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• What is the correct approach to using GWT with persistent objects?

  - by dankilman

  Hi, I am currently working on a simple web application through Google App engine using GWT. It should be noted that this is my first attempt at such a task. I have run into to following problem/dilema: I have a simple Class (getters/setters and nothing more. For the sake of clarity I will refer to this Class as DataHolder) and I want to make it persistent. To do so I have used JDO which required me to add some annotations and more specifically add a Key field to be used as the primary key. The problem is that using the Key class requires me to import com.google.appengine.api.datastore.Key which is ok on the server side, but then I can't use DataHolder on the client side, because GWT doesn't allow it (as far as I know). So I have created a sister Class ClientDataHolder which is almost identical, though it doesn't have all the JDO annotations nor the Key field. Now this actually works but It feels like I'm doing something wrong. Using this approach would require maintaining to separate classes for each entity I wish to have. So my question is: Is there a better way of doing this? Thank you.

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• How to keep Lucene index synchronized with Mysql database?

  - by ?????

  I am trying to utilize Lucene to develop full text search in my application, which need to build index based on my mysql database. I was wondering is how to keep these index synchronized with db? I came up with to ways: 1) add extra code in business logic tightly to update the search index . 2) running a separated task to rebuild the index periodically. do you have any other approaches? and what do you think is the best way? Any comments would be appreciate, thanks in advance!

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• How to detect if a form input element of type file is empty

  - by Ankur

  I have some code which reads a file through a form field of type file <input type="file" ... /> I want to give the user another option of providing a url to a file rather than having to upload it as many are already online. How can I detect when this field is empty on the server side. I am using Apache Commons FileUpload FileItemStream item = iter.next(); name = item.getFieldName(); stream = item.openStream(); if(!item.isFormField()){ if(item.toString()!=""){ .... I need to detect when item is empty. The above code doesn't work, nor does using: if(item.equals(null)){ ....

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• inter servlet communication

  - by mithun1538

  Hello everyone, I have two servlets: LoginServlet and MailServlet. LoginServlet queries a mysql table using jdbc to get a string(eMail). What I want is to forward this string to MailServlet which in turn will send an email to that e-mail ID sent by LoginServlet. My question is how do I call and send the variable eMail to MailServlet, from LoginServlet? I thought of creating an instance of the MailServlet as : MailServlet servlet = new MailServlet(); And then use the servlet object to call the function doGet() in MailServlet. But I am feeling that there is some error in this as this is not the right way to call a servlet. So how do I call and pass a variable to MailServlet?

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• XMLStreamWriter writeCharacters without escaping

  - by Felix

  How do I use XMLStreamWriter to write exactly what I put in? For instance, if I create script tag and fill it with javascript I don't want all my single quotes coming out as &apos;

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• Javascript get li values and encode them

  - by bluedaniel

  At the moment I have two (maybe more) unordered lists which are sortable with jquery and ui. The things that work are that the lists are connected, items are draggable, items can be removed and a form that adds to the list. What I need however is a function that gets all the content for li items and json encode them ready to be sent off to some db function, or something. Im new to jquery however and cant find documentation for li items. Hope Ive explained this well. Daniel

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• How do I convert jstring to wchar_t *

  - by Obediah Stane

  Let's say that on the C++ side my function takes a variable of type jstring named myString. I can convert it to an ANSI string as follows: const char* ansiString = env-GetStringUTFChars(myString, 0); is there a way of getting const wchar_t* unicodeString = ...

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• Private API and SMS content URI's on Android

  - by Shadow

  Without accessing private API's to get Content URI's, etc. for SMS, how are we expected to query this data? I am currently in the process of writing my own SMS app and I want to stay as compatible as possible. Without storing the information myself in my own database (such that I can store the text messages so that other programs can access the data when/if they delete my app) and without using private API's how the heck are we suppose to query SMS data?

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• How to create virtual path to tempdir tomcat ?

  - by quilovnic

  I want to put my images to db but i want to have a link on each image. So I have the idea to copy the image to the temp dir of tomcat (or weblogic). But I must map the tempdir to a virtual path. How do it ?

