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  • How do I limit JPQ output?

    - by den-javamaniac
    I need to limit number of entities returned by a query to some certain value inside a JPA query (through JPQL). Particularly: select m from Manual m //constraint e.g. in sql (mysql syntax) I would do it like: select * from Manual limit 1 The only solution that comes up is simply to get all entities and then choose first one, which is out of the issue. Any ideas?

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  • Accessing inter-schema tables and relations in hibernate

    - by nitesh
    There is a typical situation being faced where different tables are scattered through different schemas in Oracle database and they are related to each other (encompassing all different types of relations). How can they be represented in Hibernate using annotations as when a sessionfactory handle is created for one schema, tables in that schema can't access other related tables (foreign key relation to tables in other schema)? For a query like following, exception is thrown - "from table1 as model where model.table2Name.table2column = "+foo Exception comes as - org.hibernate.QueryException: could not resolve property: table2column of: com.test.table1 [from com.test.table1 as model where model.table2Name.table2column = 1] Here table1 and table2 are present in different schemas.

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  • Prevent duplicate entries in arraylist

    - by timyh
    Say I create some object class like so public class thing { private String name; private Integer num; public oDetails (String a, Integer b) { name = a; num = b; } ...gets/ sets/ etc Now I want to create an arraylist to hold a number of this object class like so. ArrayList<thing> myList = new ArrayList<thing>; thing first = new thing("Star Wars", 3); thing second = new thing("Star Wars", 1); myList.add(first); myList.add(second); I would like to include some sort of logic so that in this case...when we try and add object "second" rather than add a new object to the arrayList, we add second.getNum() to first.getNum(). So if you were to iterate through the ArrayList it would be "Star Wars", 4 I am having trouble coming up with an elegant way of handling this. And as the arraylist grows, searching through it to determine if there are duplicate name items becomes cumbersome. Can anyone provide some guidance on this?

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  • Direct flow depending on incoming dynamic type

    - by Improfane
    I have a listener class that accepts GUI change events in one method. The incoming event objects have a superclass of a type of GUI Event, the behaviour should depend on the dynamic type of the incoming variable. I wanted to do do lots of methods like: handleGUIEvent(EventChangedX event) handleGUIEvent(EventChangedY event) I am using a single event listener and receiving objects of various types but the behaviour should be different for each. What would you do? I do not want to use a switch statement as this would get unmaintainable.

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  • OGNL thread safety

    - by Dewfy
    I'm going to reuse OGNL library out of Struts2 scope. I have rather large set of formulas, that is why I would like to precompile all of them: Ognl.parseExpression(expressionString); But I'm not sure if precompiled expression can be used in multi-thread environment. Does anybody knows if it can be used?

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  • How can I get an image too big from a server?

    - by Daniel Calderon Mori
    I'm currenty developing for blackberry and just bumped into this problem as i was trying to download an image from a server. The servlet which the device communicates with is working correctly, as I have made a number of tests for it. But it gives me the 413 HTTP error ("Request entity too large"). I figure i will just get the bytes, uhm, portion by portion. How can i accomplish this? This is the code of the servlet (the doGet() method): try { ImageIcon imageIcon = new ImageIcon("c:\\Users\\dcalderon\\prueba.png"); Image image = imageIcon.getImage(); PngEncoder pngEncoder = new PngEncoder(image, true); output.write(pngEncoder.pngEncode()); } finally { output.close(); } Thanks. It's worth mentioning that I am developing both the client-side and the server-side.

