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Posted to users@openjpa.apache.org by Lars Vogel <la...@googlemail.com> on 2008/03/12 14:22:28 UTC
JPA - Null pointer exception
Hi,
I trying to make JPA work for me. The delivered example works without
problems, I can also successfully modify this example. The example was based
on http://openjpa.apache.org/quick-start.html.
But if I create a new project the Entity Manager returns only a NULL value.
Error:
Exception in thread "main" java.lang.NullPointerException
at hellojpa.Main.main(Main.java:44)
I use the same files as in the working example. All jars are included in the
build path. I assume that the persistence.xml is not found but to my
knowledge the classpath is correctly maintained. The path .../bin contains
the directory META-INF and here the file persistence.xml.
Any advice? I must be missing something very simple but cannot figure it
out. For example coding please see below.
Best regards, Lars
File structure:
src
- hellojpa
- Main.java
- Message.java
- META-INF
- persistence.xml
Same structure in the bin directory.
-----------persistence.xml..............
<?xml version="1.0" encoding="UTF-8"?>
<!--
Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements. See the NOTICE file
distributed with this work for additional information
regarding copyright ownership. The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied. See the License for the
specific language governing permissions and limitations
under the License.
-->
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="1.0">
<!--
A persistence unit is a set of listed persistent entities as well
the configuration of an EntityManagerFactory. We configure each
example in a separate persistence-unit.
-->
<persistence-unit name="hellojpa"
transaction-type="RESOURCE_LOCAL">
<!--
The default provider can be OpenJPA, or some other product.
This element is optional if OpenJPA is the only JPA provider
in the current classloading environment, but can be specified
in cases where there are multiple JPA implementations available.
-->
<provider>
org.apache.openjpa.persistence.PersistenceProviderImpl
</provider>
<!-- We must enumerate each entity in the persistence unit -->
<class>hellojpa.Message</class>
<properties>
<property name="openjpa.ConnectionURL"
value="jdbc:derby:C:/DerbyDatabases/hellojpa-database5;create=true" />
<property name="openjpa.ConnectionDriverName"
value="org.apache.derby.jdbc.EmbeddedDriver" />
<property name="openjpa.ConnectionUserName" value="" />
<property name="openjpa.ConnectionPassword" value="" />
<!--
Tell OpenJPA to automatically create tables in the database
for entities. Note that this should be disabled when
running against a production database, since you probably
don't want to be altering the schema at runtime.
-->
<property name="openjpa.jdbc.SynchronizeMappings"
value="buildSchema" />
</properties>
</persistence-unit>
</persistence>
-----------Main.java
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package hellojpa;
import java.util.*;
import javax.persistence.*;
/**
* A very simple, stand-alone program that stores a new entity in the
* database and then performs a query to retrieve it.
*/
public class Main {
@SuppressWarnings("unchecked")
public static void main(String[] args) {
System.out.println(System.getProperty("java.class.path"));
// Create a new EntityManagerFactory using the System properties.
// The "hellojpa" name will be used to configure based on the
// corresponding name in the META-INF/persistence.xml file
EntityManagerFactory factory = Persistence.
createEntityManagerFactory("hellojpa", System.getProperties());
// Create a new EntityManager from the EntityManagerFactory. The
// EntityManager is the main object in the persistence API, and is
// used to create, delete, and query objects, as well as access
// the current transaction
EntityManager em = factory.createEntityManager();
// Begin a new local transaction so that we can persist a new entity
em.getTransaction().begin();
// Create and persist a new Message entity
em.persist(new Message("Hello Persistence!"));
// Commit the transaction, which will cause the entity to
// be stored in the database
em.getTransaction().commit();
// It is always good practice to close the EntityManager so that
// resources are conserved.
em.close();
// Create a fresh, new EntityManager
EntityManager em2 = factory.createEntityManager();
// Perform a simple query for all the Message entities
Query q = em2.createQuery("select m from Message m");
// Go through each of the entities and print out each of their
// messages, as well as the date on which it was created
for (Message m : (List<Message>) q.getResultList()) {
System.out.println(m.getMessage()
+ " (created on: " + m.getCreated() + ")");
}
// Again, it is always good to clean up after ourselves
em2.close();
factory.close();
}
}
-----------
Re: JPA - Null pointer exception
Posted by Lars Vogel <la...@googlemail.com>.
Hi,
I documented how someone good build a small OpenJPA example:
http://www.vogella.de/articles/JavaPersistenceAPI/article.html
Thank you for your support. Best regards, Lars
2008/3/12, Lars Vogel <la...@googlemail.com>:
>
> Hi Mike,
>
> thank you, I must have been blind. Indeed the OpenJPA was missing.
>
> Thank you very, very much and sorry for such a blind spot on my side.
>
> I'll write a short summery on how to set a small OpenJPA up and post it
> later to this newsgroup for future reference.
>
> Best regards, Lars
>
>
> 2008/3/12, Michael Dick <mi...@gmail.com>:
> >
> > The only thing I noticed was that you didn't have OpenJPA specified on
> > the classpath. You must have it specified somewhere, unless you've imported
> > all the source.
> >
> > I'm sorry to say that I just replied to you personally, so the users
> > mailing list hasn't seen these last few replies. If you'd like to post the
> > sample you're using back to users@openjpa.apache.org, then maybe someone
> > else will have better luck than I did.