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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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• Semantics of repeated acknowledgments in JMS

  - by Lajos Nagy

  Suppose I decide to call acknowledgment() on a JMS message several times. Say the first call fails (for non-permanent reason). Does the success of the second (or any subsequent) call guarantee that the message is now acknowledged? Is the exact behavior of acknowledgement() specified anywhere?

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• Why do I have to explicitly cast sometimes for varargs?

  - by Daniel Lew

  I've got a Class that uses reflection a lot, so I wrote a method to help out: private <T> T callMethod(String methodName, Class[] parameterTypes, Object[] args) { try { Class c = mVar.getClass(); Method m = c.getMethod(methodName, (Class[]) parameterTypes); return (T) m.invoke(mVar, args); } // Insert exception catching here [...] } This worked well for any method that had parameters, however I had to explicitly cast parameterTypes to Class[] in order for this to work for methods with no parameters (e.g., callMethod('funName', null, null);). I've been trying to figure out why this is the case. It seems to me that if parameterTypes, when null, had no concept of what type it is (Class[]), then I'd need to cast it for getMethod(). But if that's the case, why is getMethod() able to tell the difference between null, and (Class[]) null when the method is invoked?

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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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• One account, multiple users, multiple shopping cart in a web application

  - by lemotdit

  I received a somewhat unusual request (imo) for a transactional web site. I have to implement the possibility of having multiple shopping cart for the same user. Those really are shopping carts, not order templates. I.E: A store with several departments ordering under the same account, but with a different person placing orders for a specific department only. Having more than one user per account is not an option since it would involve 'too much' management from the stores owner and the admins. Anyone had to deal with this before? The option so far is to have names for shopping cart, and a dropdown list or something alike after login to choose the cart with some kind of 'busy flag' to lock the cart if it's in use in another session.

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• Where can I find "reference barcodes" to verify barcode library output?

  - by mjustin

  This question is not about 'best' barcode library recommendation, we use various products on different platforms, and need a simple way to verify if a given barcode is correct (according to its specification). There are some free online bar code generators in the Internet, and I found many differences between their output and our library output regarding graphics and text field below the code. Now I am not sure which one is wrong, and before filing bug report I want to make sure how the correct barcode should look like. We mainly need Code128 and UCC/EAN-128 with A/B/C subcodes. Which resource would you suggest?

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• how to selectively filter items in a collection

  - by Samuel

  I use the following snippet to filter the list of selected users, where isSelected is a boolean variable. Is there a simpler way (helper function) to populate the selectedUsers collection instead of writing the following lines of code. List<User> selectedUsers = new ArrayList<User>(0); for (User user : this.getUsers()) { if (user.isSelected()) { selectedUsers.add(user.getId()); } }

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• Hibernate Annotation (Pyramid Structure - same table)

  - by fatnjazzy

  Hi, I have a person table that contains the following fields: id, name, parent_id. the parent_id is actually a FK for column id. the data should look like this (Like a pyramid): "id" "name" "parent_id" "1" "I am the Top Father" "1" "2" "My Father Is 1" "1" "3" "My Father Is 2" "2" "4" "My Father Is 2" "2" How is my bean suppose to look like? Thanks

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• Strange befaviour of spring transaction support for JPA + Hibernate +@Transactional annotation

  - by abovesun

  I found out really strange behavior on relatively simple use case, probably I can't understand it because of not deep knowledges of spring @Transactional nature, but this is quite interesting. I have simple User dao that extends spring JpaDaoSupport class and contains standard save method: @Transactional public User save(User user) { getJpaTemplate().persist(user); return user; } If was working fine until I've add new method to same class: User getSuperUser(), this method should return user with isAdmin == true, and if there is no super user in db, method should create one. Thats how it was looking like: public User createSuperUser() { User admin = null; try { admin = (User) getJpaTemplate().execute(new JpaCallback() { public Object doInJpa(EntityManager em) throws PersistenceException { return em.createQuery("select u from UserImpl u where u.admin = true").getSingleResult(); } }); } catch (EmptyResultDataAccessException ex) { User admin = new User('login', 'password'); admin.setAdmin(true); save(admin); // THIS IS THE POINT WHERE STRANGE THING COMING OUT } return admin; } As you see code is strange forward and I was very confused when found out that no transaction was created and committed on invocation of save(admin) method and no new user wasn't actually created despite @Transactional annotation. In result we have situation: when save() method invokes from outside of UserDAO class - @Transactional annotation counted and user successfully created, but if save() invokes from inside of other method of the same dao class - @Transactional annotation ignored. Here how I was change save() method to force it always create transaction. public User save(User user) { getJpaTemplate().execute(new JpaCallback() { public Object doInJpa(EntityManager em) throws PersistenceException { em.getTransaction().begin(); em.persist(user); em.getTransaction().commit(); return null; } }); return user; } As you see I manually invoke begin and commit. Any ideas?