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  • Batch processing JDBC

    - by Wai Hein
    I am practicing JDBC batch processing and having errors: error 1: Unsupported feature error 2: Execute cannot be empty or null Property files include: itemsdao.updateBookName = Update Books set bookname = ? where books.id = ? itemsdao.updateAuthorName = Update books set authorname = ? where books.id = ? I know I can execute about DML statements in one update, but I am practicing batch processing in JDBC. Below is my method public void update(Item item) { String query = null; try { connection = DbConnector.getConnection(); property = SqlPropertiesLoader.getProperties("dml.properties"); connection.setAutoCommit(false); if ( property == null ) { Logging.log.debug("dml.properties does not exist. Check property loader or file name is spelled right"); return; } query = property.getProperty("itemsdao.updateBookName"); statement = connection.prepareStatement(query); statement.setString(1, item.getBookName()); statement.setInt(2, item.getId()); statement.addBatch(query); query = property.getProperty("itemsdao.updateAuthorName"); statement = connection.prepareStatement(query); statement.setString(1, item.getAuthorName()); statement.setInt(2, item.getId()); statement.addBatch(query); statement.executeBatch(); connection.commit(); }catch (ClassNotFoundException e) { Logging.log.error("Connection class does not exist", e); } catch (SQLException e) { Logging.log.error("Violating PK constraint",e); } //helper class th finally { DbUtil.close(connection); DbUtil.closePreparedStatement(statement); }

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  • What happens if an exception is thrown during finalize()

    - by Psykocyber
    What would happen if an exception is thrown during the execution of finalize()? Is the stack unwind like normally? Does it continue finalize() and ignore the exception? Does it stop finalize() and continue GC the object? Or something else? I'm not looking for guidelines of using finalize() there are plently of pages explaining that.

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  • I have a feeling that adding fields marked with @Transient annotation to entity is very bug-prone. A

    - by Roman
    I have some philosophical feeling that adding to an entity fields which doesn't mapped to the DB is a wrong way of solving problems. But are there any concrete situations where using @Transient fields leads to implicit and hard fixing problems? For example, is it possible that adding/removing 2nd level cache will break our app when there are @Transient fields in our entities?

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  • Creating parameterized type object using annonymous class

    - by Andrei Fierbinteanu
    This might be a stupid question, but I just saw a question asking how to create a Type variable for a generic type. The consensus seemed to be that you should have a dummy method returning that type, and then use reflection to get it (in this case he wanted Map<String, String>). Something like this : public Map<String, String> dummy() { throw new Error(); } Type mapStringString = Class.forName("ThisClass").getMethod("dummy").getGenericReturnType(); My question is, not having used reflection that much, couldn't you just do something like: Type mapStringString = new ParameterizedType() { public Type getRawType() { return Map.class; } public Type getOwnerType() { return null; } public Type[] getActualTypeArguments() { return new Type[] { String.class, String.class }; } }; Would this work? If not, why not? And what are some of the dangers/problems if it does (besides being able to return some Type like Integer<String> which is obviously not possible.

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  • JPA atomic query/save for multithreaded app

    - by TofuBeer
    I am in the midst of changing my JPA code around to make use of threads. I have a separate entity manager and transaction for each thread. What I used to have (for the single threaded environment) was code like: // get object from the entity manager X x = getObjectX(jpaQuery); if(x == null) { x = new X(); x.setVariable(foo); entityManager.persist(x); } With that code in the multi threaded environment I am getting duplicate keys since, I assume, getObjectX returns null for a thread, then that thread is swapped out, the next thread calls getObjextX, also getting null, and then both threads will create and persist a new X(). Short of adding in synchronization, is there an atomic way to get/save-if-doesn't-exist a value with JPA or should I rethink my approach EDIT: I am using the latest Eclipselink and MySql 5.1

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  • StreamTokenizer Iterator Adapter help

    - by alpdog14
    I have this StreamTokenizer Iterator Adapter that is suppose to create a Tokenizer Iterator Index Builder then build the index from a STIA wrapped around a StreamTokenizer. I am having trouble implementing the hasNext and Next for my STIA, can anyone help me, here is my class: public class StreamTokenizerIteratorAdapter implements Iterator<Token> { DefaultIndexImpl index; StreamTokenizer source; public StreamTokenizerIteratorAdapter(final StreamTokenizer source) { if (source == null) throw new IllegalArgumentException("source == null"); } @Override public boolean hasNext() { return !index.isEmpty(); } public Token next() { if(!index.isEmpty()) return next(); else return null; } @Override public void remove() { throw new UnsupportedOperationException(); } } Should I be using the source element in the hasNext() and next()?

