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  • Is it a good idea to close and open hibernate sessions frequently?

    - by Gaurav
    Hi, I'm developing an application which requires that state of entities be read from a database at frequent intervals or triggers. However, once hibernate reads the state, it doesn't re-read it unless I explicitly close the session and read the entity in a new session. Is it a good idea to open a session everytime I want to read the entity and then close it afterwards? How much of an overhead does this put on the application and the database (we use a c3p0 connection pool also)? Will it be enough to simply evict the entity from the session before reading it again?

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  • why Observable snapshot observer vector

    - by han14466
    In Observable's notifyObservers method, why does the coder use arrLocal = obs.toArray();? Why does not coder iterate vector directly? Thanks public void notifyObservers(Object arg) { Object[] arrLocal; synchronized (this) { /* We don't want the Observer doing callbacks into * arbitrary code while holding its own Monitor. * The code where we extract each Observable from * the Vector and store the state of the Observer * needs synchronization, but notifying observers * does not (should not). The worst result of any * potential race-condition here is that: * 1) a newly-added Observer will miss a * notification in progress * 2) a recently unregistered Observer will be * wrongly notified when it doesn't care */ if (!changed) return; arrLocal = obs.toArray(); clearChanged(); } for (int i = arrLocal.length-1; i>=0; i--) ((Observer)arrLocal[i]).update(this, arg); }

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  • About the String#substring() method

    - by alain.janinm
    If we take a look at the String#substring method implementation : new String(offset + beginIndex, endIndex - beginIndex, value); We see that a new String is created with the same original content (parameter char [] value). So the workaround is to use new String(toto.substring(...)) to drop the reference to the original char[] value and make it eligible for GC (if no more references exist). I would like to know if there is a special reason that explain this implementation. Why the method doesn't create herself the new shorter String and why she keeps the full original value instead? The other related question is : should we always use new String(...) when dealing with substring?

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  • Generics in return types of static methods and inheritance

    - by Axel
    Generics in return types of static methods do not seem to get along well with inheritance. Please take a look at the following code: class ClassInfo<C> { public ClassInfo(Class<C> clazz) { this(clazz,null); } public ClassInfo(Class<C> clazz, ClassInfo<? super C> superClassInfo) { } } class A { public static ClassInfo<A> getClassInfo() { return new ClassInfo<A>(A.class); } } class B extends A { // Error: The return type is incompatible with A.getClassInfo() public static ClassInfo<B> getClassInfo() { return new ClassInfo<B>(B.class, A.getClassInfo()); } } I tried to circumvent this by changing the return type for A.getClassInfo(), and now the error pops up at another location: class ClassInfo<C> { public ClassInfo(Class<C> clazz) { this(clazz,null); } public ClassInfo(Class<C> clazz, ClassInfo<? super C> superClassInfo) { } } class A { public static ClassInfo<? extends A> getClassInfo() { return new ClassInfo<A>(A.class); } } class B extends A { public static ClassInfo<? extends B> getClassInfo() { // Error: The constructor ClassInfo<B>(Class<B>, ClassInfo<capture#1-of ? extends A>) is undefined return new ClassInfo<B>(B.class, A.getClassInfo()); } } What is the reason for this strict checking on static methods? And how can I get along? Changing the method name seems awkward.

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  • Unit test helper methods?

    - by Aly
    Hi, I have classes which prviously had massive methods so i subdivided the work of this method into 'helper' methods. These helper methods are declared private to enforce encapsulation - however I want to unit test the big public methods, is it good to unit test the helper methods too as if one of them fail the public method that calls it will also fail - but this way we can identify why it failed. Also in order to test these using a mock object I would need to change their visibility from private to protected, is this desirable?

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  • Implemeting web-based autocomplete for structured input

    - by ravigad
    I am looking to implement web-based autocomplete for structured commands. So, for example, suppose I was trying to implement a web-based Windows command line with autocomplete, in such a case I would want to suggest all the available commands, then, once a user selects a command, all the options for that command, then if a user enters a switch (say '-' dash or '/' slash) then offer all the switches for that command and all the relevant values that can follow, and so on. All from the same text input box. If you have used version 4.0 of JIRA, I am thinking of something similar to the JQL search input box that they have implemented. I have not managed to find any tutorials that look at this scenario end-to-end (which is a shame, because it would be great to see more applications that do this). What I am looking for is some guidance on the steps needed to implement this solution: Do you have any experience implementing such a solution and if so what components did you use? Would you use a framework such as ANTLR to provide the available options to the end user? If not what would do? Sorry for raising such a general question, but my main problem is working out how the pieces fit together as opposed to, say, how to do autocomplete or how to parse/tokenize an input command...

