permission android:name="android.permission.ACCOUNT_MANAGER"></uses-permission> <uses-permission android:name="android.permission.AUTHENTICATE_ACCOUNTS"></uses-permission> Here is the relevant portion of my LogCat output: 04-22 14:49:06.117: DEBUG/MyLibrary(4844): Address to bind: 192.168.1.14 port: 843 04-22 14:49:06.197: WARN/System.err(4844): java.net.BindException: Permission denied (maybe missing INTERNET permission) 04-22 14:49:06.207: WARN/System.err(4844): at org.apache.harmony.luni.platform.OSNetworkSystem.socketBindImpl(Native Method) 04-22 14:49:06.207: WARN/System.err(4844): at org.apache.harmony.luni.platform.OSNetworkSystem.bind(OSNetworkSystem.java:107) 04-22 14:49:06.217: WARN/System.err(4844): at org.apache.harmony.luni.net.PlainSocketImpl.bind(PlainSocketImpl.java:184) 04-22 14:49:06.217: WARN/System.err(4844): at java.net.ServerSocket.bind(ServerSocket.java:414) 04-22 14:49:06.227: WARN/System.err(4844): at org.apache.harmony.nio.internal.ServerSocketChannelImpl$ServerSocketAdapter.bind(ServerSocketChannelImpl.java:213) 04-22 14:49:06.227: WARN/System.err(4844): at java.net.ServerSocket.bind(ServerSocket.java:367) 04-22 14:49:06.237: WARN/System.err(4844): at org.apache.harmony.nio.internal.ServerSocketChannelImpl$ServerSocketAdapter.bind(ServerSocketChannelImpl.java:283) 04-22 14:49:06.237: WARN/System.err(4844): at mylibrary.net.PolicyConnection$PolicyServerWorker.(PolicyConnection.java:201) I Really hope this is a simple problem and not something complicated by the fact that the binding is occurring within a worker thread on a port less than 1024. Update Looks as if this is a privileged port issue, anyone know how to bind to ports lower than 1024 in Android? SelectorProvider provider = SelectorProvider.provider(); try { ServerSocketChannel channel = provider.openServerSocketChannel(); policySocket = channel.socket(); Log.d("MyLibrary", "Address to bind: " + device.getAddress().getAddress() + " port: 843"); InetSocketAddress addr = new InetSocketAddress(InetAddress.getByName(device.getAddress().getAddress()), 843); policySocket.bind(addr); policySocket.setReuseAddress(true); policySocket.setReceiveBufferSize(256); } catch (Exception e) { e.printStackTrace(); }

    Read the article

  • Why is javac 1.5 running so slowly compared with the Eclipse compiler?

    - by Simon Nickerson
    I have a Java Maven project with about 800 source files (some generated by javacc/JTB) which is taking a good 25 minutes to compile with javac. When I changed my pom.xml over to use the Eclipse compiler, it takes about 30 seconds to compile. Any suggestions as to why javac (1.5) is running so slowly? (I don't want to switch over to the Eclipse compiler permanently, as the plugin for Maven seems more than a little buggy.) I have a test case which easily reproduces the problem. The following code generates a number of source files in the default package. If you try to compile ImplementingClass.java with javac, it will seem to pause for an inordinately long time. import java.io.File; import java.io.FileNotFoundException; import java.io.PrintStream; public class CodeGenerator { private final static String PATH = System.getProperty("java.io.tmpdir"); private final static int NUM_TYPES = 1000; public static void main(String[] args) throws FileNotFoundException { PrintStream interfacePs = new PrintStream(PATH + File.separator + "Interface.java"); PrintStream abstractClassPs = new PrintStream(PATH + File.separator + "AbstractClass.java"); PrintStream implementingClassPs = new PrintStream(PATH + File.separator + "ImplementingClass.java"); interfacePs.println("public interface Interface<T> {"); abstractClassPs.println("public abstract class AbstractClass<T> implements Interface<T> {"); implementingClassPs.println("public class ImplementingClass extends AbstractClass<Object> {"); for (int i=0; i<NUM_TYPES; i++) { String nodeName = "Node" + i; PrintStream nodePs = new PrintStream(PATH + File.separator + nodeName + ".java"); nodePs.printf("public class %s { }\n", nodeName); nodePs.close(); interfacePs.printf("void visit(%s node, T obj);%n", nodeName); abstractClassPs.printf("public void visit(%s node, T obj) { System.out.println(obj.toString()); }%n", nodeName); } interfacePs.println("}"); abstractClassPs.println("}"); implementingClassPs.println("}"); interfacePs.close(); abstractClassPs.close(); implementingClassPs.close(); } }

    Read the article

  • Why does the definition of MyAnnotation need Documented, Inherited, Retention & RetentionPolicy?

    - by cafe
    What is the purpose of these java.lang.annotation imports in this code? Why are they needed to define MyAnnotation? import java.lang.annotation.Documented; import java.lang.annotation.Inherited; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; @Documented @Retention(RetentionPolicy.RUNTIME) @Inherited public @interface MyAnnotation { String value() default ""; }

    Read the article

  • Compiling servlets for tomcat

    - by L4N0
    Hello I am trying to modify one of the default files that comes with tomcat SessionExample.java, and trying to compile it but I get an error. javac -classpath "E:\Program Files\Apache Software Foundation\Apache Tomcat 6.0.18\lib\servlet-api.jar" SessionExample.java Gives me this error SessionExample.java:26: package util does not exist import util.HTMLFilter; ^ SessionExample.java:90: cannot find symbol symbol : variable HTMLFilter location: class SessionExample out.println(HTMLFilter.filter(name) + " = " ^ SessionExample.java:91: cannot find symbol symbol : variable HTMLFilter location: class SessionExample + HTMLFilter.filter(value) + ""); ^ 3 errors Thank you

    Read the article

  • IS classOf[] in scala 2.8 different from 2.7?

