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• How OpenStack Swift handles concurrent restful API request?

  - by Chen Xie

  I installed a swift service and was trying to know the capability of handling concurrent request. So I created massive amount of threads in Java, and sent it via the RestFUL API Not surprisingly, when the number of requests climb up, the program started to throw out exceptions. Caused by: java.net.ConnectException: Connection timed out: connect at java.net.DualStackPlainSocketImpl.connect0(Native Method) at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:69) at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339) at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200) at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182) at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:157) at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:391) at java.net.Socket.connect(Socket.java:579) at java.net.Socket.connect(Socket.java:528) at sun.net.NetworkClient.doConnect(NetworkClient.java:180) at sun.net.www.http.HttpClient.openServer(HttpClient.java:378) at sun.net.www.http.HttpClient.openServer(HttpClient.java:473) at sun.net.www.http.HttpClient.(HttpClient.java:203) But can anyone tell me how that time outhappened? I am curious of how SWIFT handles those requests. Is that by queuing the requests and because there are too many requests in the queue and wait for too long time and it's just get kicked out from the queue? If this holds, does it mean that it's an asynchronized mechanism to handle requests? Thanks.

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• ExceptionInInitializerError and UnsatisfiedLinkError

  - by Nemesis

  I downloaded the Getac Z710 Android tablet RFID library/jar from there web site. But after I called the init function: 05-19 19:23:45.315: E/AndroidRuntime(2469): FATAL EXCEPTION: main 05-19 19:23:45.315: E/AndroidRuntime(2469): java.lang.ExceptionInInitializerError 05-19 19:23:45.315: E/AndroidRuntime(2469): at com.getac.lib.rfidreader.RfidTagReaderAPI.InitRFIDReader(RfidTagReaderAPI.java:118) 05-19 19:23:45.315: E/AndroidRuntime(2469): at shipadmin.musterstation.no.MainActivity.onCreate(MainActivity.java:104) 05-19 19:23:45.315: E/AndroidRuntime(2469): at android.app.Activity.performCreate(Activity.java:5008) 05-19 19:23:45.315: E/AndroidRuntime(2469): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079) 05-19 19:23:45.315: E/AndroidRuntime(2469): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023) 05-19 19:23:45.315: E/AndroidRuntime(2469): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084) 05-19 19:23:45.315: E/AndroidRuntime(2469): at android.app.ActivityThread.access$600(ActivityThread.java:130) 05-19 19:23:45.315: E/AndroidRuntime(2469): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195) 05-19 19:23:45.315: E/AndroidRuntime(2469): at android.os.Handler.dispatchMessage(Handler.java:99) 05-19 19:23:45.315: E/AndroidRuntime(2469): at android.os.Looper.loop(Looper.java:137) 05-19 19:23:45.315: E/AndroidRuntime(2469): at android.app.ActivityThread.main(ActivityThread.java:4745) 05-19 19:23:45.315: E/AndroidRuntime(2469): at java.lang.reflect.Method.invokeNative(Native Method) 05-19 19:23:45.315: E/AndroidRuntime(2469): at java.lang.reflect.Method.invoke(Method.java:511) 05-19 19:23:45.315: E/AndroidRuntime(2469): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786) 05-19 19:23:45.315: E/AndroidRuntime(2469): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 05-19 19:23:45.315: E/AndroidRuntime(2469): at dalvik.system.NativeStart.main(Native Method) 05-19 19:23:45.315: E/AndroidRuntime(2469): Caused by: java.lang.UnsatisfiedLinkError: Couldn't load serial_port: findLibrary returned null 05-19 19:23:45.315: E/AndroidRuntime(2469): at java.lang.Runtime.loadLibrary(Runtime.java:365) 05-19 19:23:45.315: E/AndroidRuntime(2469): at java.lang.System.loadLibrary(System.java:538) 05-19 19:23:45.315: E/AndroidRuntime(2469): at android_serialport_api.SerialPort.<clinit>(SerialPort.java:69) 05-19 19:23:45.315: E/AndroidRuntime(2469): ... 16 more I tried other solutions for this, but still no luck. What would be the problem? They only have a limited documentation and support. TIA.

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• Getting a NullPointerException at seemingly random intervals, not sure why

  - by Miles

  I'm running an example from a Kinect library for Processing (http://www.shiffman.net/2010/11/14/kinect-and-processing/) and sometimes get a NullPointerException pointing to this line: int rawDepth = depth[offset]; The depth array is created in this line: int[] depth = kinect.getRawDepth(); I'm not exactly sure what a NullPointerException is, and much googling hasn't really helped. It seems odd to me that the code compiles 70% of the time and returns the error unpredictably. Could the hardware itself be affecting it? Here's the whole example if it helps: // Daniel Shiffman // Kinect Point Cloud example // http://www.shiffman.net // https://github.com/shiffman/libfreenect/tree/master/wrappers/java/processing import org.openkinect.*; import org.openkinect.processing.*; // Kinect Library object Kinect kinect; float a = 0; // Size of kinect image int w = 640; int h = 480; // We'll use a lookup table so that we don't have to repeat the math over and over float[] depthLookUp = new float[2048]; void setup() { size(800,600,P3D); kinect = new Kinect(this); kinect.start(); kinect.enableDepth(true); // We don't need the grayscale image in this example // so this makes it more efficient kinect.processDepthImage(false); // Lookup table for all possible depth values (0 - 2047) for (int i = 0; i < depthLookUp.length; i++) { depthLookUp[i] = rawDepthToMeters(i); } } void draw() { background(0); fill(255); textMode(SCREEN); text("Kinect FR: " + (int)kinect.getDepthFPS() + "\nProcessing FR: " + (int)frameRate,10,16); // Get the raw depth as array of integers int[] depth = kinect.getRawDepth(); // We're just going to calculate and draw every 4th pixel (equivalent of 160x120) int skip = 4; // Translate and rotate translate(width/2,height/2,-50); rotateY(a); for(int x=0; x<w; x+=skip) { for(int y=0; y<h; y+=skip) { int offset = x+y*w; // Convert kinect data to world xyz coordinate int rawDepth = depth[offset]; PVector v = depthToWorld(x,y,rawDepth); stroke(255); pushMatrix(); // Scale up by 200 float factor = 200; translate(v.x*factor,v.y*factor,factor-v.z*factor); // Draw a point point(0,0); popMatrix(); } } // Rotate a += 0.015f; } // These functions come from: http://graphics.stanford.edu/~mdfisher/Kinect.html float rawDepthToMeters(int depthValue) { if (depthValue < 2047) { return (float)(1.0 / ((double)(depthValue) * -0.0030711016 + 3.3309495161)); } return 0.0f; } PVector depthToWorld(int x, int y, int depthValue) { final double fx_d = 1.0 / 5.9421434211923247e+02; final double fy_d = 1.0 / 5.9104053696870778e+02; final double cx_d = 3.3930780975300314e+02; final double cy_d = 2.4273913761751615e+02; PVector result = new PVector(); double depth = depthLookUp[depthValue];//rawDepthToMeters(depthValue); result.x = (float)((x - cx_d) * depth * fx_d); result.y = (float)((y - cy_d) * depth * fy_d); result.z = (float)(depth); return result; } void stop() { kinect.quit(); super.stop(); } And here are the errors: processing.app.debug.RunnerException: NullPointerException at processing.app.Sketch.placeException(Sketch.java:1543) at processing.app.debug.Runner.findException(Runner.java:583) at processing.app.debug.Runner.reportException(Runner.java:558) at processing.app.debug.Runner.exception(Runner.java:498) at processing.app.debug.EventThread.exceptionEvent(EventThread.java:367) at processing.app.debug.EventThread.handleEvent(EventThread.java:255) at processing.app.debug.EventThread.run(EventThread.java:89) Exception in thread "Animation Thread" java.lang.NullPointerException at org.openkinect.processing.Kinect.enableDepth(Kinect.java:70) at PointCloud.setup(PointCloud.java:48) at processing.core.PApplet.handleDraw(PApplet.java:1583) at processing.core.PApplet.run(PApplet.java:1503) at java.lang.Thread.run(Thread.java:637)

