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• Google App Engine: JDO does the job, JPA does not

  - by Phuong Nguyen de ManCity fan

  I have setup a project using both Jdo and Jpa. I used Jpa Annotation to Declare my Entity. Then I setup my testCases based on LocalTestHelper (from Google App Engine Documentation). When I run the test, a call to makePersistent of Jdo:PersistenceManager is perfectly OK; a call to persist of Jpa:EntityManager raised an error: java.lang.IllegalArgumentException: Type ("org.seamoo.persistence.jpa.model.ExampleModel") is not that of an entity but needs to be for this operation at org.datanucleus.jpa.EntityManagerImpl.assertEntity(EntityManagerImpl.java:888) at org.datanucleus.jpa.EntityManagerImpl.persist(EntityManagerImpl.java:385) Caused by: org.datanucleus.exceptions.NoPersistenceInformationException: The class "org.seamoo.persistence.jpa.model.ExampleModel" is required to be persistable yet no Meta-Data/Annotations can be found for this class. Please check that the Meta-Data/annotations is defined in a valid file location. at org.datanucleus.ObjectManagerImpl.assertClassPersistable(ObjectManagerImpl.java:3894) at org.datanucleus.jpa.EntityManagerImpl.assertEntity(EntityManagerImpl.java:884) ... 27 more How can it be the case? Below is the link to the source code of the maven projects that reproduce that problem: http://seamoo.com/jpa-bug-reproduce.tar.gz Execute the maven test goal over the parent pom you will notice that 3/4 tests from org.seamoo.persistence.jdo.JdoGenericDAOImplTest passed, while all tests from org.seamoo.persistence.jpa.JpaGenericDAOImplTest failed.

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• Appengine datastore phantom entity - inconsistent state?

  - by aloo

  Getting a weird error on java appengine code that used to work fine (nothing has changed but the data in the datastore). I'm trying to iterate over the results of a query and change a few properties of the entities. The query does return a set of results, however, when I try to access the first result in the list, it throws an exception when trying to access any of its properties (but its key). Here's the exception: org.datanucleus.state.JDOStateManagerImpl isLoaded: Exception thrown by StateManager.isLoaded Could not retrieve entity of kind OnTheCan with key OnTheCan(3204258) org.datanucleus.exceptions.NucleusObjectNotFoundException: Could not retrieve entity of kind OnTheCan with key OnTheCan(3204258) at org.datanucleus.store.appengine.DatastoreExceptionTranslator.wrapEntityNotFoundException(DatastoreExceptionTranslator.java:60) And here is my code: PersistenceManager pm = PMF.get().getPersistenceManager(); Query query = null; List<OnTheCan> cans; query = pm.newQuery("SELECT this FROM " + OnTheCan.class.getName() + " WHERE open == true ORDER BY onTheCanId ASC"); query.setRange(0, num); cans = (List<OnTheCan>) query.execute(); for (OnTheCan c : cans) { System.err.println(c.getOnTheCanId()); // this works fine! getting the key works c.setOpen(false); // failure here with the above exception c.setAutoClosed(true); c.setEndTime(new Date(c.getStartTime().getTime() + 600000/*10*60*1000*/)); } pm.close(); The code throws the exception when trying to execute c.setOpen(false) - thats the first time I'm accessing or setting a property that isnt the key. So it seems there is a phantom entity in my datastore with key 3204258. THis entity doesn't really exist (queried the datastore from admin console) but for some reason its being returned by the query. Could my data store be in an inconsistent state? I've managed the following workaround by placing it as the first line in my for loop. Clearly an ugly hack: if (c.getOnTheCanId() == 3204258) { continue; } Any ideas?

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• Filter a date property between a begin and end Dates with JDOQL

  - by Sergio del Amo

  I want to code a function to get a list of Entry objects whose date field is between a beginPeriod and endPeriod I post below a code snippet which works with a HACK. I have to substract a day from the begin period date. It seems the condition great or equal does not work. Any idea why I have this issue? public static List<Entry> getEntries(Date beginPeriod, Date endPeriod) { /* TODO * The great or equal condition does not seem to work in the filter below * Substract a day and it seems to work */ Calendar calendar = Calendar.getInstance(); calendar.set(beginPeriod.getYear(), beginPeriod.getMonth(), beginPeriod.getDate() - 1); beginPeriod = calendar.getTime(); PersistenceManager pm = JdoUtil.getPm(); Query q = pm.newQuery(Entry.class); q.setFilter("this.date >= beginPeriodParam && this.date <= endPeriodParam"); q.declareParameters("java.util.Date beginPeriodParam, java.util.Date endPeriodParam"); List<Entry> entries = (List<Entry>) q.execute(beginPeriod,endPeriod); return entries; }