    - by redtank
    I have an interface from java public class IJava { ... public java.lang.Class getType(); ... } It is inherited in Scala class CScala { def getType() = classOf[Foo] } it worked in scala 2.7.7. But in 2.8.0.RC1, i get type mismatch; found : java.lang.ClassFoo required: java.lang.Class How do i get java.langClass in Scala 2.8

    Read the article

  • JMS Step 7 - How to Write to an AQ JMS (Advanced Queueing JMS) Queue from a BPEL Process

    - by John-Brown.Evans
    JMS Step 7 - How to Write to an AQ JMS (Advanced Queueing JMS) Queue from a BPEL Process ol{margin:0;padding:0} .jblist{list-style-type:disc;margin:0;padding:0;padding-left:0pt;margin-left:36pt} .c4_7{vertical-align:top;width:468pt;border-style:solid;border-color:#000000;border-width:1pt;padding:5pt 5pt 5pt 5pt} .c3_7{vertical-align:top;width:234pt;border-style:solid;border-color:#000000;border-width:1pt;padding:0pt 5pt 0pt 5pt} .c6_7{vertical-align:top;width:156pt;border-style:solid;border-color:#000000;border-width:1pt;padding:5pt 5pt 5pt 5pt} .c16_7{background-color:#ffffff;padding:0pt 0pt 0pt 0pt} .c0_7{height:11pt;direction:ltr} .c9_7{color:#1155cc;text-decoration:underline} .c17_7{color:inherit;text-decoration:inherit} .c5_7{direction:ltr} .c18_7{background-color:#ffff00} .c2_7{background-color:#f3f3f3} .c14_7{height:0pt} .c8_7{text-indent:36pt} .c11_7{text-align:center} .c7_7{font-style:italic} .c1_7{font-family:"Courier New"} .c13_7{line-height:1.0} .c15_7{border-collapse:collapse} .c12_7{font-weight:bold} .c10_7{font-size:8pt} .title{padding-top:24pt;line-height:1.15;text-align:left;color:#000000;font-size:36pt;font-family:"Arial";font-weight:bold;padding-bottom:6pt} .subtitle{padding-top:18pt;line-height:1.15;text-align:left;color:#666666;font-style:italic;font-size:24pt;font-family:"Georgia";padding-bottom:4pt} li{color:#000000;font-size:10pt;font-family:"Arial"} p{color:#000000;font-size:10pt;margin:0;font-family:"Arial"} h1{padding-top:0pt;line-height:1.15;text-align:left;color:#888;font-size:24pt;font-family:"Arial";font-weight:normal} h2{padding-top:0pt;line-height:1.15;text-align:left;color:#888;font-size:18pt;font-family:"Arial";font-weight:normal} h3{padding-top:0pt;line-height:1.15;text-align:left;color:#888;font-size:14pt;font-family:"Arial";font-weight:normal} h4{padding-top:0pt;line-height:1.15;text-align:left;color:#888;font-size:12pt;font-family:"Arial";font-weight:normal} h5{padding-top:0pt;line-height:1.15;text-align:left;color:#888;font-size:11pt;font-family:"Arial";font-weight:normal} h6{padding-top:0pt;line-height:1.15;text-align:left;color:#888;font-size:10pt;font-family:"Arial";font-weight:normal} This post continues the series of JMS articles which demonstrate how to use JMS queues in a SOA context. The previous posts were: JMS Step 1 - How to Create a Simple JMS Queue in Weblogic Server 11g JMS Step 2 - Using the QueueSend.java Sample Program to Send a Message to a JMS Queue JMS Step 3 - Using the QueueReceive.java Sample Program to Read a Message from a JMS Queue JMS Step 4 - How to Create an 11g BPEL Process Which Writes a Message Based on an XML Schema to a JMS Queue JMS Step 5 - How to Create an 11g BPEL Process Which Reads a Message Based on an XML Schema from a JMS Queue JMS Step 6 - How to Set Up an AQ JMS (Advanced Queueing JMS) for SOA Purposes This example demonstrates how to write a simple message to an Oracle AQ via the the WebLogic AQ JMS functionality from a BPEL process and a JMS adapter. If you have not yet reviewed the previous posts, please do so first, especially the JMS Step 6 post, as this one references objects created there. 1. Recap and Prerequisites In the previous example, we created an Oracle Advanced Queue (AQ) and some related JMS objects in WebLogic Server to be able to access it via JMS. Here are the objects which were created and their names and JNDI names: Database Objects Name Type AQJMSUSER Database User MyQueueTable Advanced Queue (AQ) Table UserQueue Advanced Queue WebLogic Server Objects Object Name Type JNDI Name aqjmsuserDataSource Data Source jdbc/aqjmsuserDataSource AqJmsModule JMS System Module AqJmsForeignServer JMS Foreign Server AqJmsForeignServerConnectionFactory JMS Foreign Server Connection Factory AqJmsForeignServerConnectionFactory AqJmsForeignDestination AQ JMS Foreign Destination queue/USERQUEUE eis/aqjms/UserQueue Connection Pool eis/aqjms/UserQueue 2 . Create a BPEL Composite with a JMS Adapter Partner Link This step requires that you have a valid Application Server Connection defined in JDeveloper, pointing to the application server on which you created the JMS Queue and Connection Factory. You can create this connection in JDeveloper under the Application Server Navigator. Give it any name and be sure to test the connection before completing it. This sample will write a simple XML message to the AQ JMS queue via the JMS adapter, based on the following XSD file, which consists of a single string element: stringPayload.xsd <?xml version="1.0" encoding="windows-1252" ?> <xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"                xmlns="http://www.example.org"                targetNamespace="http://www.example.org"                elementFormDefault="qualified">  <xsd:element name="exampleElement" type="xsd:string">  </xsd:element> </xsd:schema> The following steps are all executed in JDeveloper. The SOA project will be created inside a JDeveloper Application. If you do not already have an application to contain the project, you can create a new one via File > New > General > Generic Application. Give the application any name, for example JMSTests and, when prompted for a project name and type, call the project   JmsAdapterWriteAqJms  and select SOA as the project technology type. If you already have an application, continue below. Create a SOA Project Create a new project and select SOA Tier > SOA Project as its type. Name it JmsAdapterWriteAqJms . When prompted for the composite type, choose Composite With BPEL Process. When prompted for the BPEL Process, name it JmsAdapterWriteAqJms too and choose Synchronous BPEL Process as the template. This will create a composite with a BPEL process and an exposed SOAP service. Double-click the BPEL process to open and begin editing it. You should see a simple BPEL process with a Receive and Reply activity. As we created a default process without an XML schema, the input and output variables are simple strings. Create an XSD File An XSD file is required later to define the message format to be passed to the JMS