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  • Are multiply-thrown Exceptions checked or runtime?

    - by froadie
    I have an Exception chain in which method1 throws an Exception to method2 which throws the Exception on to main. For some reason, the compiler forces me to deal with the error in method2 and marks it as an error if I don't, indicating that it's a checked Exception. But when the same Exception is thrown further down the line to main, the compiler allows me to ignore it and doesn't display any errors. The original Exception in method1 is a ParseException, which is checked. But the method has a generic throws Exception clause in the header, and the same object is thrown to method2, which has an identical throws Exception clause. When and how does this Exception lose the status of being checked / caught by the compiler? Edited to clarify: public void method1() throws Exception{ // code that may generate ParseException } public void method2() throws Exception{ method1(); //compiler error } public static void main(String[] args){ method2(); //ignored by compiler }

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  • Can Bonjour browse a service with a particular name?

    - by Roman
    Bonjour provides "DNSSD.browse(serviceType,callBackObject)" method which browses for services of a particular type. If a service of the given type is found, Bonjour call "callBackObject.serviceFound". If the service is lost, Bonjour calls "callBackObject.serviceLost". I alway considered "DNSSD.browse" as a method for monitoring a particular service. Bonjour monitors a particular service and calls necessary method if the service is found (available) or lost (not available). But than I realized that "DNSSD.browse" receives (as argument) a type of service (for example "http.tcp") and there can be several services of this type. So, its probably calls "serviceFound" and "serviceLost" if any service of the specified type is found or lost, respectively. But in my application I would like to browse just for one particular service. What is the best way to do it? I have two potential solutions: When I register a service, I give it a unique type. For example: "server1.http.tcp". I register services with unique names (not types) and ask Bonjour to browse for services with particular names. But I am not sure that Bonjour provide such possibility. Can it browse for services with specific names?

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  • Can I get a table name from a join select resultset metadata

    - by Matt
    Below is my code trying to retrieve table name form Resultset ResultSet rs = stmt.executeQuery("select * from product"); ResultSetMetaData meta = rs.getMetaData(); int count = meta.getColumnCount(); for (int i=0; i<count; i++) { System.out.println(meta.getTableName(i)); } But it returns empty, no mention it is a join select resultset. Is there any other approaches to retrieve table name from reusltset metadata?

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  • Avoid having a huge collection of ids by calling a DAO.getAll()

    - by Michael Bavin
    Instead of returning a List<Long> of ids when calling PersonDao.getAll() we wanted not to have an entire collection of ids in memory. Seems like returning a org.springframework.jdbc.support.rowset.SqlRowSet and iterate over this rowset would not hold every object in memory. The only problem here is i cannot cast this row to my entity. Is there a better way for this?

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  • Using Apache Velocity with StringBuilders/CharSequences

    - by mindas
    We are using Apache Velocity for dynamic templates. At the moment Velocity has following methods for evaluation/replacing: public static boolean evaluate(Context context, Writer writer, String logTag, Reader reader) public static boolean evaluate(Context context, Writer out, String logTag, String instring) We use these methods by providing StringWriter to write evaluation results. Our incoming data is coming in StringBuilder format so we use StringBuilder.toString and feed it as instring. The problem is that our templates are fairly large (can be megabytes, tens of Ms on rare cases), replacements occur very frequently and each replacement operation triples the amount of required memory (incoming data + StringBuilder.toString() which creates a new copy + outgoing data). I was wondering if there is a way to improve this. E.g. if I could find a way to provide a Reader and Writer on top of same StringBuilder instance that only uses extra memory for in/out differences, would that be a good approach? Has anybody done anything similar and could share any source for such a class? Or maybe there any better solutions to given problem?

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  • What can cause my code to run slower when the server JIT is activated?