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• Saving twice don't update my object in JDO

  - by Javi

  Hello I have an object persisted in the GAE datastore using JDO. The object looks like this: public class MyObject implements Serializable, StoreCallback { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) @Extension(vendorName="datanucleus", key="gae.encoded-pk", value="true") private String id; @Persistent private String firstId; ... } As usually when the object is stored for the first time a new id value is generated for the identifier. I need that if I don't provide a value for firstId it sets the same value as the id. I don't want to solve it with a special getter which checks for null value in firstId and then return the id value because I want to make queries relating on firstId. I can do it in this way by saving the object twice (Probably there's a better way to do this, but I'll do it in this way until I find a better one). But it is not working. when I debug it I can see that result.firstId is set with the id value and it seems to be persisted, but when I go into the datastore I see that firstId is null (as it was saved the first time). This save method is in my DAO and it is called in another save method in the service annotated with @Transactional. Does anyone have any idea why the second object in not persisted properly? @Override public MyObject save(MyObject obj) { PersistenceManager pm = JDOHelper.getPersistenceManagerFactory("transactions-optional"); MyObject result = pm.makePersistent(obj); if(result.getFirstId() == null){ result.setFirstId(result.getId()); result = pm.makePersistent(result); } return result; } Thanks.

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• JDO difficulties in retrieving persistent vector

  - by Michael Omer

  I know there are already some posts regarding this subject, but although I tried using them as a reference, I am still stuck. I have a persistent class as follows: @PersistenceCapable(identityType = IdentityType.APPLICATION) public class GameObject implements IMySerializable{ @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) protected Key m_databaseKey; @NotPersistent private final static int END_GAME_VAR = -1000; @Persistent(defaultFetchGroup = "true") protected GameObjectSet m_set; @Persistent protected int m_databaseType = IDatabaseAccess.TYPE_NONE; where GameObjectSet is: @PersistenceCapable(identityType = IdentityType.APPLICATION) @FetchGroup(name = "mySet", members = {@Persistent(name = "m_set")}) public class GameObjectSet { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) private Key id; @Persistent private Vector<GameObjectSetPair> m_set; and GameObjectSetPair is: @PersistenceCapable(identityType = IdentityType.APPLICATION) public class GameObjectSetPair { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) private Key id; @Persistent private String key; @Persistent(defaultFetchGroup = "true") private GameObjectVar value; When I try to fetch the entire structure by fetching the GameObject, the set doesn't have any elements (they are all null) I tried adding the fetching group to the PM, but to no avail. This is my fetching code Vector<GameObject> ret = new Vector<GameObject>(); PersistenceManager pm = PMF.get().getPersistenceManager(); pm.getFetchPlan().setMaxFetchDepth(-1); pm.getFetchPlan().addGroup("mySet"); Query myQuery = pm.newQuery(GameObject.class); myQuery.setFilter("m_databaseType == objectType"); myQuery.declareParameters("int objectType"); try { List<GameObject> res = (List<GameObject>)myQuery.execute(objectType); ret = new Vector<GameObject>(res); for (int i = 0; i < ret.size(); i++) { ret.elementAt(i).getSet(); ret.elementAt(i).getSet().touchSet(); } } catch (Exception e) { } finally { pm.close(); } Does anyone have any idea? Thanks Mike

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• Can't wrap my head around appengine data store persistence

  - by aloo

  Hi, I've run into the "can't operate on multiple entity groups in a single transaction." problem when using APPENGINE FOR JAVA w/ JDO with the following code: PersistenceManager pm = PMF.get().getPersistenceManager(); Query q = pm.newQuery("SELECT this FROM " + TypeA.class.getName() + " WHERE userId == userIdParam "); q.declareParameters("String userIdParam"); List<TypeA> poos = (List<TypeA>) q.execute(userIdParam); for (TypeA a : allTypeAs) { a.setSomeField(someValue); } pm.close(); } The problem it seems is that I can't operate on a multiple entities at the same time b/c they arent in the same entity group while in a transaction. Even though it doesn't seem like I'm in a transaction, appengine generates one because I have the following set in my jdoconfig.xml: <property name="datanucleus.appengine.autoCreateDatastoreTxns" value="true"/> Fine. So far I think I understand. BUT - if I replace TypeA in the above code, with TypeB - I don't get the error. I don't believe there is anything different between type a and type b - they both have the same key structure. They do have different fields but that shouldn't matter, right? My question is - what could possible be different between TypeA and TypeB that they give this different behavior? And consequently what do you I fundamentally misunderstand that this behavior could even exist.... Thanks.