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• Try and catch error trapping. why is it so significant

  - by oded

  sorry if it sounds dumb ' as i am i a process of learnning java i try to understand , why on earth i should "try" a method to catch errors. it looks to me like the concept is:- ' letting a process run assuming its not properly developed. should i always assume that a program based on classes and inheritance is bound for unexpected errors, which i should handle with such a heavy tools like try catch throw throws ? should all java programs be included withing try catch framework? Thanks Oded.

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• Integrating Oracle Forms Applications 11g Into SOA (4-6/Mai/10)

  - by Claudia Costa

  Workshop Description This is a Free workshop of 3 days is targeted at Oracle Forms professionals interested in integrating Oracle Forms into a Service Oriented Architecture. The workshop highlights how Forms can be part of a Service Oriented Architecture, how the Oracle Forms functionalities make it possible to integrate existing (or new) Forms applications with new or existing development utilizing the Service Oriented Architecture concepts. The goal is to understand the incremental approach that Forms provides to developers who need to extend their business platform to JEE, allowing Oracle Forms customers to retain their investment in Oracle Forms while leveraging the opportunities offered by complementing technologies. During the event the attendees will implement the Oracle Forms functionalities that make it possible to integrate with SOA. Register Now! Prerequisites ·         Knowledge of the Oracle Forms development environment (mandatory) ·         Basic knowledge of the Oracle database ·         Basic knowledge of the Java Programming Language ·         Basic knowledge of Oracle Jdeveloper or another Java IDE   System Requirements   This workshop requires attendees to provide their own laptops for this class. Attendee laptops must meet the following minimum hardware/software requirements:   ·         Laptop/PC with minimum 4 GB RAM ·         Oracle Database ·         Oracle Forms 11g R1 PS1 (WebLogic Server 10.1.3.2 + Portal, Forms, Reports and Discoverer ) ·         Oracle JDeveloper 11g R1 PS1 http://download.oracle.com/otn/java/jdeveloper/1112/jdevstudio11112install.exe ·         TCP-IP Loopback Adapter Installation (before the SOASuite installation) ·         Oracle SOASuite 11g R1 PS1 (without BAM component) When asked for an admin password, please use 'welcome1 http://download.oracle.com/otn/nt/middleware/11g/ofm_rcu_win_11.1.1.2.0_disk1_1of1.zip http://download.oracle.com/otn/nt/middleware/11g/ofm_soa_generic_11.1.1.2.0_disk1_1of1.zip ·         Oracle BI Publisher 10.1.3.4.1 http://download.oracle.com/otn/nt/ias/101341/bipublisher_windows_x86_101341.zip ·         Oracle BI Publisher Desktop 10.1.3.4. http://download.oracle.com/otn/nt/ias/101341/bipublisher_desktop_windows_x86_101341.zip   ·         At least 1 Oracle Forms solution already upgraded to the Oracle FMW 11g platform.   ------------------------------------------------------------------------------------------   Horário e Local:   4-6 de Maio / 9:30-18:00h Oracle, Porto Salvo Register Here Para mais informação por favor contacte: [email protected]

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• TOTD #166: Using NoSQL database in your Java EE 6 Applications on GlassFish - MongoDB for now!