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  • Common Utility for Exception Searching

    - by Andrew
    I wrote this little helper method to search the exception chain for a particular exception (either equals or super class). However, this seems like a solution to a common problem, so was thinking it must already exist somewhere, possibly in a library I have already imported. So, any ideas on if/where this might exist? boolean exceptionSearch(Exception base, Class<?> search) { Throwable e = base; do { if (search.isAssignableFrom(e.getClass())) { return true; } } while ((e = e.getCause()) != null); return false; }

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  • JavaFX InternalFrame or WindowNode

    - by user1493549
    I was looking for an InternalFrame for JavaFX. Apparently I it seems like there is no InternalFrame available. How does one create an MDI application with JavaFX? I have tried to simulate this behavior by using a custom Region that can be dragged around. Is that the way to go? What about typical window elements such as titlebar, possibility to resize etc. Do I have to implement that myself via custom controls? Thanks, miho

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  • password is auto-completed despite setting redisplay=false in JSP (Struts)

    - by lmcgowin
    So I have a web application on Tomcat, built on top of Struts 1.1. Here is a snippet of my JSP, it's a login. <html:form action = "LoginAction" focus = "username"> <table> <tr><td align = "right">User name: </td> <td><html:text property = "username"/> </td></tr> <tr><td align = "right">Password: </td><td><html:password property = "password" redisplay = "false"/></td></tr> </table> </html:form> Snippet from struts-html-1.1.tld: <tag> <name>password</name> <tagclass>org.apache.struts.taglib.html.PasswordTag</tagclass> <attribute> <name>redisplay</name> <required>false</required> <rtexprvalue>true</rtexprvalue> </attribute> </tag> Resulting HTML: Having trouble getting this to post as code but the relevant part is an input tag of type 'password' with no reference to redisplay, autocomplete, etc. It is my understanding that the redisplay element should be passed through Struts to appear in the HTML.

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  • Xml output on HTML

    - by umitunal
    Hi, My xml data = &lt;Item "/api/items/4000000002011"&gt;&lt;ItemID&gt;4000000002011&lt;/ItemID&gt;&lt;Name&gt;Sample Item1&lt;/Name&gt;&lt;Description&gt;Sample Description&lt;/Description&gt;&lt;Rate&gt;34.00&lt;/Rate&gt;&lt;Tax1Name&gt;PST&lt;/Tax1Name&gt;&lt;Tax1Percentage&gt;8&lt;/Tax1Percentage&gt;&lt;Tax2Name/&gt;&lt;Tax2Percentage/&gt;&lt;/Item&gt; Html output=<Item uri="/api/items/4000000002011"> <ItemID>4000000002011</ItemID><Name>Sample Item1</Name><Description>Sample Description</Description><Rate>34.00</Rate><Tax1Name>PST</Tax1Name><Tax1Percentage>8</Tax1Percentage><Tax2Name/><Tax2Percentage/></Item> I want to html output.How do I? <Item "/api/items/4000000002011"> <ItemID>4000000002011</ItemID> <Name>Sample Item1</Name> <Description>Sample Description</Description> <Rate>34.00</Rate> <Tax1Name>PST</Tax1Name> <Tax1Percentage>8</Tax1Percentage> <Tax2Name/> <Tax2Percentage/> </Item>

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  • JSP Component Creation

    - by jboyd
    When creating JSP pages one thing that I'd often like is the ability to do something like this: <jsp:include page="fancystoryrenderer.jsp" value="${aStoryObjectInMyModel}/> ... fancystoryrenderer.jsp <div id="fancymainbody"> ... ${theStory.title} ... </div> The main important characteristics of this is that I can reuse the same component on the same JSP page in different places without having to copy paste the component and give the story variables different names, notice that the story is called "theStory" in the JSP and not "aStoryObjectInMyModel", the linkage between our model has been broken by the view, which is a good thing in this case How do you do this?

