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• Java enviroment book recommendations

  - by ipavlic

  I come from a C# background and would like to learn Java. Programming and Java as a language are not a problem. What is bewildering to me is the sheer amount of various choices in "Java environment" - Ivy, Maven, Ant, JAXB, Glassfish, JBoss, Struts, Spring are just some of the names that I keep seeing. I am looking for "who is who" and "who works together" beginner's guide. Is there such a book? Something similar?

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• Maker Faire Report - Teaching Kids Java SE Embedded for Internet of Things (IoT)

  - by hinkmond

  I had a great time at this year's Maker Faire 2014 in San Mateo, Calif. where Jake Kuramoto and the AppsLab crew including Noel Portugal, Anthony Lai, Raymond, and Tony set up a super demo at the DiY table. It was a simple way to learn how Java SE Embedded technology could be used to code the Internet of Things (IoT) devices on the table. The best part of our set-up was seeing the kids sit down and do some coding without all the complexity of a Computer Science course. It was very encouraging to see how interested the kids were when walking them through the programming steps, then seeing their eyes light up when telling them, "You just coded a Java enabled Internet of Things device!" as the Raspberry Pi-connected devices turned on or started to move from their Java Embedded program. See: The AppsLab at Maker Faire It will be interesting to see how this next generation of kids grow up with all these Internet of Things devices around them and watch how they will program them. Hopefully, they will be using Java SE Embedded technology to do so. From the looks of it at this year's Maker Faire, we might have a bunch of motivated young Java SE Embedded coders coming up the ranks soon. Well, they have to get through middle school first, but they're on their way! Hinkmond

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• Where to after a year of java? [closed]

  - by avatarX

  I've just finished a my first year of programming Java at varsity and I have a three month break. In terms of my development would it be better to: Cover Java in more depth to acquire a more intermediate level of ability Learn a new programming language (if so which) to a similar level as my current Java ability Spend timing learning introductory discrete maths, algorithms and data structures I'm also open to any other possibilities that would be beneficial but that could be covered in about 3 months.

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• take my Java skills to the next level

  - by waingram

  I am well versed in the basics of Java programming, although through most of my career I have been maintaining, upgrading, and debugging someone else's Java code. I am mainly familiar with basic servlet applications. I have a strong beginner knowledge of Maven and Ant. I have more web development with Ruby on Rails, but would like to bring my Java skills up to par with regard to web development. It seems the world of Java is so big, I have no idea what the next logical step is for me. Spring? JAX-RB? EJBs? What is the next logical step for someone like me and how would you recommend I approach it?

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• Which platform to choose from .Net or Java [closed]

  - by SahilMahajanMj

  I know that there is a lot healthy discussion about this topic. but my case is entirely different from these discussions. I have just passed out my graduation. During the graduation period, i had done C#.net and java as well. Now i am working as Android programmer in a company. In the recent times, i have heard a lot about pros and cons of these platforms. What our seniors used to suggest that, ASP.net is a lot better than JSP for website developement. .net provides us lot of in built tools and API's for building powerfull applications. Java's platform independancy has always been issue among them. Security fetures are more in java. .Net has more powerfull IDE's. Now i am a bit confused on which platform to choose from these. I found java better from two, so did i prefer to choose android. Also, the discussion always ends with an issue that java has no scope for job as far has .net does. I would like to hear suggestions on this topic, but it would be better, if you consider indian IT market for this discussion.

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• From Java to Javascript? [duplicate]

  - by theGreenCabbage

  This question already has an answer here: Are there any OO-principles that are practically applicable for Javascript? 2 answers I am primarily a Java programmer. Because of its OO principles and the general paradigm of Java programming, like wrapping things in static variables, and having things return specific types, heavily aids me in "visualizing" a program. Instead of thinking of a big program, I can, instead, focus on smaller organized parts of my eventual program, and add functionality and build up from there. Thus, I have trouble programming in other languages. Or at least, I have not been able to program in the same ability as I do in Java compared to other languages. I know Javascript has OO principles, so I'd like to learn this language in a OO-based like I would program with Java. Is this possible?

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• Collision: Vector class (java)

  - by user8363

  When handling collision detection / response and you need a Vector class, do you need to create that class yourself or is there a java class you can use? A vector class should have methods like: subtract(Vector v), normalize(), dotProduct(Vector v), ... At the moment it seems logical to use classes like java.awt.Rectangle and java.awt.Polygon to calculate collisions. Would I be right to use these classes for this purpose? My question is not about how to implement collision detection, I know how that works. However I'm wondering what would be a correct and clean way to implement it in java since I'm fairly new to the language and to application development in general.

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• Does anybody develops Java desktop applications? [closed]

  - by Eirc man

  I was just wondering if there are there developers making java software for desktops. Is it even worth it, do any developers do that for living. I am making a chat application using sockets and and java GUI, just for fun, but then I wanted to see some examples of desktop apps, but did not find many. I have heard that Netbeans, is made using java, but the Netbeans in my Windows to me it seems like any other native Windows application

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• Is this Java 7 security thread an issue if you have Java 7 installed but not as the default?

  - by user1361315

  I have a MBP with osx mountain lion installed, and I believe from what I read Mac's only ship with Java 6 by default. I'm not at my computer at the moment, but I am pretty sure I have installed Java 7 but it isn't my default java version (I think I installed it and I have to explicitly reference it to use it). Does this mean I am safe from this particular thread? Reference: http://www.pcworld.com/businesscenter/article/261748/researchers_find_critical_vulnerability_in_java_7_patch_hours_after_release.html

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• Can't open Minecraft with java

  - by Shingaling

  I know this has been asked here before, but none of the solutions have worked for me. I have a fresh install of Ubuntu 12.04 on my system and I installed Open Java 7 and I downloaded Minecraft. I right clicked Minecraft went to properties and set it as an executable and then went to open with and Java is no where to be found in the list. I made a new Java desktop file in /usr/share/applications and now when I go to the list Java is there and I set Minecraft to open with it by default but when I open it nothing at all happens. Now how am I supposed to get Minecraft to work?