  - by arungupta

  The Java EE 6 platform includes Java Persistence API to work with RDBMS. The JPA specification defines a comprehensive API that includes, but not restricted to, how a database table can be mapped to a POJO and vice versa, provides mechanisms how a PersistenceContext can be injected in a @Stateless bean and then be used for performing different operations on the database table and write typesafe queries. There are several well known advantages of RDBMS but the NoSQL movement has gained traction over past couple of years. The NoSQL databases are not intended to be a replacement for the mainstream RDBMS. As Philosophy of NoSQL explains, NoSQL database was designed for casual use where all the features typically provided by an RDBMS are not required. The name "NoSQL" is more of a category of databases that is more known for what it is not rather than what it is. The basic principles of NoSQL database are: No need to have a pre-defined schema and that makes them a schema-less database. Addition of new properties to existing objects is easy and does not require ALTER TABLE. The unstructured data gives flexibility to change the format of data any time without downtime or reduced service levels. Also there are no joins happening on the server because there is no structure and thus no relation between them. Scalability and performance is more important than the entire set of functionality typically provided by an RDBMS. This set of databases provide eventual consistency and/or transactions restricted to single items but more focus on CRUD. Not be restricted to SQL to access the information stored in the backing database. Designed to scale-out (horizontal) instead of scale-up (vertical). This is important knowing that databases, and everything else as well, is moving into the cloud. RBDMS can scale-out using sharding but requires complex management and not for the faint of heart. Unlike RBDMS which require a separate caching tier, most of the NoSQL databases comes with integrated caching. Designed for less management and simpler data models lead to lower administration as well. There are primarily three types of NoSQL databases: Key-Value stores (e.g. Cassandra and Riak) Document databases (MongoDB or CouchDB) Graph databases (Neo4J) You may think NoSQL is panacea but as I mentioned above they are not meant to replace the mainstream databases and here is why: RDBMS have been around for many years, very stable, and functionally rich. This is something CIOs and CTOs can bet their money on without much worry. There is a reason 98% of Fortune 100 companies run Oracle :-) NoSQL is cutting edge, brings excitement to developers, but enterprises are cautious about them. Commercial databases like Oracle are well supported by the backing enterprises in terms of providing support resources on a global scale. There is a full ecosystem built around these commercial databases providing training, performance tuning, architecture guidance, and everything else. NoSQL is fairly new and typically backed by a single company not able to meet the scale of these big enterprises. NoSQL databases are good for CRUDing operations but business intelligence is extremely important for enterprises to stay competitive. RDBMS provide extensive tooling to generate this data but that was not the original intention of NoSQL databases and is lacking in that area. Generating any meaningful information other than CRUDing require extensive programming. Not suited for complex transactions such as banking systems or other highly transactional applications requiring 2-phase commit. SQL cannot be used with NoSQL databases and writing simple queries can be involving. Enough talking, lets take a look at some code. This blog has published multiple blogs on how to access a RDBMS using JPA in a Java EE 6 application. This Tip Of The Day (TOTD) will show you can use MongoDB (a document-oriented database) with a typical 3-tier Java EE 6 application. Lets get started! The complete source code of this project can be downloaded here. Download MongoDB for your platform from here (1.8.2 as of this writing) and start the server as: arun@ArunUbuntu:~/tools/mongodb-linux-x86_64-1.8.2/bin$./mongod./mongod --help for help and startup optionsSun Jun 26 20:41:11 [initandlisten] MongoDB starting : pid=11210port=27017 dbpath=/data/db/ 64-bit Sun Jun 26 20:41:11 [initandlisten] db version v1.8.2, pdfile version4.5Sun Jun 26 20:41:11 [initandlisten] git version:433bbaa14aaba6860da15bd4de8edf600f56501bSun Jun 26 20:41:11 [initandlisten] build sys info: Linuxbs-linux64.10gen.cc 2.6.21.7-2.ec2.v1.2.fc8xen #1 SMP Fri Nov 2017:48:28 EST 2009 x86_64 BOOST_LIB_VERSION=1_41Sun Jun 26 20:41:11 [initandlisten] waiting for connections on port 27017Sun Jun 26 20:41:11 [websvr] web admin interface listening on port 28017 The default directory for the database is /data/db and needs to be created as: sudo mkdir -p /data/db/sudo chown `id -u` /data/db You can specify a different directory using "--dbpath" option. Refer to Quickstart for your specific platform. Using NetBeans, create a Java EE 6 project and make sure to enable CDI and add JavaServer Faces framework. Download MongoDB Java Driver (2.6.3 of this writing) and add it to the project library by selecting "Properties", "LIbraries", "Add Library...", creating a new library by specifying the location of the JAR file, and adding the library to the created project. Edit the generated "index.xhtml" such that it looks like: <h1>Add a new movie</h1><h:form> Name: <h:inputText value="#{movie.name}" size="20"/><br/> Year: <h:inputText value="#{movie.year}" size="6"/><br/> Language: <h:inputText value="#{movie.language}" size="20"/><br/> <h:commandButton actionListener="#{movieSessionBean.createMovie}" action="show" title="Add" value="submit"/></h:form> This page has a simple HTML form with three text boxes and a submit button. The text boxes take name, year, and language of a movie and the submit button invokes the "createMovie" method of "movieSessionBean" and then render "show.xhtml". Create "show.xhtml" ("New" -> "Other..." -> "Other" -> "XHTML File") such that it looks like: <head> <title><h1>List of movies</h1></title> </head> <body> <h:form> <h:dataTable value="#{movieSessionBean.movies}" var="m" > <h:column><f:facet name="header">Name</f:facet>#{m.name}</h:column> <h:column><f:facet name="header">Year</f:facet>#{m.year}</h:column> <h:column><f:facet name="header">Language</f:facet>#{m.language}</h:column> </h:dataTable> </h:form> This page shows the name, year, and language of all movies stored in the database so far. The list of movies is returned by "movieSessionBean.movies" property. Now create the "Movie" class such that it looks like: import com.mongodb.BasicDBObject;import com.mongodb.BasicDBObject;import com.mongodb.DBObject;import javax.enterprise.inject.Model;import javax.validation.constraints.Size;/** * @author arun */@Modelpublic class Movie { @Size(min=1, max=20) private String name; @Size(min=1, max=20) private String language; private int year; // getters and setters for "name", "year", "language" public BasicDBObject toDBObject() { BasicDBObject doc = new BasicDBObject(); doc.put("name", name); doc.put("year", year); doc.put("language", language); return doc; } public static Movie fromDBObject(DBObject doc) { Movie m = new Movie(); m.name = (String)doc.get("name"); m.year = (int)doc.get("year"); m.language = (String)doc.get("language"); return m; } @Override public String toString() { return name + ", " + year + ", " + language; }} Other than the usual boilerplate code, the key methods here are "toDBObject" and "fromDBObject". These methods provide a conversion from "Movie" -> "DBObject" and vice versa. The "DBObject" is a MongoDB class that comes as part of the mongo-2.6.3.jar file and which we added to our project earlier.  The complete javadoc for 2.6.3 can be seen here. Notice, this class also uses Bean Validation constraints and will be honored by the JSF layer. Finally, create "MovieSessionBean" stateless EJB with all the business logic such that it looks like: package org.glassfish.samples;import com.mongodb.BasicDBObject;import com.mongodb.DB;import com.mongodb.DBCollection;import com.mongodb.DBCursor;import com.mongodb.DBObject;import com.mongodb.Mongo;import java.net.UnknownHostException;import java.util.ArrayList;import java.util.List;import javax.annotation.PostConstruct;import javax.ejb.Stateless;import javax.inject.Inject;import javax.inject.Named;/** * @author arun */@Stateless@Namedpublic class MovieSessionBean { @Inject Movie movie; DBCollection movieColl; @PostConstruct private void initDB() throws UnknownHostException { Mongo m = new Mongo(); DB db = m.getDB("movieDB"); movieColl = db.getCollection("movies"); if (movieColl == null) { movieColl = db.createCollection("movies", null); } } public void createMovie() { BasicDBObject doc = movie.toDBObject(); movieColl.insert(doc); } public List<Movie> getMovies() { List<Movie> movies = new ArrayList(); DBCursor cur = movieColl.find(); System.out.println("getMovies: Found " + cur.size() + " movie(s)"); for (DBObject dbo : cur.toArray()) { movies.add(Movie.fromDBObject(dbo)); } return movies; }} The database is initialized in @PostConstruct. Instead of a working with a database table, NoSQL databases work with a schema-less document. The "Movie" class is the document in our case and stored in the collection "movies". The collection allows us to perform query functions on all movies. The "getMovies" method invokes "find" method on the collection which is equivalent to the SQL query "select * from movies" and then returns a List<Movie>. Also notice that there is no "persistence.xml" in the project. Right-click and run the project to see the output as: Enter some values in the text box and click on enter to see the result as: If you reached here then you've successfully used MongoDB in your Java EE 6 application, congratulations! Some food for thought and further play ... SQL to MongoDB mapping shows mapping between traditional SQL -> Mongo query language. Tutorial shows fun things you can do with MongoDB. Try the interactive online shell  The cookbook provides common ways of using MongoDB In terms of this project, here are some tasks that can be tried: Encapsulate database management in a JPA persistence provider. Is it even worth it because the capabilities are going to be very different ? MongoDB uses "BSonObject" class for JSON representation, add @XmlRootElement on a POJO and how a compatible JSON representation can be generated. This will make the fromXXX and toXXX methods redundant.