adapter. In this step, we create a simple XSD file, containing a string variable and add it to the project. First select the xsd item in the left-hand navigation tree to ensure that the XSD file is created under that item. Select File > New > General > XML and choose XML Schema. Call it stringPayload.xsd  and when the editor opens, select the Source view. then replace the contents with the contents of the stringPayload.xsd example above and save the file. You should see it under the XSD item in the navigation tree. Create a JMS Adapter Partner Link We will create the JMS adapter as a service at the composite level. If it is not already open, double-click the composite.xml file in the navigator to open it. From the Component Palette, drag a JMS adapter over onto the right-hand swim lane, under External References. This will start the JMS Adapter Configuration Wizard. Use the following entries: Service Name: JmsAdapterWrite Oracle Enterprise Messaging Service (OEMS): Oracle Advanced Queueing AppServer Connection: Use an existing application server connection pointing to the WebLogic server on which the connection factory created earlier is located. You can use the “+” button to create a connection directly from the wizard, if you do not already have one. Adapter Interface > Interface: Define from operation and schema (specified later) Operation Type: Produce Message Operation Name: Produce_message Produce Operation Parameters Destination Name: Wait for the list to populate. (Only foreign servers are listed here, because Oracle Advanced Queuing was selected earlier, in step 3) .         Select the foreign server destination created earlier, AqJmsForeignDestination (queue) . This will automatically populate the Destination Name field with the name of the foreign destination, queue/USERQUEUE . JNDI Name: The JNDI name to use for the JMS connection. This is the JNDI name of the connection pool created in the WebLogic Server.JDeveloper does not verify the value entered here. If you enter a wrong value, the JMS adapter won’t find the queue and you will get an error message at runtime. In our example, this is the value eis/aqjms/UserQueue Messages URL: We will use the XSD file we created earlier, stringPayload.xsd to define the message format for the JMS adapter. Press the magnifying glass icon to search for schema files. Expand Project Schema Files > stringPayload.xsd and select exampleElement : string . Press Next and Finish, which will complete the JMS Adapter configuration. Wire the BPEL Component to the JMS Adapter In this step, we link the BPEL process/component to the JMS adapter. From the composite.xml editor, drag the right-arrow icon from the BPEL process to the JMS adapter’s in-arrow.   This completes the steps at the composite level. 3. Complete the BPEL Process Design Invoke the JMS Adapter Open the BPEL component by double-clicking it in the design view of the composite.xml. This will display the BPEL process in the design view. You should see the JmsAdapterWrite partner link under one of the two swim lanes. We want it in the right-hand swim lane. If JDeveloper displays it in the left-hand lane, right-click it and choose Display > Move To Opposite Swim Lane. An Invoke activity is required in order to invoke the JMS adapter. Drag an Invoke activity between the Receive and Reply activities. Drag the right-hand arrow from the Invoke activity to the JMS adapter partner link. This will open the Invoke editor. The correct default values are entered automatically and are fine for our purposes. We only need to define the input variable to use for the JMS adapter. By pressing the green “+” symbol, a variable of the correct type can be auto-generated, for example with the name Invoke1_Produce_Message_InputVariable. Press OK after creating the variable. Assign Variables Drag an Assign activity between the Receive and Invoke activities. We will simply copy the input variable to the JMS adapter and, for completion, so the process has an output to print, again to the process’s output variable. Double-click the Assign activity and create two Copy rules: for the first, drag Variables > inputVariable > payload > client:process > client:input_string to Invoke1_Produce_Message_InputVariable > body > ns2:exampleElement for the second, drag the same input variable to outputVariable > payload > client:processResponse > client:result This will create two copy rules, similar to the following: Press OK. This completes the BPEL and Composite design. 4. Compile and Deploy the Composite Compile the process by pressing the Make or Rebuild icons or by right-clicking the project name in the navigator and selecting Make... or Rebuild... If the compilation is successful, deploy it to the SOA server connection defined earlier. (Right-click the project name in the navigator, select Deploy to Application Server, choose the application server connection, choose the partition on the server (usually default) and press Finish. You should see the message ----  Deployment finished.  ---- in the Deployment frame, if the deployment was successful. 5. Test the Composite Execute a Test Instance In a browser, log in to the Enterprise Manager 11g Fusion Middleware Control (EM) for your SOA installation. Navigate to SOA > soa-infra (soa_server1) > default (or wherever you deployed your composite) and click on  JmsAdapterWriteAqJms [1.0] , then press the Test button. Enter any string into the text input field, for example “Test message from JmsAdapterWriteAqJms” then press Test Web Service. If the instance is successful, you should see the same text you entered in the Response payload frame. Monitor the Advanced Queue The test message will be written to the advanced queue created at the top of this sample. To confirm it, log in to the database as AQJMSUSER and query the MYQUEUETABLE database table. For example, from a shell window with SQL*Plus sqlplus aqjmsuser/aqjmsuser SQL> SELECT user_data FROM myqueuetable; which will display the message contents, for example Similarly, you can use the JDeveloper Database Navigator to view the contents. Use a database connection to the AQJMSUSER and in the navigator, expand Queues Tables and select MYQUEUETABLE. Select the Data tab and scroll to the USER_DATA column to view its contents. This concludes this example. The following post will be the last one in this series. In it, we will learn how to read the message we just wrote using a BPEL process and AQ JMS. Best regards John-Brown Evans Oracle Technology Proactive Support Delivery

