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  • Java - learning / migrating fast

    - by Yippie-Kai-Yay
    Hello! This is not one of those questions like "How do I learn Java extremely fast, I know nothing about programming, but I heard Java is cool, yo". I have an interview for a Java Software Developer in a couple of weeks and the thing is that I think that I know C++ really good and I am somewhat good at C# (like, here I can probably answer on a lot of questions related to these languages), but I have almost zero experience with Java. I have a lot of projects written in both languages, I participiated in several open-source projects (mostly C++, though). Now, what should I do (in your opinion) to prepare myself for this Java interview. I guess migrating from C# to Java should be kind of fast, especially when you know a lot about programming in global, patterns, modern techniques and have a lot of practical experience behind you. But still two weeks is obviously not enough to get Java in-depth - so what should I focus on to have the best chances to pass the interview? Thank you.

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  • Maker Faire 2012 Attendees build with Java Technology

    - by hinkmond
    Looks like Daniel Green, systems engineer from Oracle, and the panel of Java experts had a successful Java Technology booth at this year's Maker Faire 2012. See: Maker Faire 2012 adds Java Here's a quote: "We made a huge impact for Java and Oracle, creating positive perception, building brand awareness, and introducing fun and engaging ways for future technologists to learn Java programming," says Michelle Kovac, Oracle director, Java Marketing and Operations. Good stuff, considering all the future developers of exploding robots and fire-breathing dragon metal sculptures attend the Maker Faire. They can blow up stuff with Java technology just as effectively as other programming languages. Hinkmond

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  • Java Plugin - Firefox

    - by Tomassino
    Having trouble getting Java to work with Firefox (22), I have followed the advice in this question and on the official Java site, but nothing seems to work. I have the latest Java (1.7.0_25) in /opt/java and have set a symlink in /usr/libs/mozilla/plugins for the libnpjp2.so file. I can see the file in the terminal and Java runs fine. However Firefox shows nothing in about:plugins. I have also run export JAVA_HOME="/opt/java/jre1.7.0_05/bin/java" to be on the safe side. I know there are multiple plugin directories such as /usr/lib/firefox/plugins and /usr/lib/firefox-addons/plugins, but all my current plugins show they are located in /usr/lib/mozilla/plugins when viewing the about:plugins page. A bit stuck on where to go next?

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  • How to design good & continuous tiles

    - by Mikalichov
    I have trouble designing tiles so that when assembled, they don't look like tiles, but look like an homogeneous thing. For example on the image below: even though the main part of the grass is only one tile, you don't "see" the grid; you know where it is if you look a bit carefully, but it is not obvious. Whereas when I design tiles, you can only see "oh, jeez, 64 times the same tile". A bit like on that image: (taken from a gamedev.stackexchange question, sorry; no critic about the game, but it proves my point, and actually has better tile design that what I manage) I think the main problem is that I design them so they are independent, there is no junction between two tiles if put closed to each other. I think having the tiles more "continuous" would have a smoother effect, but can't manage to do it, it seems overly complex to me. I think it is probably simpler than I think once you know how to do it, but couldn't find a tutorial on that specific point. Is there a known method to design continuous / homogeneous tiles? (my terminology might be totally wrong, don't hesitate to correct me)

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  • Understanding the Java Ecosystem

    - by syrion
    I have traditionally had the "luxury" of being a one-man development team. I've used Python extensively, have a reasonable command of Perl, PHP, and JavaScript. My problem is Java. I can write Java code. I'm not great at it--unlike Python, I rarely make use of anything unique to Java when I'm writing it. Furthermore, my experience is mostly in simple GUI/console programming. Unfortunately, I'm currently pursuing an IT degree where Java is the lingua franca. My database class is requiring that our projects be written in Java using servlets, and I just can't wrap my head around the ecosystem. Is there a good online overview of or tutorial on how the Java web ecosystem works? I have Thinking in Java, but it's mostly just the language itself (which I understand well enough to get by). I have looked at the Sun servlet tutorial, but it seems outdated.

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  • Active - like-minded Java mailing lists

    - by Lewis Robbins
    I need to find an active Java mailing list, I have looked onto the GNU Java mailing list, to my surprise there had been not too much activity this month, it also focused on any GNU related Java - I'd really help me progress my Java ability, if I had an active, likeminded Java mailing list. Questions' that are not suited to Stackoverflow, or provide little benefit to any user that see's the question: discussing a new API change; best practices; open source discussion; trivia type questions on Java ArrayList boxining-unboxing; Community atmosphere. I also read Jon Skeets blog post about his previous Java/C# mailing lists examples - I did not catch any names, though I did they would be of benefit to me, if I had access to any of them.

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  • how to learn Java

    - by Sarang
    This question I am asking because I couldn't find any source which gives complete overview of java development. I just want to know where java technology currently in market & what is preferable for development ! Java always remain top programming language for development point of view. However, java is combo of, j2ee, j2me, jsp, jsf, spring, other frameworks, ui components, jndi, networking tools and various other "J" are there ! However, learning java is definitely dependent on the development requirement, but still, to be a well-experienced java developer, what is the organised way of learning java? What is preferable in current technology ? and what is deprecated, currently ?

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  • How can I design good continuous (seamless) tiles?

    - by Mikalichov
    I have trouble designing tiles so that when assembled, they don't look like tiles, but look like a homogeneous thing. For example, see the image below: Even though the main part of the grass is only one tile, you don't "see" the grid; you know where it is if you look a bit carefully, but it is not obvious. Whereas when I design tiles, you can only see "oh, jeez, 64 times the same tile," like in this image: (I took this from another GDSE question, sorry; not be critical of the game, but it proves my point. And actually has better tile design that what I manage, anyway.) I think the main problem is that I design them so they are independent, there is no junction between two tiles if put closed to each other. I think having the tiles more "continuous" would have a smoother effect, but can't manage to do it, it seems overly complex to me. I think it is probably simpler than I think once you know how to do it, but couldn't find a tutorial on that specific point. Is there a known method to design continuous / homogeneous tiles? (My terminology might be totally wrong, don't hesitate to correct me.)