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• TOTD #166: Using NoSQL database in your Java EE 6 Applications on GlassFish - MongoDB for now!

  - by arungupta

  The Java EE 6 platform includes Java Persistence API to work with RDBMS. The JPA specification defines a comprehensive API that includes, but not restricted to, how a database table can be mapped to a POJO and vice versa, provides mechanisms how a PersistenceContext can be injected in a @Stateless bean and then be used for performing different operations on the database table and write typesafe queries. There are several well known advantages of RDBMS but the NoSQL movement has gained traction over past couple of years. The NoSQL databases are not intended to be a replacement for the mainstream RDBMS. As Philosophy of NoSQL explains, NoSQL database was designed for casual use where all the features typically provided by an RDBMS are not required. The name "NoSQL" is more of a category of databases that is more known for what it is not rather than what it is. The basic principles of NoSQL database are: No need to have a pre-defined schema and that makes them a schema-less database. Addition of new properties to existing objects is easy and does not require ALTER TABLE. The unstructured data gives flexibility to change the format of data any time without downtime or reduced service levels. Also there are no joins happening on the server because there is no structure and thus no relation between them. Scalability and performance is more important than the entire set of functionality typically provided by an RDBMS. This set of databases provide eventual consistency and/or transactions restricted to single items but more focus on CRUD. Not be restricted to SQL to access the information stored in the backing database. Designed to scale-out (horizontal) instead of scale-up (vertical). This is important knowing that databases, and everything else as well, is moving into the cloud. RBDMS can scale-out using sharding but requires complex management and not for the faint of heart. Unlike RBDMS which require a separate caching tier, most of the NoSQL databases comes with integrated caching. Designed for less management and simpler data models lead to lower administration as well. There are primarily three types of NoSQL databases: Key-Value stores (e.g. Cassandra and Riak) Document databases (MongoDB or CouchDB) Graph databases (Neo4J) You may think NoSQL is panacea but as I mentioned above they are not meant to replace the mainstream databases and here is why: RDBMS have been around for many years, very stable, and functionally rich. This is something CIOs and CTOs can bet their money on without much worry. There is a reason 98% of Fortune 100 companies run Oracle :-) NoSQL is cutting edge, brings excitement to developers, but enterprises are cautious about them. Commercial databases like Oracle are well supported by the backing enterprises in terms of providing support resources on a global scale. There is a full ecosystem built around these commercial databases providing training, performance tuning, architecture guidance, and everything else. NoSQL is fairly new and typically backed by a single company not able to meet the scale of these big enterprises. NoSQL databases are good for CRUDing operations but business intelligence is extremely important for enterprises to stay competitive. RDBMS provide extensive tooling to generate this data but that was not the original intention of NoSQL databases and is lacking in that area. Generating any meaningful information other than CRUDing require extensive programming. Not suited for complex transactions such as banking systems or other highly transactional applications requiring 2-phase commit. SQL cannot be used with NoSQL databases and writing simple queries can be involving. Enough talking, lets take a look at some code. This blog has published multiple blogs on how to access a RDBMS using JPA in a Java EE 6 application. This Tip Of The Day (TOTD) will show you can use MongoDB (a document-oriented database) with a typical 3-tier Java EE 6 application. Lets get started! The complete source code of this project can be downloaded here. Download MongoDB for your platform from here (1.8.2 as of this writing) and start the server as: arun@ArunUbuntu:~/tools/mongodb-linux-x86_64-1.8.2/bin$./mongod./mongod --help for help and startup optionsSun Jun 26 20:41:11 [initandlisten] MongoDB starting : pid=11210port=27017 dbpath=/data/db/ 64-bit Sun Jun 26 20:41:11 [initandlisten] db version v1.8.2, pdfile version4.5Sun Jun 26 20:41:11 [initandlisten] git version:433bbaa14aaba6860da15bd4de8edf600f56501bSun Jun 26 20:41:11 [initandlisten] build sys info: Linuxbs-linux64.10gen.cc 2.6.21.7-2.ec2.v1.2.fc8xen #1 SMP Fri Nov 2017:48:28 EST 2009 x86_64 BOOST_LIB_VERSION=1_41Sun Jun 26 20:41:11 [initandlisten] waiting for connections on port 27017Sun Jun 26 20:41:11 [websvr] web admin interface listening on port 28017 The default directory for the database is /data/db and needs to be created as: sudo mkdir -p /data/db/sudo chown `id -u` /data/db You can specify a different directory using "--dbpath" option. Refer to Quickstart for your specific platform. Using NetBeans, create a Java EE 6 project and make sure to enable CDI and add JavaServer Faces framework. Download MongoDB Java Driver (2.6.3 of this writing) and add it to the project library by selecting "Properties", "LIbraries", "Add Library...", creating a new library by specifying the location of the JAR file, and adding the library to the created project. Edit the generated "index.xhtml" such that it looks like: <h1>Add a new movie</h1><h:form> Name: <h:inputText value="#{movie.name}" size="20"/><br/> Year: <h:inputText value="#{movie.year}" size="6"/><br/> Language: <h:inputText value="#{movie.language}" size="20"/><br/> <h:commandButton actionListener="#{movieSessionBean.createMovie}" action="show" title="Add" value="submit"/></h:form> This page has a simple HTML form with three text boxes and a submit button. The text boxes take name, year, and language of a movie and the submit button invokes the "createMovie" method of "movieSessionBean" and then render "show.xhtml". Create "show.xhtml" ("New" -> "Other..." -> "Other" -> "XHTML File") such that it looks like: <head> <title><h1>List of movies</h1></title> </head> <body> <h:form> <h:dataTable value="#{movieSessionBean.movies}" var="m" > <h:column><f:facet name="header">Name</f:facet>#{m.name}</h:column> <h:column><f:facet name="header">Year</f:facet>#{m.year}</h:column> <h:column><f:facet name="header">Language</f:facet>#{m.language}</h:column> </h:dataTable> </h:form> This page shows the name, year, and language of all movies stored in the database so far. The list of movies is returned by "movieSessionBean.movies" property. Now create the "Movie" class such that it looks like: import com.mongodb.BasicDBObject;import com.mongodb.BasicDBObject;import com.mongodb.DBObject;import javax.enterprise.inject.Model;import javax.validation.constraints.Size;/** * @author arun */@Modelpublic class Movie { @Size(min=1, max=20) private String name; @Size(min=1, max=20) private String language; private int year; // getters and setters for "name", "year", "language" public BasicDBObject toDBObject() { BasicDBObject doc = new BasicDBObject(); doc.put("name", name); doc.put("year", year); doc.put("language", language); return doc; } public static Movie fromDBObject(DBObject doc) { Movie m = new Movie(); m.name = (String)doc.get("name"); m.year = (int)doc.get("year"); m.language = (String)doc.get("language"); return m; } @Override public String toString() { return name + ", " + year + ", " + language; }} Other than the usual boilerplate code, the key methods here are "toDBObject" and "fromDBObject". These methods provide a conversion from "Movie" -> "DBObject" and vice versa. The "DBObject" is a MongoDB class that comes as part of the mongo-2.6.3.jar file and which we added to our project earlier.  The complete javadoc for 2.6.3 can be seen here. Notice, this class also uses Bean Validation constraints and will be honored by the JSF layer. Finally, create "MovieSessionBean" stateless EJB with all the business logic such that it looks like: package org.glassfish.samples;import com.mongodb.BasicDBObject;import com.mongodb.DB;import com.mongodb.DBCollection;import com.mongodb.DBCursor;import com.mongodb.DBObject;import com.mongodb.Mongo;import java.net.UnknownHostException;import java.util.ArrayList;import java.util.List;import javax.annotation.PostConstruct;import javax.ejb.Stateless;import javax.inject.Inject;import javax.inject.Named;/** * @author arun */@Stateless@Namedpublic class MovieSessionBean { @Inject Movie movie; DBCollection movieColl; @PostConstruct private void initDB() throws UnknownHostException { Mongo m = new Mongo(); DB db = m.getDB("movieDB"); movieColl = db.getCollection("movies"); if (movieColl == null) { movieColl = db.createCollection("movies", null); } } public void createMovie() { BasicDBObject doc = movie.toDBObject(); movieColl.insert(doc); } public List<Movie> getMovies() { List<Movie> movies = new ArrayList(); DBCursor cur = movieColl.find(); System.out.println("getMovies: Found " + cur.size() + " movie(s)"); for (DBObject dbo : cur.toArray()) { movies.add(Movie.fromDBObject(dbo)); } return movies; }} The database is initialized in @PostConstruct. Instead of a working with a database table, NoSQL databases work with a schema-less document. The "Movie" class is the document in our case and stored in the collection "movies". The collection allows us to perform query functions on all movies. The "getMovies" method invokes "find" method on the collection which is equivalent to the SQL query "select * from movies" and then returns a List<Movie>. Also notice that there is no "persistence.xml" in the project. Right-click and run the project to see the output as: Enter some values in the text box and click on enter to see the result as: If you reached here then you've successfully used MongoDB in your Java EE 6 application, congratulations! Some food for thought and further play ... SQL to MongoDB mapping shows mapping between traditional SQL -> Mongo query language. Tutorial shows fun things you can do with MongoDB. Try the interactive online shell  The cookbook provides common ways of using MongoDB In terms of this project, here are some tasks that can be tried: Encapsulate database management in a JPA persistence provider. Is it even worth it because the capabilities are going to be very different ? MongoDB uses "BSonObject" class for JSON representation, add @XmlRootElement on a POJO and how a compatible JSON representation can be generated. This will make the fromXXX and toXXX methods redundant.