> >
> > -Mike
> >
> > On Wed, Mar 12, 2008 at 3:53 PM, Lars Vogel <la...@googlemail.com>
> > wrote:
> >
> > > Hi Mike,
> > >
> > > thank you. I don't see a difference to "my" setup.
> > >
> > > If anyone wants to look at my project I uploaded it:
> > > http://www.jnerlich.de/JPAExample.zip
> > >
> > > Cheers, Lars
> > >
> > >
> > > 2008/3/12, Michael Dick <mi...@gmail.com>:
> > > >
> > > > Hi Lars,
> > > >
> > > > Here's what I'm using. I don't see anything obviously wrong the ones
> > > > you sent me though.
> > > >
> > > > -Mike
> > > >
> > > > On Wed, Mar 12, 2008 at 2:52 PM, Lars Vogel <
> > > > lars.vogel@googlemail.com> wrote:
> > > >
> > > > > Hi Mike,
> > > > >
> > > > > I'm running it in Eclipse. Yes, please send me your .classpath and
> > > > > .project files. Mine are also attached for reference.
> > > > >
> > > > > Best regards, Lars
> > > > >
> > > > > <?xml version="1.0" encoding="UTF-8"?>
> > > > > <projectDescription>
> > > > > <name>hellopja</name>
> > > > > <comment></comment>
> > > > > <projects>
> > > > > </projects>
> > > > > <buildSpec>
> > > > > <buildCommand>
> > > > > <name>org.eclipse.jdt.core.javabuilder</name>
> > > > > <arguments>
> > > > > </arguments>
> > > > > </buildCommand>
> > > > > </buildSpec>
> > > > > <natures>
> > > > > <nature>org.eclipse.jdt.core.javanature</nature>
> > > > > </natures>
> > > > > </projectDescription>
> > > > >
> > > > > <?xml version="1.0" encoding="UTF-8"?>
> > > > > <classpath>
> > > > > <classpathentry kind="src" path="src"/>
> > > > > <classpathentry kind="con" path="
> > > > > org.eclipse.jdt.launching.JRE_CONTAINER"/>
> > > > > <classpathentry kind="lib" path="C:/Documents and
> > > > > Settings/vogella/Desktop/Documents/08_MyDocuments/15_EclipseLibs/openjpa/commons-
> > > > > collections-3.2.jar"/>
> > > > > <classpathentry kind="lib" path="C:/Documents and
> > > > > Settings/vogella/Desktop/Documents/08_MyDocuments/15_EclipseLibs/openjpa/commons-
> > > > > lang-2.1.jar"/>
> > > > > <classpathentry kind="lib" path="C:/Documents and
> > > > > Settings/vogella/Desktop/Documents/08_MyDocuments/15_EclipseLibs/openjpa/commons-
> > > > > logging-1.0.4.jar"/>
> > > > > <classpathentry kind="lib" path="C:/Documents and
> > > > > Settings/vogella/Desktop/Documents/08_MyDocuments/15_EclipseLibs/openjpa/commons-
> > > > > pool-1.3.jar"/>
> > > > > <classpathentry kind="lib" path="C:/Documents and
> > > > > Settings/vogella/Desktop/Documents/08_MyDocuments/15_EclipseLibs/openjpa/derby-
> > > > > 10.2.2.0.jar"/>
> > > > > <classpathentry kind="lib" path="C:/Documents and
> > > > > Settings/vogella/Desktop/Documents/08_MyDocuments/15_EclipseLibs/openjpa/geronimo-jms_1.1_spec-
> > > > > 1.0.1.jar"/>
> > > > > <classpathentry kind="lib" path="C:/Documents and
> > > > > Settings/vogella/Desktop/Documents/08_MyDocuments/15_EclipseLibs/openjpa/geronimo-jpa_3.0_spec-
> > > > > 1.0.jar"/>
> > > > > <classpathentry kind="lib" path="C:/Documents and
> > > > > Settings/vogella/Desktop/Documents/08_MyDocuments/15_EclipseLibs/openjpa/geronimo-jta_1.1_spec-
> > > > > 1.1.jar"/>
> > > > > <classpathentry kind="lib" path="C:/Documents and
> > > > > Settings/vogella/Desktop/Documents/08_MyDocuments/15_EclipseLibs/openjpa/serp-
> > > > > 1.13.1.jar"/>
> > > > > <classpathentry kind="output" path="bin"/>
> > > > > </classpath>
> > > > >
> > > > >
> > > > > 2008/3/12, Michael Dick <mi...@gmail.com>:
> > > > >
> > > > > > Hi Lars,
> > > > > >
> > > > > > How are you running the program? You mention projects so you're
> > > > > > probably using either Eclipse or Netbeans. I tried something similar to what
> > > > > > you've posted and it worked for me in Eclipse. I can send you the .classpath
> > > > > > and .project files if that will help.
> > > > > >
> > > > > > -Mike
> > > > > >
> > > > > > On Wed, Mar 12, 2008 at 10:22 AM, Lars Vogel <
> > > > > > lars.vogel@googlemail.com> wrote:
> > > > > >
> > > > > > > Hi Venkatesch,
> > > > > > >
> > > > > > > I did also modify the orginal persistence.xml so that is
> > > > > > > exactly the same as
> > > > > > > my example to be able to run Main.java directly without the
> > > > > > > ant script.