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  • New Java Tutorials Updated

    - by hinkmond
    The new Java Tutorials are here! The new Java Tutorials are here! So what? So, you can read them on your iPad thingie--if that's how you roll, that is... See: Read New Java Tutorials Here's a quote: What's New The Java Tutorials are continuously updated to keep up with changes to the Java Platform and to incorporate feedback from our readers. Recent updates include the following features: The Generics lesson has been completely reworked... The Java Tutorials are now available in two ebook formats: mobi ebook files for Kindle. ePub ebook files for iPad, Nook, and other eReaders that support the ePub format. Just kick back, open up your favorite tablet or eReader and learn all about the new things in the Java platform. Nice. All you need now is a cool drink and you're all set! Hinkmond

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  • New to Java Programming - Error help

    - by JJJ
    I am going through a Java book and drafting the examples and have run into the following error when compiling this code. Any help would be appreciated thank you. Error: Main.java:3: class Addition is public, should be declared in a file named Addition.java public class Addition        ^ 1 error Code: import java.io.*; import java.util.Scanner; public class Addition {   public static void main(String[] args) { java.util.Scanner input = new java.util.Scanner(System.in);  int number1; int number2; int sum; System.out.print( "Enter first digit: " ); number1 = input.nextInt(); System.out.print( "Enter second digit:" ); number2 = input.nextInt(); sum = number1 + number2; System.out.printf( "Sum is %d\n, sum" );      } }

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  • From J2EE to Java EE: what has changed?

    - by Bruno.Borges
    See original @Java_EE tweet on 29 May 2014 Yeap, it has been 8 years since the term J2EE was replaced, and still some people refer to it (mostly recruiters, luckily!). But then comes the question: what has changed besides the name? Our community friend Abhishek Gupta worked on this question and provided an excellent response titled "What's in a name? Java EE? J2EE?". But let me give you a few highlights here so you don't lose yourself with YATO (yet another tab opened): J2EE used to be an infrastructure and resources provider only, requiring developers to depend on external 3rd-party frameworks to then implement application requirements or improve productivity J2EE used to require hundreds of XML lines of codes to define just a dozen of resources like EJBs, MDBs, Servlets, and so on J2EE used to support only EAR (Enterprise Archives) with a bunch of other archives like JARs and WARs just to run a simple Web application And so on, and so on! It was a great technology but still required a lot of work to get something up and running. Remember xDoclet? Remember Struts? The old days of pure Hibernate code? Or when Ajax became a trending topic and we were all implementing it with DWR Servlet? Still, we J2EE developers survived, and learned, and helped evolve the platform to a whole new level of DX (Developer Experience). A new DX for J2EE suggested a new name. One that referred to the platform as the Enterprise Edition of Java, because "Java is why we're here" quoting Bill Shannon. The release of Java EE 5 included so many features that clearly showed developers the platform was going after all those DX gaps. Radical simplification of the persistence model with the introduction of JPA Support of Annotations following the launch of Java SE 5.0 Updated XML APIs with the introduction of StAX Drastic simplification of the EJB component model (with annotations!) Convention over Configuration and Dependency Injection A few bullets you may say but that represented a whole new DX and a vision for upcoming versions. Clearly, the release of Java EE 5 helped drive the future of the platform by reducing the number of XMLs, Java Interfaces, simplified configurations, provided convention-over-configuration, etc! We then saw the release of Java EE 6 with even more great features like Managed Beans, CDI, Bean Validation, improved JSP and Servlets APIs, JASPIC, the posisbility to deploy plain WARs and so many other improvements it is difficult to list in one sentence. And we've gotta give Spring Framework some credit here: thanks to Rod Johnson and team, concepts like Dependency Injection fit perfectly into the Java EE Platform. Clearly, Spring used to be one of the most inspiring frameworks for the Java EE platform, and it is great to see things like Pivotal and Spring supporting JSR 352 Batch API standard! Cooperation to keep improving DX at maximum in the server-side Java landscape.  The master piece result of these previous releases is seen and called today as Java EE 7, which by providing a newly and improved JavaServer Faces release, with new features for Web Development like WebSockets API, improved JAX-RS, and JSON-P, but also including Batch API and so many other great improvements, has increased developer productivity and brought innovation to server-side Java developers. Java EE is not just a new name (which was introduced back in May 2006!) but a new Developer Experience for server-side Java developers. To show you why we are here and where we are going (see the Java EE 8 update), we wanted to share with you a draft of the new Java EE logos that the evangelist team created, to help you spread the word about Java EE. You can get access to these images at the Java EE Platform Facebook Album, or the Google+ Java EE Platform Album whichever is better for you, but don't forget to like and/or +1 those social network profiles :-) A message to all job recruiters: stop using J2EE and start using Java EE if you want to find great Java EE 5, Java EE 6, or Java EE 7 developers To not only save you recruiter valuable characters when tweeting that job opportunity but to also match the correct term, we invite you to replace long terms like "Java/J2EE" or even worse "#Java #J2EE #JEE" or all these awkward combinations with the only acceptable hashtag: #JavaEE. And to prove that Java EE is catching among developers and even recruiters, and that J2EE is past, let me highlight here how are the jobs trends! The image below is from Indeed.com trends page, for the following keywords: J2EE, Java/J2EE, Java/JEE, JEE. As you can see, J2EE is indeed going away, while JEE saw some increase. Perhaps because some people are just lazy to type "Java" but at the same time they are aware that J2EE (the '2') is past. We shall forgive that for a while :-) Another proof that J2EE is going away is by looking at its trending statistics at Google. People have been showing less and less interest in the term J2EE. See the chart below:  Recruiter, if you still need proof that J2EE is past, that Java EE is trending, and that other job recruiters are seeking for Java EE developers, and that the developer community is aware of the new term, perhaps these other charts can show you what term you should be using. See for example the Job Trends for Java EE at Indeed.com and notice where it started... 2006! 8 years ago :-) Last but not least, the Google Trends for Java EE term (including the still wrong but forgivable JavaEE term) shows us that the new term is catching up very well. J2EE is past. Oh, and don't worry about the curves going down. We developers like to be hipsters sometimes and today only AngularJS, NodeJS, BigData are going up. Java EE and other traditional server-side technologies such as Spring, or even from other platforms such as Ruby on Rails, PHP, Grails, are pretty much consolidated and the curves... well, they are consolidated too. So If you are a Java EE developer, drop that J2EE from your résumé, and let recruiters also know that this term is past. Embrace Java EE, and enjoy a new developer experience for server-side Java developers. Java EE on TwitterJava EE on Google+Java EE on Facebook