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• Installing Chrome Java Plugin

  - by kyleskool

  I've been trying to install the Java plugin for Chrome for a couple hours now, and I figured it was time to ask people with more experience. I can't seem to get it working. My current Java version is the 64-bit OpenJDK 1.6.0_24. I tried installing the IcedTea plugin to no avail. I have Ubuntu 12.04 64-bit installed at the moment. When I tried testing if java was enabled in Chrome, any website with a Java applet would not load (when I disabled the plugin, they loaded, but not the applet). I followed the instructions from here: http://technonstop.com/install-java-plugin-ubuntu-linux which said to create this script and run it: JAVA_HOME=/usr/lib/jvm/jdk1.7.0 MOZILLA_HOME=~/.mozilla mkdir $MOZILLA_HOME/plugins ln -s $JAVA_HOME/jre/lib/i386/libnpjp2.so $MOZILLA_HOME/plugins Note: You may need to change the value of JAVA_HOME so that it correctly points to your installation of the JDK. 64-bit users will need to change the final line to: ln -s $JAVA_HOME/jre/lib/amd64/libnpjp2.so $MOZILLA_HOME/plugins but this did not work as well. I just test it in Firefox and it's working. Still nothing for Chrome

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• Problem Installing older TestNG plugin on Eclipse 3.5

  - by Stefan

  I'm trying to install TestNG 5.11 on eclipse 3.5 and gettign the following. eclipse.buildId=unknown java.version=1.6.0_19 java.vendor=Sun Microsystems Inc. BootLoader constants: OS=win32, ARCH=x86, WS=win32, NL=no_NO Framework arguments: -product org.eclipse.epp.package.jee.product Command-line arguments: -os win32 -ws win32 -arch x86 -product org.eclipse.epp.package.jee.product Error Mon Jun 07 15:45:53 CEST 2010 Artifact not found: org.eclipse.update.feature,org.testng.eclipse,5.11.0.28. java.io.FileNotFoundException: "http://beust.com/eclipse/features/org.testng.eclipse_5.11.0.28.jar" at org.eclipse.equinox.internal.p2.repository.RepositoryStatusHelper.checkFileNotFound(RepositoryStatusHelper.java:289) at org.eclipse.equinox.internal.p2.repository.FileReader.checkException(FileReader.java:352) at org.eclipse.equinox.internal.p2.repository.FileReader.sendRetrieveRequest(FileReader.java:326) at org.eclipse.equinox.internal.p2.repository.FileReader.readInto(FileReader.java:263) at org.eclipse.equinox.internal.p2.repository.RepositoryTransport.download(RepositoryTransport.java:71) at org.eclipse.equinox.internal.p2.repository.RepositoryTransport.download(RepositoryTransport.java:127) at org.eclipse.equinox.internal.p2.artifact.repository.simple.SimpleArtifactRepository.downloadArtifact(SimpleArtifactRepository.java:468) at org.eclipse.equinox.internal.p2.artifact.repository.simple.SimpleArtifactRepository.downloadArtifact(SimpleArtifactRepository.java:451) at org.eclipse.equinox.internal.p2.artifact.repository.simple.SimpleArtifactRepository.getArtifact(SimpleArtifactRepository.java:518) at org.eclipse.equinox.internal.p2.artifact.repository.MirrorRequest.getArtifact(MirrorRequest.java:200) at org.eclipse.equinox.internal.p2.artifact.repository.MirrorRequest.transferSingle(MirrorRequest.java:175) at org.eclipse.equinox.internal.p2.artifact.repository.MirrorRequest.transfer(MirrorRequest.java:159) at org.eclipse.equinox.internal.p2.artifact.repository.MirrorRequest.perform(MirrorRequest.java:95) at org.eclipse.equinox.internal.p2.artifact.repository.simple.SimpleArtifactRepository.getArtifact(SimpleArtifactRepository.java:507) at org.eclipse.equinox.internal.p2.artifact.repository.simple.DownloadJob.run(DownloadJob.java:64) at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55) Error Mon Jun 07 15:45:53 CEST 2010 Artifact not found: osgi.bundle,org.testng.eclipse,5.11.0.28. java.io.FileNotFoundException: "http://beust.com/eclipse/plugins/org.testng.eclipse_5.11.0.28.jar" at org.eclipse.equinox.internal.p2.repository.RepositoryStatusHelper.checkFileNotFound(RepositoryStatusHelper.java:289) at org.eclipse.equinox.internal.p2.repository.FileReader.checkException(FileReader.java:352) at org.eclipse.equinox.internal.p2.repository.FileReader.sendRetrieveRequest(FileReader.java:326) at org.eclipse.equinox.internal.p2.repository.FileReader.readInto(FileReader.java:263) at org.eclipse.equinox.internal.p2.repository.RepositoryTransport.download(RepositoryTransport.java:71) at org.eclipse.equinox.internal.p2.repository.RepositoryTransport.download(RepositoryTransport.java:127) at org.eclipse.equinox.internal.p2.artifact.repository.simple.SimpleArtifactRepository.downloadArtifact(SimpleArtifactRepository.java:468) at org.eclipse.equinox.internal.p2.artifact.repository.simple.SimpleArtifactRepository.downloadArtifact(SimpleArtifactRepository.java:451) at org.eclipse.equinox.internal.p2.artifact.repository.simple.SimpleArtifactRepository.getArtifact(SimpleArtifactRepository.java:518) at org.eclipse.equinox.internal.p2.artifact.repository.MirrorRequest.getArtifact(MirrorRequest.java:200) at org.eclipse.equinox.internal.p2.artifact.repository.MirrorRequest.transferSingle(MirrorRequest.java:175) at org.eclipse.equinox.internal.p2.artifact.repository.MirrorRequest.transfer(MirrorRequest.java:159) at org.eclipse.equinox.internal.p2.artifact.repository.MirrorRequest.perform(MirrorRequest.java:95) at org.eclipse.equinox.internal.p2.artifact.repository.simple.SimpleArtifactRepository.getArtifact(SimpleArtifactRepository.java:507) at org.eclipse.equinox.internal.p2.artifact.repository.simple.DownloadJob.run(DownloadJob.java:64) at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55) Error Mon Jun 07 15:45:53 CEST 2010 session context was:(profile=epp.package.jee, phase=org.eclipse.equinox.internal.provisional.p2.engine.phases.Collect, operand=, action=). I'm kinda stuck so I would really like help. Thanks

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• DateFormat conversion problem in java?