> > > > > > >
> > > > > > > So in both cases I'm not using the build.xml file anymore. The
> > > > > > > only
> > > > > > > difference I see is that one version runs the other not.
> > > > > > >
> > > > > > > Best egards, Lars
> > > > > > >
> > > > > > > 2008/3/12, Addanki, Venkatesh <Venkatesh.Addanki@aquilent.com
> > > > > > > >:
> > > > > > > >
> > > > > > > > Lars,
> > > > > > > >
> > > > > > > > One obvious difference between your code and the out of box
> > > > > > > sample is
> > > > > > > > the way the driver class and its properties are specified.
> > > > > > > build.xml vs
> > > > > > > > persistence.xml. It looks like the
> > > > > > > org.apache.derby.jdbc.EmbeddedDriver
> > > > > > > > class from your persistence.xml is not being found or the
> > > > > > > connection url
> > > > > > > > is not getting through.
> > > > > > > >
> > > > > > > > Regards
> > > > > > > >
> > > > > > > > V
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > > -----Original Message-----
> > > > > > > > From: Lars Vogel [mailto:lars.vogel@googlemail.com]
> > > > > > > > Sent: Wednesday, March 12, 2008 9:22 AM
> > > > > > > > To: users@openjpa.apache.org
> > > > > > > > Subject: JPA - Null pointer exception
> > > > > > > >
> > > > > > > > Hi,
> > > > > > > >
> > > > > > > > I trying to make JPA work for me. The delivered example
> > > > > > > works without
> > > > > > > > problems, I can also successfully modify this example. The
> > > > > > > example was
> > > > > > > > based on http://openjpa.apache.org/quick-start.html.
> > > > > > > >
> > > > > > > > But if I create a new project the Entity Manager returns
> > > > > > > only a NULL
> > > > > > > > value.
> > > > > > > > Error:
> > > > > > > >
> > > > > > > > Exception in thread "main" java.lang.NullPointerException
> > > > > > > > at hellojpa.Main.main(Main.java:44)
> > > > > > > >
> > > > > > > >
> > > > > > > > I use the same files as in the working example. All jars are
> > > > > > > included in
> > > > > > > > the build path. I assume that the persistence.xml is not
> > > > > > > found but to my
> > > > > > > > knowledge the classpath is correctly maintained. The path
> > > > > > > .../bin
> > > > > > > > contains the directory META-INF and here the file
> > > > > > > persistence.xml.
> > > > > > > >
> > > > > > > > Any advice? I must be missing something very simple but
> > > > > > > cannot figure it
> > > > > > > > out. For example coding please see below.
> > > > > > > >
> > > > > > > > Best regards, Lars
> > > > > > > >
> > > > > > > > File structure:
> > > > > > > >
> > > > > > > > src
> > > > > > > > - hellojpa
> > > > > > > > - Main.java
> > > > > > > > - Message.java
> > > > > > > > - META-INF
> > > > > > > > - persistence.xml
> > > > > > > >
> > > > > > > > Same structure in the bin directory.
> > > > > > > >
> > > > > > > >
> > > > > > > > -----------persistence.xml..............
> > > > > > > >
> > > > > > > > <?xml version="1.0" encoding="UTF-8"?>
> > > > > > > > <!--
> > > > > > > > Licensed to the Apache Software Foundation (ASF) under
> > > > > > > one
> > > > > > > > or more contributor license agreements. See the NOTICE
> > > > > > > file
> > > > > > > > distributed with this work for additional information
> > > > > > > > regarding copyright ownership. The ASF licenses this
> > > > > > > file
> > > > > > > > to you under the Apache License, Version 2.0 (the
> > > > > > > > "License"); you may not use this file except in
> > > > > > > compliance
> > > > > > > > with the License. You may obtain a copy of the License
> > > > > > > at
> > > > > > > >
> > > > > > > > http://www.apache.org/licenses/LICENSE-2.0
> > > > > > > >
> > > > > > > > Unless required by applicable law or agreed to in
> > > > > > > writing,
> > > > > > > > software distributed under the License is distributed on
> > > > > > > an
> > > > > > > > "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
> > > > > > > > KIND, either express or implied. See the License for
> > > > > > > the
> > > > > > > > specific language governing permissions and limitations
> > > > > > > > under the License.
> > > > > > > > -->
> > > > > > > > <persistence xmlns="http://java.sun.com/xml/ns/persistence"
> > > > > > > > xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
> > > > > > > version="1.0">
> > > > > > > >
> > > > > > > > <!--
> > > > > > > > A persistence unit is a set of listed persistent
> > > > > > > entities as
> > > > > > > > well
> > > > > > > > the configuration of an EntityManagerFactory. We
> > > > > > > configure each
> > > > > > > > example in a separate persistence-unit.
> > > > > > > > -->
> > > > > > > > <persistence-unit name="hellojpa"
> > > > > > > > transaction-type="RESOURCE_LOCAL">
> > > > > > > > <!--
> > > > > > > > The default provider can be OpenJPA, or some
> > > > > > > other product.
> > > > > > > > This element is optional if OpenJPA is the only
> > > > > > > JPA provider
> > > > > > > > in the current classloading environment, but can
> > > > > > > be
> > > > > > > > specified
> > > > > > > > in cases where there are multiple JPA
> > > > > > > implementations
> > > > > > > > available.