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• UBJsonReader (Libgdx) unable to to read UBJson from Python(Blender)

  - by daniel

  I am working on an export tool from Blender to Libgdx, exports like custom attributes and other information (Almost completed), this is a very cool tool that will speed up a lot your works, after I completed I will send to public to contribute forum, Export format is uses python's Standard Json module and readable text, it of course works fine, but I wanna also have a Binary Json export for faster load, so users can Export Straight to Libgdx, but after I search I found that UBJson with draft9.py (simpleubjson 0.6.1) encode is seems matches with one FBXConverter's UBJsonWriter( Xoppa wrote), but when I export, I am not able to read the file, and send this errors (Java heap space) seems this is a different between byte sizes in UBJson(python) and UBJsonReader. how can I write a correct one in python that matches with Libgdx's UBJsonReader, and would be cross-platform? Exception in thread "LWJGL Application" com.badlogic.gdx.utils.GdxRuntimeException: java.lang.OutOfMemoryError: Java heap space at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:120) Caused by: java.lang.OutOfMemoryError: Java heap space at com.badlogic.gdx.utils.UBJsonReader.readString(UBJsonReader.java:162) at com.badlogic.gdx.utils.UBJsonReader.parseString(UBJsonReader.java:150) at com.badlogic.gdx.utils.UBJsonReader.parseObject(UBJsonReader.java:112) at com.badlogic.gdx.utils.UBJsonReader.parse(UBJsonReader.java:59) at com.badlogic.gdx.utils.UBJsonReader.parse(UBJsonReader.java:52) at com.badlogic.gdx.utils.UBJsonReader.parse(UBJsonReader.java:36) at com.badlogic.gdx.utils.UBJsonReader.parse(UBJsonReader.java:45) at com.me.gdximportexport.GdxImportExport.create(GdxImportExport.java:43) at com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop(LwjglApplication.java:136) at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:114) Tested on UbuntuStudio 13.10 with OpenJdk 7, and Windows 7 with jdk 7 Thanks for any guides.

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• JBoss Seam project can not be run/deployed

