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  • Hibernate is performing unwanted SELECTs on call to saveOrUpdate

    - by digiarnie
    Let's say I have a House entity which maps to many Person entities. I then load an existing House which has 20 occupants. beginTransaction(); House house = houseDao.find(1L); commitTransaction(); Later in the code, I can then add a new Person to the House: ... List<Person> people = house.getPeople(); people.add(new Person("Dilbert")); .... When I make the call: session.saveOrUpdate(house); Hibernate performs 21 queries: 1 to SELECT the House and 20 to SELECT each existing Person in the House. I'm sure it's a small issue on my part, however, what should I do so that I can add a new Person to the house without having such a heavy hit on the database in this situation? This is all done within the same session.

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  • Is it possible to use instanceof when passing objects between Threads?

    - by Risser
    I've run into an issue where instanceof works, and then it doesn't. Going into details is difficult, but I think this might be the problem: Reading this: http://www.theserverside.com/news/thread.tss?thread_id=40229 (search for Thread.currentThread), it seems to imply that, even if the two objects are the same class, if you pass them between threads with different class loaders, instanceof (and isAssignableFrom) might still fail. This certainly would explain the behavior I'm having, but I was wondering if anyone could verify it? (I wish the article linked at the beginning of the discussion was still available, but it doesn't seem like it is.) Thanks, Peter

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  • Connection Pool Strategy: Good, Bad or Ugly?

    - by Drew
    I'm in charge of developing and maintaining a group of Web Applications that are centered around similar data. The architecture I decided on at the time was that each application would have their own database and web-root application. Each application maintains a connection pool to its own database and a central database for shared data (logins, etc.) A co-worker has been positing that this strategy will not scale because having so many different connection pools will not be scalable and that we should refactor the database so that all of the different applications use a single central database and that any modifications that may be unique to a system will need to be reflected from that one database and then use a single pool powered by Tomcat. He has posited that there is a lot of "meta data" that goes back and forth across the network to maintain a connection pool. My understanding is that with proper tuning to use only as many connections as necessary across the different pools (low volume apps getting less connections, high volume apps getting more, etc.) that the number of pools doesn't matter compared to the number of connections or more formally that the difference in overhead required to maintain 3 pools of 10 connections is negligible compared to 1 pool of 30 connections. The reasoning behind initially breaking the systems into a one-app-one-database design was that there are likely going to be differences between the apps and that each system could make modifications on the schema as needed. Similarly, it eliminated the possibility of system data bleeding through to other apps. Unfortunately there is not strong leadership in the company to make a hard decision. Although my co-worker is backing up his worries only with vagueness, I want to make sure I understand the ramifications of multiple small databases/connections versus one large database/connection pool.

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  • How can I change jtable height at runtime

    - by wniroshan
    I hava a JFrame with multiple JPanels of similar width aligned one below other. I use one of these JPanels to display a JTable which is the last JPanel of the lot. This JPanel has a JScrollpane as a child component. This is where I try to add my table dynamically. Initial height of this JScrollpane is set to 40. I designed above template using Netbeans 6.8 Now I'm trying to add the table to the JPanel. When a button is pressed below code snippet is called. The class which includes this code extends javax.swing.JFrame class. I am expecting below code would adjust table height according to the row count and display the table. SearchTable = new JTable(RowData, DisplayNames) { @Override public boolean isCellEditable(int rowIndex, int vColIndex) { return false; } }; // if row count is less than 10 then display all the rows without a scroll bar if (SearchTable.getRowCount() < 10) { pnl_tblpanel.setPreferredSize(new Dimension(625, SearchTable.getRowHeight() * (SearchTable.getRowCount() + 4))); scr_tblholder.setPreferredSize(new Dimension(625, SearchTable.getRowHeight() * (SearchTable.getRowCount() + 4))); } else {// if row count is more than 10 display first 10 rows and add a scroll bar pnl_tblpanel.setPreferredSize(new Dimension(625, SearchTable.getRowHeight() * (10 + 2))); scr_tblholder.setAutoscrolls(true); } //pnl_tblpanel.add(scr_tblholder); scr_tblholder.setViewportView(SearchTable); //pnl_tblpanel.repaint(); pnl_tblpanel.validate(); this.validate(); //this.repaint(); pnl_tblpanel.setVisible(true); this.pack(); The table displays, but the table height is not changed according to the row count. It stays its default value. I have been trying many combinations of validate and repaint but nothing worked. (More in desperation) Can anyone shed some light on this Thank you

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  • Can I use Pub/Sub model with Many Publishers and Only One Subscriber?

    - by rauch
    I need to send some files from different machines to only one Server. As I understand, I can use JMS api + (for example) ActiveMQ as broker. There are two models: p2p and pub/sub. I would like to use pub/sub model, but the problem is that I haven`t few subscribers, I have only one Subscriber(Server) and many Publishers. The question is the following: can I use pub/sub model for my situation and How can I send files from different machines to Only One Topic, on that Server sibscribed? May be any other ideas, thanks a lot.

