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• casting Collection<SomeClass> to Collection<SomeSuperClass>

  - by skrebbel

  Hi all, I'm sure this has been answered before, but I really cannot find it. I have a java class SomeClass and an abstract class SomeSuperClass. SomeClass extends SomeSuperClass. Another abstract method has a method that returns a Collection<SomeSuperClass>. In an implementation class, I have a Collection<SomeClass> myCollection I understand that I cannot just return myCollection, because Collection<SomeClass> does not inherit from Collection<SomeSuperClass>. Nevertheless, I know that everything in myCollection is a SomeSuperClass because after all, they're SomeClass objects which extend SomeSuperClass. How can I make this work? I.e. I want public class A { private Collection<SomeClass> myCollection; public Collection<SomeSuperClass> getCollection() { return myCollection; //compile error! } } The only way I've found is casting via a non-generic type and getting unchecked warnings and whatnot. There must be a more elegant way, though? I feel that also using Collections.checkedSet() and friends are not needed, since it is statically certain that the returned collection only contains SomeClass objects (this would not be the case when downcasting instead of upcasting, but that's not what I'm doing). What am I missing? Thanks!

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• Hibernate and parent/child relations

  - by Marco

  Hi to all, I'm using Hibernate in a Java application, and i feel that something could be done better for the management of parent/child relationships. I've a complex set of entities, that have some kind of relationships between them (one-to-many, many-to-many, one-to-one, both unidirectional and bidirectional). Every time an entity is saved and it has a parent, to estabilish the relationship the parent has to add the child to its collection (considering a one-to-may relationship). For example: Parent p = (Parent) session.load(Parent.class, pid); Child c = new Child(); c.setParent(p); p.getChildren().add(c); session.save(c); session.flush(); In the same way, if i remove a child then i have to explicitly remove it from the parent collection too. Child c = (Child) session.load(Child.class, cid); session.delete(c); Parent p = (Parent) session.load(Parent.class, pid); p.getChildren().remove(c); session.flush(); I was wondering if there are some best practices out there to do this jobs in a different way: when i save a child entity, automatically add it to the parent collection. If i remove a child, automatically update the parent collection by removing the child, etc. For example, Child c = new Child(); c.setParent(p); session.save(c); // Automatically update the parent collection session.flush(); or Child c = (Child) session.load(Child.class, cid); session.delete(c); // Automatically updates its parents (could be more than one) session.flush(); Anyway, it would not be difficult to implement this behaviour, but i was wondering if exist some standard tools or well known libraries that deals with this issue. And, if not, what are the reasons? Thanks

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• Validate XSD with XML .

  - by munish

  I want to know how to validate XML with XSD . XML is not of an element type but a complex type . Since validator class's validate method compare only element type. So basically I want to valide XSD's complex type with an XML. e.g. Basic XSD below xs:element name="Customer"> <xs:complexType> <xs:sequence> <xs:element name="Dob" type="xs:date" /> <xs:element name="Address"> <xs:complexType> <xs:sequence> <xs:element name="Line1" type="xs:string" /> <xs:element name="Line2" type="xs:string" /> </xs:sequence> </xs:complexType> </xs:element> </xs:sequence> </xs:complexType> </xs:element> We can assume we have multiple complex type in the Customer element. MY XML is <Address> <Line1>34 thingy street, someplace</Line1> <Line2>sometown, w1w8uu </Line2> </Address> How I validate my XML with XSD. Kindly post your suggestions in java

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• If statement is ignored

  - by user2898120

  I am making a simple matchmaker as a learning project in JAVA. My program so far just asks a few questions, but I wanted to do gender specific questions, so I asked for their sex (m or f) and then attempted to add a message that only showed if sex was m. The dialog should say "well done, you are male!". Else it restarts method. Every time, no matter what I type it restarts the program. Here is my code: import javax.swing.JOptionPane; public class Main { public static void main(String[] args){ setVars(); } public static void setVars(){ String name = JOptionPane.showInputDialog(null, "What is your name?"); String sAge = JOptionPane.showInputDialog(null, "What is your age?"); String sex = JOptionPane.showInputDialog(null, "What is your sex?\n(Enter m or f)"); if (sex == "m"){ JOptionPane.showMessageDialog(null, "Well done, you are male.\nKeep Going!"); } int age = Integer.parseInt(sAge); String chars = JOptionPane.showInputDialog(null, "Name three charectaristics"); } }