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  • Refactoring common method header and footer

    - by David Wong
    I have the following chunk of header and footer code appearing in alot of methods. Is there a cleaner way of implementing this? Session sess = factory.openSession(); Transaction tx; try { tx = sess.beginTransaction(); //do some work ... tx.commit(); } catch (Exception e) { if (tx!=null) tx.rollback(); throw e; } finally { sess.close(); } The class in question is actually an EJB 2.0 SessionBean which looks like: public class PersonManagerBean implements SessionBean { public void addPerson(String name) { // boilerplate // dostuff // boilerplate } public void deletePerson(Long id) { // boilerplate // dostuff // boilerplate } }

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  • Can I override spring beans instatiated with component scanning?

    - by Pablojim
    If I use component scanning in Spring 2.5 but then also define a controller in xml. Do I get two instances of this bean in my application context? If so which instance will be called for its related RequestMappings? <bean id="myController" class="domain.MyController"> <property name="filters"> <list> <ref local="filter1"/> <ref local="filter2"/> </list> </property> </bean>

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  • Compiling error with API 10

    - by Suhel De Corser
    I was following the basic tutorials on developers.android.com and came by creating the activity named DisplayMessageActivity. It is a blank activity with all the specifications given as shown in the tutorial. FYI, I am using Min SDK = API 8, Target SDK = API 16, Compile with = API 10 The next thing is that there are two errors: "The method getActionBar() is undefined for the type DisplayMessageActivity "home cannot be resolved or is not a field" I tried changing the API to 14 which called for another problem, it wants the minimum API to be 11. That solves these problems, but the main problem is so many devices still use Gingerbread or maybe FroYo. Can't I write for them? Do I have to go higher? How to write for them?

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  • XML Doc to JSP to TIFF

    - by SPD
    We have around 100 word templates, every time user gets a business request he goes into shared folder select the template he/she wants and enter information and save it as tiff, these tiffs later processed by some batch program. I am trying to automate this process. So I defined an XML which has Template information like <Template id="1"> <Section id="1"> <fieldName id="1">Date</fieldName> <fieldValue></fieldValue> <fieldtype></fieldType> <fieldProperty>textField</fieldProperty> </Section> <Section id="2"> <fieldName id="2">Claim#</fieldName> <fieldValue></fieldValue> <fieldtype></fieldType> <fieldProperty>textField</fieldProperty> </Section> </Template> Based on the template values I generate the JSP on fly. Now I would like to generate a TIFF file out of it in specified format. I am not sure how to handle this requirement. *edited the original question.

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  • Andriond send event from first activity and receive on the second.

    - by jitm
    Hello, I have two activities. The first activity display list of the users with short info. And after select some user I go to the second activity for display full info about this user. For send event I used startActivityForResult(); for receive event in socond activity and added public void onActivityResult(int requestCode, int resultCode, Intent data). After start project I send intend from first activity and I do not receive in the second :(. How I can receive sent event in second activity? Thank you...

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  • The name/identity of the invoker of a web service

    - by Swamy g
    I have a SOAP web service which I call from two clients using axis2. Can the web service know from which of these two clients the call originated from? If so, how do I know that during runtime? Is there any API provided to lookup the name of the invoker of a particular web service by that web service. Thanks.

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  • Whats wrong with this method?

    - by David
    Here's the method: public static String CPUcolor () { System.out.println ("What color am I?") ; String s = getIns() ; System.out.println ("are you sure I'm "+s+"? (Y/N)") ; String a = getIns() ; while (!((a.equals ("y")) || (a.equals ("Y")) || (a.equals ("n")) || (a.equals ("N")))) { System.out.println ("try again") ; a = getIns () ; } if (a.equals ("n") || a.equals("N")) {CPUcolor() ;} System.out.println ("I am "+s) ; return s ; } here is a possible output of this method (y's and n's are user inputs): What color am I? red are you sure I'm red? (Y/N) N What color am I? blue are you sure I'm blue? (Y/N) N What color am I? Yellow are you sure I'm Yellow? (Y/N) y I am Yellow I am blue I am red Why is it that the line's "I am blue" and "I am Blue" printed? Why are they printed in reverse order with red, the first entered, printed last?

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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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  • How to send exceptions to exceptionController?

    - by ivar
    <bean class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver"> <property name="mappedHandlers"> <set> <ref bean="exceptionController" /> </set> </property> <property name="defaultErrorView" value="tiles/content/error" /> </bean> I'm trying to send exceptions to a controller so I can create a redirect. If I comment out the mappedHandlers part then the error tile is displayed but it is only a tile. The rest of the tiles load normally. I need to make a redirect in the controller so I can show an error page not just an error tile. I can't find enough information or an example how the exception invokes some method in exceptionController.

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  • How do I correct feature envy in this case?