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  • Can I write a module/filter that gets fired before the web app get's run in Tomcat?

    - by Blankman
    Can I write a module/filter that gets put into the processing pipleline in Tomcat BEFORE the web application even gets run? Something that I could turn on/off for each web application that tomcat is handling. is this possible? So basically it would be a re-usable filter that hooks into the web pipeline that could alter the requests behavior or perform/modify the requests. One example would be to log all ip's, or redirect based on the url, block the request, etc.

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  • How to avoid StaleObjectStateException when transaction updates thousands of entities?

    - by ThinkFloyd
    We are using Hibernate 3.6.0.Final with JPA 2 and Spring 3.0.5 for a large scale enterprise application running on tomcat 7 and MySQL 5.5. Most of the transactions in application, lives for less than a second and update 5-10 entities but in some use cases we need to update more than 10-20K entities in single transaction, which takes few minutes and hence more than 70% of times such transaction fails with StaleObjectStateException because some of those entities got updated by some other transaction. We generally maintain version column in all tables and in case of StaleObjectStateException we generally retry but since these longs transactions are anyways very long so if we keep on retrying then also I am not very sure that we'll be able to escape StaleObjectStateException. Also lot of activities keep updating these entities in busy hours so we cannot go with pessimistic approach because it can potentially halt many activities in system. Please suggest how to fix such long transaction issue because we cannot spawn thousands of independent and small transactions because we cannot afford messed up data in case of some failed & some successful transactions.

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  • Making an efficient algorithm

    - by James P.
    Here's my recent submission for the FB programming contest (qualifying round only requires to upload program output so source code doesn't matter). The objective is to find two squares that add up to a given value. I've left it as it is as an example. It does the job but is too slow for my liking. Here's the points that are obviously eating up time: List of squares is being recalculated for each call of getNumOfDoubleSquares(). This could be precalculated or extended when needed. Both squares are being checked for when it is only necessary to check for one (complements). There might be a more efficient way than a double-nested loop to find pairs. Other suggestions? Besides this particular problem, what do you look for when optimizing an algorithm? public static int getNumOfDoubleSquares( Integer target ){ int num = 0; ArrayList<Integer> squares = new ArrayList<Integer>(); ArrayList<Integer> found = new ArrayList<Integer>(); int squareValue = 0; for( int j=0; squareValue<=target; j++ ){ squares.add(j, squareValue); squareValue = (int)Math.pow(j+1,2); } int squareSum = 0; System.out.println( "Target=" + target ); for( int i = 0; i < squares.size(); i++ ){ int square1 = squares.get(i); for( int j = 0; j < squares.size(); j++ ){ int square2 = squares.get(j); squareSum = square1 + square2; if( squareSum == target && !found.contains( square1 ) && !found.contains( square2 ) ){ found.add(square1); found.add(square2); System.out.println( "Found !" + square1 +"+"+ square2 +"="+ squareSum); num++; } } } return num; }

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  • Where does that randomness come from ?

    - by Jules Olléon
    I'm working on a data mining research project and use code from a big svn. Apparently one of the methods I use from that svn uses randomness somewhere without asking for a seed, which makes 2 calls to my program return different results. That's annoying for what I want to do, so I'm trying to locate that "uncontrolled" randomness. Since the classes I use depend on many other, that's pretty painful to do by hand. Any idea how I could find where that randomness comes from ?

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  • Dynamically Insert Variables into DB Table using PreparedStatement

    - by gran_profaci
    I was working with PreparedStatement today and noticed that it used setString() setTimestamp() etc. to insert variables into the DB. I basically have 20 tables each with at least 15 columns and it would not be feasible for me to manuallt write down all the setters. Considering that I have an ArrayList "Vals" which contains all the variables to be inputted in String format (obtained by getString() using PreparedStatement itself), is there any way I can do an insert without using expressly using the Setters? That would save me a lot of time.

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