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• JSESSIONID collision between two servers on same ip but different ports

  - by Steve Armstrong

  I've got a situation where I have two different webapps running on a single server, using different ports. They're both running Java's Jetty servlet container, so they both use a cookie parameter named JSESSIONID to track the session id. These two webapps are fighting over the session id. Open a Firefox tab, and go to WebApp1 WebApp1's HTTP response has a set-cookie header with JSESSIONID=1 Firefox now has a Cookie header with JSESSIONID=1 in all it's HTTP requests to WebApp1 Open a second Firefox tab, and go to WebApp2 The HTTP reqeust to WebApp2 also has a Cookie header with JSESSIONID=1, but in the doGet, when I call req.getSession(false); I get null. And if I call req.getSession(true) I get a new Session object, but then the HTTP response from WebApp2 has a set-cookie header with JSESSIONID=20 Now, WebApp2 has a working Session, but WebApp1's session is gone. Going to WebApp1 will give me a new session, blowing away WebApp2's session. Continue forever So the Sessions are thrashing between each web app. I'd really like for the req.getSession(false) to return a valid session if there's already a JSESSIONID cookie defined. One option is to basically reimplement the Session framework with a HashMap and cookies called WEBAPP1SESSIONID and WEBAPP2SESSIONID, but that sucks, and means I'll have to hack the new Session stuff into ActionServlet and a few other places. This must be a problem others have encountered. Is Jetty's HttpServletRequest.getSession(boolean) just crappy?

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• Retrieving Json via HTML request from Jboss server

  - by Seth Solomon

  I am running into a java.net.SocketException: Unexpected end of file from server when I am trying to query some JSON from my JBoss server. I am hoping someone can spot where I am going wrong. Or does anyone have any suggestions of a better way to pull this JSON from my Jboss server? try{ URL u = new URL("http://localhost:9990/management/subsystem/datasources/data-source/MySQLDS/statistics?read-resource&include-runtime=true&recursive=true"); HttpURLConnection c = (HttpURLConnection) u.openConnection(); String encoded = Base64.encode(("username"+":"+"password").getBytes()); c.setRequestMethod("POST"); c.setRequestProperty("Authorization", "Basic "+encoded); c.setRequestProperty("Content-Type","application/json"); c.setUseCaches(false); c.setAllowUserInteraction(false); c.setConnectTimeout(5000); c.setReadTimeout(5000); c.connect(); int status = c.getResponseCode(); // throws the exception here switch (status) { case 200: case 201: BufferedReader br = new BufferedReader(new InputStreamReader(c.getInputStream())); StringBuilder sb = new StringBuilder(); String line; while ((line = br.readLine()) != null) { sb.append(line+"\n"); } br.close(); System.out.println(sb.toString()); break; default: System.out.println(status); break; } } catch (Exception e) { e.printStackTrace(); }

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• Modeling multiple polymorphic relationships using Hibernate

  - by f-potter

  Ruby on Rails has polymorphic relations which are really useful for implementing functionality such as commenting, tagging and rating to name a few. We can have a comment, tag or rating class which has a many to one polymorphic relationship with a commentable, taggable and rateable object. Also, a given domain object can choose to implement any combination of such relations. So, it can for example be commentable, taggable and rateable at the same time. I couldn't think up of a straightforward way to duplicate this functionality in Hibernate. Ideally, there would be a Comment class which will have a many to one relationship with a Commentable class and a Commentable class will conversely have a one to many relationship with Comments. It will be ideal if the concrete domain classes can inherit from a number of such classes, say Commentable and Taggable. Things seem a little complicated as a Java class can only extend one other class and some code might end up being duplicated across a number of classes. I wanted to know what are the best practices for modeling such relationships neatly and concisely using Hibernate?

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• Shape object in Processing, translate individual shapes.