  - by user1494328

  I created sample application in Seam framework (Seam Web Project) and JBoss Server 7.1. When I try run application, console dislays: 23:29:35,419 ERROR [org.jboss.msc.service.fail] (MSC service thread 1-3) MSC00001: Failed to start service jboss.deployment.unit."secoundProject-ds.xml".PARSE: org.jboss.msc.service.StartException in service jboss.deployment.unit."secoundProject-ds.xml".PARSE: Failed to process phase PARSE of deployment "secoundProject-ds.xml" at org.jboss.as.server.deployment.DeploymentUnitPhaseService.start(DeploymentUnitPhaseService.java:119) [jboss-as-server-7.1.1.Final.jar:7.1.1.Final] at org.jboss.msc.service.ServiceControllerImpl$StartTask.startService(ServiceControllerImpl.java:1811) [jboss-msc-1.0.2.GA.jar:1.0.2.GA] at org.jboss.msc.service.ServiceControllerImpl$StartTask.run(ServiceControllerImpl.java:1746) [jboss-msc-1.0.2.GA.jar:1.0.2.GA] at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) [rt.jar:1.6.0_24] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) [rt.jar:1.6.0_24] at java.lang.Thread.run(Thread.java:662) [rt.jar:1.6.0_24] Caused by: org.jboss.as.server.deployment.DeploymentUnitProcessingException: IJ010061: Unexpected element: local-tx-datasource at org.jboss.as.connector.deployers.processors.DsXmlDeploymentParsingProcessor.deploy(DsXmlDeploymentParsingProcessor.java:85) at org.jboss.as.server.deployment.DeploymentUnitPhaseService.start(DeploymentUnitPhaseService.java:113) [jboss-as-server-7.1.1.Final.jar:7.1.1.Final] ... 5 more Caused by: org.jboss.jca.common.metadata.ParserException: IJ010061: Unexpected element: local-tx-datasource at org.jboss.jca.common.metadata.ds.DsParser.parseDataSources(DsParser.java:183) at org.jboss.jca.common.metadata.ds.DsParser.parse(DsParser.java:119) at org.jboss.jca.common.metadata.ds.DsParser.parse(DsParser.java:82) at org.jboss.as.connector.deployers.processors.DsXmlDeploymentParsingProcessor.deploy(DsXmlDeploymentParsingProcessor.java:80) ... 6 more 23:29:35,452 INFO [org.jboss.as.server.deployment] (MSC service thread 1-4) JBAS015877: Stopped deployment secoundProject-ds.xml in 1ms 23:29:35,455 INFO [org.jboss.as.server] (DeploymentScanner-threads - 2) JBAS015863: Replacement of deployment "secoundProject-ds.xml" by deployment "secoundProject-ds.xml" was rolled back with failure message {"JBAS014671: Failed services" => {"jboss.deployment.unit.\"secoundProject-ds.xml\".PARSE" => "org.jboss.msc.service.StartException in service jboss.deployment.unit.\"secoundProject-ds.xml\".PARSE: Failed to process phase PARSE of deployment \"secoundProject-ds.xml\""}} 23:29:35,457 INFO [org.jboss.as.server.deployment] (MSC service thread 1-1) JBAS015876: Starting deployment of "secoundProject-ds.xml" 23:29:35,920 ERROR [org.jboss.msc.service.fail] (MSC service thread 1-1) MSC00001: Failed to start service jboss.deployment.unit."secoundProject-ds.xml".PARSE: org.jboss.msc.service.StartException in service jboss.deployment.unit."secoundProject-ds.xml".PARSE: Failed to process phase PARSE of deployment "secoundProject-ds.xml" at org.jboss.as.server.deployment.DeploymentUnitPhaseService.start(DeploymentUnitPhaseService.java:119) [jboss-as-server-7.1.1.Final.jar:7.1.1.Final] at org.jboss.msc.service.ServiceControllerImpl$StartTask.startService(ServiceControllerImpl.java:1811) [jboss-msc-1.0.2.GA.jar:1.0.2.GA] at org.jboss.msc.service.ServiceControllerImpl$StartTask.run(ServiceControllerImpl.java:1746) [jboss-msc-1.0.2.GA.jar:1.0.2.GA] at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) [rt.jar:1.6.0_24] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) [rt.jar:1.6.0_24] at java.lang.Thread.run(Thread.java:662) [rt.jar:1.6.0_24] Caused by: org.jboss.as.server.deployment.DeploymentUnitProcessingException: IJ010061: Unexpected element: local-tx-datasource at org.jboss.as.connector.deployers.processors.DsXmlDeploymentParsingProcessor.deploy(DsXmlDeploymentParsingProcessor.java:85) at org.jboss.as.server.deployment.DeploymentUnitPhaseService.start(DeploymentUnitPhaseService.java:113) [jboss-as-server-7.1.1.Final.jar:7.1.1.Final] ... 5 more Caused by: org.jboss.jca.common.metadata.ParserException: IJ010061: Unexpected element: local-tx-datasource at org.jboss.jca.common.metadata.ds.DsParser.parseDataSources(DsParser.java:183) at org.jboss.jca.common.metadata.ds.DsParser.parse(DsParser.java:119) at org.jboss.jca.common.metadata.ds.DsParser.parse(DsParser.java:82) at org.jboss.as.connector.deployers.processors.DsXmlDeploymentParsingProcessor.deploy(DsXmlDeploymentParsingProcessor.java:80) ... 6 more 23:29:35,952 INFO [org.jboss.as.controller] (DeploymentScanner-threads - 2) JBAS014774: Service status report JBAS014777: Services which failed to start: service jboss.deployment.unit."secoundProject-ds.xml".PARSE: org.jboss.msc.service.StartException in service jboss.deployment.unit."secoundProject-ds.xml".PARSE: Failed to process phase PARSE of deployment "secoundProject-ds.xml" My secoundProject-ds.xml: <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE datasources PUBLIC "-//JBoss//DTD JBOSS JCA Config 1.5//EN" "http://www.jboss.org/j2ee/dtd/jboss-ds_1_5.dtd"> <datasources> <local-tx-datasource> <jndi-name>secoundProjectDatasource</jndi-name> <use-java-context>true</use-java-context> <connection-url>jdbc:mysql://localhost:3306/database</connection-url> <driver-class>com.mysql.jdbc.Driver</driver-class> <user-name>root</user-name> <password></password> </local-tx-datasource> </datasources> When I comment tags errors disappear, but application is disabled in browser (The requested resource (/secoundProject/) is not available.). What should I do to fix this problem?

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• SOCharts: Charts by Tags

  - by abhin4v

  Screenshot I created this small app as a weekend hack. It shows the reputations, upvotes, downvotes and accepted answers for a user against the tags for the answers. About I wanted to know how may upvotes I was away from getting the bronze badge for the clojure tag. But I could not find any straightforward way of doing that. So I wrote this app (in Clojure, of course). The SO API is used for the data and the charts are created using the Google Chart API. The charts are opened in the default browser. License Licensed under EPL 1.0. Download If you have Clojure and Leiningen installed, you can simply get the code from https://gist.github.com/725331, save it as socharts.clj and then run lein repl -e "(load \"socharts\")(refer 'socharts.socharts)(-main)" for launching the Swing UI If you don't have Clojure installed, but have Java then download the standalone jar from http://dl.dropbox.com/u/5247/socharts-1.0.0-standalone.jar and run it as javaw -jar socharts-1.0.0-standalone.jar Once the UI is launched, just type your user id in the input box and press <ENTER>. It will take some time to download the data from the SO API (the progress bar shows the download progress) and then it will open the charts in your default browser. You can also run it as a command line app by running lein repl -e "(load \"socharts\")(refer 'socharts.socharts)(-main <userid>)" or java -jar socharts-1.0.0-standalone.jar <userid> where you replace <userid> with your user id. Be warned that because of a missing feature in the SO API, it will fetch the data for each question you have answered. So the maximum limit is 10000 answers (the SO API call limit). Platform All platforms with Java 1.6. Contact You can reach me at abhinav [at] abhinavsarkar [dot] net. Please report bugs/comments/suggestions as answers to this post. Code Code was written in Clojure with the UI in Swing. It is available at https://gist.github.com/725331. It's a public gist so your can fork it if you like to do some changes.

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• Mismanaged Session Cookie Issue Fixed for EBS in JRE 1.6.0_23

  - by Steven Chan

  At last:  some good news for those of you affected by the mismanaged session cookie issue in E-Business Suite environments.  This issue is resolved by the latest Sun Java Runtime Environment 1.6.0_23 (a.k.a. JRE 6u23, internal version 1.6.0_23-b05).See the 1.6.0_23 Update Release Notes for details about what has changed in this release.  This release is available for download from the usual Sun channels and through the 'Java Automatic Update' mechanism.This JRE release has been certified with both Oracle E-Business Suite Release 11i and 12.  We recommend this release for all E-Business Suite users.