  - by androidbase Praveen

  my input String is : 2010-03-24T17:28:50.000Z output pattern is like: DateFormat formatter1 = new SimpleDateFormat("EEE. MMM. d. yyyy"); i convert this like this: formatter1.format(new Date("2010-03-24T17:28:50.000Z"));//illegalArgumentException here the string "2010-03-24T17:28:50.000Z" ouput should be like this: Thu. Mar. 24. 2010 idea but i get a illegalArgumentException. Dont know why? any idea?? stacktrace message is: 04-08 19:50:28.326: WARN/System.err(306): java.lang.IllegalArgumentException 04-08 19:50:28.345: WARN/System.err(306): at java.util.Date.parse(Date.java:447) 04-08 19:50:28.355: WARN/System.err(306): at java.util.Date.<init>(Date.java:157) 04-08 19:50:28.366: WARN/System.err(306): at com.example.brown.Bru_Tube$SelectDataTask.doInBackground(Bru_Tube.java:222) 04-08 19:50:28.366: WARN/System.err(306): at com.example.brown.Bru_Tube$SelectDataTask.doInBackground(Bru_Tube.java:1) 04-08 19:50:28.405: WARN/System.err(306): at android.os.AsyncTask$2.call(AsyncTask.java:185) 04-08 19:50:28.415: WARN/System.err(306): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305) 04-08 19:50:28.415: WARN/System.err(306): at java.util.concurrent.FutureTask.run(FutureTask.java:137) 04-08 19:50:28.446: WARN/System.err(306): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068) 04-08 19:50:28.456: WARN/System.err(306): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561) 04-08 19:50:28.466: WARN/System.err(306): at java.lang.Thread.run(Thread.java:1096)

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• Whats wrong with this HQL query?

  - by ManBugra

  did i encounter a hibernate bug or do i have an error i dont see: select enty.number from EntityAliasName enty where enty.myId in ( select cons.myId from Consens cons where cons.number in ( select ord.number from Orders ord where ord.customer = :customer and ord.creationDate < ( select max(ord.creationDate) from Orders ord where ord.customer = :customer ) ) ) what i do get is the following: org.hibernate.util.StringHelper.root(StringHelper.java:257) Caused by: java.lang.NullPointerException at org.hibernate.util.StringHelper.root(StringHelper.java:257) at org.hibernate.persister.entity.AbstractEntityPersister.getSubclassPropertyTableNumber(AbstractEntityPersister.java:1391) at org.hibernate.persister.entity.BasicEntityPropertyMapping.toColumns(BasicEntityPropertyMapping.java:54) at org.hibernate.persister.entity.AbstractEntityPersister.toColumns(AbstractEntityPersister.java:1367) at org.hibernate.hql.ast.tree.FromElement.getIdentityColumn(FromElement.java:320) at org.hibernate.hql.ast.tree.IdentNode.resolveAsAlias(IdentNode.java:154) at org.hibernate.hql.ast.tree.IdentNode.resolve(IdentNode.java:100) at org.hibernate.hql.ast.tree.FromReferenceNode.resolve(FromReferenceNode.java:117) at org.hibernate.hql.ast.tree.FromReferenceNode.resolve(FromReferenceNode.java:113) at org.hibernate.hql.ast.HqlSqlWalker.resolve(HqlSqlWalker.java:854) at org.hibernate.hql.antlr.HqlSqlBaseWalker.propertyRef(HqlSqlBaseWalker.java:1172) at org.hibernate.hql.antlr.HqlSqlBaseWalker.propertyRefLhs(HqlSqlBaseWalker.java:5167) at org.hibernate.hql.antlr.HqlSqlBaseWalker.propertyRef(HqlSqlBaseWalker.java:1133) at org.hibernate.hql.antlr.HqlSqlBaseWalker.selectExpr(HqlSqlBaseWalker.java:1993) at org.hibernate.hql.antlr.HqlSqlBaseWalker.selectExprList(HqlSqlBaseWalker.java:1932) at org.hibernate.hql.antlr.HqlSqlBaseWalker.selectClause(HqlSqlBaseWalker.java:1476) at org.hibernate.hql.antlr.HqlSqlBaseWalker.query(HqlSqlBaseWalker.java:580) at org.hibernate.hql.antlr.HqlSqlBaseWalker.selectStatement(HqlSqlBaseWalker.java:288) at org.hibernate.hql.antlr.HqlSqlBaseWalker.statement(HqlSqlBaseWalker.java:231) at org.hibernate.hql.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:254) at org.hibernate.hql.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:185) at org.hibernate.hql.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:136) at org.hibernate.engine.query.HQLQueryPlan.<init>(HQLQueryPlan.java:101) at org.hibernate.engine.query.HQLQueryPlan.<init>(HQLQueryPlan.java:80) at org.hibernate.engine.query.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:94) at org.hibernate.impl.SessionFactoryImpl.checkNamedQueries(SessionFactoryImpl.java:484) at org.hibernate.impl.SessionFactoryImpl.<init>(SessionFactoryImpl.java:394) at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1341) using: Hibernate 3.3.2.GA / postgresql

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• NetBeans not liking libraries in lib-src

