JPA, java persistence Api, troubleshooting

Hi everybody.
I have a small but boring problem.
I am new at Netbeans and Java Sdk.
I downloaded Netbeans 6.1 and SDK 6.
I tried to exercise "simple database application" in the netbeans web page.
A error encountered that:
24.Tem.2008 10:04:16 org.jdesktop.application.Application$1 run
SEVERE: Application class simpleAp.simpleAp failed to launch
*javax.persistence.PersistenceException: No Persistence provider for EntityManager named simpleAppPU*: The following providers:
oracle.toplink.essentials.PersistenceProvider
oracle.toplink.essentials.ejb.cmp3.EntityManagerFactoryProvider
Returned null to createEntityManagerFactory.
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:154)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:83)
I can't fix this. anybody know the solution??
hanks, good work.

Assalamu Alaikum,
Check in persistence.xml whether persistence-unit is same in Persistence.createEntityManagerFactory*("simpleAppPU")* or not. It should be same.
persistence.xml is like as follows:
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
<persistence-unit name="*simpleAppPU*" transaction-type="RESOURCE_LOCAL">
<provider>oracle.toplink.essentials.PersistenceProvider</provider>
<class>Users</class>
<properties>
<property name="toplink.jdbc.user" value="root"/>
<property name="toplink.jdbc.password" value="password"/>
<property name="toplink.jdbc.url" value="jdbc:mysql://localhost:3306/innosched"/>
<property name="toplink.jdbc.driver" value="com.mysql.jdbc.Driver"/>
</properties>
</persistence-unit>
</persistence>