    - by durandai
    I am doing some optimizations on an MPEG decoder. To ensure my optimizations aren't breaking anything I have a test suite that benchmarks the entire codebase (both optimized and original) as well as verifying that they both produce identical results (basically just feeding a couple of different streams through the decoder and crc32 the outputs). When using the "-server" option with the Sun 1.6.0_18, the test suite runs about 12% slower on the optimized version after warmup (in comparison to the default "-client" setting), while the original codebase gains a good boost running about twice as fast as in client mode. While at first this seemed to be simply a warmup issue to me, I added a loop to repeat the entire test suite multiple times. Then execution times become constant for each pass starting at the 3rd iteration of the test, still the optimized version stays 12% slower than in the client mode. I am also pretty sure its not a garbage collection issue, since the code involves absolutely no object allocations after startup. The code consists mainly of some bit manipulation operations (stream decoding) and lots of basic floating math (generating PCM audio). The only JDK classes involved are ByteArrayInputStream (feeds the stream to the test and excluding disk IO from the tests) and CRC32 (to verify the result). I also observed the same behaviour with Sun JDK 1.7.0_b98 (only that ist 15% instead of 12% there). Oh, and the tests were all done on the same machine (single core) with no other applications running (WinXP). While there is some inevitable variation on the measured execution times (using System.nanoTime btw), the variation between different test runs with the same settings never exceeded 2%, usually less than 1% (after warmup), so I conclude the effect is real and not purely induced by the measuring mechanism/machine. Are there any known coding patterns that perform worse on the server JIT? Failing that, what options are available to "peek" under the hood and observe what the JIT is doing there?

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  • how to know which special character is there in a file?

    - by Pangea
    My app needs to process text files during a batch process. Occassionally I receive a file with some special character at the end of the file. I am not sure what that special character is. Is there anyway I can find what that character is so that I can tell the other team which is producing that file. I have used mozilla's library to guess the file encoding and it says UTF-8.

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  • Relation many-to-many with attributes : how ?

    - by mada
    Hi, Excuse me for my poor english in advance as it is not my mother tongue. Like in this example: http://www.xylax.net/hibernate/manytomany.html But i have in the table foo-bar 2 attributes which are not part of the primary or foreign keys.: one boolean(A) & one string(B). I know how to map it without attributes but not in this case. I have not found an answer in the documentation. I need to know please how to map it & what kind of collection i have to declare in my class Foo. Thanks in advance for your answer. I really appreciate the time given by you.

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  • JavaME - LWUIT images eat up all the memory

    - by Marko
    Hi, I'm writing a MIDlet using LWUIT and images seem to eat up incredible amounts of memory. All the images I use are PNGs and are packed inside the JAR file. I load them using the standard Image.createImage(URL) method. The application has a number of forms and each has a couple of labels an buttons, however I am fairly certain that only the active form is kept in memory (I know it isn't very trustworthy, but Runtime.freeMemory() seems to confirm this). The application has worked well in 240x320 resolution, but moving it to 480x640 and using appropriately larger images for UI started causing out of memory errors to show up. What the application does, among other things, is download remote images. The application seems to work fine until it gets to this point. After downloading a couple of PNGs and returning to the main menu, the out of memory error is encountered. Naturally, I looked into the amount of memory the main menu uses and it was pretty shocking. It's just two labels with images and four buttons. Each button has three images used for style.setIcon, setPressedIcon and setRolloverIcon. Images range in size from 15 to 25KB but removing two of the three images used for every button (so 8 images in total), Runtime.freeMemory() showed a stunning 1MB decrease in memory usage. The way I see it, I either have a whole lot of memory leaks (which I don't think I do, but memory leaks aren't exactly known to be easily tracked down), I am doing something terribly wrong with image handling or there's really no problem involved and I just need to scale down. If anyone has any insight to offer, I would greatly appreciate it.

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  • Where about should my main class be created in a project?

    - by Dan
    The problem is where a class should be created in my code. An example is I have a UI class and a main logic class that controls other objects. Should the main logic class create the UI object, or should the UI object create the instance of the main logic class? An explanation of which method is best and why would be ideal. Thanks.

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  • JBoss RMI Transaction

    - by EasyName
    Hi, How can i can achieve remote transaction while using Remote EJB (over RMI/IIOP or RMI/JRMP). Is that JBoss 4.0 support this kind of transaction or should i use jotm or atomikos? Thanks in advance

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  • How to get the EJB listening port?