  - by DJTripleThreat

  I'm working on a project with a group that is using Eclipse, but I'm using Netbeans. Up until today this wasn't an issue. When updating from the repo they have added some source code as a library under a directory called /lib-src. When I try to compile the code I get an error that it can't find certain packages... these are the packages under /lib-src. Using NetBeans I can add the library as a folder so now the references to those packages are happy. However, I'm getting this new error when compiling: UNEXPECTED TOP-LEVEL ERROR: java.lang.OutOfMemoryError: Java heap space at java.util.HashMap.addEntry(HashMap.java:753) at java.util.HashMap.put(HashMap.java:385) at com.android.dx.dex.file.ClassDataItem.addStaticField(ClassDataItem.java:134) at com.android.dx.dex.file.ClassDefItem.addStaticField(ClassDefItem.java:280) at com.android.dx.dex.cf.CfTranslator.processFields(CfTranslator.java:159) at com.android.dx.dex.cf.CfTranslator.translate0(CfTranslator.java:130) at com.android.dx.dex.cf.CfTranslator.translate(CfTranslator.java:85) at com.android.dx.command.dexer.Main.processClass(Main.java:297) at com.android.dx.command.dexer.Main.processFileBytes(Main.java:276) at com.android.dx.command.dexer.Main.access$100(Main.java:56) at com.android.dx.command.dexer.Main$1.processFileBytes(Main.java:228) at com.android.dx.cf.direct.ClassPathOpener.processOne(ClassPathOpener.java:134) at com.android.dx.cf.direct.ClassPathOpener.processDirectory(ClassPathOpener.java:190) at com.android.dx.cf.direct.ClassPathOpener.processOne(ClassPathOpener.java:122) at com.android.dx.cf.direct.ClassPathOpener.processDirectory(ClassPathOpener.java:190) at com.android.dx.cf.direct.ClassPathOpener.processOne(ClassPathOpener.java:122) at com.android.dx.cf.direct.ClassPathOpener.processDirectory(ClassPathOpener.java:190) at com.android.dx.cf.direct.ClassPathOpener.processOne(ClassPathOpener.java:122) at com.android.dx.cf.direct.ClassPathOpener.processDirectory(ClassPathOpener.java:190) at com.android.dx.cf.direct.ClassPathOpener.processOne(ClassPathOpener.java:122) at com.android.dx.cf.direct.ClassPathOpener.processDirectory(ClassPathOpener.java:190) at com.android.dx.cf.direct.ClassPathOpener.processOne(ClassPathOpener.java:122) at com.android.dx.cf.direct.ClassPathOpener.processDirectory(ClassPathOpener.java:190) at com.android.dx.cf.direct.ClassPathOpener.processOne(ClassPathOpener.java:122) at com.android.dx.cf.direct.ClassPathOpener.processDirectory(ClassPathOpener.java:190) at com.android.dx.cf.direct.ClassPathOpener.processOne(ClassPathOpener.java:122) at com.android.dx.cf.direct.ClassPathOpener.process(ClassPathOpener.java:108) at com.android.dx.command.dexer.Main.processOne(Main.java:245) at com.android.dx.command.dexer.Main.processAllFiles(Main.java:183) at com.android.dx.command.dexer.Main.run(Main.java:139) at com.android.dx.command.dexer.Main.main(Main.java:120) at com.android.dx.command.Main.main(Main.java:87) /home/aaron/NetBeansProjects/xbmc-remote/nbproject/build-impl.xml:411: exec returned: 3 BUILD FAILED (total time: 1 minute 25 seconds) I can include the build-impl.xml file if you need it, but I don't think that is main issue. Any ideas?

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• does red5 read tomcat-users.xml