    Read the article

  • value types in the vm

    - by john.rose
    value types in the vm p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Times} p.p2 {margin: 0.0px 0.0px 14.0px 0.0px; font: 14.0px Times} p.p3 {margin: 0.0px 0.0px 12.0px 0.0px; font: 14.0px Times} p.p4 {margin: 0.0px 0.0px 15.0px 0.0px; font: 14.0px Times} p.p5 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Courier} p.p6 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Courier; min-height: 17.0px} p.p7 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Times; min-height: 18.0px} p.p8 {margin: 0.0px 0.0px 0.0px 36.0px; text-indent: -36.0px; font: 14.0px Times; min-height: 18.0px} p.p9 {margin: 0.0px 0.0px 12.0px 0.0px; font: 14.0px Times; min-height: 18.0px} p.p10 {margin: 0.0px 0.0px 12.0px 0.0px; font: 14.0px Times; color: #000000} li.li1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Times} li.li7 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Times; min-height: 18.0px} span.s1 {font: 14.0px Courier} span.s2 {color: #000000} span.s3 {font: 14.0px Courier; color: #000000} ol.ol1 {list-style-type: decimal} Or, enduring values for a changing world. Introduction A value type is a data type which, generally speaking, is designed for being passed by value in and out of methods, and stored by value in data structures. The only value types which the Java language directly supports are the eight primitive types. Java indirectly and approximately supports value types, if they are implemented in terms of classes. For example, both Integer and String may be viewed as value types, especially if their usage is restricted to avoid operations appropriate to Object. In this note, we propose a definition of value types in terms of a design pattern for Java classes, accompanied by a set of usage restrictions. We also sketch the relation of such value types to tuple types (which are a JVM-level notion), and point out JVM optimizations that can apply to value types. This note is a thought experiment to extend the JVM’s performance model in support of value types. The demonstration has two phases.  Initially the extension can simply use design patterns, within the current bytecode architecture, and in today’s Java language. But if the performance model is to be realized in practice, it will probably require new JVM bytecode features, changes to the Java language, or both.  We will look at a few possibilities for these new features. An Axiom of Value In the context of the JVM, a value type is a data type equipped with construction, assignment, and equality operations, and a set of typed components, such that, whenever two variables of the value type produce equal corresponding values for their components, the values of the two variables cannot be distinguished by any JVM operation. Here are some corollaries: A value type is immutable, since otherwise a copy could be constructed and the original could be modified in one of its components, allowing the copies to be distinguished. Changing the component of a value type requires construction of a new value. The equals and hashCode operations are strictly component-wise. If a value type is represented by a JVM reference, that reference cannot be successfully synchronized on, and cannot be usefully compared for reference equality. A value type can be viewed in terms of what it doesn’t do. We can say that a value type omits all value-unsafe operations, which could violate the constraints on value types.  These operations, which are ordinarily allowed for Java object types, are pointer equality comparison (the acmp instruction), synchronization (the monitor instructions), all the wait and notify methods of class Object, and non-trivial finalize methods. The clone method is also value-unsafe, although for value types it could be treated as the identity function. Finally, and most importantly, any side effect on an object (however visible) also counts as an value-unsafe operation. A value type may have methods, but such methods must not change the components of the value. It is reasonable and useful to define methods like toString, equals, and hashCode on value types, and also methods which are specifically valuable to users of the value type. Representations of Value Value types have two natural representations in the JVM, unboxed and boxed. An unboxed value consists of the components, as simple variables. For example, the complex number x=(1+2i), in rectangular coordinate form, may be represented in unboxed form by the following pair of variables: /*Complex x = Complex.valueOf(1.0, 2.0):*/ double x_re = 1.0, x_im = 2.0; These variables might be locals, parameters, or fields. Their association as components of a single value is not defined to the JVM. Here is a sample computation which computes the norm of the difference between two complex numbers: double distance(/*Complex x:*/ double x_re, double x_im,         /*Complex y:*/ double y_re, double y_im) {     /*Complex z = x.minus(y):*/     double z_re = x_re - y_re, z_im = x_im - y_im;     /*return z.abs():*/     return Math.sqrt(z_re*z_re + z_im*z_im); } A boxed representation groups component values under a single object reference. The reference is to a ‘wrapper class’ that carries the component values in its fields. (A primitive type can naturally be equated with a trivial value type with just one component of that type. In that view, the wrapper class Integer can serve as a boxed representation of value type int.) The unboxed representation of complex numbers is practical for many uses, but it fails to cover several major use cases: return values, array elements, and generic APIs. The two components of a complex number cannot be directly returned from a Java function, since Java does not support multiple return values. The same story applies to array elements: Java has no ’array of structs’ feature. (Double-length arrays are a possible workaround for complex numbers, but not for value types with heterogeneous components.) By generic APIs I mean both those which use generic types, like Arrays.asList and those which have special case support for primitive types, like String.valueOf and PrintStream.println. Those APIs do not support unboxed values, and offer some problems to boxed values. Any ’real’ JVM type should have a story for returns, arrays, and API interoperability. The basic problem here is that value types fall between primitive types and object types. Value types are clearly more complex than primitive types, and object types are slightly too complicated. Objects are a little bit dangerous to use as value carriers, since object references can be compared for pointer equality, and can be synchronized on. Also, as many Java programmers have observed, there is often a performance cost