  - by Zain

  I am relatively new to Processing but have been working in Java for about 2 years now. I am facing difficulty though with the translate() function for objects as well as objects in general in processing. I went through the examples and tried to replicate the manners by which they instantiated the objects but cannot seem to even get the shapes to appear on the screen no less move them. I instantiate the objects into an array using a nested for loop and expect a grid of the objects to be rendered. However, nothing at all is rendered. My nested for loop structure to instantiate the tiles: for(int i=0; i<102; i++){ for(int j=0; j<102; j++){ tiles[i][j]=new tile(i,0,j); tiles[i][j].display(); } } And the constructors for the tile class: tile(int x, int y, int z){ this.x=x; this.y=y; this.z=z; beginShape(); vertex(x,y,z); vertex(x+1,y,z); vertex(x+1,y,z-1); vertex(x,y,z-1); endShape(); } Nothing is rendered at all when this runs. Furthermore, if this is of any concern, my translations(movements) are done in a method I wrote for the tile class called move which simply calls translate. Is this the correct way? How should one approach this? I can't seem to understand at all how to render/create/translate individual objects/shapes. Thanks for any help any of you are able to provide!

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• How do I read text from a serial port?

  - by user2164

  I am trying to read data off of a Windows serial port through Java. I have the javax.comm libraries and am able to get some data but not correct data. When I read the port into a byte array and convert it to text I get a series of characters but no real text string. I have tried to specify the byte array as being both "UTF-8" and "US-ASCII". Does anyone know how to get real text out of this? Here is my code: while (inputStream.available() > 0) { int numBytes = inputStream.read(readBuffer); System.out.println("Reading from " + portId.getName() + ": "); System.out.println("Read " + numBytes + " bytes"); } System.out.println(new String(readBuffer)); System.out.println(new String(readBuffer, "UTF-8")); System.out.println(new String(readBuffer, "US-ASCII")); the output of the first three lines will not let me copy and paste (I assume because they are not normal characters). Here is the output of the Hex: 78786000e67e9e60061e8606781e66e0869e98e086f89898861878809e1e9880 I am reading from a Hollux GPS device which does output in string format. I know this for sure because I did it through C#. The settings that I am using for communication which I know are right from the work in the C# app are: Baud Rate: 9600 Databits: 8 Stop bit: 1 parity: none

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• How build my own Application Setting

  - by adisembiring

  I want to build a ApplicationSetting for my application. The ApplicationSetting can be stored in a properties file or in a database table. The settings are stored in key-value pairs. E.g. ftp.host = blade ftp.username = dummy ftp.pass = pass content.row_pagination = 20 content.title = How to train your dragon. I have designed it as follows: Application settings reader: interface IApplicationSettingReader { read(); } DatabaseApplicationSettingReader { dao appSettingDao; AppSettings read() { List<AppSettingEntity> listEntity = appSettingsDao.findAll(); Map<String, String> map = new HaspMap<String, String>(); foreach (AppSettingEntity entity : listEntity) { map.put(entity.getConfigName(), entity.getConfigValue()); } return new AppSettings(map); } } DatabaseApplicationSettingReader { dao appSettingDao; AppSettings read() { //read from some properties file return new AppSettings(map); } } Application settings class: AppSettings { private static AppSettings instance; private Map map; Public AppSettings(Map map) { this.map = map; } public static AppSettings getInstance() { if (instance == null) { throw new RuntimeException("Object not configure yet"); } return instance; } public static configure(IApplicationSettingReader reader) { instance = reader.read(); } public String getFtpSetting(String param) { return map.get("ftp." + param); } public String getContentSetting(String param) { return map.get("content." + param); } } Test class: AppSettingsTest { IApplicationSettingReader reader; @Before public void setUp() throws Exception { reader = new DatabaseApplicationSettingReader(); } @Test public void getContentSetting_should_get_content_title() { AppSettings.configure(reader); Instance settings = AppSettings.getInstance(); String title = settings.getContentSetting("title"); assertNotNull(title); Sysout(title); } } My questions are: Can you give your opinion about my code, is there something wrong? I configure my application setting once, while the application start, I configure the application setting with appropriate reader (DbReader or PropertiesReader), I make it singleton. The problem is, when some user edit the database or file directly to database or file, I can't get the changed values. Now, I want to implement something like ApplicationSettingChangeListener. So if the data changes, I will refresh my application settings. Do you have any suggestions how this can be implemented?

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• What does flushing thread local memory to global memory mean?