  - by baba

  Hi, I have been busy creating an app for Red5. Imagine what was my surprise when I tried to configure basic/digest authentication and I couldn't. What struck me as strange is that I have a running tomcat instance that works and authenticates correctly with the following xmls: web.xml (part of) <security-constraint> <web-resource-collection> <web-resource-name>A Protected Page</web-resource-name> <url-pattern>/stats.jsp</url-pattern> </web-resource-collection> <auth-constraint> <description/> <role-name>tomcat</role-name> </auth-constraint> </security-constraint> <login-config> <auth-method>DIGEST</auth-method> <realm-name>BLAAAAAAAAAAAAAAAAA</realm-name> </login-config> <security-role> <description/> <role-name>tomcat</role-name> </security-role> and a tomcat-users.xml in /conf that looks kinda like this: <?xml version="1.0" encoding="UTF-8"?> <tomcat-users> <role rolename="tomcat"/> <user username="ide" password="bogus" roles="tomcat"/> </tomcat-users> The annoying thing is that configuration authenticates correctly when on tomcat's servlet container, but on the red5's modified one, it just keeps asking for authentication. Am I becoming mad or it should work like a charm? Red5 is version 0_9_1 The stats.jsp is accessible in both servlet containers, the only difference is that when you input the correct password and username in tomcat, you are logged in, and in red5 you are not, it just keeps asking you for the password. Any pointers? Am I missing something? Here is a stack trace of the error I receive AT the moment I try the login: Caused by: java.io.IOException: Unable to locate a login configuration at com.sun.security.auth.login.ConfigFile.init(ConfigFile.java:250) [na:1.6.0_22] at com.sun.security.auth.login.ConfigFile.<init>(ConfigFile.java:91) [na:1.6.0_22] ... 27 common frames omitted [ERROR] [http-127.0.0.1-5080-1] org.apache.catalina.realm.JAASRealm - Cannot find message associated with key jaasRealm.unexpectedError java.lang.SecurityException: Unable to locate a login configuration at com.sun.security.auth.login.ConfigFile.<init>(ConfigFile.java:93) [na:1.6.0_22] at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) [na:1.6.0_22] at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39) [na:1.6.0_22] at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) [na:1.6.0_22] at java.lang.reflect.Constructor.newInstance(Constructor.java:513) [na:1.6.0_22] at java.lang.Class.newInstance0(Class.java:355) [na:1.6.0_22] at java.lang.Class.newInstance(Class.java:308) [na:1.6.0_22] at javax.security.auth.login.Configuration$3.run(Configuration.java:247) [na:1.6.0_22] at java.security.AccessController.doPrivileged(Native Method) [na:1.6.0_22] at javax.security.auth.login.Configuration.getConfiguration(Configuration.java:242) [na:1.6.0_22] at javax.security.auth.login.LoginContext$1.run(LoginContext.java:237) [na:1.6.0_22] at java.security.AccessController.doPrivileged(Native Method) [na:1.6.0_22] at javax.security.auth.login.LoginContext.init(LoginContext.java:234) [na:1.6.0_22] at javax.security.auth.login.LoginContext.<init>(LoginContext.java:403) [na:1.6.0_22] at org.apache.catalina.realm.JAASRealm.authenticate(JAASRealm.java:394) [catalina-6.0.24.jar:na] at org.apache.catalina.realm.JAASRealm.authenticate(JAASRealm.java:357) [catalina-6.0.24.jar:na] at org.apache.catalina.authenticator.DigestAuthenticator.findPrincipal(DigestAuthenticator.java:283) [catalina-6.0.24.jar:na] at org.apache.catalina.authenticator.DigestAuthenticator.authenticate(DigestAuthenticator.java:176) [catalina-6.0.24.jar:na] at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:523) [catalina-6.0.24.jar:na] at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) [catalina-6.0.24.jar:na] at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) [catalina-6.0.24.jar:na] at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:555) [catalina-6.0.24.jar:na] at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) [catalina-6.0.24.jar:na] at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) [catalina-6.0.24.jar:na] at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:852) [tomcat-coyote-6.0.24.jar:na] at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) [tomcat-coyote-6.0.24.jar:na] at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) [tomcat-coyote-6.0.24.jar:na] at java.lang.Thread.run(Thread.java:662) [na:1.6.0_22] Caused by: java.io.IOException: Unable to locate a login configuration at com.sun.security.auth.login.ConfigFile.init(ConfigFile.java:250) [na:1.6.0_22] at com.sun.security.auth.login.ConfigFile.<init>(ConfigFile.java:91) [na:1.6.0_22] ... 27 common frames omitted In addition, here is the configuration of red5-web.properties webapp.contextPath=/project Even futher information: Seems to me like it is using the right realm: MemoryRealm [INFO] [main] org.red5.server.tomcat.TomcatLoader - Setting connector: org.apache.catalina.connector.Connector [INFO] [main] org.red5.server.tomcat.TomcatLoader - Address to bind: /127.0.0.1:5080 [INFO] [main] org.red5.server.tomcat.TomcatLoader - Setting realm: org.apache.catalina.realm.MemoryRealm [INFO] [main] org.red5.server.tomcat.TomcatLoader - Loading tomcat context [INFO] [main] org.red5.server.tomcat.TomcatLoader - Server root: C:/Program Files/Red5 [INFO] [main] org.red5.server.tomcat.TomcatLoader - Config root: C:/Program Files/Red5/conf [INFO] [main] org.red5.server.tomcat.TomcatLoader - Application root: C:/Program Files/Red5/webapps [INFO] [main] org.red5.server.tomcat.TomcatLoader - Starting Tomcat servlet engine [INFO] [main] org.apache.catalina.startup.Embedded - Starting tomcat server [INFO] [main] org.apache.catalina.core.StandardEngine - Starting Servlet Engine: Apache Tomcat/6.0.26 However, immediately after bootstraping Tomcat, I am presented with the following error: Exception in thread "Launcher:/administration" org.springframework.beans.factory.BeanDefinitionStoreException: Could not resolve bean definition resource pattern [/WEB-INF/red5-*.xml]; nested exception is java.io.FileNotFoundException: ServletContext resource [/WEB-INF/] cannot be resolved to URL because it does not exist at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:190) at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:149) at org.springframework.web.context.support.XmlWebApplicationContext.loadBeanDefinitions(XmlWebApplicationContext.java:124) at org.springframework.web.context.support.XmlWebApplicationContext.loadBeanDefinitions(XmlWebApplicationContext.java:93) at org.springframework.context.support.AbstractRefreshableApplicationContext.refreshBeanFactory(AbstractRefreshableApplicationContext.java:130) at org.springframework.context.support.AbstractApplicationContext.obtainFreshBeanFactory(AbstractApplicationContext.java:458) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:388) at org.red5.server.tomcat.TomcatLoader$1.run(TomcatLoader.java:594) Caused by: java.io.FileNotFoundException: ServletContext resource [/WEB-INF/] cannot be resolved to URL because it does not exist at org.springframework.web.context.support.ServletContextResource.getURL(ServletContextResource.java:132) at org.springframework.core.io.support.PathMatchingResourcePatternResolver.isJarResource(PathMatchingResourcePatternResolver.java:414) at org.springframework.core.io.support.PathMatchingResourcePatternResolver.findPathMatchingResources(PathMatchingResourcePatternResolver.java:343) at org.springframework.core.io.support.PathMatchingResourcePatternResolver.getResources(PathMatchingResourcePatternResolver.java:282) at org.springframework.context.support.AbstractApplicationContext.getResources(AbstractApplicationContext.java:1156) at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:177) ... 7 more This error is kinda strange, because after this it seems that /WEB-INF/ is found by the rest of the program by the following output: [INFO] [Launcher:/SOSample] org.springframework.beans.factory.config.PropertyPlaceholderConfigurer - Loading properties file from ServletContext resource [/WEB-INF/red5-web.properties] [INFO] [Launcher:/installer] org.springframework.beans.factory.config.PropertyPlaceholderConfigurer - Loading properties file from ServletContext resource [/WEB-INF/red5-web.properties] [INFO] [Launcher:/] org.springframework.beans.factory.config.PropertyPlaceholderConfigurer - Loading properties file from ServletContext resource [/WEB-INF/red5-web.properties] [INFO] [Launcher:/LiveMedia] org.springframework.beans.factory.config.PropertyPlaceholderConfigurer - Loading properties file from ServletContext resource [/WEB-INF/red5-web.properties] What really annoys me is that, as you can see in the output, when I try to login, I get a JAASRealm-related exception, but in the debug output when Tomcat is loading, it is clear to me that it expects a MemoryRealm. I was wondering where and how in red5.xml should I specify bean properties such that I force red5 to use MemoryRealm that is under /conf/tomcat-users.xml, because it certainly doesn't do so now. It seems like the biggest question I have posted so far, but I tried to explain it as fully as possible as to avoid confusion.