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  • Java RMI (Server: TCP Connection Idle/Client: Unmarshalexception (EOFException))

    - by Perry Dahl Christensen
    I'm trying to implement Sun Tutorials RMI application that calculates Pi. I'm having some serious problems and I cant find the solution eventhough I've been searching the entire web and several javaskilled people. I'm hoping you can put an end to my frustrations. The crazy thing is that I can run the application from the cmd on my desktop computer. Trying the exact same thing with the exact same code in the exact same directories on my laptop produces the following errors. The problem occures when I try to connect the client to the server. I don't believe that the error is due to my policyfile as I can run it on the desktop. It must be elsewhere. Have anyone tried the same and can you give me a hint as to where my problem is, please? POLICYFILE SERVER: grant { permission java.security.AllPermissions; permission java.net.SocketPermission"*", "connect, resolve"; }; POLICYFILE CLIENT: grant { permission java.security.AllPermissions; permission java.net.SocketPermission"*", "connect, resolve"; }; SERVERSIDE ERRORS: Microsoft Windows XP [Version 5.1.2600] (C) Copyright 1985-2001 Microsoft Corp. C:\Documents and Settings\STUDENTcd\ C:start rmiregistry C:java -cp c:\java;c:\java\compute.jar -Djava.rmi.server.codebase=file:/c:/jav a/compute.jar -Djava.rmi.server.hostname=localhost -Djava.security.policy=c:/jav a/servertest.policy engine.ComputeEngine ComputeEngine bound Exception in thread "RMI TCP Connection(idle)" java.security.AccessControlExcept ion: access denied (java.net.SocketPermission 127.0.0.1:1440 accept,resolve) at java.security.AccessControlContext.checkPermission(Unknown Source) at java.security.AccessController.checkPermission(Unknown Source) at java.lang.SecurityManager.checkPermission(Unknown Source) at java.lang.SecurityManager.checkAccept(Unknown Source) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.checkAcceptPermi ssion(Unknown Source) at sun.rmi.transport.tcp.TCPTransport.checkAcceptPermission(Unknown Sour ce) at sun.rmi.transport.Transport$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at sun.rmi.transport.Transport.serviceCall(Unknown Source) at sun.rmi.transport.tcp.TCPTransport.handleMessages(Unknown Source) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(Unknown Sou rce) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(Unknown Sour ce) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source ) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at java.lang.Thread.run(Unknown Source) CLIENTSIDE ERRORS: Microsoft Windows XP [Version 5.1.2600] (C) Copyright 1985-2001 Microsoft Corp. C:\Documents and Settings\STUDENTcd\ C:java -cp c:\java;c:\java\compute.jar -Djava.rmi.server.codebase=file:\C:\jav a\files\ -Djava.security.policy=c:/java/clienttest.policy client.ComputePi local host 45 ComputePi exception: java.rmi.UnmarshalException: Error unmarshaling return header; nested exception is: java.io.EOFException at sun.rmi.transport.StreamRemoteCall.executeCall(Unknown Source) at sun.rmi.server.UnicastRef.invoke(Unknown Source) at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(Unkn own Source) at java.rmi.server.RemoteObjectInvocationHandler.invoke(Unknown Source) at $Proxy0.executeTask(Unknown Source) at client.ComputePi.main(ComputePi.java:18) Caused by: java.io.EOFException at java.io.DataInputStream.readByte(Unknown Source) ... 6 more C: Thanks in advance Perry

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  • java.sql.SQLWarning: [Microsoft][SQLServer 2000 Driver for JDBC]Database changed to X