  - by Jack Griffith

  Hi, I am aware that the purpose of volatile variables in Java is that writes to such variables are immediately visible to other threads. I am also aware that one of the effects of a synchronized block is to flush thread-local memory to global memory. I have never fully understood the references to 'thread-local' memory in this context. I understand that data which only exists on the stack is thread-local, but when talking about objects on the heap my understanding becomes hazy. I was hoping that to get comments on the following points: When executing on a machine with multiple processors, does flushing thread-local memory simply refer to the flushing of the CPU cache into RAM? When executing on a uniprocessor machine, does this mean anything at all? If it is possible for the heap to have the same variable at two different memory locations (each accessed by a different thread), under what circumstances would this arise? What implications does this have to garbage collection? How aggressively do VMs do this kind of thing? Overall, I think am trying to understand whether thread-local means memory that is physically accessible by only one CPU or if there is logical thread-local heap partitioning done by the VM? Any links to presentations or documentation would be immensely helpful. I have spent time researching this, and although I have found lots of nice literature, I haven't been able to satisfy my curiosity regarding the different situations & definitions of thread-local memory. Thanks very much.

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• RegularExpression-esque search matching Objects in List

  - by Pindatjuh

  I'm currently working on an implementation of the following idea, and I was wondering if there is any literature on this subject. Working with Java, but the principle applies on any language with a decent type-system, I like to implement: matching Objects from a List using a RegularExpression-esque search: So let's say I have a List containing List<Object> x = new ArrayList<Object>(); x.add(new Object()); x.add("Hello World"); x.add("Second String"); x.add(5); // Integer (auto-boxing) x.add(6); // Integer Then I create a "Regular Expression" (not working with a stream of characters, but working with a stream of Objects), and instead of character-classes, I use type-system properties: [String][Integer] And this would match one sublist: {Match["Second String", 5]}. The expression: [String:length()<15] Will match two sublist (each of length 1) containing a String which instance is passing the expression instance.length() < 5: {Match["Hello World"],Match["Second String"]}. [Object][Object] Matches any pair in the List: {Match[Object,"Hello World"],Match["Second String", 5]}, in a streamed manner (no overlapping matches). Ofcourse, my implementation will have grouping, lookahead/lookbehinds and is hierarchical (i.e. matching n elements from Lists in Lists), etc. The above merely illustrates the concept. Is there a name for this principle, and is there literature available on it?

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• Foosball result prediction

  - by Wolf

  In our office, we regularly enjoy some rounds of foosball / table football after work. I have put together a small java program that generates random 2vs2 lineups from the available players and stores the match results in a database afterwards. The current prediction of the outcome uses a simple average of all previous match results from the 4 involved players. This gives a very rough estimation, but I'd like to replace it with something more sophisticated, taking into account things like: players may be good playing as attacker but bad as defender (or vice versa) players do well against a specific opponent / bad against others some teams work well together, others don't skills change over time What would be the best algorithm to predict the game outcome as accurately as possible? Someone suggested using a neural network for this, which sounds quite interesting... but I do not have enough knowledge on the topic to say if that could work, and I also suspect it might take too many games to be reasonably trained. EDIT: Had to take a longer break from this due to some project deadlines. To make the question more specific: Given the following mysql table containing all matches played so far: table match_result match_id int pk match_start datetime duration int (match length in seconds) blue_defense int fk to table player blue_attack int fk to table player red_defense int fk to table player red_attack int fk to table player score_blue int score_red int How would you write a function predictResult(blueDef, blueAtk, redDef, redAtk) {...} to estimate the outcome as closely as possible, executing any sql, doing calculations or using external libraries?

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• wsimport generate a client with cookies

  - by dierre

  I'm generating a client for a SOAP 1.2 service using wsimport from the jaxws-maven-plugin in maven with the following execution: <groupId>org.jvnet.jax-ws-commons</groupId> <artifactId>jaxws-maven-plugin</artifactId> <version>2.2</version> <executions> <execution> <goals> <goal>wsimport</goal> </goals> <configuration> <sourceDestDir>${project.basedir}/src/main/java</sourceDestDir> <wsdlUrls> <wsdlUrl>${webservice.url}</wsdlUrl> </wsdlUrls> <extension>true</extension> </configuration> </execution> The first time the client call the proxy, the load balancer generate a cookie and sends it back. The client should send it back so the load balancer knows where (which server) is dedicated to a specific client (the idea is that the first time the client get a server and the cookie identifies the server, then the load balancer sends the client to the same server for every call) Now, is there a way to tell to the plugin to enable automatically the cookie handling?

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• I want to read program content from command line.