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• Reasons of getting a java.lang.VerifyError

  - by JeroenWyseur

  I'm investigating the following java.lang.VerifyError java.lang.VerifyError: (class: be/post/ehr/wfm/application/serviceorganization/report/DisplayReportServlet, method: getMonthData signature: (IILjava/util/Collection;Ljava/util/Collection;Ljava/util/HashMap;Ljava/util/Collection;Ljava/util/Locale;Lorg/apache/struts/util/MessageRe˜̴MtÌ´MÚw€mçw€mp:”MŒŒ at java.lang.Class.getDeclaredConstructors0(Native Method) at java.lang.Class.privateGetDeclaredConstructors(Class.java:2357) at java.lang.Class.getConstructor0(Class.java:2671) It occurs when the jboss server in which the servlet is deployed is started. It is compiled with jdk-1.5.0_11 and I tried to recompile it with jdk-1.5.0_15 without succes. That is the compilation runs fine but when deployed, the java.lang.VerifyError occurs. When I changed the methodname and got the following error: java.lang.VerifyError: (class: be/post/ehr/wfm/application/serviceorganization/r eport/DisplayReportServlet, method: getMD signature: (IILjava/util/Collection;Lj ava/util/Collection;Ljava/util/HashMap;Ljava/util/Collection;Ljava/util/Locale;L org/apache/struts/util/MessageResources-á+ÿ+àN|+ÿ+àN+Üw-Çm+ºw-ÇmX#+ûM|X+öM at java.lang.Class.getDeclaredConstructors0(Native Method) at java.lang.Class.privateGetDeclaredConstructors(Class.java:2357 at java.lang.Class.getConstructor0(Class.java:2671) at java.lang.Class.newInstance0(Class.java:321) at java.lang.Class.newInstance(Class.java:303) You can see that more of the method signature is shown. The actual method signature is private PgasePdfTable getMonthData(int month, int year, Collection dayTypes, Collection calendarDays, HashMap bcSpecialDays, Collection activityPeriods, Locale locale, MessageResources resources) throws Exception { I already tried looking to it with javap and that gives the method signature as it should be. When my other colleagues check out the code, compile it and deploy it, they have the same problem. When the build server picks up the code and deploys it on development or testing environments (HPUX), the same error occurs. Also an automated testing machine running ubuntu shows the same error during server startup. The rest of the application runs ok, only that one servlet is out of order. Any ideas where to look would be helpful.

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• PHP/Java Bridge - Access Java objects in PHP

  - by Omer Hassan

  I have a Red5 application which defines some public Java methods. When I start the server, an object of the application class gets created. I am trying to call the public methods of the application class from PHP using the existing instance of the Java application class. So here's my Java application: public class App extends org.red5.server.adapter.ApplicationAdapter { public boolean appStart(IScope app) { // This method gets called when the application starts // and an object of this App class is created. return true; } // This is the method I would like to call from PHP. public void f() { } } From PHP, I would like to get access to the App object that is created and call the method f() on it. I have tried playing around with this thing called "context". So in the Java method App.appStart(), I did this: // Save a reference to this App object to be retrieved later in PHP. new PhpScriptContextFactory().getContext().put("x", this); And in PHP, I tried to access the saved object like this: require_once("http://localhost:5080/JavaBridge/java/Java.inc"); var_dump(java_is_null(java_context()->get("x"))); Unfortunately, the java_is_null() function in PHP returns true. I also tried saving the App object in a static variable of App class but when I access that variable in PHP, its value is null.

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• Java XHTML Doclet: fatal exception

  - by Cheeso

  Has anyone used XHTML Doclet, and can you provide some hints as to how to get it to work successfully? I run it like this: \sunjdk\bin\javadoc -doclet net.sourceforge.xhtmldoclet.Doclet -docletpath c:\sw\java\XHTML_Doclet_0.4.jar -d <output> [class files here] (all on one line) When I run it I get this: javadoc: error - In doclet class net.sourceforge.xhtmldoclet.Doclet, method validOptions has thrown an exception java.lang.reflect.InvocationTargetException java.lang.Error: Fatal: Resource (net.sourceforge.xhtmldoclet.resources.doclet) for javadoc doclets is missing. at com.sun.tools.doclets.internal.toolkit.util.MessageRetriever.getText(MessageRetriever.java:110) at com.sun.tools.doclets.internal.toolkit.util.MessageRetriever.getText(MessageRetriever.java:92) at com.sun.tools.doclets.internal.toolkit.util.MessageRetriever.getText(MessageRetriever.java:81) at com.sun.tools.doclets.internal.toolkit.Configuration.getText(Configuration.java:634) at com.sun.tools.doclets.internal.toolkit.Configuration.generalValidOptions(Configuration.java:515) at net.sourceforge.xhtmldoclet.Config.validOptions(Unknown Source) at net.sourceforge.xhtmldoclet.Doclet.validOptions(Unknown Source) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at com.sun.tools.javadoc.DocletInvoker.invoke(DocletInvoker.java:269) at com.sun.tools.javadoc.DocletInvoker.validOptions(DocletInvoker.java:198) at com.sun.tools.javadoc.Start.parseAndExecute(Start.java:317) at com.sun.tools.javadoc.Start.begin(Start.java:128) at com.sun.tools.javadoc.Main.execute(Main.java:41) at com.sun.tools.javadoc.Main.main(Main.java:31) 1 error It seems like it ought to just work. What am I doing wrong?