to using wrapper objects, even on modern JVMs. Even so, wrapper classes are a good starting point for talking about value types. If there were a set of structural rules and restrictions which would prevent value-unsafe operations on value types, wrapper classes would provide a good notation for defining value types. This note attempts to define such rules and restrictions. Let’s Start Coding Now it is time to look at some real code. Here is a definition, written in Java, of a complex number value type. @ValueSafe public final class Complex implements java.io.Serializable {     // immutable component structure:     public final double re, im;     private Complex(double re, double im) {         this.re = re; this.im = im;     }     // interoperability methods:     public String toString() { return "Complex("+re+","+im+")"; }     public List<Double> asList() { return Arrays.asList(re, im); }     public boolean equals(Complex c) {         return re == c.re && im == c.im;     }     public boolean equals(@ValueSafe Object x) {         return x instanceof Complex && equals((Complex) x);     }     public int hashCode() {         return 31*Double.valueOf(re).hashCode()                 + Double.valueOf(im).hashCode();     }     // factory methods:     public static Complex valueOf(double re, double im) {         return new Complex(re, im);     }     public Complex changeRe(double re2) { return valueOf(re2, im); }     public Complex changeIm(double im2) { return valueOf(re, im2); }     public static Complex cast(@ValueSafe Object x) {         return x == null ? ZERO : (Complex) x;     }     // utility methods and constants:     public Complex plus(Complex c)  { return new Complex(re+c.re, im+c.im); }     public Complex minus(Complex c) { return new Complex(re-c.re, im-c.im); }     public double abs() { return Math.sqrt(re*re + im*im); }     public static final Complex PI = valueOf(Math.PI, 0.0);     public static final Complex ZERO = valueOf(0.0, 0.0); } This is not a minimal definition, because it includes some utility methods and other optional parts.  The essential elements are as follows: The class is marked as a value type with an annotation. The class is final, because it does not make sense to create subclasses of value types. The fields of the class are all non-private and final.  (I.e., the type is immutable and structurally transparent.) From the supertype Object, all public non-final methods are overridden. The constructor is private. Beyond these bare essentials, we can observe the following features in this example, which are likely to be typical of all value types: One or more factory methods are responsible for value creation, including a component-wise valueOf method. There are utility methods for complex arithmetic and instance creation, such as plus and changeIm. There are static utility constants, such as PI. The type is serializable, using the default mechanisms. There are methods for converting to and from dynamically typed references, such as asList and cast. The Rules In order to use value types properly, the programmer must avoid value-unsafe operations.  A helpful Java compiler should issue errors (or at least warnings) for code which provably applies value-unsafe operations, and should issue warnings for code which might be correct but does not provably avoid value-unsafe operations.  No such compilers exist today, but to simplify our account here, we will pretend that they do exist. A value-safe type is any class, interface, or type parameter marked with the @ValueSafe annotation, or any subtype of a value-safe type.  If a value-safe class is marked final, it is in fact a value type.  All other value-safe classes must be abstract.  The non-static fields of a value class must be non-public and final, and all its constructors must be private. Under the above rules, a standard interface could be helpful to define value types like Complex.  Here is an example: @ValueSafe public interface ValueType extends java.io.Serializable {     // All methods listed here must get redefined.     // Definitions must be value-safe, which means     // they may depend on component values only.     List<? extends Object> asList();     int hashCode();     boolean equals(@ValueSafe Object c);     String toString(); } //@ValueSafe inherited from supertype: public final class Complex implements ValueType { … The main advantage of such a conventional interface is that (unlike an annotation) it is reified in the runtime type system.  It could appear as an element type or parameter bound, for facilities which are designed to work on value types only.  More broadly, it might assist the JVM to perform dynamic enforcement of the rules for value types. Besides types, the annotation @ValueSafe can mark fields, parameters, local variables, and methods.  (This is redundant when the type is also value-safe, but may be useful when the type is Object or another supertype of a value type.)  Working forward from these annotations, an expression E is defined as value-safe if it satisfies one or more of the following: The type of E is a value-safe type. E names a field, parameter, or local variable whose declaration is marked @ValueSafe. E is a call to a method whose declaration is marked @ValueSafe. E is an assignment to a value-safe variable, field reference, or array reference. E is a cast to a value-safe type from a value-safe expression. E is a conditional expression E0 ? E1 : E2, and both E1 and E2 are value-safe. Assignments to value-safe expressions and initializations of value-safe names must take their values from value-safe expressions. A value-safe expression may not be the subject of a value-unsafe operation.  In particular, it cannot be synchronized on, nor can it be compared with the “==” operator, not even with a null or with another value-safe type. In a program where all of these rules are followed, no value-type value will be subject to a value-unsafe operation.  Thus, the prime axiom of value types will be satisfied, that no two value type will be distinguishable as long as their component values are equal. More Code To illustrate these rules, here are some usage examples for Complex: Complex pi = Complex.valueOf(Math.PI, 0); Complex zero = pi.changeRe(0);  //zero = pi; zero.re = 0; ValueType vtype = pi; @SuppressWarnings("value-unsafe")   Object obj = pi; @ValueSafe Object obj2 = pi; obj2 = new Object();  // ok List<Complex> clist = new ArrayList<Complex>(); clist.add(pi);  // (ok assuming List.add param is @ValueSafe) List<ValueType> vlist = new ArrayList<ValueType>(); vlist.add(pi);  // (ok) List<Object> olist = new ArrayList<Object>(); olist.add(pi);  // warning: "value-unsafe" boolean z = pi.equals(zero); boolean z1 = (pi == zero);  // error: reference comparison on value type boolean z2 = (pi == null);  // error: reference comparison on value type boolean z3 = (pi == obj2);  // error: reference comparison on value type synchronized (pi) { }  // error: synch of value, unpredictable result synchronized (obj2) { }  // unpredictable result Complex qq = pi; qq = null;  // possible NPE; warning: “null-unsafe" qq = (Complex) obj;  // warning: “null-unsafe" qq = Complex.cast(obj);  // OK @SuppressWarnings("null-unsafe")   Complex empty = null;  // possible NPE qq = empty;  // possible NPE (null pollution) The Payoffs It follows from this that either the JVM or the java compiler can replace boxed value-type values with unboxed ones, without affecting normal computations.  