> > > > > > > > -->
> > > > > > > >
> > > > > > > > <provider>
> > > > > > > >
> > > > > > > org.apache.openjpa.persistence.PersistenceProviderImpl
> > > > > > > > </provider>
> > > > > > > >
> > > > > > > >
> > > > > > > > <!-- We must enumerate each entity in the
> > > > > > > persistence unit -->
> > > > > > > > <class>hellojpa.Message</class>
> > > > > > > >
> > > > > > > > <properties>
> > > > > > > > <property name="openjpa.ConnectionURL"
> > > > > > > >
> > > > > > > >
> > > > > > > value="jdbc:derby:C:/DerbyDatabases/hellojpa-database5;create=true" />
> > > > > > > > <property name="openjpa.ConnectionDriverName"
> > > > > > > > value="org.apache.derby.jdbc.EmbeddedDriver"
> > > > > > > />
> > > > > > > > <property name="openjpa.ConnectionUserName"
> > > > > > > value="" />
> > > > > > > > <property name="openjpa.ConnectionPassword"
> > > > > > > value="" />
> > > > > > > >
> > > > > > > > <!--
> > > > > > > > Tell OpenJPA to automatically create tables
> > > > > > > in the
> > > > > > > > database
> > > > > > > > for entities. Note that this should be
> > > > > > > disabled when
> > > > > > > > running against a production database, since
> > > > > > > you
> > > > > > > > probably
> > > > > > > > don't want to be altering the schema at
> > > > > > > runtime.
> > > > > > > > -->
> > > > > > > > <property name="openjpa.jdbc.SynchronizeMappings
> > > > > > > "
> > > > > > > > value="buildSchema" />
> > > > > > > >
> > > > > > > > </properties>
> > > > > > > > </persistence-unit>
> > > > > > > >
> > > > > > > > </persistence>
> > > > > > > >
> > > > > > > >
> > > > > > > > -----------Main.java
> > > > > > > >
> > > > > > > > /*
> > > > > > > > * Licensed to the Apache Software Foundation (ASF) under
> > > > > > > one
> > > > > > > > * or more contributor license agreements. See the NOTICE
> > > > > > > file
> > > > > > > > * distributed with this work for additional information
> > > > > > > > * regarding copyright ownership. The ASF licenses this
> > > > > > > file
> > > > > > > > * to you under the Apache License, Version 2.0 (the
> > > > > > > > * "License"); you may not use this file except in
> > > > > > > compliance
> > > > > > > > * with the License. You may obtain a copy of the License
> > > > > > > at
> > > > > > > > *
> > > > > > > > * http://www.apache.org/licenses/LICENSE-2.0
> > > > > > > > *
> > > > > > > > * Unless required by applicable law or agreed to in
> > > > > > > writing,
> > > > > > > > * software distributed under the License is distributed on
> > > > > > > an
> > > > > > > > * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
> > > > > > > > * KIND, either express or implied. See the License for
> > > > > > > the
> > > > > > > > * specific language governing permissions and limitations
> > > > > > > > * under the License.
> > > > > > > > */
> > > > > > > > package hellojpa;
> > > > > > > >
> > > > > > > > import java.util.*;
> > > > > > > > import javax.persistence.*;
> > > > > > > >
> > > > > > > >
> > > > > > > > /**
> > > > > > > > * A very simple, stand-alone program that stores a new
> > > > > > > entity in the
> > > > > > > > * database and then performs a query to retrieve it.
> > > > > > > > */
> > > > > > > > public class Main {
> > > > > > > >
> > > > > > > > @SuppressWarnings("unchecked")
> > > > > > > > public static void main(String[] args) {
> > > > > > > > System.out.println(System.getProperty("
> > > > > > > java.class.path"));
> > > > > > > > // Create a new EntityManagerFactory using the
> > > > > > > System
> > > > > > > > properties.
> > > > > > > > // The "hellojpa" name will be used to configure
> > > > > > > based on the
> > > > > > > > // corresponding name in the
> > > > > > > META-INF/persistence.xml file
> > > > > > > > EntityManagerFactory factory = Persistence.
> > > > > > > > createEntityManagerFactory("hellojpa",
> > > > > > > > System.getProperties());
> > > > > > > >
> > > > > > > > // Create a new EntityManager from the
> > > > > > > EntityManagerFactory. The
> > > > > > > > // EntityManager is the main object in the
> > > > > > > persistence API, and
> > > > > > > > is
> > > > > > > > // used to create, delete, and query objects, as
> > > > > > > well as access
> > > > > > > > // the current transaction
> > > > > > > > EntityManager em = factory.createEntityManager();
> > > > > > > >
> > > > > > > > // Begin a new local transaction so that we can
> > > > > > > persist a new
> > > > > > > > entity
> > > > > > > > em.getTransaction().begin();
> > > > > > > >
> > > > > > > > // Create and persist a new Message entity
> > > > > > > > em.persist(new Message("Hello Persistence!"));
> > > > > > > >
> > > > > > > > // Commit the transaction, which will cause the
> > > > > > > entity to
> > > > > > > > // be stored in the database
> > > > > > > > em.getTransaction().commit();
> > > > > > > >
> > > > > > > > // It is always good practice to close the
> > > > > > > EntityManager so that
> > > > > > > > // resources are conserved.