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• [Netbeans 6.9] Java MethodOverloading error with double values

  - by Nimitips

  Here is a part of my code I'm having trouble with: ===Class Overload=== public class Overload { public void testOverLoadeds() { System.out.printf("Square of integer 7 is %d\n",square(7)); System.out.printf("Square of double 7.5 is %d\n",square(7.5)); }//..end testOverloadeds public int square(int intValue) { System.out. printf("\nCalled square with int argument: %d\n",intValue); return intValue * intValue; }//..end square int public double square(double doubleValue) { System.out.printf("\nCalled square with double argument: %d\n", doubleValue); return doubleValue * doubleValue; }//..end square double }//..end class overload ===Main=== public static void main(String[] args) { Overload methodOverload = new Overload(); methodOverload.testOverLoadeds(); } It compiles with no error, however when I try to run it the output is: Called square with int argument: 7 Square of integer 7 is 49 Exception in thread "main" java.util.IllegalFormatConversionException: d != java.lang.Double at java.util.Formatter$FormatSpecifier.failConversion(Formatter.java:3999) at java.util.Formatter$FormatSpecifier.printInteger(Formatter.java:2709) at java.util.Formatter$FormatSpecifier.print(Formatter.java:2661) at java.util.Formatter.format(Formatter.java:2433) at java.io.PrintStream.format(PrintStream.java:920) at java.io.PrintStream.printf(PrintStream.java:821) at methodoverload.Overload.square(Overload.java:19) at methodoverload.Overload.testOverLoadeds(Overload.java:8) at methodoverload.Main.main(Main.java:9) Called square with double argument:Java Result: 1 What am I doing wrong? I'm on Ubuntu 10.10, Netbeans 6.9. Thanks.

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• Writing to a file in a servlet

  - by ankur verma

  I am working in a servlet and has this code : public void doPost(blah blah){ response.setContentType("text/html"); String datasent = request.getParameter("dataSent"); System.out.println(datasent); try{ FileWriter writer = new FileWriter("C:/xyz.txt"); writer.write("hello"); System.out.println("I wrote"); }catch(Exception ex){ ex.printStackTrace(); } response.getWriter().write("I am from server"); } But everytime it is throwing an error saying Access Denied.. Even when there is no lock on that file and there is no file whose name is C:/xyz.txt what should I do? ;( java.io.FileNotFoundException: C:\xyz.txt (Access is denied) at java.io.FileOutputStream.open(Native Method) at java.io.FileOutputStream.<init>(FileOutputStream.java:212) at java.io.FileOutputStream.<init>(FileOutputStream.java:104) at java.io.FileWriter.<init>(FileWriter.java:63) at test.TestServlet.doPost(TestServlet.java:49) at javax.servlet.http.HttpServlet.service(HttpServlet.java:641) at javax.servlet.http.HttpServlet.service(HttpServlet.java:722) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:306) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:161) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:108) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:558) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:379) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:243) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:259) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:237) at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:281) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) at java.lang.Thread.run(Thread.java:722)

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• SSL connection hangs as client hello (curl, openssl client, apt-get, wget, everything)

  - by Niklas B

  Hi, I've run into a problem on my Debian VPS (a xen domU) regarding SSL. Namely almost all SSL connections hangs at client hello. For example: # curl -vI https://graph.facebook.com About to connect() to graph.facebook.com port 443 (#0) Trying 66.220.146.48... connected Connected to graph.facebook.com (66.220.146.48) port 443 (#0) successfully set certificate verify locations: CAfile: none CApath: /etc/ssl/certs SSLv3, TLS handshake, Client hello (1): It's the same when using the openssl client. However, some of the SSL traffic works (for example https://www.nordea.se). Server #uname -a Linux server.com 2.6.26-1-xen-amd64 #1 SMP Fri Mar 13 21:39:38 UTC 2009 x86_64 GNU/Linux It does however work on my Dom 0 (the main xen host). Apt-get I can't even run apt-get update with the debian security sources (hangs on reading headers) Open SSL At the begining I thought I had an old openssl client (0.9.8o-4) since I appeared to have a newer on the Dom 0 (0.9.8g-15+lenny8) but doing a manuanl update on the openssl deb didn't help. Open SSL Client This is the full output of when the openssl client hangs: http://pastebin.com/PAjwMap9 Closing thoughts I've Googled the crap out of this, and I'm not getting any further. I've seen problems with curl, apt-get etc. but they are all specific relating to the very application - not general for the system. Any thoughts?

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• Spring security problem, Error creating bean with name 'org.springframework.web.servlet.mvc.annotati