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  • Creating a fancy search bar with Swing components

    - by Kavon Farvardin
    I'm trying to come up with an elegant recreation of the search bar component in Thunderbird. The clear button doesn't appear until there is text in the box, so that screen-shot is a bit inaccurate. Should I use a layered pane and get some buttons to float above the box? (but then getting the text to not appear below the buttons would be hacky) Maybe just put buttons at the ends of the search bar and have it somehow blend in? Any ideas or maybe a style reconsideration is welcome, thank you.

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  • How to trigger code on two different servers in a WAS cluster?

    - by Dean J
    I have an administrative page in a web application that resets the cache, but it only resets the cache on the current JVM. The web application is deployed as a cluster to two WAS servers. Any way that I can elegantly have the "clear cache" button on each server trigger the method on both JVMs? Edit: The original developer just wrote a singleton holding a HashMap to be the cache in question. Lightweight and (previously) worked just fine for the requirements. It caches content pulled from six or seven web services for specified amounts of time. Edit: The entire application in question is three pages, so the elegant solution might well be the lightest solution.

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  • Calling and consuming a JBoss Web Service from JavaScript (AJAX)

    - by Andreas Grech
    I am fiddling around with JBOSS's Web Services, and I have created the following: http://127.0.0.1:8080/IM/TestService?wsdl Now I need to access Web Methods from that Web Service from JavaScript. Say I have a web method named foo in TestService, how do I make an ajax call to it? I tried accessing the method via http://127.0.0.1:8080/IM/TestService/foo, but I'm getting an HTTP Status 404.

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  • Android - Memory leak when dynamically building UI with image resource backgrounds

    - by Rich
    I have an Activity that I swear is leaking memory. The app I'm working on does a lot with images, so I've had to be pretty stingy with memory when working directly with Bitmaps. I added an Activity, and now if you use this new Activity it basically puts me over the edge with mem usage and I end up throwing the "Bitmap exceeds VM budget" exception. If you never launch this Activity, everything is smooth as it was previously. I started reading about memory leaks, and I think that I have a similar situation to what is described in the article in the Android docs. I'm dynamically creating a bunch of image views and adding a BackgroundDrawable from the resources and adding an OnClickListener as well. I imagine I have to do some cleanup when the Activity hits onPause in its life cycle, but I'd like to know specifically what is the correct way. Here is the code that should demonstrate the objects I'm working with... LinearLayout templateContainer; . . . ImageView imgTemplatePreview = (ImageView) item.findViewById(R.id.imgTemplatePreview); . . . imgTemplatePreview.setBackgroundDrawable(getResources().getDrawable(previewId)); imgTemplatePreview.setOnClickListener(imgClick); templateContainer.addView(item);

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  • utf-8 convertion doesn't work always

    - by Marco Piccinni
    I searched into other stack before to type here and I didn't find anythong similar. I have to scrape different utf-8 webpages which contain text like "Oggi è una bellissima giornata" the problem is on the characther "è" I extract this text with jtidy and xpath query expression and I convert it with byte[] content = filteredEncodedString.getBytes("utf-8"); String result = new String(content,"utf-8"); where filteredEncodedString contains the text "Oggi è una bellissima giornata". This procedures works on the most webpages analyzed so far but in some case it doesn't extract a utf-8 string. Page encoding is always the same as the text is similar. Any ideas about the problem? thanks Marco

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  • Correct way to add objects to an ArrayList

    - by ninjasense
    I am trying to add an object to an arraylist but when I view the results of the array list, it keeps adding the same object over and over to the arraylist. I was wondering what the correct way to implement this would be. public static ArrayList<Person> parsePeople(String responseData) { ArrayList<Person> People = new ArrayList<Person>(); try { JSONArray jsonPeople = new JSONArray(responseData); if (!jsonPeople.isNull(0)) { for (int i = 0; i < jsonPeople.length(); i++) { Person.add(new Person(jsonPeople.getJSONObject(i))); } } } catch (JSONException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (Exception e) { } return People; } I have double checked my JSONArray data and made sure they are not duplicates. It seems to keep adding the first object over and over.

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  • In ArrayBlockingQueue, why copy final member field into local final variable?

    - by mjlee
    In ArrayBlockingQueue, any method that requires lock will get set 'final' local variable before calling 'lock()'. public boolean offer(E e) { if (e == null) throw new NullPointerException(); final ReentrantLock lock = this.lock; lock.lock(); try { if (count == items.length) return false; else { insert(e); return true; } } finally { lock.unlock(); } } Is there any reason to set a local variable 'lock' from 'this.lock' when field 'this.lock' is final also. Additionally, it also set local variable of E[] before acting on. private E extract() { final E[] items = this.items; E x = items[takeIndex]; items[takeIndex] = null; takeIndex = inc(takeIndex); --count; notFull.signal(); return x; } Is there any reason for copying to local final variable?

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  • JPA and aggregate functions. How do I use the result of the query?