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• Illegal Argument Exception in Google Wave App

  - by Yoenhofen

  I'm writing a Google Wave robot and I just messed something up. It was working just fine but now I'm getting an IllegalArgument exception on the line that includes query.execute. Am I doing something stupid? I've seen several code samples very similar to what I'm doing. I can include the code of the WaveUpdate class if necessary. The intent here is to select all WaveUpdate members that have an updateDateTime in the last hour. PersistenceManager pm = PMF.get().getPersistenceManager(); try { Query query = pm.newQuery(WaveUpdate.class); query.setFilter("emailAddress > '' && updateDateTime > referenceDateTime"); query.declareParameters("java.util.Date referenceDateTime"); Calendar referenceDateTime = Calendar.getInstance(); referenceDateTime.add(Calendar.HOUR_OF_DAY, -1); List<WaveUpdate> updates = (List<WaveUpdate>) query.execute(referenceDateTime.getTime());

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• Google App Engine datastore encoding?

  - by sernaferna

  I'm using the GAE datastore for a Java application, and storing some text that will be in numerous languages. In my servlet, I'm first checking to see if there's any data in the data store, and, if not, I'm creating some, similar to the following: ArrayList<Lang> list = new ArrayList<Lang>(); list.add(new Lang("EN", "English", 1)); list.add(new Lang("ES", "Español", 0)); //more languages here... PersistenceManager pm = PMF.get().getPersistenceManager(); for(Lang l : list) { pm.makePersistent(l); } Since this is using JDO, I guess I should include the relevent parts of the Lang class too: @PersistenceCapable public class Lang { @PrimaryKey private String code; @Persistent private String name; @Persistent private int popularity; // getters & setters & constructors... } However, the non-ASCII characters are giving me grief. I've set my Eclipse project to use the UTF-8 encoding instead of the default Cp1252, so I think I'm okay from that perspective, but when I use the App Engine Data Viewer to look at my data, that Español entry becomes Español, and when I click on it to view it, I get a 500 Server Error. (There are some other entries with right-to-left text that don't even show up in the Data Viewer at all, but one problem at a time...) Is there anything special I can do in my code to set the character encoding, or specify to GAE that the data I'm storing is UTF-8? Or is the problem on the Eclipse side, and is there something I should be doing with my Java code?

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• Google App-Engine Java Batch Update

  - by Manjoor

  I need to upload a .csv file and save the records in bigtable. My application successfully parse 200 the records in the csv files and save to table. Here is my code to save the data. for (int i=0;i<lines.length -1;i++) //lines hold total records in csv file { String line = lines[i]; //The record have 3 columns integer,integer,Text if(line.length() > 15) { int n = line.indexOf(","); if (n>0) { int ID = lInteger.parseInt(ine.substring(0,n)); int n1 = line.indexOf(",", n + 2); if(n1 > n) { int Col1 = Integer.parseInt(line.substring(n + 1, n1)); String Col2 = line.substring(n1 + 1); myTable uu = new myTable(); uu.setId(ID); uu.setCol1(MobNo); Text t = new Text(Col2); uu.setCol2(t); PersistenceManager pm = PMF.get().getPersistenceManager(); pm.makePersistent(uu); pm.close(); } } } } But when no of records grow it gives timeout error. The csv file may have upto 800 records. Is it possible to do that in App-Engine? (something like batch update)

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• Google App Engine error Object Manager has been closed

  - by newbie

  I had following error from Google App Engine when I was trying to iterate list in JSP page with EL. Object Manager has been closed I solved problem with following coe, but I don't think that it is very good solution to this problem: public List<Item> getItems() { PersistenceManager pm = getPersistenceManager(); Query query = pm.newQuery("select from " + Item.class.getName()); List<Item> items = (List<Items>) query.execute(); List<Item> items2 = new ArrayList<Item>(); // This line solved my problem Collections.copy(items, items2); // and this also pm.close(); return (List<Item>) items; } When I tried to use pm.detachCopyAll(items) it gave same error. I understood that detachCopyAll() method should do same what I did, but that method should be part of data nucelus, so it should be used instead of my owm methods. So why dosen't detachCopyAll() work at all?