  - by benaissa

  Hello; I'm developping a web application with spring mvc, i started by developping the web application after i'm trying to add spring security; but i have this message, and i don't find a solution, thanks 16-04-2010 12:10:22:296 6062 ERROR org.springframework.web.servlet.DispatcherServlet - Context initialization failed org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping': Initialization of bean failed; nested exception is java.lang.NoClassDefFoundError: org/springframework/beans/factory/generic/GenericBeanFactoryAccessor at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:527) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:286) at org.springframework.web.servlet.DispatcherServlet.createDefaultStrategy(DispatcherServlet.java:770) at org.springframework.web.servlet.DispatcherServlet.getDefaultStrategies(DispatcherServlet.java:737) at org.springframework.web.servlet.DispatcherServlet.initHandlerMappings(DispatcherServlet.java:518) at org.springframework.web.servlet.DispatcherServlet.initStrategies(DispatcherServlet.java:410) at org.springframework.web.servlet.DispatcherServlet.onRefresh(DispatcherServlet.java:398) at org.springframework.web.servlet.FrameworkServlet.onApplicationEvent(FrameworkServlet.java:474) at org.springframework.context.event.GenericApplicationListenerAdapter.onApplicationEvent(GenericApplicationListenerAdapter.java:51) at org.springframework.context.event.SourceFilteringListener.onApplicationEventInternal(SourceFilteringListener.java:97) at org.springframework.context.event.SourceFilteringListener.onApplicationEvent(SourceFilteringListener.java:68) at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:97) at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:301) at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:888) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:426) at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:402) at org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:316) at org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:282) at org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:126) at javax.servlet.GenericServlet.init(GenericServlet.java:212) at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1173) at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:809) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:129) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:852) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) at java.lang.Thread.run(Thread.java:619) Caused by: java.lang.NoClassDefFoundError: org/springframework/beans/factory/generic/GenericBeanFactoryAccessor at org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping.determineUrlsForHandler(DefaultAnnotationHandlerMapping.java:113) at org.springframework.web.servlet.handler.AbstractDetectingUrlHandlerMapping.detectHandlers(AbstractDetectingUrlHandlerMapping.java:79) at org.springframework.web.servlet.handler.AbstractDetectingUrlHandlerMapping.initApplicationContext(AbstractDetectingUrlHandlerMapping.java:57) at org.springframework.context.support.ApplicationObjectSupport.initApplicationContext(ApplicationObjectSupport.java:119) at org.springframework.web.context.support.WebApplicationObjectSupport.initApplicationContext(WebApplicationObjectSupport.java:69) at org.springframework.context.support.ApplicationObjectSupport.setApplicationContext(ApplicationObjectSupport.java:73) at org.springframework.context.support.ApplicationContextAwareProcessor.invokeAwareInterfaces(ApplicationContextAwareProcessor.java:99) at org.springframework.context.support.ApplicationContextAwareProcessor.postProcessBeforeInitialization(ApplicationContextAwareProcessor.java:82) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsBeforeInitialization(AbstractAutowireCapableBeanFactory.java:394) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1405) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519) ... 32 more Caused by: java.lang.ClassNotFoundException: org.springframework.beans.factory.generic.GenericBeanFactoryAccessor at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1516) at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1361) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320) ... 43 more

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• 50 Billion Served: Java Embedded on Devices

  - by Tori Wieldt

  It doesn't matter if it is 50 billion or 24 billion, just suffice it to stay that there will be MANY connected devices in the year 2020. With just 24 billion devices, they will outnumber humans six to one! So as a developer, you don't want to ignore this opportunity. What if you could use your Java skills and deploy an app to a fraction of these devices (don't be greedy, how about just, say, 118,000 of them)? Fareed Suliman, Java ME Product Manager had lots of good news for Java Developers in his presentation Modernizing the Explosion of Advanced Microcontrollers with Embedded Java at ARM TechCon in Santa Clara, CA last week. "A radical architecture shift is underway in this space, from proprietary to standards-based," he explained.  He pointed out several advantages to using Embedded Java for devices: Java is a proven and open standard. Java provides connectivity, encryption, location, and web services APIs. You don't have to focus on and keep reinventing the plumbing below the JVM. Abstracting the software from the hardware allows you to repeat your app across many devices. Abstracting the software from the hardware allows allows parallel development so you can get your app done more quickly. You already know Java (or you can hire lots of Java talent). Java is a full ecosystem, with Java Embedded plugins for IDEs like Eclipse and NetBeans. Java ME allows for in-field software upgrades. Suliman mentioned two ways developers can start using Java Embedded today:  Java ME Embedded Suite 7.0 Oracle Java Embedded Suite is a new packaged solution from Oracle (including Java DB, GlassFish for Embedded Suite, Jersey Web Services Framework, and Oracle Java SE Embedded 7 platform), created to provide value added services for collecting, managing, and transmitting data to embedded devices such as gateways and concentrators. Oracle Java ME Embedded 3.2 Oracle Java ME Embedded 3.2 is designed and optimized to meet the unique requirements of small embedded, low power devices such as micro-controllers and other resource-constrained hardware without screens or user interfaces. Think tiny. Really tiny. And think big.  Read more about Java Embedded at the Oracle Technology Network, and read The Java Source blog Java Embedded Releases from September.

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• Java: How to manage UDP client-server state

  - by user92947

  I am trying to write a Java application that works similar to MapReduce. There is a server and several workers. Workers may come and go as they please and the membership to the group has a soft-state. To become a part of the group, the worker must send a UDP datagram to the server, but to continue to be part of the group, the worker must send the UDP datagram to the server every 5 minutes. In order to accommodate temporary errors, a worker is allowed to miss as many as two consecutive periodic UDP datagrams. So, the server must keep track of the current set of workers as well as the last time each worker had sent a UDP datagram. I've implemented a class called WorkerListener that implements Runnable and listens to UDP datagrams on a particular UDP port. Now, to keep track of active workers, this class may maintain a HashSet (or HashMap). When a datagram is received, the server may query the HashSet to check if it is a new member. If so, it can add the new worker to the group by adding an entry into the HashSet. If not, it must reset a "timer" for the worker, noting that it has just heard from the corresponding worker. I'm using the word timer in a generic sense. It doesn't have to be a clock of sorts. Perhaps this could also be implemented using int or long variables. Also, the server must run a thread that continuously monitors the timers for the workers to see that a client that times out on two consecutive datagram intervals, it is removed from the HashSet. I don't want to do this in the WorkerListener thread because it would be blocking on the UDP datagram receive() function. If I create a separate thread to monitor the worker HashSet, it would need to be a different class, perhaps WorkerRegistrar. I must share the HashSet with that thread. Mutual exclusion must also be implemented, then. My question is, what is the best way to do this? Pointers to some sample implementation would be great. I want to use the barebones JDK implementation, and not some fancy state maintenance API that takes care of everything, because I want this to be a useful demonstration for a class that I am teaching. Thanks

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