    - by adisembiring
    Hi all, I'm using Hibernate 3.2.1 and database SQLServer2000 while I'm try to insert some data using my dao, some warning occurred like this: java.sql.SQLWarning: [Microsoft][SQLServer 2000 Driver for JDBC]Database changed to BTN_SPP_DB at com.microsoft.jdbc.base.BaseWarnings.createSQLWarning(Unknown Source) at com.microsoft.jdbc.base.BaseWarnings.get(Unknown Source) at com.microsoft.jdbc.base.BaseConnection.getWarnings(Unknown Source) at org.hibernate.util.JDBCExceptionReporter.logAndClearWarnings(JDBCExceptionReporter.java:22) at org.hibernate.jdbc.ConnectionManager.closeConnection(ConnectionManager.java:443) at org.hibernate.jdbc.ConnectionManager.aggressiveRelease(ConnectionManager.java:400) at org.hibernate.jdbc.ConnectionManager.afterTransaction(ConnectionManager.java:287) at org.hibernate.jdbc.JDBCContext.afterTransactionCompletion(JDBCContext.java:221) at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:119) at co.id.hanoman.btnmw.spp.dao.TagihanDao.save(TagihanDao.java:43) at co.id.hanoman.btnmw.spp.dao.TagihanDao.save(TagihanDao.java:1) at co.id.hanoman.btnmw.spp.dao.test.TagihanDaoTest.testSave(TagihanDaoTest.java:81) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.junit.internal.runners.TestMethodRunner.executeMethodBody(TestMethodRunner.java:99) at org.junit.internal.runners.TestMethodRunner.runUnprotected(TestMethodRunner.java:81) at org.junit.internal.runners.BeforeAndAfterRunner.runProtected(BeforeAndAfterRunner.java:34) at org.junit.internal.runners.TestMethodRunner.runMethod(TestMethodRunner.java:75) at org.junit.internal.runners.TestMethodRunner.run(TestMethodRunner.java:45) at org.junit.internal.runners.TestClassMethodsRunner.invokeTestMethod(TestClassMethodsRunner.java:66) at org.junit.internal.runners.TestClassMethodsRunner.run(TestClassMethodsRunner.java:35) at org.junit.internal.runners.TestClassRunner$1.runUnprotected(TestClassRunner.java:42) at org.junit.internal.runners.BeforeAndAfterRunner.runProtected(BeforeAndAfterRunner.java:34) at org.junit.internal.runners.TestClassRunner.run(TestClassRunner.java:52) at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:45) at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:460) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:673) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:386) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:196) my hibernate initialization log is: 2010-04-26 22:54:05,203 INFO [Version] Hibernate Annotations 3.3.0.GA 2010-04-26 22:54:05,234 INFO [Environment] Hibernate 3.2.1 2010-04-26 22:54:05,234 INFO [Environment] hibernate.properties not found 2010-04-26 22:54:05,234 INFO [Environment] Bytecode provider name : cglib 2010-04-26 22:54:05,234 INFO [Environment] using JDK 1.4 java.sql.Timestamp handling 2010-04-26 22:54:05,343 INFO [Configuration] configuring from resource: /hibernate.cfg.xml 2010-04-26 22:54:05,343 INFO [Configuration] Configuration resource: /hibernate.cfg.xml 2010-04-26 22:54:05,406 DEBUG [DTDEntityResolver] trying to resolve system-id [http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd] 2010-04-26 22:54:05,406 DEBUG [DTDEntityResolver] recognized hibernate namespace; attempting to resolve on classpath under org/hibernate/ 2010-04-26 22:54:05,406 DEBUG [DTDEntityResolver] located [http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd] in classpath 2010-04-26 22:54:05,453 DEBUG [Configuration] hibernate.dialect=org.hibernate.dialect.SQLServerDialect 2010-04-26 22:54:05,453 DEBUG [Configuration] hibernate.connection.driver_class=com.microsoft.jdbc.sqlserver.SQLServerDriver 2010-04-26 22:54:05,453 DEBUG [Configuration] hibernate.connection.url=jdbc:microsoft:sqlserver://12.56.11.65:1433;databaseName=BTN_SPP_DB 2010-04-26 22:54:05,453 DEBUG [Configuration] hibernate.connection.username=spp 2010-04-26 22:54:05,453 DEBUG [Configuration] hibernate.connection.password=spp

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  • Development: SDK for Social Net

    - by loldop
    I have a task: development sdk for social networking service like facebook, twitter and etc. At now i'm developing facebook-extension-sdk which based on facebook-ios-sdk 3.0. But not all social networking services have good sdks. And all time i improved my facebook-extension-sdk, when i see ugly code :( Please, advise me good techniques to development these sdks (like design-patterns or your own experience or good books/sites). Thanks!

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  • Cleanest RESTful design for purely "action" calls?

    - by Josh Handel
    Hello all, I am sticking my toe in the RESTful waters and I just can't find a "satisfactory" solution to how to handle truely "action" oriented calls on a RESTful service? My quandry can be broken down into two parts. 1) Transactional calls: I understand the idea of having an ActionTransactor that you get a resource too with a post, update the parameters and then commit with a PUT (as described all over the place and in the Orilly RESTful Web services book).. But I struggle with the idea of keeping URLs with states present for ever.. If we really honestly don't need to keep a transaction for ever can we kill the resource URI? do URIs need to be perminate or can they be transiant URIs that expire 2) Non transactional calls: these might be calls to perform some workflow that spans multiple resources but having a resource just doesn't make since.. An example might be to re-generating some calculated ans cached value like a large aggreget or re-indexing blog or some such "purely" action. Anyways, I'm curious about the communities thoughts on this... Thus far, I've read that Overloading Post is the cleanest way to handle part 2.. But there is an equal amount of argument against that approach as well. And (to me) its not self documenting which I though was one of the key design goals of RESTful APIs.