  - by Alexandre Dominos

  I am trying to update a program which was wrotten in 1995 with pascal or c. I am not sure about programming language. Command line program. Now I am coded in C#. And I want to read program command line content. Is it possible? I tried something. But not succesfull. They are: private void aboutToolStripMenuItem_Click(object sender, EventArgs e) { // Redirect the output stream of the child process. p.StartInfo.UseShellExecute = false; p.StartInfo.RedirectStandardOutput = true; p.StartInfo.FileName = "osl.exe"; p.Start(); logs.AppendText("Timer Started\n"); timer1.Enabled = true; } private void timer1_Tick(object sender, EventArgs e) { // write somethingg and read what is the program doing on command line? // What is the program printint? etc... // I try this code but not enough for mo. // logs.AppendText("d:" + p.StandardOutput.ReadToEnd()+"\n"); } private void p_Exited(object sender, EventArgs e) { timer1.Enabled = false; } i am open to any idea in java,cpp,c,c#.

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• how to modify the textfield in jasper report using java

  - by stanley

  i have created a textfield in jasper reports, Using java how do i modify the textfield properties like width, postion etc

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• What's wrong with this code

  - by javacode

  I am getting the compiler error. Can anybody debug this? import javax.mail.*; import javax.mail.internet.*; import java.util.*; public class SendMail { public static void main(String [] args) { SendMail sm=new SendMail(); sm.postMail("[email protected]","hi","hello","[email protected]"); } public void postMail( String recipients[ ], String subject, String message , String from) throws MessagingException { boolean debug = false; //Set the host smtp address Properties props = new Properties(); props.put("mail.smtp.host", "webmail.emailmyname.com"); // create some properties and get the default Session Session session = Session.getDefaultInstance(props, null); session.setDebug(debug); // create a message Message msg = new MimeMessage(session); // set the from and to address InternetAddress addressFrom = new InternetAddress(from); msg.setFrom(addressFrom); InternetAddress[] addressTo = new InternetAddress[recipients.length]; for (int i = 0; i < recipients.length; i++) { addressTo[i] = new InternetAddress(recipients[i]); } msg.setRecipients(Message.RecipientType.TO, addressTo); // Optional : You can also set your custom headers in the Email if you Want msg.addHeader("MyHeaderName", "myHeaderValue"); // Setting the Subject and Content Type msg.setSubject(subject); msg.setContent(message, "text/plain"); Transport.send(msg); } }

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• Copy a directory from a jar file

  - by Macarse

  Hi. I recently finished and application and created a jar file. One of my classes creates an output directory populating it with files from it's resource. The code is something like this: // Copy files from dir "template" in this class resource to output. private void createOutput(File output) throws IOException { File template = new File(FileHelper.URL2Path(getClass().getResource("template"))); FileHelper.copyDirectory(template, output); } The problem is that now that I am running for a jar, this doesn't work. I tried without luck: Using Streams to solve similar stuff on other classes but it doesn't work with dirs. Code was similar to http://www.exampledepot.com/egs/java.io/CopyFile.html Creating the File template with new File(getClass().getResource("template").toUri()) While writting this I was thinking about instead of having a template dir in the resource path having a zip file of it. Doing it this way I could get the file as an inputStream and unzip it where I need to. But I am not sure if it's the correct way. Thanks for reading!

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• Is a GWT app running on Google App Engine protected from CSRF

  - by gerdemb

  I'm developing a GWT app running on the Google App Engine and wondering if I need to worry about Cross-site request forgery or is that automatically taken care of for me? For every RPC request that requires authentication, I have the following code: public class BookServiceImpl extends RemoteServiceServlet implements BookService { public void deleteInventory(Key<Inventory> inventoryKey) throws NotLoggedInException, InvalidStateException, NotFoundException { DAO dao = new DAO(); // This will throw NotLoggedInException if user is not logged in User user = dao.getCurrentUser(); // Do deletion here } } public final class DAO extends DAOBase { public User getCurrentUser() throws NotLoggedInException { currentUser = UserServiceFactory.getUserService().getCurrentUser(); if(currentUser == null) { throw new NotLoggedInException(); } return currentUser; } I couldn't find any documentation on how the UserService checks authentication. Is it enough to rely on the code above or do I need to to more? I'm a beginner at this, but from what I understand to avoid CSRF attacks some of the strategies are: adding an authentication token in the request payload instead of just checking a cookie checking the HTTP Referer header I can see that I have cookies set from Google with what look like SID values, but I can't tell from the serialized Java objects in the payloads if tokens are being passed or not. I also don't know if the Referer header is being used or not. So, am I worrying about a non-issue? If not, what is the best strategy here? This is a common enough problem, that there must be standard solutions out there...