    - by RMorrisey
    I have some code that looks like: class Parent { private Intermediate intermediateContainer; public Intermediate getIntermediate(); } class Intermediate { private Child child; public Child getChild() {...} public void intermediateOp(); } class Child { public void something(); public void somethingElse(); } class Client { private Parent parent; public void something() { parent.getIntermediate().getChild().something(); } public void somethingElse() { parent.getIntermediate().getChild().somethingElse(); } public void intermediate() { parent.getIntermediate().intermediateOp(); } } I understand that is an example of the "feature envy" code smell. The question is, what's the best way to fix it? My first instinct is to put the three methods on parent: parent.something(); parent.somethingElse(); parent.intermediateOp(); ...but I feel like this duplicates code, and clutters the API of the Parent class (which is already rather busy). Do I want to store the result of getIntermediate(), and/or getChild(), and keep my own references to these objects?

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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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  • How do I detect the colillison of components?

    - by Coupon22
    How do I detect the collision of components, specifically JLabels (or ImageIcons?)?I have tried this: add(test1); test1.setLocation(x, y); add(test2); test1.setLocation(x1, y1); validate(); if(intersects(test1, test2)) { ehealth-=50; } public boolean intersects(JLabel testa, JLabel testb) { boolean b3 = false; if(testa.contains(testb.getX(), testb.getY())) { b3 = true; } return b3; } When I run this, it does nothing! I used to use rectangle, but it didn't go well with me. I was thinking about an image with a border (using paint.net) and moving an imageicon, but I don't know how to get the x of an imageicon or detect collision. I don't know how to detect collision of a label or increase the location either. I have searched for collision detection with components/ImageIcons, but nothing has came up. I have also searched for getting the x of ImageIcons.

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  • Has anyone tried the "objectify" library for Google App Engine?

    - by Spines
    I was using JDO for my google app engine project but got fed up with the additional 5 seconds it adds to my cold start time. I was planning on just writing stuff directly to the database with the low level datastore api, but then I came accross the objectify project ( http://code.google.com/p/objectify-appengine/ ). Apparently its a super light wrapper above the low level api. Does anyone have experiences with this library that they could share?

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  • Use of private constructor to prevent instantiation of class?

    - by cringe
    Hi guys! Right now I'm thinking about adding a private constructor to a class that only holds some String constants. public class MyStrings { // I want to add this: private MyString() {} public static final String ONE = "something"; public static final String TWO = "another"; ... } Is there any performance or memory overhead if I add a private constructor to this class to prevent someone to instantiate it? Do you think it's necessary at all or that private constructors for this purpose are a waste of time and code clutter?

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  • How to get the set of beans that are to be created in Spring?

    - by cyborg
    So here's the scenario: I have a Spring XML configuration with some lazy-beans, some not lazy-beans and some beans that depend on other beans. Eventually Spring will resolve all this so that only the beans that are meant to be created are created. The question: how can I programmatically tell what this set is? When I use context.getBean(name) that initializes the bean. BeanDefinition.isLazyInit() will only tell me how I defined the bean. Any other ideas? ETA: In DefaultListableBeanFactory: public void preInstantiateSingletons() throws BeansException { if (this.logger.isInfoEnabled()) { this.logger.info("Pre-instantiating singletons in " + this); } synchronized (this.beanDefinitionMap) { for (Iterator it = this.beanDefinitionNames.iterator(); it.hasNext();) { String beanName = (String) it.next(); RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName); if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) { if (isFactoryBean(beanName)) { FactoryBean factory = (FactoryBean) getBean(FACTORY_BEAN_PREFIX + beanName); if (factory instanceof SmartFactoryBean && ((SmartFactoryBean) factory).isEagerInit()) { getBean(beanName); } } else { getBean(beanName); } } } } } The set of instantiable beans is initialized. When initializing this set any beans not in this set referenced by this set will also be created. From looking through the source it does not look like there's going to be any easy way to answer my question.

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  • How to unselect checkbox in chrome browser

    - by hudi
    in my wicket application I have 3 checkbox in form: add(new CheckBox("1").setOutputMarkupId(true)); add(new CheckBox("2").setOutputMarkupId(true)); add(new CheckBox("3").setOutputMarkupId(true)); form also contain behavior which unselect checboxes add(new AjaxEventBehavior("onclick") { private static final long serialVersionUID = 1L; @Override protected void onEvent(AjaxRequestTarget target) { List<Component> components = new ArrayList<Component>(); if (target.getLastFocusedElementId() != null) { if (target.getLastFocusedElementId().equals("1")) { components.add(get("2")); components.add(get("3")); } else if (target.getLastFocusedElementId().equals("2")) { components.add(get("1")); } else if (target.getLastFocusedElementId().equals("3")) { components.add(get("1")); } for (Component component : components) { component.setDefaultModelObject(null); target.add(component); } } } }); this works good on mozilla browser but in chrome this doesnt work. How I can improve to work this on chrome too ? UPDATE problem is in: target.getLastFocusedElementId() in mozilla this return what I want but in chrome it always return null but I dont know wh UPDATE 2 google chrome has bug in focus element: http://code.google.com/p/chromium/issues/detail?id=1383&can=1&q=window.focus%20type%3aBug&colspec=ID%20Stars%20Pri%20Area%20Type%20Status%20Summary%20Modified%20Owner so I need to do this in other way

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