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  • What is the best software design to use in this scenario

    - by domdefelice
    I need to generate HTML snippets using jQuery. The creation of those snippets depends on some data. The data is stored server-side, in session (where PHP is used). At the moment I achieved this - retrieving the data from the server via AJAX in form of JSON - and building the snippets via specific javascript functions that read those data The problem is that the complexity of the data is getting bigger and hence the serialization into JSON is getting even more difficult since I can't do it automatically. I can't do it automatically because some information are sensible so I generate a "stripped" version to send to the client. I know it is difficult to understand without any code to read, but I am hoping this is a common scenario and would be glad for any tip, suggestion or even design-pattern you can give me. Should I store both a complete and a stripped data on the server and then use some library to automatically generate the JSON from the stripped data? But this also means I have to get the two data synchronized. Or maybe I could move the logic server-side, this way avoiding sending the data. But this means sending javascript code (since I rely on jQuery). Maybe not a good idea. Feel free to ask me more details if this is not clear. Thank you for any help

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  • Level Design V.S. Modeler

    - by Ecurbed
    From what I understand being a level designer and a character/environment/object/etc Modeler are two different jobs, yet sometimes it feels like a Modeler can also do the job of the level designer. I know this also depends on the scale of the game. For small games maybe they are one and the same, but for bigger games they become two different jobs. I understand a background in some modeling could not hurt when it comes to level design, but the question I have is: Do jobs prefer people who can model for level designing? This way they can kill two birds with one stone and have someone to create the assets and design the level. What is your opinion of the training? Does level design contain skill sets that make them completely different from what a modeler can do, or is this an easy transition for a modeler to become a level designer? Can you be a bad level designer but a good modeler and vice versa?

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  • The Java Specialist: An Interview with Java Champion Heinz Kabutz

    - by Janice J. Heiss
    Dr. Heinz Kabutz is well known for his Java Specialists’ Newsletter, initiated in November 2000, where he displays his acute grasp of the intricacies of the Java platform for an estimated 70,000 readers; for his work as a consultant; and for his workshops and trainings at his home on the Island of Crete where he has lived since 2006 -- where he is known to curl up on the beach with his laptop to hack away, in between dips in the Mediterranean. Kabutz was born of German parents and raised in Cape Town, South Africa, where he developed a love of programming in junior high school through his explorations on a ZX Spectrum computer. He received a B.S. from the University of Cape Town, and at 25, a Ph.D., both in computer science. He will be leading a two-hour hands-on lab session, HOL6500 – “Finding and Solving Java Deadlocks,” at this year’s JavaOne that will explore what causes deadlocks and how to solve them. Q: Tell us about your JavaOne plans.A: I am arriving on Sunday evening and have just one hands-on-lab to do on Monday morning. This is the first time that a non-Oracle team is doing a HOL at JavaOne under Oracle's stewardship and we are all a bit nervous about how it will turn out. Oracle has been immensely helpful in getting us set up. I have a great team helping me: Kirk Pepperdine, Dario Laverde, Benjamin Evans and Martijn Verburg from jClarity, Nathan Reynolds from Oracle, Henri Tremblay of OCTO Technology and Jeff Genender of Savoir Technologies. Monday will be hard work, but after that, I will hopefully get to network with fellow Java experts, attend interesting sessions and just enjoy San Francisco. Oh, and my kids have already given me a shopping list of things to get, like a GoPro Hero 2 dive housing for shooting those nice videos of Crete. (That's me at the beginning diving down.) Q: What sessions are you attending that we should know about?A: Sometimes the most unusual sessions are the best. I avoid the "big names". They often are spread too thin with all their sessions, which makes it difficult for them to deliver what I would consider deep content. I also avoid entertainers who might be good at presenting but who do not say that much.In 2010, I attended a session by Vladimir Yaroslavskiy where he talked about sorting. Although he struggled to speak English, what he had to say was spectacular. There was hardly anybody in the room, having not heard of Vladimir before. To me that was the highlight of 2010. Funnily enough, he was supposed to speak with Joshua Bloch, but if you remember, Google cancelled. If Bloch has been there, the room would have been packed to capacity.Q: Give us an update on the Java Specialists’ Newsletter.A: The Java Specialists' Newsletter continues being read by an elite audience around the world. The apostrophe in the name is significant.  It is a newsletter for Java specialists. When I started it twelve years ago, I was trying to find non-obvious things in Java to write about. Things that would be interesting to an advanced audience.As an April Fool's joke, I told my readers in Issue 44 that subscribing would remain free, but that they would have to pay US$5 to US$7 depending on their geographical location. I received quite a few angry emails from that one. I would have not earned that much from unsubscriptions. Most readers stay for a very long time.After Oracle bought Sun, the Java community held its breath for about two years whilst Oracle was figuring out what to do with Java. For a while, we were quite concerned that there was not much progress shown by Oracle. My newsletter still continued, but it was quite difficult finding new things to write about. We have probably about 70,000 readers, which is quite a small number for a Java publication. However, our readers are the top in the Java industry. So I don't mind having "only" 70000 readers, as long as they are the top 0.7%.Java concurrency is a very important topic that programmers think they should know about, but often neglect to fully understand. I continued writing about that and made some interesting discoveries. For example, in Issue 165, I showed how we can get thread starvation with the ReadWriteLock. This was a bug in Java 5, which was corrected in Java 6, but perhaps a bit too much. Whereas we could get starvation of writers in Java 5, in Java 6 we could now get starvation of readers. All of these interesting findings make their way into my courseware to help companies avoid these pitfalls.Another interesting discovery was how polymorphism works in the Server HotSpot compiler in Issue 157 and Issue 158. HotSpot can inline methods from interfaces that have only one implementation class in the JVM. When a new subclass is instantiated and called for the first time, the JVM will undo the previous optimization and re-optimize differently.Here is a little memory puzzle for your readers: public class JavaMemoryPuzzle {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzle jmp = new JavaMemoryPuzzle();    jmp.f();  }}When you run this you will always get an OutOfMemoryError, even though the local variable data is no longer visible outside of the code block.So here comes the puzzle, that I'd like you to ponder a bit. If you very politely ask the VM to release memory, then you don't get an OutOfMemoryError: public class JavaMemoryPuzzlePolite {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    for(int i=0; i<10; i++) {      System.out.println("Please be so kind and release memory");    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzlePolite jmp = new JavaMemoryPuzzlePolite();    jmp.f();    System.out.println("No OutOfMemoryError");  }}Why does this work? When I published this in my newsletter, I received over 400 emails from excited readers around the world, most of whom sent me the wrong explanation. After the 300th wrong answer, my replies became unfortunately a bit curt. Have a look at Issue 174 for a detailed explanation, but before you do, put on your thinking caps and try to figure it out yourself. Q: What do you think Java developers should know that they currently do not know?A: They should definitely get to know more about concurrency. It is a tough subject that most programmers try to avoid. Unfortunately we do come in contact with it. And when we do, we need to know how to protect ourselves and how to solve tricky system errors.Knowing your IDE is also useful. Most IDEs have a ton of shortcuts, which can make you a lot more productive in moving code around. Another thing that is useful is being able to read GC logs. Kirk Pepperdine has a great talk at JavaOne that I can recommend if you want to learn more. It's this: CON5405 – “Are Your Garbage Collection Logs Speaking to You?” Q: What are you looking forward to in Java 8?A: I'm quite excited about lambdas, though I must confess that I have not studied them in detail yet. Maurice Naftalin's Lambda FAQ is quite a good start to document what you can do with them. I'm looking forward to finding all the interesting bugs that we will now get due to lambdas obscuring what is really going on underneath, just like we had with generics.I am quite impressed with what the team at Oracle did with OpenJDK's performance. A lot of the benchmarks now run faster.Hopefully Java 8 will come with JSR 310, the Date and Time API. It still boggles my mind that such an important API has been left out in the cold for so long.What I am not looking forward to is losing perm space. Even though some systems run out of perm space, at least the problem is contained and they usually manage to work around it. In most cases, this is due to a memory leak in that region of memory. Once they bundle perm space with the old generation, I predict that memory leaks in perm space will be harder to find. More contracts for us, but also more pain for our customers. Originally published on blogs.oracle.com/javaone.