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• Adding or reading some of the contact fields in sybian using j2me

  - by learn

  I want to add or read the fields of cotact like i am getting the telephone home no ContactList clist; Contact con; String no; if(cList.isSupportedAttribute(Contact.TEL, Contact.ATTR_HOME)) { con.addString(Contact.TEL, Contact.ATTR_HOME, no); } and mobile no if(cList.isSupportedAttribute(Contact.TEL, Contact.ATTR_MOBILE)) { con.addString(Contact.TEL, Contact.ATTR_MOBILE, mb); } now i want to get the fields internet telephone, push to talk, mobile(home), mobile(business), dtmf, shareview, sip, children, spouse and some more fields please help me.. Thanks in advance

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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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• Ant - Run several servers on different terminals in build.xml

  - by user209691

  Hi, I want to write a buil.xml file that should open a new terminal for every client/server i want to use for testings. How can i do that? i tried this code to run for example the 'ls' command on the newly created terminal. He created the terminal but doesn't run the cmd. thanks.

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• Create automatically only getters in Eclipse

  - by lerad

  In Eclipse is it possible to create automatically Getters and Setters for a field. But I have a lot of private fields for which only getters should exist. Is somewhere in Eclipse a "create Getters" Function which does not create setters too? Well, it is not so much work to write getters, but doing it automatically would be nice :) Thank you, lerad

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• GWT + JDO + ArrayList

  - by dvieira

  Hi, I'm getting a Null ArrayList in a program i'm developing. For testing purposes I created this really small example that still has the same problem. I already tried diferent Primary Keys, but the problem persists. Any ideas or suggestions? 1-Employee class @PersistenceCapable(identityType = IdentityType.APPLICATION) public class Employee { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) @Extension(vendorName="datanucleus", key="gae.encoded-pk", value="true") private String key; @Persistent private ArrayList<String> nicks; public Employee(ArrayList<String> nicks) { this.setNicks(nicks); } public String getKey() { return key; } public void setNicks(ArrayList<String> nicks) { this.nicks = nicks; } public ArrayList<String> getNicks() { return nicks; } } 2-EmployeeService public class BookServiceImpl extends RemoteServiceServlet implements EmployeeService { public void addEmployee(){ ArrayList<String> nicks = new ArrayList<String>(); nicks.add("name1"); nicks.add("name2"); Employee employee = new Employee(nicks); PersistenceManager pm = PMF.get().getPersistenceManager(); try { pm.makePersistent(employee); } finally { pm.close(); } } /** * @return * @throws NotLoggedInException * @gwt.typeArgs <Employee> */ public Collection<Employee> getEmployees() { PersistenceManager pm = getPersistenceManager(); try { Query q = pm.newQuery("SELECT FROM " + Employee.class.getName()); Collection<Employee> list = pm.detachCopyAll((Collection<Employee>)q.execute()); return list; } finally { pm.close(); } } }

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• Maven profile for single module

  - by c0mrade

  I have a multi module maven project, which builds successfully, I'd like to build just one of the modules I have. How would I do that with profiles ? I could do it from console in two ways, one way is go to the child module and mvn package or I could use reactor to build just one module. Can I do the same thing with profiles? By modifying POM? Thank you EDIT If is impossible from POM, can I do it from settings.xml ?

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• using Hibernate to loading 20K products, modifying the entity and updating to db

  - by Blankman

  I am using hibernate to update 20K products in my database. As of now I am pulling in the 20K products, looping through them and modifying some properties and then updating the database. so: load products foreach products session begintransaction productDao.MakePersistant(p); session commit(); As of now things are pretty slow compared to your standard jdbc, what can I do to speed things up? I am sure I am doing something wrong here.

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