Fields and variables of value types can be split into their unboxed components.  Non-static methods on value types can be transformed into static methods which take the components as value parameters. Some common questions arise around this point in any discussion of value types. Why burden the programmer with all these extra rules?  Why not detect programs automagically and perform unboxing transparently?  The answer is that it is easy to break the rules accidently unless they are agreed to by the programmer and enforced.  Automatic unboxing optimizations are tantalizing but (so far) unreachable ideal.  In the current state of the art, it is possible exhibit benchmarks in which automatic unboxing provides the desired effects, but it is not possible to provide a JVM with a performance model that assures the programmer when unboxing will occur.  This is why I’m writing this note, to enlist help from, and provide assurances to, the programmer.  Basically, I’m shooting for a good set of user-supplied “pragmas” to frame the desired optimization. Again, the important thing is that the unboxing must be done reliably, or else programmers will have no reason to work with the extra complexity of the value-safety rules.  There must be a reasonably stable performance model, wherein using a value type has approximately the same performance characteristics as writing the unboxed components as separate Java variables. There are some rough corners to the present scheme.  Since Java fields and array elements are initialized to null, value-type computations which incorporate uninitialized variables can produce null pointer exceptions.  One workaround for this is to require such variables to be null-tested, and the result replaced with a suitable all-zero value of the value type.  That is what the “cast” method does above. Generically typed APIs like List<T> will continue to manipulate boxed values always, at least until we figure out how to do reification of generic type instances.  Use of such APIs will elicit warnings until their type parameters (and/or relevant members) are annotated or typed as value-safe.  Retrofitting List<T> is likely to expose flaws in the present scheme, which we will need to engineer around.  Here are a couple of first approaches: public interface java.util.List<@ValueSafe T> extends Collection<T> { … public interface java.util.List<T extends Object|ValueType> extends Collection<T> { … (The second approach would require disjunctive types, in which value-safety is “contagious” from the constituent types.) With more transformations, the return value types of methods can also be unboxed.  This may require significant bytecode-level transformations, and would work best in the presence of a bytecode representation for multiple value groups, which I have proposed elsewhere under the title “Tuples in the VM”. But for starters, the JVM can apply this transformation under the covers, to internally compiled methods.  This would give a way to express multiple return values and structured return values, which is a significant pain-point for Java programmers, especially those who work with low-level structure types favored by modern vector and graphics processors.  The lack of multiple return values has a strong distorting effect on many Java APIs. Even if the JVM fails to unbox a value, there is still potential benefit to the value type.  Clustered computing systems something have copy operations (serialization or something similar) which apply implicitly to command operands.  When copying JVM objects, it is extremely helpful to know when an object’s identity is important or not.  If an object reference is a copied operand, the system may have to create a proxy handle which points back to the original object, so that side effects are visible.  Proxies must be managed carefully, and this can be expensive.  On the other hand, value types are exactly those types which a JVM can “copy and forget” with no downside. Array types are crucial to bulk data interfaces.  (As data sizes and rates increase, bulk data becomes more important than scalar data, so arrays are definitely accompanying us into the future of computing.)  Value types are very helpful for adding structure to bulk data, so a successful value type mechanism will make it easier for us to express richer forms of bulk data. Unboxing arrays (i.e., arrays containing unboxed values) will provide better cache and memory density, and more direct data movement within clustered or heterogeneous computing systems.  They require the deepest transformations, relative to today’s JVM.  There is an impedance mismatch between value-type arrays and Java’s covariant array typing, so compromises will need to be struck with existing Java semantics.  It is probably worth the effort, since arrays of unboxed value types are inherently more memory-efficient than standard Java arrays, which rely on dependent pointer chains. It may be sufficient to extend the “value-safe” concept to array declarations, and allow low-level transformations to change value-safe array declarations from the standard boxed form into an unboxed tuple-based form.  Such value-safe arrays would not be convertible to Object[] arrays.  Certain connection points, such as Arrays.copyOf and System.arraycopy might need additional input/output combinations, to allow smooth conversion between arrays with boxed and unboxed elements. Alternatively, the correct solution may have to wait until we have enough reification of generic types, and enough operator overloading, to enable an overhaul of Java arrays. Implicit Method Definitions The example of class Complex above may be unattractively complex.  I believe most or all of the elements of the example class are required by the logic of value types. If this is true, a programmer who writes a value type will have to write lots of error-prone boilerplate code.  On the other hand, I think nearly all of the code (except for the domain-specific parts like plus and minus) can be implicitly generated. Java has a rule for implicitly defining a class’s constructor, if no it defines no constructors explicitly.  