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  • The Java Specialist: An Interview with Java Champion Heinz Kabutz

    - by Janice J. Heiss
    Dr. Heinz Kabutz is well known for his Java Specialists’ Newsletter, initiated in November 2000, where he displays his acute grasp of the intricacies of the Java platform for an estimated 70,000 readers; for his work as a consultant; and for his workshops and trainings at his home on the Island of Crete where he has lived since 2006 -- where he is known to curl up on the beach with his laptop to hack away, in between dips in the Mediterranean. Kabutz was born of German parents and raised in Cape Town, South Africa, where he developed a love of programming in junior high school through his explorations on a ZX Spectrum computer. He received a B.S. from the University of Cape Town, and at 25, a Ph.D., both in computer science. He will be leading a two-hour hands-on lab session, HOL6500 – “Finding and Solving Java Deadlocks,” at this year’s JavaOne that will explore what causes deadlocks and how to solve them. Q: Tell us about your JavaOne plans.A: I am arriving on Sunday evening and have just one hands-on-lab to do on Monday morning. This is the first time that a non-Oracle team is doing a HOL at JavaOne under Oracle's stewardship and we are all a bit nervous about how it will turn out. Oracle has been immensely helpful in getting us set up. I have a great team helping me: Kirk Pepperdine, Dario Laverde, Benjamin Evans and Martijn Verburg from jClarity, Nathan Reynolds from Oracle, Henri Tremblay of OCTO Technology and Jeff Genender of Savoir Technologies. Monday will be hard work, but after that, I will hopefully get to network with fellow Java experts, attend interesting sessions and just enjoy San Francisco. Oh, and my kids have already given me a shopping list of things to get, like a GoPro Hero 2 dive housing for shooting those nice videos of Crete. (That's me at the beginning diving down.) Q: What sessions are you attending that we should know about?A: Sometimes the most unusual sessions are the best. I avoid the "big names". They often are spread too thin with all their sessions, which makes it difficult for them to deliver what I would consider deep content. I also avoid entertainers who might be good at presenting but who do not say that much.In 2010, I attended a session by Vladimir Yaroslavskiy where he talked about sorting. Although he struggled to speak English, what he had to say was spectacular. There was hardly anybody in the room, having not heard of Vladimir before. To me that was the highlight of 2010. Funnily enough, he was supposed to speak with Joshua Bloch, but if you remember, Google cancelled. If Bloch has been there, the room would have been packed to capacity.Q: Give us an update on the Java Specialists’ Newsletter.A: The Java Specialists' Newsletter continues being read by an elite audience around the world. The apostrophe in the name is significant.  It is a newsletter for Java specialists. When I started it twelve years ago, I was trying to find non-obvious things in Java to write about. Things that would be interesting to an advanced audience.As an April Fool's joke, I told my readers in Issue 44 that subscribing would remain free, but that they would have to pay US$5 to US$7 depending on their geographical location. I received quite a few angry emails from that one. I would have not earned that much from unsubscriptions. Most readers stay for a very long time.After Oracle bought Sun, the Java community held its breath for about two years whilst Oracle was figuring out what to do with Java. For a while, we were quite concerned that there was not much progress shown by Oracle. My newsletter still continued, but it was quite difficult finding new things to write about. We have probably about 70,000 readers, which is quite a small number for a Java publication. However, our readers are the top in the Java industry. So I don't mind having "only" 70000 readers, as long as they are the top 0.7%.Java concurrency is a very important topic that programmers think they should know about, but often neglect to fully understand. I continued writing about that and made some interesting discoveries. For example, in Issue 165, I showed how we can get thread starvation with the ReadWriteLock. This was a bug in Java 5, which was corrected in Java 6, but perhaps a bit too much. Whereas we could get starvation of writers in Java 5, in Java 6 we could now get starvation of readers. All of these interesting findings make their way into my courseware to help companies avoid these pitfalls.Another interesting discovery was how polymorphism works in the Server HotSpot compiler in Issue 157 and Issue 158. HotSpot can inline methods from interfaces that have only one implementation class in the JVM. When a new subclass is instantiated and called for the first time, the JVM will undo the previous optimization and re-optimize differently.Here is a little memory puzzle for your readers: public class JavaMemoryPuzzle {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzle jmp = new JavaMemoryPuzzle();    jmp.f();  }}When you run this you will always get an OutOfMemoryError, even though the local variable data is no longer visible outside of the code block.So here comes the puzzle, that I'd like you to ponder a bit. If you very politely ask the VM to release memory, then you don't get an OutOfMemoryError: public class JavaMemoryPuzzlePolite {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    for(int i=0; i<10; i++) {      System.out.println("Please be so kind and release memory");    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzlePolite jmp = new JavaMemoryPuzzlePolite();    jmp.f();    System.out.println("No OutOfMemoryError");  }}Why does this work? When I published this in my newsletter, I received over 400 emails from excited readers around the world, most of whom sent me the wrong explanation. After the 300th wrong answer, my replies became unfortunately a bit curt. Have a look at Issue 174 for a detailed explanation, but before you do, put on your thinking caps and try to figure it out yourself. Q: What do you think Java developers should know that they currently do not know?A: They should definitely get to know more about concurrency. It is a tough subject that most programmers try to avoid. Unfortunately we do come in contact with it. And when we do, we need to know how to protect ourselves and how to solve tricky system errors.Knowing your IDE is also useful. Most IDEs have a ton of shortcuts, which can make you a lot more productive in moving code around. Another thing that is useful is being able to read GC logs. Kirk Pepperdine has a great talk at JavaOne that I can recommend if you want to learn more. It's this: CON5405 – “Are Your Garbage Collection Logs Speaking to You?” Q: What are you looking forward to in Java 8?A: I'm quite excited about lambdas, though I must confess that I have not studied them in detail yet. Maurice Naftalin's Lambda FAQ is quite a good start to document what you can do with them. I'm looking forward to finding all the interesting bugs that we will now get due to lambdas obscuring what is really going on underneath, just like we had with generics.I am quite impressed with what the team at Oracle did with OpenJDK's performance. A lot of the benchmarks now run faster.Hopefully Java 8 will come with JSR 310, the Date and Time API. It still boggles my mind that such an important API has been left out in the cold for so long.What I am not looking forward to is losing perm space. Even though some systems run out of perm space, at least the problem is contained and they usually manage to work around it. In most cases, this is due to a memory leak in that region of memory. Once they bundle perm space with the old generation, I predict that memory leaks in perm space will be harder to find. More contracts for us, but also more pain for our customers.