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• Why does Hibernate ignore the JPA2 standardized properties in my persistence.xml?

  - by Ophidian

  I have an extremely simple web application running in Tomcat using Spring 3.0.1, Hibernate 3.5.1, JPA 2, and Derby. I am defining all of my database connectivity in persistence.xml and merely using Spring for dependency injection. I am using embedded Derby as my database. Everything works correctly when I define the driver and url properties in persistence.xml in the classic Hibernate manner as thus: <property name="hibernate.connection.driver_class" value="org.apache.derby.jdbc.EmbeddedDriver"/> <property name="hibernate.connection.url" value="jdbc:derby:webdb;create=true"/> The problems occur when I switch my configuration to the JPA2 standardized properties as thus: <property name="javax.persistence.jdbc.driver" value="org.apache.derby.jdbc.EmbeddedDriver"/> <property name="javax.persistence.jdbc.url" value="jdbc:derby:webdb;create=true"/> When using the JPA2 property keys, the application bails hard with the following exception: java.lang.UnsupportedOperationException: The user must supply a JDBC connection Does anyone know why this is failing? NOTE: I have copied the javax... property strings straight from the Hibernate reference documentation, so a typo is extremely unlikely.

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• How do I use Google's Gson API to deserialize JSON properly?

  - by FK82

  Hi, In short, this is a sketch of the JSON object I want to parse in JAVA: { object1: { item1: //[String | Array | Object] , item2: // ... //<> more items object2: { // } //<> more objects } These are the POJO s I created for parsing (I'll leave out the import statements for brevity's sake): (1) The representation of the complete JSON object public class JObjectContainer { private List<JObject> jObjects ; public JObjectContainer() { // } //get & set methods } (2) The representation of the nested objects: public class JObject { private String id ; private List<JNode> jObjects ; public JObject() { // } //get & set methods } (3) The representation of the items: public class JNode { private JsonElement item1 ; private JsonElement item2 ; //<> more item fields public JNode() { // } //get & set methods } Now, creating a Gson instance (FileReader for importing the jsonFile), Gson gson = new Gson() ; JObjectContainer joc = gson(jsonFile,JObjectContainer.class) ; I get a NullPointerException whenever I try to access the parseable object (e.g. through a ListIterator). Gson does however create an object of the class I specified and does not throw any subsequent errors. I know that this has been done before. So, what am I missing? TIA

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• Huge file in Clojure and Java heap space error

  - by trzewiczek

  I posted before on a huge XML file - it's a 287GB XML with Wikipedia dump I want ot put into CSV file (revisions authors and timestamps). I managed to do that till some point. Before I got the StackOverflow Error, but now after solving the first problem I get: java.lang.OutOfMemoryError: Java heap space error. My code (partly taken from Justin Kramer answer) looks like that: (defn process-pages [page] (let [title (article-title page) revisions (filter #(= :revision (:tag %)) (:content page))] (for [revision revisions] (let [user (revision-user revision) time (revision-timestamp revision)] (spit "files/data.csv" (str "\"" time "\";\"" user "\";\"" title "\"\n" ) :append true))))) (defn open-file [file-name] (let [rdr (BufferedReader. (FileReader. file-name))] (->> (:content (data.xml/parse rdr :coalescing false)) (filter #(= :page (:tag %))) (map process-pages)))) I don't show article-title, revision-user and revision-title functions, because they just simply take data from a specific place in the page or revision hash. Anyone could help me with this - I'm really new in Clojure and don't get the problem.

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• How does CDI injection work in MDBs and @Scheduled beans?