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• App Engine - Query using a class member as parameter

  - by Zach

  I have a simple class, relevant details below: @PersistenceCapable(identityType = IdentityType.APPLICATION) public class SimpleCategory implements Serializable{ ... public static enum type{ Course, Category, Cuisine } @Persistent public type t; ... } I am attempting to query all SimpleCategory objects of the same type. public SimpleCategory[] getCategories(SimpleCategory.type type) { PersistenceManager pm = PMF.get().getPersistenceManager(); try{ Query q = pm.newQuery(SimpleCategory.class); q.setFilter("t == categoryType"); q.declareParameters("SimpleCategory.type categoryType"); List<SimpleCategory> cats = (List<SimpleCategory>) q.execute(type); ... } This results in a ClassNotResolvedException for SimpleCategory.type. The google hits I've found so far recommended to: Use query.declareImports to specify the class i.e. q.declareImports("com.test.zach.SimpleCategory.type"); Specify the fully qualified name of SimpleCategory in declareParameters Neither of these suggestions has worked. By removing .type and recompiling, I can verify that declareParameters can see SimpleCategory just fine, it simply cannot see the SimpleCategory.type, despite the fact that the remainder of the method has full visibility to it. What am I missing?

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• ArrayList throwing exception on retrieval from google datastore (with gwt, java)

  - by sumeet

  I'm using Google Web Toolkit with java and google datastore as database. The entity class has arraylist and on trying to retrieve the data from data base I'm getting the exception: Type 'org.datanucleus.sco.backed.ArrayList' was not included in the set of types which can be serialized by this SerializationPolicy or its Class object could not be loaded. For security purposes, this type will not be serialized. I'm using JPA. Entity code: package com.ver2.DY.client; import java.io.Serializable; import java.util.ArrayList; import javax.jdo.annotations.IdGeneratorStrategy; import javax.jdo.annotations.PersistenceCapable; import javax.jdo.annotations.Persistent; import javax.jdo.annotations.PrimaryKey; import com.google.gwt.user.client.rpc.IsSerializable; @PersistenceCapable public class ChatInfo implements Serializable, IsSerializable{ @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) private Long topicId; @Persistent private String chatTopic; @Persistent private ArrayList messages = new ArrayList(); @Persistent private boolean isFirstPost; public ChatInfo() { } public Long getTopicId() { return topicId; } public void setTopicId(Long topicId) { this.topicId = topicId; } public String getChatTopic() { return chatTopic; } public void setChatTopic(String chatTopic) { this.chatTopic = chatTopic; } public ArrayList getMessages() { return messages; } public void addMessage(String newMsg) { messages.add(newMsg); } public boolean isFirstPost() { return isFirstPost; } public void setFirstPost(boolean isFirstPost) { this.isFirstPost = isFirstPost; } } Method in db class: @Transactional public ChatInfo[] getAllChat() { PersistenceManager pm = PMF.get().getPersistenceManager(); List chats = null; ChatInfo[] infos = null; String query = "select from " + ChatInfo.class.getName(); try{ chats = (List) pm.newQuery(query).execute(); infos = new ChatInfo[chats.size()]; for(int i=0;i } It is a bit strange because earlier I was able to insert and retrieve the data but it now throwing an exception. On searching the web I could find that I need to convert the Arraylist from some DataNucleus type to java util but not sure how to do that.

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• Persistance JDO - How to query a property of a collection with JDOQL?