Likewise, there are rules for providing default access modifiers for interface members.  Because of the highly regular structure of value types, it might be reasonable to perform similar implicit transformations on value types.  Here’s an example of a “highly implicit” definition of a complex number type: public class Complex implements ValueType {  // implicitly final     public double re, im;  // implicitly public final     //implicit methods are defined elementwise from te fields:     //  toString, asList, equals(2), hashCode, valueOf, cast     //optionally, explicit methods (plus, abs, etc.) would go here } In other words, with the right defaults, a simple value type definition can be a one-liner.  The observant reader will have noticed the similarities (and suitable differences) between the explicit methods above and the corresponding methods for List<T>. Another way to abbreviate such a class would be to make an annotation the primary trigger of the functionality, and to add the interface(s) implicitly: public @ValueType class Complex { … // implicitly final, implements ValueType (But to me it seems better to communicate the “magic” via an interface, even if it is rooted in an annotation.) Implicitly Defined Value Types So far we have been working with nominal value types, which is to say that the sequence of typed components is associated with a name and additional methods that convey the intention of the programmer.  A simple ordered pair of floating point numbers can be variously interpreted as (to name a few possibilities) a rectangular or polar complex number or Cartesian point.  The name and the methods convey the intended meaning. But what if we need a truly simple ordered pair of floating point numbers, without any further conceptual baggage?  Perhaps we are writing a method (like “divideAndRemainder”) which naturally returns a pair of numbers instead of a single number.  Wrapping the pair of numbers in a nominal type (like “QuotientAndRemainder”) makes as little sense as wrapping a single return value in a nominal type (like “Quotient”).  What we need here are structural value types commonly known as tuples. For the present discussion, let us assign a conventional, JVM-friendly name to tuples, roughly as follows: public class java.lang.tuple.$DD extends java.lang.tuple.Tuple {      double $1, $2; } Here the component names are fixed and all the required methods are defined implicitly.  The supertype is an abstract class which has suitable shared declarations.  The name itself mentions a JVM-style method parameter descriptor, which may be “cracked” to determine the number and types of the component fields. The odd thing about such a tuple type (and structural types in general) is it must be instantiated lazily, in response to linkage requests from one or more classes that need it.  The JVM and/or its class loaders must be prepared to spin a tuple type on demand, given a simple name reference, $xyz, where the xyz is cracked into a series of component types.  (Specifics of naming and name mangling need some tasteful engineering.) Tuples also seem to demand, even more than nominal types, some support from the language.  (This is probably because notations for non-nominal types work best as combinations of punctuation and type names, rather than named constructors like Function3 or Tuple2.)  At a minimum, languages with tuples usually (I think) have some sort of simple bracket notation for creating tuples, and a corresponding pattern-matching syntax (or “destructuring bind”) for taking tuples apart, at least when they are parameter lists.  Designing such a syntax is no simple thing, because it ought to play well with nominal value types, and also with pre-existing Java features, such as method parameter lists, implicit conversions, generic types, and reflection.  That is a task for another day. Other Use Cases Besides complex numbers and simple tuples there are many use cases for value types.  Many tuple-like types have natural value-type representations. These include rational numbers, point locations and pixel colors, and various kinds of dates and addresses. Other types have a variable-length ‘tail’ of internal values. The most common example of this is String, which is (mathematically) a sequence of UTF-16 character values. Similarly, bit vectors, multiple-precision numbers, and polynomials are composed of sequences of values. Such types include, in their representation, a reference to a variable-sized data structure (often an array) which (somehow) represents the sequence of values. The value type may also include ’header’ information. Variable-sized values often have a length distribution which favors short lengths. In that case, the design of the value type can make the first few values in the sequence be direct ’header’ fields of the value type. In the common case where the header is enough to represent the whole value, the tail can be a shared null value, or even just a null reference. Note that the tail need not be an immutable object, as long as the header type encapsulates it well enough. This is the case with String, where the tail is a mutable (but never mutated) character array. Field types and their order must be a globally visible part of the API.  The structure of the value type must be transparent enough to have a globally consistent unboxed representation, so that all callers and callees agree about the type and order of components  that appear as parameters, return types, and array elements.  This is a trade-off between efficiency and encapsulation, which is forced on us when we remove an indirection enjoyed by boxed representations.  A JVM-only transformation would not care about such visibility, but a bytecode transformation would need to take care that (say) the components of complex numbers would not get swapped after a redefinition of Complex and a partial recompile.  Perhaps constant pool references to value types need to declare the field order as assumed by each API user. This brings up the delicate status of private fields in a value type.  It must always be possible to load, store, and copy value types as coordinated groups, and the JVM performs those movements by moving individual scalar values between locals and stack.  If a component field is not public, what is to prevent hostile code from plucking it out of the tuple using a rogue aload or astore instruction?  Nothing but the verifier, so we may need to give it more smarts, so that it treats value types as inseparable groups of stack slots or locals (something like long or double). My initial thought was to make the fields always public, which would make the security problem moot.  