  - by Nils-Petter Nilsen

  I'm working on a large Java EE 6 application that is deployed on JBoss 6 Final. My current tasks involve using @Inject consistently instead of @EJB, but I'm running into some problems on some types of beans, specifically @MessageDriven beans and beans with @Scheduled methods. What happens is that if I'm unlucky with the timing (for @Schedule) or if there are messages in the MDBs' queues at startup, instantiation of the beans will fail because the injected resources (which are EJBs themselves) are not bound yet. Because I use @Inject, I'm guessing that the EJB container considers my beans to be ready, since the container itself does not care about @Inject; it probably simply assumes that since there are no @EJB injections, the beans are ready for use. The injected CDI proxies will then fail because the resources to inject aren't actually bound yet. Tiny example: @Stateless @LocalBean public class MySupportingBean { public void doSomething() { ... } } @Singleton public class MyScheduledBean { @Inject private MySupportingBean supportingBean; @Schedule(second = "*/1", hour = "*", minute = "*", persistent = false) public void onTimeout() { supportingBean.doSomething(); } } The above example will probably not fail often because there are only two beans, but the project I'm working on binds lots of EJBs, which will amplify the problem. But it might fail because there is no guarantee that MySupportingBean is bound first, and if onTimeout is invoked before MySupportingBean is bound, then instantiation of MyScheduledBean will fail. If I used @EJB instead, MyScheduledBean wouldn't be bound until the dependency to MySupportingBean was satisfied. Note that the example will not fail in onTimeout itself, but when CDI attempts to inject MySupportingBean. I've read a lot of posts on different forums where many people argue that @Inject is always better. Generally, I agree, but how do they handle @Schedule or @MessageDriven combined with @Inject? In my experience, it comes down to dumb luck whether the beans will work or not in those cases, and the beans will fail arbitrarily, depending on which order the EJBs are deployed in, and when @Schedule or onMessage are invoked.

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• What are the alternatives to public fields?

  - by James

  I am programming a game in java, and as the question title suggestions i am using public fields in my classes. (for the time being) From what i have seen public fields are bad and i have some understanding why. (but if someone could clarify why you should not use them, that would be appreciated) The thing is that also from what i have seen, (and it seems logical) is that using private fields, but using getters and setters to access them is also not good as it defeats the point of using private fields in the first place. So, my question is, what are the alternatives? or do i really have to use private fields with getters and setters? For reference here is one of my classes, and some of its methods. I will elaborate more if needs be. //The player's fields. public double health; public String name; public double goldCount; public double maxWeight; public double currentWeight; public double maxBackPckSlts; public double usedBackPckSlts; // The current back pack slots in use public double maxHealth; // Maximum amount of health public ArrayList<String> backPack = new ArrayList<String>(); //This method happens when ever the player dynamically takes damage(i.e. when it is not scripted for the player to take damage. //Parameters will be added to make it dynamic so the player can take any spread of damage. public void beDamaged(double damage) { this.health -= damage; if (this.health < 0) { this.health = 0; } } public void gainHealth(double gainedHp) { this.health += gainedHp; if (this.health > this.maxHealth) { this.health = this.maxHealth; } }

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• Turning a JSON list into a POJO

  - by Josh L

  I'm having trouble getting this bit of JSON into a POJO. I'm using Jackson configured like this: protected ThreadLocal<ObjectMapper> jparser = new ThreadLocal<ObjectMapper>(); public void receive(Object object) { try { if (object instanceof String && ((String)object).length() != 0) { ObjectDefinition t = null ; if (parserChoice==0) { if (jparser.get()==null) { jparser.set(new ObjectMapper()); } t = jparser.get().readValue((String)object, ObjectDefinition.class); } Object key = t.getKey(); if (key == null) return; transaction.put(key,t); } } catch (Exception e) { e.printStackTrace(); } } Here's the JSON that needs to be turned into a POJO: { "id":"exampleID1", "entities":{ "tags":[ { "text":"textexample1", "indices":[ 2, 14 ] }, { "text":"textexample2", "indices":[ 31, 36 ] }, { "text":"textexample3", "indices":[ 37, 43 ] } ] } And lastly, here's what I currently have for the java class: protected Entities entities; @JsonIgnoreProperties(ignoreUnknown = true) protected class Entities { public Entities() {} protected Tags tags; @JsonIgnoreProperties(ignoreUnknown = true) protected class Tags { public Tags() {} protected String text; public String getText() { return text; } public void setText(String text) { this.text = text; } }; public Tags getTags() { return tags; } public void setTags(Tags tags) { this.tags = tags; } }; //Getters & Setters ... I've been able to translate the more simple objects into a POJO, but the list has me stumped. Any help is appreciated. Thanks!

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