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  • The Template Method Design Pattern using C# .Net

    - by nijhawan.saurabh
    First of all I'll just put this pattern in context and describe its intent as in the GOF book:   Template Method: Define the skeleton of an algorithm in an operation, deferring some steps to Subclasses. Template Method lets subclasses redefine certain steps of an algorithm without changing the Algorithm's Structure.    Usage: When you are certain about the High Level steps involved in an Algorithm/Work flow you can use the Template Pattern which allows the Base Class to define the Sequence of the Steps but permits the Sub classes to alter the implementation of any/all steps.   Example in the .Net framework: The most common example is the Asp.Net Page Life Cycle. The Page Life Cycle has a few methods which are called in a sequence but we have the liberty to modify the functionality of any of the methods by overriding them.   Sample implementation of Template Method Pattern:   Let's see the class diagram first:            Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:8.0pt; mso-para-margin-left:0in; line-height:107%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi; mso-font-kerning:1.0pt; mso-ligatures:standard;}   And here goes the code:EmailBase.cs     1 using System;     2 using System.Collections.Generic;     3 using System.Linq;     4 using System.Text;     5 using System.Threading.Tasks;     6      7 namespace TemplateMethod     8 {     9     public abstract class EmailBase    10     {    11     12         public bool SendEmail()    13         {    14             if (CheckEmailAddress() == true) // Method1 in the sequence    15             {    16                 if (ValidateMessage() == true) // Method2 in the sequence    17                 {    18                     if (SendMail() == true) // Method3 in the sequence    19                     {    20                         return true;    21                     }    22                     else    23                     {    24                         return false;    25                     }    26     27                 }    28                 else    29                 {    30                     return false;    31                 }    32     33             }    34             else    35             {    36                 return false;    37     38             }    39     40     41         }    42     43         protected abstract bool CheckEmailAddress();    44         protected abstract bool ValidateMessage();    45         protected abstract bool SendMail();    46     47     48     }    49 }    50    EmailYahoo.cs      1 using System;     2 using System.Collections.Generic;     3 using System.Linq;     4 using System.Text;     5 using System.Threading.Tasks;     6      7 namespace TemplateMethod     8 {     9     public class EmailYahoo:EmailBase    10     {    11     12         protected override bool CheckEmailAddress()    13         {    14             Console.WriteLine("Checking Email Address : YahooEmail");    15             return true;    16         }    17         protected override bool ValidateMessage()    18         {    19             Console.WriteLine("Validating Email Message : YahooEmail");    20             return true;    21         }    22     23     24         protected override bool SendMail()    25         {    26             Console.WriteLine("Semding Email : YahooEmail");    27             return true;    28         }    29     30     31     }    32 }    33   EmailGoogle.cs      1 using System;     2 using System.Collections.Generic;     3 using System.Linq;     4 using System.Text;     5 using System.Threading.Tasks;     6      7 namespace TemplateMethod     8 {     9     public class EmailGoogle:EmailBase    10     {    11     12         protected override bool CheckEmailAddress()    13         {    14             Console.WriteLine("Checking Email Address : GoogleEmail");    15             return true;    16         }    17         protected override bool ValidateMessage()    18         {    19             Console.WriteLine("Validating Email Message : GoogleEmail");    20             return true;    21         }    22     23     24         protected override bool SendMail()    25         {    26             Console.WriteLine("Semding Email : GoogleEmail");    27             return true;    28         }    29     30     31     }    32 }    33   Program.cs      1 using System;     2 using System.Collections.Generic;     3 using System.Linq;     4 using System.Text;     5 using System.Threading.Tasks;     6      7 namespace TemplateMethod     8 {     9     class Program    10     {    11         static void Main(string[] args)    12         {    13             Console.WriteLine("Please choose an Email Account to send an Email:");    14             Console.WriteLine("Choose 1 for Google");    15             Console.WriteLine("Choose 2 for Yahoo");    16             string choice = Console.ReadLine();    17     18             if (choice == "1")    19             {    20                 EmailBase email = new EmailGoogle(); // Rather than newing it up here, you may use a factory to do so.    21                 email.SendEmail();    22     23             }    24             if (choice == "2")    25             {    26                 EmailBase email = new EmailYahoo(); // Rather than newing it up here, you may use a factory to do so.    27                 email.SendEmail();    28             }    29         }    30     }    31 }    32    Final Words: It's very obvious that why the Template Method Pattern is a popular pattern, everything at last revolves around Algorithms and if you are clear with the steps involved it makes real sense to delegate the duty of implementing the step's functionality to the sub classes. Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:8.0pt; mso-para-margin-left:0in; line-height:107%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi; mso-font-kerning:1.0pt; mso-ligatures:standard;}