> > > > > > > > em.close();
> > > > > > > >
> > > > > > > > // Create a fresh, new EntityManager
> > > > > > > > EntityManager em2 = factory.createEntityManager();
> > > > > > > >
> > > > > > > > // Perform a simple query for all the Message
> > > > > > > entities
> > > > > > > > Query q = em2.createQuery("select m from Message
> > > > > > > m");
> > > > > > > >
> > > > > > > > // Go through each of the entities and print out
> > > > > > > each of their
> > > > > > > > // messages, as well as the date on which it was
> > > > > > > created
> > > > > > > > for (Message m : (List<Message>) q.getResultList())
> > > > > > > {
> > > > > > > > System.out.println(m.getMessage()
> > > > > > > > + " (created on: " + m.getCreated() + ")");
> > > > > > > > }
> > > > > > > >
> > > > > > > > // Again, it is always good to clean up after
> > > > > > > ourselves
> > > > > > > > em2.close();
> > > > > > > > factory.close();
> > > > > > > > }
> > > > > > > > }
> > > > > > > >
> > > > > > > > -----------
> > > > > > > >
> > > > > > >
> > > > > >
> > > > > >
> > > > >
> > > >
> > > >
> > >
> >
>
Re: JPA - Null pointer exception
Posted by Lars Vogel <la...@googlemail.com>.
Hi Mike,
thank you, I must have been blind. Indeed the OpenJPA was missing.
Thank you very, very much and sorry for such a blind spot on my side.
I'll write a short summery on how to set a small OpenJPA up and post it
later to this newsgroup for future reference.
Best regards, Lars
2008/3/12, Michael Dick <mi...@gmail.com>:
>
> The only thing I noticed was that you didn't have OpenJPA specified on the
> classpath. You must have it specified somewhere, unless you've imported all
> the source.
>
> I'm sorry to say that I just replied to you personally, so the users
> mailing list hasn't seen these last few replies. If you'd like to post the
> sample you're using back to users@openjpa.apache.org, then maybe someone
> else will have better luck than I did.
>
> -Mike
>
> On Wed, Mar 12, 2008 at 3:53 PM, Lars Vogel <la...@googlemail.com>
> wrote:
>
> > Hi Mike,
> >
> > thank you. I don't see a difference to "my" setup.
> >
> > If anyone wants to look at my project I uploaded it:
> > http://www.jnerlich.de/JPAExample.zip
> >
> > Cheers, Lars
> >
> >
> > 2008/3/12, Michael Dick <mi...@gmail.com>:
> > >
> > > Hi Lars,
> > >
> > > Here's what I'm using. I don't see anything obviously wrong the ones
> > > you sent me though.
> > >
> > > -Mike
> > >
> > > On Wed, Mar 12, 2008 at 2:52 PM, Lars Vogel <la...@googlemail.com>
> > > wrote:
> > >
> > > > Hi Mike,
> > > >
> > > > I'm running it in Eclipse. Yes, please send me your .classpath and
> > > > .project files. Mine are also attached for reference.
> > > >
> > > > Best regards, Lars
> > > >
> > > > <?xml version="1.0" encoding="UTF-8"?>
> > > > <projectDescription>
> > > > <name>hellopja</name>
> > > > <comment></comment>
> > > > <projects>
> > > > </projects>
> > > > <buildSpec>
> > > > <buildCommand>
> > > > <name>org.eclipse.jdt.core.javabuilder</name>
> > > > <arguments>
> > > > </arguments>
> > > > </buildCommand>
> > > > </buildSpec>
> > > > <natures>
> > > > <nature>org.eclipse.jdt.core.javanature</nature>
> > > > </natures>
> > > > </projectDescription>
> > > >
> > > > <?xml version="1.0" encoding="UTF-8"?>
> > > > <classpath>
> > > > <classpathentry kind="src" path="src"/>
> > > > <classpathentry kind="con" path="
> > > > org.eclipse.jdt.launching.JRE_CONTAINER"/>
> > > > <classpathentry kind="lib" path="C:/Documents and
> > > > Settings/vogella/Desktop/Documents/08_MyDocuments/15_EclipseLibs/openjpa/commons-
> > > > collections-3.2.jar"/>
> > > > <classpathentry kind="lib" path="C:/Documents and
> > > > Settings/vogella/Desktop/Documents/08_MyDocuments/15_EclipseLibs/openjpa/commons-
> > > > lang-2.1.jar"/>
> > > > <classpathentry kind="lib" path="C:/Documents and
> > > > Settings/vogella/Desktop/Documents/08_MyDocuments/15_EclipseLibs/openjpa/commons-
> > > > logging-1.0.4.jar"/>
> > > > <classpathentry kind="lib" path="C:/Documents and
> > > > Settings/vogella/Desktop/Documents/08_MyDocuments/15_EclipseLibs/openjpa/commons-
> > > > pool-1.3.jar"/>
> > > > <classpathentry kind="lib" path="C:/Documents and
> > > > Settings/vogella/Desktop/Documents/08_MyDocuments/15_EclipseLibs/openjpa/derby-
> > > > 10.2.2.0.jar"/>
> > > > <classpathentry kind="lib" path="C:/Documents and
> > > > Settings/vogella/Desktop/Documents/08_MyDocuments/15_EclipseLibs/openjpa/geronimo-jms_1.1_spec-
> > > > 1.0.1.jar"/>
> > > > <classpathentry kind="lib" path="C:/Documents and
> > > > Settings/vogella/Desktop/Documents/08_MyDocuments/15_EclipseLibs/openjpa/geronimo-jpa_3.0_spec-
> > > > 1.0.jar"/>
> > > > <classpathentry kind="lib" path="C:/Documents and
> > > > Settings/vogella/Desktop/Documents/08_MyDocuments/15_EclipseLibs/openjpa/geronimo-jta_1.1_spec-
> > > > 1.1.jar"/>
> > > > <classpathentry kind="lib" path="C:/Documents and
> > > > Settings/vogella/Desktop/Documents/08_MyDocuments/15_EclipseLibs/openjpa/serp-
> > > > 1.13.1.jar"/>
> > > > <classpathentry kind="output" path="bin"/>
> > > > </classpath>
> > > >
> > > >
> > > > 2008/3/12, Michael Dick <mi...@gmail.com>:
> > > >
> > > > > Hi Lars,
> > > > >
> > > > > How are you running the program? You mention projects so you're
> > > > > probably using either Eclipse or Netbeans. I tried something similar to what
> > > > > you've posted and it worked for me in Eclipse. I can send you the .classpath
> > > > > and .project files if that will help.