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• Absent Code attribute in method that is not native or abstract

  - by kerry

  I got the following, quite puzzling error today when running a unit test: java.lang.ClassFormatError: Absent Code attribute in method that is not native or abstract in class file javax/servlet/http/Cookie A google search found this post, which explains that it is caused by having an interface in the classpath, and not an actual implementation. In this case it’s the java-ee interface. To fix this I added the jetty servlet api implementation to my pom: jetty javax.servlet test Piece of cake. I have run in to this before, so I figured I would capture the fix here in case I run in to it again.

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• How to Upgrade Oracle JDK and remove old JDK settings

  - by obysr

  i searched and not found how to upgrade oracle jdk in here. I'm not satisfied with OpenJDK7 because it doesn't come with Java Compiler. I has installed and configured Sun Java SDK 6 and i want to upgrade to Oracle JDK 7. I searched ppas from launchpad an wubp8 but it didn't work. How should I do to upgrade Sun JDK 6 to Oracle JDK 7 and also clearly remove all Sun JDK 6 settings? I'm very grateful for your answers. Sorry for my english

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• Java Champion Jorge Vargas on Extreme Programming, Geolocalization, and Latin American Programmers

  - by Janice J. Heiss

  In a new interview, up on otn/java, titled “An Interview with Java Champion Jorge Vargas,” Jorge Vargas, a leading Mexican developer, discusses the process of introducing companies to Enterprise JavaBeans through the application of Extreme Programming. Among other things, he gives workshops about building code with agile techniques and creates a master project to build all apps based on Scrum, XP methods and Kanban. He focuses on building core components such as security, login, and menus. Vargas remarks, “This may sound easy, but it’s not—the process takes months and hundreds of hours, but it can be controlled, and with small iterations, we can translate customer requirements and problems of legacy systems to the new system.” In regard to his work with geolocalization, he says: “We have launched a beta program of Yumbling, a geolocalization-based app, with mobile clients for BlackBerry, iPhone, Android, and Nokia, with a Web interface. The first challenge was to design a simple universal mechanism providing information to all clients and to minimize maintenance provision to them. I try not to generalize a lot—to avoid low performance or misunderstanding in processing data. We use the latest Java EE technology—during the last five years, I’ve taught people how to use Java EE efficiently.” Check out the interview here.

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• Is it worth learning either GWT or Vaadin?

  - by NimChimpsky

  I consider myself a decent java/web developer. In my career I have always used servlets and ejb's with a web front end, most recently incoporating jquery and ajax. I can see the theoretical benefit of using GWT or Vaadin: it is my understanding they convert Java code to the required JavaScript/HTML. So the developer gets the benefit of cross browser compatibility and compile time error checking (of web GUI elements). My question is threefold: Are there any other benefits I am missing that would be gained using Vaadin or GWT? I am actually quite confident and productive using HTML and JavaScript - so will I actually see any benefit? Or will it just make my knowledge of these areas redundant (as they are handled by GWT/Vaadin)? Will the end result be that I can create enterprise scale data driven websites in a reasonably short time? I can however already do this, and I have not wasted any time learning GWT/Vaadin.

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• how to concatenate two strings in shell script in 3.13.0-34-generic kernel

  - by saikrishna

  I want to concatenate two strings for the shell file im getting error when i have created the shell file in following manner could you please suggest how to get it set export APP_HOME="/home/sfptladmin/ArchivalDaemon" export JAVA_HOME="/usr/lib/jvm/java-7-oracle/jre" export LIBPATH="/home/sfptladmin/ArchivalDaemon/lib" export CPATH=$APP_HOME/conf export CPATH=$CPATH:$LIBPATH/commons-beanutils-core-1.7.0.jar export CPATH=$CPATH:$LIBPATH/commons-collections-3.2.jar export CPATH=$CPATH:$LIBPATH/commons-io-1.4.jar export CPATH=$CPATH:$LIBPATH/commons-lang.jar export CPATH=$CPATH:$LIBPATH/commons-net.jar export CPATH=$CPATH:$LIBPATH/dataloader-27.0.1-uber.jar export CPATH=$CPATH:$LIBPATH/dom4j-1.6.1.jar export CPATH=$CPATH:$LIBPATH/log4j-1.2.15.jar export CPATH=$CPATH:$LIBPATH/opencsv2.3.jar export CPATH=$CPATH:$LIBPATH/poi-3.7.jar export CPATH=$CPATH:$LIBPATH/poi-ooxml-3.7.jar export CPATH=$CPATH:$LIBPATH/poi-ooxml-schemas-3.7.jar export CPATH=$CPATH:$LIBPATH/wsc-23-min.jar export CPATH=$CPATH:$LIBPATH/xmlbeans-2.5.0.jar export CPATH=$CPATH:$LIBPATH/archival-daemon-main.jar export CPATH=$CPATH:$LIBPATH/sbmclasspath.jar export CPATH=$CPATH java -Xms256m -Xmx512m -classpath $CPATH "-Dfile.encoding=UTF-8" com.genpact.proflow.daemon.archival.manager.ArchivalManager echo $CPATH

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• How could this diagram of the current most lucrative technologies be improved?

  - by Edward Tanguay

  I'm giving a talk in April 2011 on the "Developer English" and showing my non-developer audience, mostly English teachers, various diagrams to explain how developers see their industry etc. One of these diagrams is "Hot Technologies", basically, if you want to become a developer, what technologies should you learn to have the highest chance of (1) getting a job (2) making a good salary, and (3) work with the most exciting technology. This is a draft I made just to get some ideas out, basically C#, PHP, Java are where the bulk of the jobs are. Mobile development has a big future. JavaScript is becoming more and more important, and I want to list "minor technologies" such a Python, Ruby on Rails to the side, I assume e.g. that in general, there are a much smaller percentage of jobs in these technologies as in C#, PHP, Java. How could this diagram be improved?

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• Why eclipse is hanging while in debug mode ?

  - by Pratik

  We are developing our web application using JAVA GWT framework. We are using Eclipse Indigo as a development GUI. We are facing problems while debugging the JAVA gwt application in eclipse. Most of the time, Eclipse hangs while debugging. We tried to increase the memory buffer size in eclipse but no luck. We had tried to run the eclipse in various environment like Windows, Fedora 16, Cent OS. but some how not getting positive results. Can anyone help me out to decide which OS, and eclipse or version should we have to use so can able to resolve the hanging issue? Thanks in advance. Pratik

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• What is the start point in game development? Where to start?