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  • Is there a design pattern for chained observers?

    - by sharakan
    Several times, I've found myself in a situation where I want to add functionality to an existing Observer-Observable relationship. For example, let's say I have an Observable class called PriceFeed, instances of which are created by a variety of PriceSources. Observers on this are notified whenever the underlying PriceSource updates the PriceFeed with a new price. Now I want to add a feature that allows a (temporary) override to be set on the PriceFeed. The PriceSource should still update prices on the PriceFeed, but for as long as the override is set, whenever a consumer asks PriceFeed for it's current value, it should get the override. The way I did this was to introduce a new OverrideablePriceFeed that is itself both an Observer and an Observable, and that decorates the actual PriceFeed. It's implementation of .getPrice() is straight from Chain of Responsibility, but how about the handling of Observable events? When an override is set or cleared, it should issue it's own event to Observers, as well as forwarding events from the underlying PriceFeed. I think of this as some kind of a chained observer, and was curious if there's a more definitive description of a similar pattern.

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  • How to design network protocols

    - by dandroid
    As a programmer, you work on your software design skills. You learn about things such as modularity and reusability and how you can achieve them in code. There's plenty of literature on the subject and engineers talk about it all the time. What about if you want to design network protocols? How do you judge that protocol X is badly designed while Y is well designed? (eg. in programming you are often pointed out to a well-written piece of code in order to learn from it - what is the equivalent for network protocols?) For example, suppose I want to design a P2P protocol similar to BitTorrent or I want to make a better version of the Socks protocol. How would I go about doing a good job on this? Thanks!

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  • Green Website Design

    - by Christofian
    This is kindove a strange question, but... There was a site called Blackle ( http://www.blackle.com/) which "claimed" to save energy by using a black background (it doesn't: see here: http://skeptics.stackexchange.com/questions/4373/how-much-energy-does-displaying-a-webpage-with-a-black-background-actually-save). However, blackle and it's idea of "green website design" interested me, and I was wondering if there are any ways to design an energy saving website that actually save energy. If anyone knows of any, please post them here. If nobody has any, then I guess there isn't a way to save energy through website design...

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  • Advice about a website design [closed]

    - by Dimitri
    I am web developer newbie. It doesn't mean that I don't know html/css/javascript but I am not good for web design. I am making a website for friend about a barber shop but I am not totally happy of my work due to lack of design. I would like to have some advice about the website and how can I improve the design? The website is in french because i am french. Here is the website : http://afrostyle92.fr/.

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  • Spring to Java EE, Part Three - new tech article on otn/java

    - by Janice J. Heiss
    In a new article up on otn/java, Java EE expert David Heffelfinger continues his series exploring the relative strengths and weaknesses of Java EE and Spring. Here, he demonstrates how easy it is to develop the data layer of an application using Java EE, JPA, and the NetBeans IDE instead of the Spring Framework.In the first two parts of the series, he generated a complete Java EE application by using JavaServer Faces (JSF) 2.0, Enterprise JavaBeans (EJB) 3.1, and Java Persistence API (JPA) 2.0 from Spring’s Pet Clinic MySQL schema, thus showing how easy it is to develop an application whose functionality equaled that of the Spring sample application.In his new article, Heffelfinger tweaks the application to make it more user friendly.From the article:“The generated application displays primary keys on some of the pages, and these keys are surrogate primary keys—meaning that they have no business value and are used strictly as a unique identifier—so there is no reason why they should be visible to the user. In addition, we will modify some of the generated labels to make them more user-friendly.”He concludes the article with a summary:“The Java EE version of the application is not a straight port of the Spring version. For example, the Java EE version enables us to create, update, and delete veterinarians as well as veterinary specialties, whereas the Spring version of the application enables us only to view veterinarians and specialties. Additionally, the Spring version has a single page for managing/viewing owners, pets, and visits, whereas the Java EE version of the application has separate pages for each of these entities.The other thing we should keep in mind is that we didn’t actually write a lot of the code and markup for the Java EE version of the application, because the bulk of it was generated by the NetBeans wizard.” Have a look at the complete article here.

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