> > > > >
> > > > > -Mike
> > > > >
> > > > > On Wed, Mar 12, 2008 at 10:22 AM, Lars Vogel <
> > > > > lars.vogel@googlemail.com> wrote:
> > > > >
> > > > > > Hi Venkatesch,
> > > > > >
> > > > > > I did also modify the orginal persistence.xml so that is exactly
> > > > > > the same as
> > > > > > my example to be able to run Main.java directly without the ant
> > > > > > script.
> > > > > >
> > > > > > So in both cases I'm not using the build.xml file anymore. The
> > > > > > only
> > > > > > difference I see is that one version runs the other not.
> > > > > >
> > > > > > Best egards, Lars
> > > > > >
> > > > > > 2008/3/12, Addanki, Venkatesh <Ve...@aquilent.com>:
> > > > > > >
> > > > > > > Lars,
> > > > > > >
> > > > > > > One obvious difference between your code and the out of box
> > > > > > sample is
> > > > > > > the way the driver class and its properties are specified.
> > > > > > build.xml vs
> > > > > > > persistence.xml. It looks like the
> > > > > > org.apache.derby.jdbc.EmbeddedDriver
> > > > > > > class from your persistence.xml is not being found or the
> > > > > > connection url
> > > > > > > is not getting through.
> > > > > > >
> > > > > > > Regards
> > > > > > >
> > > > > > > V
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > -----Original Message-----
> > > > > > > From: Lars Vogel [mailto:lars.vogel@googlemail.com]
> > > > > > > Sent: Wednesday, March 12, 2008 9:22 AM
> > > > > > > To: users@openjpa.apache.org
> > > > > > > Subject: JPA - Null pointer exception
> > > > > > >
> > > > > > > Hi,
> > > > > > >
> > > > > > > I trying to make JPA work for me. The delivered example works
> > > > > > without
> > > > > > > problems, I can also successfully modify this example. The
> > > > > > example was
> > > > > > > based on http://openjpa.apache.org/quick-start.html.
> > > > > > >
> > > > > > > But if I create a new project the Entity Manager returns only
> > > > > > a NULL
> > > > > > > value.
> > > > > > > Error:
> > > > > > >
> > > > > > > Exception in thread "main" java.lang.NullPointerException
> > > > > > > at hellojpa.Main.main(Main.java:44)
> > > > > > >
> > > > > > >
> > > > > > > I use the same files as in the working example. All jars are
> > > > > > included in
> > > > > > > the build path. I assume that the persistence.xml is not found
> > > > > > but to my
> > > > > > > knowledge the classpath is correctly maintained. The path
> > > > > > .../bin
> > > > > > > contains the directory META-INF and here the file
> > > > > > persistence.xml.
> > > > > > >
> > > > > > > Any advice? I must be missing something very simple but cannot
> > > > > > figure it
> > > > > > > out. For example coding please see below.
> > > > > > >
> > > > > > > Best regards, Lars
> > > > > > >
> > > > > > > File structure:
> > > > > > >
> > > > > > > src
> > > > > > > - hellojpa
> > > > > > > - Main.java
> > > > > > > - Message.java
> > > > > > > - META-INF
> > > > > > > - persistence.xml
> > > > > > >
> > > > > > > Same structure in the bin directory.
> > > > > > >
> > > > > > >
> > > > > > > -----------persistence.xml..............
> > > > > > >
> > > > > > > <?xml version="1.0" encoding="UTF-8"?>
> > > > > > > <!--
> > > > > > > Licensed to the Apache Software Foundation (ASF) under one
> > > > > > > or more contributor license agreements. See the NOTICE
> > > > > > file
> > > > > > > distributed with this work for additional information
> > > > > > > regarding copyright ownership. The ASF licenses this file
> > > > > > > to you under the Apache License, Version 2.0 (the
> > > > > > > "License"); you may not use this file except in compliance
> > > > > > > with the License. You may obtain a copy of the License at
> > > > > > >
> > > > > > > http://www.apache.org/licenses/LICENSE-2.0
> > > > > > >
> > > > > > > Unless required by applicable law or agreed to in writing,
> > > > > > > software distributed under the License is distributed on
> > > > > > an
> > > > > > > "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
> > > > > > > KIND, either express or implied. See the License for the
> > > > > > > specific language governing permissions and limitations
> > > > > > > under the License.