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at com.sap.tc.webdynpro.serverimpl.wdc.sessionctx.AbstractDispatchHandler.service(AbstractDispatchHandler.java:116)
at com.sap.engine.services.servlets_jsp.server.deploy.impl.module.IRequestDispatcherImpl.dispatch(IRequestDispatcherImpl.java:93)
at com.sap.tc.webdynpro.serverimpl.wdc.sessionctx.ExecutionContextDispatcher.dispatchToRequestManager(ExecutionContextDispatcher.java:140)
at com.sap.tc.webdynpro.serverimpl.core.sessionctx.AbstractExecutionContextDispatcher.dispatch(AbstractExecutionContextDispatcher.java:92)
at com.sap.tc.webdynpro.serverimpl.core.sessionctx.AbstractExecutionContextDispatcher.dispatch(AbstractExecutionContextDispatcher.java:104)
at com.sap.tc.webdynpro.serverimpl.core.AbstractDispatcherServlet.doContent(AbstractDispatcherServlet.java:87)
at com.sap.tc.webdynpro.serverimpl.core.AbstractDispatcherServlet.doPost(AbstractDispatcherServlet.java:61)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
at com.sap.engine.services.servlets_jsp.server.Invokable.invoke(Invokable.java:66)
at com.sap.engine.services.servlets_jsp.server.Invokable.invoke(Invokable.java:32)
at com.sap.engine.services.servlets_jsp.server.HttpHandlerImpl.runServlet(HttpHandlerImpl.java:431)
at com.sap.engine.services.servlets_jsp.server.HttpHandlerImpl.handleRequest(HttpHandlerImpl.java:289)
at com.sap.engine.services.httpserver.server.RequestAnalizer.startServlet(RequestAnalizer.java:387)
at com.sap.engine.services.httpserver.server.RequestAnalizer.startServlet(RequestAnalizer.java:376)
at com.sap.engine.services.servlets_jsp.filters.ServletSelector.process(ServletSelector.java:85)
at com.sap.engine.services.httpserver.chain.AbstractChain.process(AbstractChain.java:71)
at com.sap.engine.services.servlets_jsp.filters.ApplicationSelector.process(ApplicationSelector.java:160)
at com.sap.engine.services.httpserver.chain.AbstractChain.process(AbstractChain.java:71)
at com.sap.engine.services.httpserver.filters.WebContainerInvoker.process(WebContainerInvoker.java:67)
at com.sap.engine.services.httpserver.chain.HostFilter.process(HostFilter.java:9)
at com.sap.engine.services.httpserver.chain.AbstractChain.process(AbstractChain.java:71)
at com.sap.engine.services.httpserver.filters.ResponseLogWriter.process(ResponseLogWriter.java:60)
at com.sap.engine.services.httpserver.chain.HostFilter.process(HostFilter.java:9)
at com.sap.engine.services.httpserver.chain.AbstractChain.process(AbstractChain.java:71)
at com.sap.engine.services.httpserver.filters.DefineHostFilter.process(DefineHostFilter.java:27)
at com.sap.engine.services.httpserver.chain.ServerFilter.process(ServerFilter.java:12)
at com.sap.engine.services.httpserver.chain.AbstractChain.process(AbstractChain.java:71)
at com.sap.engine.services.httpserver.filters.MonitoringFilter.process(MonitoringFilter.java:29)
at com.sap.engine.services.httpserver.chain.ServerFilter.process(ServerFilter.java:12)
at com.sap.engine.services.httpserver.chain.AbstractChain.process(AbstractChain.java:71)
at com.sap.engine.services.httpserver.server.Processor.chainedRequest(Processor.java:309)
at com.sap.engine.services.httpserver.server.Processor$FCAProcessorThread.run(Processor.java:222)
at com.sap.engine.core.thread.impl3.ActionObject.run(ActionObject.java:37)
at java.security.AccessController.doPrivileged(Native Method)
at com.sap.engine.core.thread.impl3.SingleThread.execute(SingleThread.java:152)
at com.sap.engine.core.thread.impl3.SingleThread.run(SingleThread.java:247)
Caused by: javax.ejb.EJBException: Cannot perform injection over bean instance [email protected]5db311 for bean demo.sap.com/jpacas~ear*annotation|demo.sap.com~jpacas~ejbmodule.jar*annotation|com.sap.demo.jpacas.modeled.appsrv.jpaservice.jpaservice; nested exception is: com.sap.engine.lib.injection.InjectionException: Injection on field em of instance [email protected]5db311 failed. Could not get a value to be injected from the factory.
at com.sap.engine.services.ejb3.runtime.impl.Interceptors_DependencyInjection.invoke(Interceptors_DependencyInjection.java:25)
at com.sap.engine.services.ejb3.runtime.impl.Interceptors_EJBContext30DependencyInjection.invoke(Interceptors_EJBContext30DependencyInjection.java:11)
at com.sap.engine.services.ejb3.runtime.impl.AbstractInvocationContext.proceed(AbstractInvocationContext.java:177)
at com.sap.engine.services.ejb3.runtime.impl.Interceptors_StatesTransition.invoke(Interceptors_StatesTransition.java:19)
at com.sap.engine.services.ejb3.runtime.impl.AbstractInvocationContext.proceed(AbstractInvocationContext.java:177)
at com.sap.engine.services.ejb3.runtime.impl.Interceptors_ApplicationInstancesCreator.invoke(Interceptors_ApplicationInstancesCreator.java:53)
at com.sap.engine.services.ejb3.runtime.impl.AbstractInvocationContext.proceed(AbstractInvocationContext.java:177)
at com.sap.engine.services.ejb3.runtime.impl.Interceptors_Resource.invoke(Interceptors_Resource.java:71)
at com.sap.engine.services.ejb3.runtime.impl.AbstractInvocationContext.proceed(AbstractInvocationContext.java:177)
at com.sap.engine.services.ejb3.runtime.impl.AbstractInvocationContext.proceed(AbstractInvocationContext.java:189)
at com.sap.engine.services.ejb3.runtime.impl.Interceptors_NewBeanContext.invoke(Interceptors_NewBeanContext.java:17)
at com.sap.engine.services.ejb3.runtime.impl.AbstractInvocationContext.proceed(AbstractInvocationContext.java:177)
at com.sap.engine.services.ejb3.runtime.impl.DefaultInvocationChainsManager.startCallback(DefaultInvocationChainsManager.java:147)
at com.sap.engine.services.ejb3.runtime.impl.StatelessInstanceLifecycleManager.makeExist(StatelessInstanceLifecycleManager.java:108)
at com.sap.engine.services.ejb3.runtime.impl.StatelessInstanceLifecycleManager.access$000(StatelessInstanceLifecycleManager.java:23)
at com.sap.engine.services.ejb3.runtime.impl.StatelessInstanceLifecycleManager$PoolUserImpl.createObject(StatelessInstanceLifecycleManager.java:34)
at com.sap.engine.services.ejb3.util.pool.ContainerPoolImpl.doResizeOneStepUp(ContainerPoolImpl.java:373)
... 113 more
Caused by: com.sap.engine.lib.injection.InjectionException: Injection on field em of instance [email protected]5db311 failed. Could not get a value to be injected from the factory.
at com.sap.engine.lib.injection.FieldInjector.inject(FieldInjector.java:115)
at com.sap.engine.lib.injection.InjectionMatrix.inject(InjectionMatrix.java:45)
at com.sap.engine.services.ejb3.runtime.impl.Interceptors_DependencyInjection.invoke(Interceptors_DependencyInjection.java:22)
... 129 more
Caused by: com.sap.engine.services.orpersistence.container.exceptions.ResourceException: Persistence unit 'CAR_AL' requested from archive 'demo.sap.com~jpacas~ejbmodule.jar' is not present in application 'demo.sap.com/jpacas~ear' or is not visible to the requested archive.
at com.sap.engine.services.orpersistence.container.ORPersistenceObjectFactory.getPersistenceUnitInfo(ORPersistenceObjectFactory.java:213)
at com.sap.engine.services.orpersistence.container.ORPersistenceObjectFactory.getObjectInstance(ORPersistenceObjectFactory.java:59)
at com.sap.engine.lib.injection.ReferenceObjectFactory.getObject(ReferenceObjectFactory.java:65)
at com.sap.engine.lib.injection.FieldInjector.inject(FieldInjector.java:113)
... 131 more
Close