  - by Sergio del Amo

  I want to build an application where a user identified by an email address can have several application accounts. Each account can have one o more users. I am trying to use the JDO Storage capabilities with Google App Engine Java. Here is my attempt: @PersistenceCapable @Inheritance(strategy = InheritanceStrategy.NEW_TABLE) public class AppAccount { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) private Long id; @Persistent private String companyName; @Persistent List<Invoices> invoices = new ArrayList<Invoices>(); @Persistent List<AppUser> users = new ArrayList<AppUser>(); // Getter Setters and Other Fields } @PersistenceCapable @EmbeddedOnly public class AppUser { @Persistent private String username; @Persistent private String firstName; @Persistent private String lastName; // Getter Setters and Other Fields } When a user logs in, I want to check how many accounts does he belongs to. If he belongs to more than one he will be presented with a dashboard where he can click which account he wants to load. This is my code to retrieve a list of app accounts where he is registered. public static List<AppAccount> getUserAppAccounts(String username) { PersistenceManager pm = JdoUtil.getPm(); Query q = pm.newQuery(AppAccount.class); q.setFilter("users.username == usernameParam"); q.declareParameters("String usernameParam"); return (List<AppAccount>) q.execute(username); } But I get the next error: SELECT FROM invoices.server.AppAccount WHERE users.username == usernameParam PARAMETERS String usernameParam: Encountered a variable expression that isn't part of a join. Maybe you're referencing a non-existent field of an embedded class. org.datanucleus.store.appengine.FatalNucleusUserException: SELECT FROM com.softamo.pelicamo.invoices.server.AppAccount WHERE users.username == usernameParam PARAMETERS String usernameParam: Encountered a variable expression that isn't part of a join. Maybe you're referencing a non-existent field of an embedded class. at org.datanucleus.store.appengine.query.DatastoreQuery.getJoinClassMetaData(DatastoreQuery.java:1154) at org.datanucleus.store.appengine.query.DatastoreQuery.addLeftPrimaryExpression(DatastoreQuery.java:1066) at org.datanucleus.store.appengine.query.DatastoreQuery.addExpression(DatastoreQuery.java:846) at org.datanucleus.store.appengine.query.DatastoreQuery.addFilters(DatastoreQuery.java:807) at org.datanucleus.store.appengine.query.DatastoreQuery.performExecute(DatastoreQuery.java:226) at org.datanucleus.store.appengine.query.JDOQLQuery.performExecute(JDOQLQuery.java:85) at org.datanucleus.store.query.Query.executeQuery(Query.java:1489) at org.datanucleus.store.query.Query.executeWithArray(Query.java:1371) at org.datanucleus.jdo.JDOQuery.execute(JDOQuery.java:243) at com.softamo.pelicamo.invoices.server.Store.getUserAppAccounts(Store.java:82) at com.softamo.pelicamo.invoices.test.server.StoreTest.testgetUserAppAccounts(StoreTest.java:39) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20) at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28) at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:76) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50) at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191) at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184) at org.junit.runners.ParentRunner.run(ParentRunner.java:236) at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:46) at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197) Any idea? I am getting JDO persistance totally wrong?

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• Why can't Java servlet sent out an object ?

  - by Frank

  I use the following method to send out an object from a servlet : public void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException { String Full_URL=request.getRequestURL().append("?"+request.getQueryString()).toString(); String Contact_Id=request.getParameter("Contact_Id"); String Time_Stamp=Get_Date_Format(6),query="select from "+Contact_Info_Entry.class.getName()+" where Contact_Id == '"+Contact_Id+"' order by Contact_Id desc"; PersistenceManager pm=null; try { pm=PMF.get().getPersistenceManager(); // note that this returns a list, there could be multiple, DataStore does not ensure uniqueness for non-primary key fields List<Contact_Info_Entry> results=(List<Contact_Info_Entry>)pm.newQuery(query).execute(); Write_Serialized_XML(response.getOutputStream(),results.get(0)); } catch (Exception e) { Send_Email(Email_From,Email_To,"Check_License_Servlet Error [ "+Time_Stamp+" ]",new Text(e.toString()+"\n"+Get_Stack_Trace(e)),null); } finally { pm.close(); } } /** Writes the object and CLOSES the stream. Uses the persistance delegate registered in this class. * @param os The stream to write to. * @param o The object to be serialized. */ public static void writeXMLObject(OutputStream os,Object o) { // Classloader reference must be set since netBeans uses another class loader to loead the bean wich will fail in some circumstances. ClassLoader oldClassLoader=Thread.currentThread().getContextClassLoader(); Thread.currentThread().setContextClassLoader(Check_License_Servlet.class.getClassLoader()); XMLEncoder encoder=new XMLEncoder(os); encoder.setExceptionListener(new ExceptionListener() { public void exceptionThrown(Exception e) { e.printStackTrace(); }}); encoder.writeObject(o); encoder.flush(); encoder.close(); Thread.currentThread().setContextClassLoader(oldClassLoader); } private static ByteArrayOutputStream writeOutputStream=new ByteArrayOutputStream(16384); /** Writes an object to XML. * @param out The boject out to write to. [ Will not be closed. ] * @param o The object to write. */ public static synchronized void writeAsXML(ObjectOutput out,Object o) throws IOException { writeOutputStream.reset(); writeXMLObject(writeOutputStream,o); byte[] Bt_1=writeOutputStream.toByteArray(); byte[] Bt_2=new Des_Encrypter().encrypt(Bt_1,Key); out.writeInt(Bt_2.length); out.write(Bt_2); out.flush(); out.close(); } public static synchronized void Write_Serialized_XML(OutputStream Output_Stream,Object o) throws IOException { writeAsXML(new ObjectOutputStream(Output_Stream),o); } At the receiving end the code look like this : File_Url="http://"+Site_Url+App_Dir+File_Name; try { Contact_Info_Entry Online_Contact_Entry=(Contact_Info_Entry)Read_Serialized_XML(new URL(File_Url)); } catch (Exception e) { e.printStackTrace(); } private static byte[] readBuf=new byte[16384]; public static synchronized Object readAsXML(ObjectInput in) throws IOException { // Classloader reference must be set since netBeans uses another class loader to load the bean which will fail under some circumstances. ClassLoader oldClassLoader=Thread.currentThread().getContextClassLoader(); Thread.currentThread().setContextClassLoader(Tool_Lib_Simple.class.getClassLoader()); int length=in.readInt(); readBuf=new byte[length]; in.readFully(readBuf,0,length); byte Bt[]=new Des_Encrypter().decrypt(readBuf,Key); XMLDecoder dec=new XMLDecoder(new ByteArrayInputStream(Bt,0,Bt.length)); Object o=dec.readObject(); Thread.currentThread().setContextClassLoader(oldClassLoader); in.close(); return o; } public static synchronized Object Read_Serialized_XML(URL File_Url) throws IOException { return readAsXML(new ObjectInputStream(File_Url.openStream())); } But I can't get the object from the Java app that's on the receiving end, why ? The error messages look like this : java.lang.ClassNotFoundException: PayPal_Monitor.Contact_Info_Entry Continuing ... java.lang.NullPointerException: target should not be null Continuing ... java.lang.NullPointerException: target should not be null Continuing ... java.lang.NullPointerException: target should not be null Continuing ...