  - by Dragon

  I understand, I'm not unique with such a question, there are a lot of questions like this one. But I hope you'll take a minute and maybe can give me a piece of advice. I have an idea to develop games, but I don't know where is the start point in game development. The learning curve isn't as straight as in learning of a programming language, but I want to give it a try. I have some experience with OOP and programming in general. I know (not too deep) C#, Java programming languages. I searched info on where to start, read a lot of blogs, forums and so on. Once I decided "stop wandering around, just start develop a game" and I started. At the moment I have a console version of very simple game (RPS - rock-paper-scissors) developed with C#. It has different modes: "player vs cpu" and "player vs player". Some time later I looked at the code and decided that it should be refactored or even redeveloped from the scratch. And I thought that time "GUI is what I need. I can add logic later." And now I'm here. I've already decided to make RPS with GUI, then make multiplayer and so on. I'm not thinking about 3D now, 2D is enough. It doesn't matter what language to use: C# or Java, I found frameworks for both - XNA (C#) and Slick (Java). Both are good for 2D game development. But I know nothing about sprites, how to bind objects on the screen and so on. You can say "you don't need it for such simple game like RPS", but RPS is the beginning, I have some ideas like "Tower Defense" game... you know, everybody has ideas, wishes.... and this knowledge is useful and in some way obligatory. So what is the start point to achieve my plans, ideas, wishes? Where to start? Is it possible to make game development learning curve a little bit straight? Or there're ways that amateur and game development beginners use for years? Thank you for you answers and advise in advance. P.S Sorry for that this post turned out an essay, but I tried to express my wish to start acting. Hope I managed to do it.

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• How to create contracts in python

  - by recluze

  I am just moving to python from Java and have a question about the way the two do things. My question relates to contracts. An example: an application defines an interface that all plugins must implement and then the main application can call it. In Java: public interface IPlugin { public Image modify(Image img); } public class MainApp { public main_app_logic() { String pluginName = "com.example.myplugin"; IPlugin x = (IPlugin) Class.forName(pluginName); x.modify(someimg); } } The plugin implements the interface and we use reflection in main app to call it. That way, there's a contract between the main app and the plugin that both can refer to. How does one go about doing something similar in Python? And also, which approach is better? p.s. I'm not posting this on SO because I'm much more concerned with the philosophy behind the two approaches.

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• Advice for beginner programmer

  - by user3461957

  I am beginner in software development. I noticed when I try to learn one technology let's say .NET I loose my grip over other for example Java. I thought it would be better to concentrate on one technology either Java or .NET to make significant advancement and be an expert, because they can be many details which one can ignore when keeps on changing between technologies. Is my decision right? Do experts choose this approach? Update: Should I pursue my career knowing one technology or not?

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• javac -cp : cannot find symbol problem [migrated]

  - by LivingThing

  I have 3 classes CustomerAddress, Customer and CustomerMain. Customer has a import statement : import org.abc.customers.CustomerAddress; While CustomerMain has an import statement : import org.abc.customers.CustomerAddress; import org.abc.customers.Customer; The package for all of these classes are package org.abc.customer Now, this program works fine on eclipse but when i try to compile and run on cmd prompt it would not compile javac CustomerAddress.java compiles fine then since Customer depends on CustomerAddress i give javac -cp . Customer.java but the compiler complains error cannot find symbol CustomerAddress Thanks

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• Can one draw a cube using different method/drawing mode?

  - by den-javamaniac

  Hi. I've just started learning gamedev (in particular android EGL based) and have ran over a code from Pro Android Games 2 that looks as follows: /* * Copyright (C) 2007 Google Inc. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package opengl.scenes.cubes; import java.nio.ByteBuffer; import java.nio.ByteOrder; import java.nio.IntBuffer; import javax.microedition.khronos.opengles.GL10; public class Cube { public Cube(){ int one = 0x10000; int vertices[] = { -one, -one, -one, one, -one, -one, one, one, -one, -one, one, -one, -one, -one, one, one, -one, one, one, one, one, -one, one, one, }; int colors[] = { 0, 0, 0, one, one, 0, 0, one, one, one, 0, one, 0, one, 0, one, 0, 0, one, one, one, 0, one, one, one, one, one, one, 0, one, one, one, }; byte indices[] = { 0, 4, 5, 0, 5, 1, 1, 5, 6, 1, 6, 2, 2, 6, 7, 2, 7, 3, 3, 7, 4, 3, 4, 0, 4, 7, 6, 4, 6, 5, 3, 0, 1, 3, 1, 2 }; // Buffers to be passed to gl*Pointer() functions // must be direct, i.e., they must be placed on the // native heap where the garbage collector cannot vbb.asIntBuffer() // move them. // // Buffers with multi-byte datatypes (e.g., short, int, float) // must have their byte order set to native order ByteBuffer vbb = ByteBuffer.allocateDirect(vertices.length*4); vbb.order(ByteOrder.nativeOrder()); mVertexBuffer = vbb.asIntBuffer(); mVertexBuffer.put(vertices); mVertexBuffer.position(0); ByteBuffer cbb = ByteBuffer.allocateDirect(colors.length*4); cbb.order(ByteOrder.nativeOrder()); mColorBuffer = cbb.asIntBuffer(); mColorBuffer.put(colors); mColorBuffer.position(0); mIndexBuffer = ByteBuffer.allocateDirect(indices.length); mIndexBuffer.put(indices); mIndexBuffer.position(0); } public void draw(GL10 gl) { gl.glFrontFace(GL10.GL_CW); gl.glVertexPointer(3, GL10.GL_FIXED, 0, mVertexBuffer); gl.glColorPointer(4, GL10.GL_FIXED, 0, mColorBuffer); gl.glDrawElements(GL10.GL_TRIANGLES, 36, GL10.GL_UNSIGNED_BYTE, mIndexBuffer); } private IntBuffer mVertexBuffer; private IntBuffer mColorBuffer; private ByteBuffer mIndexBuffer;} So it suggests to draw a cube using triangles. My question is: can I draw the same cube using GL_TPOLYGON? If so, isn't that an easier/more understandable way to do things?

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• Is there an algorithm for a pool game?

  - by Dmitri

  Hello! I am looking for algorithm to calculate direction and speed of balls in a pool game. I am sure there has to be some type of open source code for this since pool games are some of the oldest computer games I can remember. I mean, when one ball hits another, I need a algorithm to calculate direction of both of them. It will depend of exact angle of where they hit each other and on speed. I want to practice Java coding, so I am looking for java code or package that has this type of code.

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• Hiring a swing developer - Need some tough assignments

  - by Jay

  I am trying to hire a java swing developer, who would most likely work on a java 1.4 based swing app. I have finalized 2-3 people and I would like to give them a one week assignment on Swing. It has to be a really tough one - something that they can't just copy from the internet and something that tests their in-depth knowledge on Swing. I can think of things like split screen windows, and custom UI controls that would involve custom paining. If you were to prepare such an assignment, what would you do? Please share your thoughts/experiences.

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