> > > > > > > -->
> > > > > > > <persistence xmlns="http://java.sun.com/xml/ns/persistence"
> > > > > > > xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
> > > > > > version="1.0">
> > > > > > >
> > > > > > > <!--
> > > > > > > A persistence unit is a set of listed persistent
> > > > > > entities as
> > > > > > > well
> > > > > > > the configuration of an EntityManagerFactory. We
> > > > > > configure each
> > > > > > > example in a separate persistence-unit.
> > > > > > > -->
> > > > > > > <persistence-unit name="hellojpa"
> > > > > > > transaction-type="RESOURCE_LOCAL">
> > > > > > > <!--
> > > > > > > The default provider can be OpenJPA, or some other
> > > > > > product.
> > > > > > > This element is optional if OpenJPA is the only
> > > > > > JPA provider
> > > > > > > in the current classloading environment, but can
> > > > > > be
> > > > > > > specified
> > > > > > > in cases where there are multiple JPA
> > > > > > implementations
> > > > > > > available.
> > > > > > > -->
> > > > > > >
> > > > > > > <provider>
> > > > > > >
> > > > > > org.apache.openjpa.persistence.PersistenceProviderImpl
> > > > > > > </provider>
> > > > > > >
> > > > > > >
> > > > > > > <!-- We must enumerate each entity in the persistence
> > > > > > unit -->
> > > > > > > <class>hellojpa.Message</class>
> > > > > > >
> > > > > > > <properties>
> > > > > > > <property name="openjpa.ConnectionURL"
> > > > > > >
> > > > > > >
> > > > > > value="jdbc:derby:C:/DerbyDatabases/hellojpa-database5;create=true" />
> > > > > > > <property name="openjpa.ConnectionDriverName"
> > > > > > > value="org.apache.derby.jdbc.EmbeddedDriver"
> > > > > > />
> > > > > > > <property name="openjpa.ConnectionUserName"
> > > > > > value="" />
> > > > > > > <property name="openjpa.ConnectionPassword"
> > > > > > value="" />
> > > > > > >
> > > > > > > <!--
> > > > > > > Tell OpenJPA to automatically create tables in
> > > > > > the
> > > > > > > database
> > > > > > > for entities. Note that this should be
> > > > > > disabled when
> > > > > > > running against a production database, since
> > > > > > you
> > > > > > > probably
> > > > > > > don't want to be altering the schema at
> > > > > > runtime.
> > > > > > > -->
> > > > > > > <property name="openjpa.jdbc.SynchronizeMappings"
> > > > > > > value="buildSchema" />
> > > > > > >
> > > > > > > </properties>
> > > > > > > </persistence-unit>
> > > > > > >
> > > > > > > </persistence>
> > > > > > >
> > > > > > >
> > > > > > > -----------Main.java
> > > > > > >
> > > > > > > /*
> > > > > > > * Licensed to the Apache Software Foundation (ASF) under one
> > > > > > > * or more contributor license agreements. See the NOTICE
> > > > > > file
> > > > > > > * distributed with this work for additional information
> > > > > > > * regarding copyright ownership. The ASF licenses this file
> > > > > > > * to you under the Apache License, Version 2.0 (the
> > > > > > > * "License"); you may not use this file except in compliance
> > > > > > > * with the License. You may obtain a copy of the License at
> > > > > > > *
> > > > > > > * http://www.apache.org/licenses/LICENSE-2.0
> > > > > > > *
> > > > > > > * Unless required by applicable law or agreed to in writing,
> > > > > > > * software distributed under the License is distributed on
> > > > > > an
> > > > > > > * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
> > > > > > > * KIND, either express or implied. See the License for the
> > > > > > > * specific language governing permissions and limitations
> > > > > > > * under the License.
> > > > > > > */
> > > > > > > package hellojpa;
> > > > > > >
> > > > > > > import java.util.*;
> > > > > > > import javax.persistence.*;
> > > > > > >
> > > > > > >
> > > > > > > /**
> > > > > > > * A very simple, stand-alone program that stores a new
> > > > > > entity in the
> > > > > > > * database and then performs a query to retrieve it.
> > > > > > > */
> > > > > > > public class Main {
> > > > > > >
> > > > > > > @SuppressWarnings("unchecked")
> > > > > > > public static void main(String[] args) {
> > > > > > > System.out.println(System.getProperty("java.class.path
> > > > > > "));
> > > > > > > // Create a new EntityManagerFactory using the System
> > > > > > > properties.
> > > > > > > // The "hellojpa" name will be used to configure based
> > > > > > on the
> > > > > > > // corresponding name in the META-INF/persistence.xml
> > > > > > file
> > > > > > > EntityManagerFactory factory = Persistence.