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• Problem detaching entire object graph in GAE-J with JDO

  - by tempy

  I am trying to load the full object graph for User, which contains a collection of decks, which then contains a collection of cards, as such: User: @PersistenceCapable(detachable = "true") @Inheritance(strategy = InheritanceStrategy.SUBCLASS_TABLE) @FetchGroup(name = "decks", members = { @Persistent(name = "_Decks") }) public abstract class User { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) protected Key _ID; @Persistent protected String _UniqueIdentifier; @Persistent(mappedBy = "_Owner") @Element(dependent = "true") protected Set<Deck> _Decks; protected User() { } } Each Deck has a collection of Cards, as such: @PersistenceCapable(detachable = "true") @FetchGroup(name = "cards", members = { @Persistent(name = "_Cards") }) public class Deck { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) private Key _ID; @Persistent String _Name; @Persistent(mappedBy = "_Parent") @Element(dependent = "true") private Set<Card> _Cards = new HashSet<Card>(); @Persistent private Set<String> _Tags = new HashSet<String>(); @Persistent private User _Owner; } And finally, each card: @PersistenceCapable public class Card { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) private Key _ID; @Persistent private Text _Question; @Persistent private Text _Answer; @Persistent private Deck _Parent; } I am trying to retrieve and then detach the entire object graph. I can see in the debugger that it loads fine, but then when I get to detaching, I can't make anything beyond the User object load. (No Decks, no Cards). At first I tried without a transaction to simply "touch" all the fields on the attached object before detaching, but that didn't help. Then I tried adding everything to the default fetch group, but that just generated warnings about GAE not supporting joins. I tried setting the fetch plan's max fetch depth to -1, but that didn't do it. Finally, I tried using FetchGroups as you can see above, and then retrieving with the following code: PersistenceManager pm = _pmf.getPersistenceManager(); pm.setDetachAllOnCommit(true); pm.getFetchPlan().setGroup("decks"); pm.getFetchPlan().setGroup("cards"); Transaction tx = pm.currentTransaction(); Query query = null; try { tx.begin(); query = pm.newQuery(GoogleAccountsUser.class); //Subclass of User query.setFilter("_UniqueIdentifier == TheUser"); query.declareParameters("String TheUser"); List<User> results = (List<User>)query.execute(ID); //ID = Supplied parameter //TODO: Test for more than one result and throw if(results.size() == 0) { tx.commit(); return null; } else { User usr = (User)results.get(0); //usr = pm.detachCopy(usr); tx.commit(); return usr; } } finally { query.closeAll(); if (tx.isActive()) { tx.rollback(); } pm.close(); } This also doesn't work, and I'm running out of ideas...

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