    - by Alotor
    I'm currently developing a library for monitoring calls to several remote services (WebServices, EJBs...). One of the parameters that i would like to register is the port from which a EJB is called (a Stateless Session Bean invoked like a remote object) There is any standarised way of getting the port? Or should I inspect the JNDI tree for this kind of information? I'm using the EJB 2.1 spec, but it's also posible for me to use EJB 3

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  • Retrieve only the superclass from a class hierarchy

    - by user1792724
    I have an scenario as the following: @Entity @Table(name = "ANIMAL") @Inheritance(strategy = InheritanceType.JOINED) public class Animal implements Serializable { @Id @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "S_ANIMAL") @SequenceGenerator(name = "S_ANIMAL", sequenceName = "S_ANIMAL", allocationSize = 1) public int getNumero() { return numero; } public void setNumero(int numero) { this.numero = numero; } . . . } and as the subclass: @Entity @Table(name = "DOG") public class Dog extends Animal { private static final long serialVersionUID = -7341592543130659641L; . . . } I have a JPA Select statement like this: SELECT a FROM Animal a; I'm using Hibernate 3.3.1 As I can see the framework retrieves instances of Animal and also of Dog using a left outer join. Is there a way to Select only the "part" Animal? I mean, the previous Select will get all the Animals, those that are only Animals but not Dogs and those that are Dogs. I want them all, but in the case of Dogs I want to only retrieve the "Animal part" of them. I found the @org.hibernate.annotations.Entity(polymorphism = PolymorphismType.EXPLICIT) but as I could see this only works if Animal isn't an @Entity. Thanks a lot.

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  • How a servlet can get the absolute path to a file outside of the servlet?

    - by WolfmanDragon
    We have been using System.getProperties("user.dir") to get the location of a properties file. Now that it has been deployed on Tomcat(via servlet), the System call is giving the location as tomcat and not at the location at where the properties file exist. How can we call the the properties file dynamically? Given: Tomcat is not the only way the app will be deployed We have no control on where the app may be placed. Relative paths will not work as that Vista is being used and Vista breaks relative paths. This must work on all OS, including(but not limited to) Linux, XP and Vista. EDIT I implied this, but in case I was not clear enough, I have no way of knowing the path String.

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  • HibernateFilter.doFilter ServletException?

    - by Austin R
    I have pretty much zero experience setting up servers, but currently my job is to set one up (don't ask why). It's an an apache-tomcat6 server. I followed some instructions step by step, and when it came time to test that everything was working, here's what I got: I know this is a bit of a shot in the dark, but does anyone know what I can do to fix this? Please let me know if there's any further information I can provide to help!

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  • Where do I put javaassist code?

    - by DutrowLLC
    I have an application running on google app engine. I'm using restlets and I have a couple of layers set up including the restlet layer, the model layer, the business layer, and the data layer. I'm attempting to use javaassist to modify some classes, but I'm unsure where to actually put the code. I tried to put the code in the static initialization block: public class Person { String firstName; String getFirstName(){return null;} static{ ClassPool pool = ClassPool.getDefault(); try { CtClass CtPerson = pool.get("Person"); CtMethod CtGetFirstName = CtPerson.getDeclaredMethod("GetFirstName"); CtGetFirstName.setBody("return firstName;"); CtPerson.toClass(); } catch (Exception e) { e.printStackTrace(); } } } ...but that resulted in this error: javassist.CannotCompileException:.....attempted duplicate class definition...". I guess it makes sense that I can't edit the class file in the middle of its generation. I know the code works because I was able to run it correctly by simply putting it in a location that would run when I sent the program a command. (accessed a Restlet resource). The code ran fine if an instance of the class had not already been instantiated, however once I instantiated an instance of the affected class, the javaassist code failed. I assume I need to put this code somewhere that it will only run either: once after the program starts, directly before a class is instantiated for the first time, or even better, during compile time.

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