But public is not always the right answer; consider the case of String, where the underlying mutable character array must be encapsulated to prevent security holes.  I believe we can win back both sides of the tradeoff, by training the verifier never to split up the components in an unboxed value.  Just as the verifier encapsulates the two halves of a 64-bit primitive, it can encapsulate the the header and body of an unboxed String, so that no code other than that of class String itself can take apart the values. Similar to String, we could build an efficient multi-precision decimal type along these lines: public final class DecimalValue extends ValueType {     protected final long header;     protected private final BigInteger digits;     public DecimalValue valueOf(int value, int scale) {         assert(scale >= 0);         return new DecimalValue(((long)value << 32) + scale, null);     }     public DecimalValue valueOf(long value, int scale) {         if (value == (int) value)             return valueOf((int)value, scale);         return new DecimalValue(-scale, new BigInteger(value));     } } Values of this type would be passed between methods as two machine words. Small values (those with a significand which fits into 32 bits) would be represented without any heap data at all, unless the DecimalValue itself were boxed. (Note the tension between encapsulation and unboxing in this case.  It would be better if the header and digits fields were private, but depending on where the unboxing information must “leak”, it is probably safer to make a public revelation of the internal structure.) Note that, although an array of Complex can be faked with a double-length array of double, there is no easy way to fake an array of unboxed DecimalValues.  (Either an array of boxed values or a transposed pair of homogeneous arrays would be reasonable fallbacks, in a current JVM.)  Getting the full benefit of unboxing and arrays will require some new JVM magic. Although the JVM emphasizes portability, system dependent code will benefit from using machine-level types larger than 64 bits.  For example, the back end of a linear algebra package might benefit from value types like Float4 which map to stock vector types.  This is probably only worthwhile if the unboxing arrays can be packed with such values. More Daydreams A more finely-divided design for dynamic enforcement of value safety could feature separate marker interfaces for each invariant.  An empty marker interface Unsynchronizable could cause suitable exceptions for monitor instructions on objects in marked classes.  More radically, a Interchangeable marker interface could cause JVM primitives that are sensitive to object identity to raise exceptions; the strangest result would be that the acmp instruction would have to be specified as raising an exception. @ValueSafe public interface ValueType extends java.io.Serializable,         Unsynchronizable, Interchangeable { … public class Complex implements ValueType {     // inherits Serializable, Unsynchronizable, Interchangeable, @ValueSafe     … It seems possible that Integer and the other wrapper types could be retro-fitted as value-safe types.  This is a major change, since wrapper objects would be unsynchronizable and their references interchangeable.  It is likely that code which violates value-safety for wrapper types exists but is uncommon.  It is less plausible to retro-fit String, since the prominent operation String.intern is often used with value-unsafe code. We should also reconsider the distinction between boxed and unboxed values in code.  The design presented above obscures that distinction.  As another thought experiment, we could imagine making a first class distinction in the type system between boxed and unboxed representations.  Since only primitive types are named with a lower-case initial letter, we could define that the capitalized version of a value type name always refers to the boxed representation, while the initial lower-case variant always refers to boxed.  For example: complex pi = complex.valueOf(Math.PI, 0); Complex boxPi = pi;  // convert to boxed myList.add(boxPi); complex z = myList.get(0);  // unbox Such a convention could perhaps absorb the current difference between int and Integer, double and Double. It might also allow the programmer to express a helpful distinction among array types. As said above, array types are crucial to bulk data interfaces, but are limited in the JVM.  Extending arrays beyond the present limitations is worth thinking about; for example, the Maxine JVM implementation has a hybrid object/array type.  Something like this which can also accommodate value type components seems worthwhile.  On the other hand, does it make sense for value types to contain short arrays?  And why should random-access arrays be the end of our design process, when bulk data is often sequentially accessed, and it might make sense to have heterogeneous streams of data as the natural “jumbo” data structure.  These considerations must wait for another day and another note. More Work It seems to me that a good sequence for introducing such value types would be as follows: Add the value-safety restrictions to an experimental version of javac. Code some sample applications with value types, including Complex and DecimalValue. Create an experimental JVM which internally unboxes value types but does not require new bytecodes to do so.  Ensure the feasibility of the performance model for the sample applications. Add tuple-like bytecodes (with or without generic type reification) to a major revision of the JVM, and teach the Java compiler to switch in the new bytecodes without code changes. A staggered roll-out like this would decouple language changes from bytecode changes, which is always a convenient thing. A similar investigation should be applied (concurrently) to array types.  In this case, it seems to me that the starting point is in the JVM: Add an experimental unboxing array data structure to a production JVM, perhaps along the lines of Maxine hybrids.  No bytecode or language support is required at first; everything can be done with encapsulated unsafe operations and/or method handles. Create an experimental JVM which internally unboxes value types but does not require new bytecodes to do so.  Ensure the feasibility of the performance model for the sample applications. Add tuple-like bytecodes (with or without generic type reification) to a major revision of the JVM, and teach the Java compiler to switch in the new bytecodes without code changes. That’s enough musing me for now.  Back to work!

    Read the article

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

< Previous Page | 626 627 628 629 630 631 632 633 634 635 636 637  | Next Page >