With Java Persistence, are DAOs (data access objects) still needed?

I have just looked at the Java Persistence tutorial and it says each table row of a database can be represented as a Java Persistence entity instance.
The definition of an "entity" is very much like how you would define the class of an equivalent DAO.
So I am wondering... should DAOs still be used ? or can persistence entities completely replace them?

Hi,
I am saying that if you use JPA then you will not be making a DAO class, for example if you have a Person.java object you will not need to make a PersonDAO.java object.
For example, if using JPA you Person.java object would look like this example below...
Of course, the classes that call person object may need to call some JPA manager APIs or some JTA transaction APIs. If you use EJB session beans to call the JP{A entity then you dont have to have any code, as ou can see here
https://blueprints.dev.java.net/bpcatalog/ee5/persistence/ejbfacade.html
if you do not use EJBs in a pure web app then you will likely manually write code to manage transactions and entity manager APIs such as
https://blueprints.dev.java.net/bpcatalog/ee5/persistence/webfacade.html
See Person.java entuty example below and see there is no DAO code.
@Entity
public class Person implements java.io.Serializable {
    private int personId;
    private String userName;
    private String firstName;
    private String lastName;
    private String summary;
    public Person() { }
@Id
public int getPersonId() {
return personId;
public String getUserName() {
return userName;
public String getFirstName() {
return firstName;
public String getLastName() {
return lastName;
public String getSummary(){
return summary;
public void setPersonId(int personId) {
this.personId = personId;
public void setUserName(String userName) {
this.userName = userName;
public void setFirstName(String firstName) {
this.firstName = firstName;
public void setLastName(String lastName) {
this.lastName = lastName;
public void setSummary(String summary) {
this.summary = summary;
}

JPA, java persistence Api, troubleshooting

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