    - by Bogdan
    Hey guys, I'm new to ORM stuff and I need some help understanding something. Let's assume I have the following standard SQL query: SELECT *, COUNT(test.testId) AS noTests FROM inspection LEFT JOIN test ON inspection.inspId = test.inspId GROUP BY inspection.inspId which I want to use in JPA. I have an Inspection entity with a one-to-many relationship to a Test entity. (an inspection has many tests) I tried writing this in JPQL: Query query = em.createQuery("SELECT insp, COUNT(???what???) FROM Inspection insp LEFT JOIN insp.testList " + "GROUP BY insp.inspId"); 1) How do I write the COUNT clause? I'd have to apply count to elements from the test table but testList is a collection, so I can't do smth like COUNT(insp.testList.testId) 2) Assuming 1 is resolved, what type of object will be returned. It will definitely not be an Inspection object... How do I use the result?

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  • data to be saved in SQLite and want to retrive data from there

    - by Mona
    In android, is it possible that we insert our database in SQLite and get back that data on our EditText boxes. I want to get data from database and populate it in my application activity. How can i do that. I want to save, update and delete my database in SQLite and most important i want to get data from database that is saved in SQLite tables. How can it be possible. Kindly guide. I will be thankfull to you

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  • How to use @BeforeClass and @AfterClass in JunitPerf?

    - by allenzzzxd
    Hi, I want to do some actions before the whole test suite (also after the suite). So I wrote like: public class PerformanceTest extends TestCase { @BeforeClass public static void suiteSetup() throws Exception { //do something } @AfterClass public static void suiteSetup() throws Exception { //do something } @Before public void setUp() throws Exception { //do something } @After public void tearDown() throws Exception { //do something } public PerformanceTest(String testName){ super(testName); } public static Test suite() { TestSuite suite = new TestSuite(); Test testcase1 = new PerformanceTest("DoTest1"); Test loadTest1 = new LoadTest(testcase1, n); Test testcase2 = new PerformanceTest("DoTest2"); Test loadTest2 = new LoadTest(testcase2, n); } public void DoTest1 throws Throwable{ //do something } public void DoTest2 throws Throwable{ //do something } } But I found that it never reach the code in @BeforeClass and @AfterClass. So how could I do to solve this problem? Or is there other way to realize this? Thank you for your help.

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  • Batch insert mode with hibernate and oracle: seems to be dropping back to slow mode silently

    - by Chris
    I'm trying to get a batch insert working with Hibernate into Oracle, according to what i've read here: http://docs.jboss.org/hibernate/core/3.3/reference/en/html/batch.html , but with my benchmarking it doesn't seem any faster than before. Can anyone suggest a way to prove whether hibernate is using batch mode or not? I hear that there are numerous reasons why it may silently drop into normal mode (eg associations and generated ids) so is there some way to find out why it has gone non-batch? My hibernate.cfg.xml contains this line which i believe is all i need to enable batch mode: <property name="jdbc.batch_size">50</property> My insert code looks like this: List<LogEntry> entries = ..a list of 100 LogEntry data classes... Session sess = sessionFactory.getCurrentSession(); for(LogEntry e : entries) { sess.save(e); } sess.flush(); sess.clear(); My 'logentry' class has no associations, the only interesting field is the id: @Entity @Table(name="log_entries") public class LogEntry { @Id @GeneratedValue public Long id; ..other fields - strings and ints... However, since it is oracle, i believe the @GeneratedValue will use the sequence generator. And i believe that only the 'identity' generator will stop bulk inserts. So if anyone can explain why it isn't running in batch mode, or how i can find out for sure if it is or isn't in batch mode, or find out why hibernate is silently dropping back to slow mode, i'd be most grateful. Thanks

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  • How to amend return value design in OO manner?

    - by FrontierPsycho
    Hello. I am no newb on OO programming, but I am faced with a puzzling situation. I have been given a program to work on and extend, but the previous developers didn't seem that comfortable with OO, it seems they either had a C background or an unclear understanding of OO. Now, I don't suggest I am a better developer, I just think that I can spot some common OO errors. The difficult task is how to amend them. In my case, I see a lot of this: if (ret == 1) { out.print("yadda yadda"); } else if (ret == 2) { out.print("yadda yadda"); } else if (ret == 3) { out.print("yadda yadda"); } else if (ret == 0) { out.print("yadda yadda"); } else if (ret == 5) { out.print("yadda yadda"); } else if (ret == 6) { out.print("yadda yadda"); } else if (ret == 7) { out.print("yadda yadda"); } ret is a value returned by a function, in which all Exceptions are swallowed, and in the catch blocks, the above values are returned explicitly. Oftentimes, the Exceptions are simply swallowed, with empty catch blocks. It's obvious that swalllowing exceptions is wrong OO design. My question concerns the use of return values. I believe that too is wrong, however I think that using Exceptions for control flow is equally wrong, and I can't think of anything to replace the above in a correct, OO manner. Your input, please?

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