> > > > > > > createEntityManagerFactory("hellojpa",
> > > > > > > System.getProperties());
> > > > > > >
> > > > > > > // Create a new EntityManager from the
> > > > > > EntityManagerFactory. The
> > > > > > > // EntityManager is the main object in the persistence
> > > > > > API, and
> > > > > > > is
> > > > > > > // used to create, delete, and query objects, as well
> > > > > > as access
> > > > > > > // the current transaction
> > > > > > > EntityManager em = factory.createEntityManager();
> > > > > > >
> > > > > > > // Begin a new local transaction so that we can
> > > > > > persist a new
> > > > > > > entity
> > > > > > > em.getTransaction().begin();
> > > > > > >
> > > > > > > // Create and persist a new Message entity
> > > > > > > em.persist(new Message("Hello Persistence!"));
> > > > > > >
> > > > > > > // Commit the transaction, which will cause the entity
> > > > > > to
> > > > > > > // be stored in the database
> > > > > > > em.getTransaction().commit();
> > > > > > >
> > > > > > > // It is always good practice to close the
> > > > > > EntityManager so that
> > > > > > > // resources are conserved.
> > > > > > > em.close();
> > > > > > >
> > > > > > > // Create a fresh, new EntityManager
> > > > > > > EntityManager em2 = factory.createEntityManager();
> > > > > > >
> > > > > > > // Perform a simple query for all the Message entities
> > > > > > > Query q = em2.createQuery("select m from Message m");
> > > > > > >
> > > > > > > // Go through each of the entities and print out each
> > > > > > of their
> > > > > > > // messages, as well as the date on which it was
> > > > > > created
> > > > > > > for (Message m : (List<Message>) q.getResultList()) {
> > > > > > > System.out.println(m.getMessage()
> > > > > > > + " (created on: " + m.getCreated() + ")");
> > > > > > > }
> > > > > > >
> > > > > > > // Again, it is always good to clean up after
> > > > > > ourselves
> > > > > > > em2.close();
> > > > > > > factory.close();
> > > > > > > }
> > > > > > > }
> > > > > > >
> > > > > > > -----------
> > > > > > >
> > > > > >
> > > > >
> > > > >
> > > >
> > >
> > >
> >
>
Re: JPA - Null pointer exception
Posted by Lars Vogel <la...@googlemail.com>.
Hi Venkatesch,
I did also modify the orginal persistence.xml so that is exactly the same as
my example to be able to run Main.java directly without the ant script.
So in both cases I'm not using the build.xml file anymore. The only
difference I see is that one version runs the other not.
Best egards, Lars
2008/3/12, Addanki, Venkatesh <Ve...@aquilent.com>:
>
> Lars,
>
> One obvious difference between your code and the out of box sample is
> the way the driver class and its properties are specified. build.xml vs
> persistence.xml. It looks like the org.apache.derby.jdbc.EmbeddedDriver
> class from your persistence.xml is not being found or the connection url
> is not getting through.
>
> Regards
>
> V
>
>
>
> -----Original Message-----
> From: Lars Vogel [mailto:lars.vogel@googlemail.com]
> Sent: Wednesday, March 12, 2008 9:22 AM
> To: users@openjpa.apache.org
> Subject: JPA - Null pointer exception
>
> Hi,
>
> I trying to make JPA work for me. The delivered example works without
> problems, I can also successfully modify this example. The example was
> based on http://openjpa.apache.org/quick-start.html.
>
> But if I create a new project the Entity Manager returns only a NULL
> value.
> Error:
>
> Exception in thread "main" java.lang.NullPointerException
> at hellojpa.Main.main(Main.java:44)
>
>
> I use the same files as in the working example. All jars are included in
> the build path. I assume that the persistence.xml is not found but to my
> knowledge the classpath is correctly maintained. The path .../bin
> contains the directory META-INF and here the file persistence.xml.
>
> Any advice? I must be missing something very simple but cannot figure it
> out. For example coding please see below.
>
> Best regards, Lars
>
> File structure:
>
> src
> - hellojpa
> - Main.java
> - Message.java
> - META-INF
> - persistence.xml
>
> Same structure in the bin directory.
>
>
> -----------persistence.xml..............
>
> <?xml version="1.0" encoding="UTF-8"?>
> <!--
> Licensed to the Apache Software Foundation (ASF) under one
> or more contributor license agreements. See the NOTICE file
> distributed with this work for additional information
> regarding copyright ownership. The ASF licenses this file
> to you under the Apache License, Version 2.0 (the
> "License"); you may not use this file except in compliance
> with the License. You may obtain a copy of the License at
>
> http://www.apache.org/licenses/LICENSE-2.0
>
> Unless required by applicable law or agreed to in writing,
> software distributed under the License is distributed on an
> "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
> KIND, either express or implied. See the License for the
> specific language governing permissions and limitations
> under the License.
> -->
> <persistence xmlns="http://java.sun.com/xml/ns/persistence"
> xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="1.0">
>
> <!--
> A persistence unit is a set of listed persistent entities as
> well
> the configuration of an EntityManagerFactory. We configure each
> example in a separate persistence-unit.
> -->
> <persistence-unit name="hellojpa"
> transaction-type="RESOURCE_LOCAL">
> <!--
> The default provider can be OpenJPA, or some other product.
> This element is optional if OpenJPA is the only JPA provider
> in the current classloading environment, but can be
> specified
> in cases where there are multiple JPA implementations
> available.
> -->
>
> <provider>
> org.apache.openjpa.persistence.PersistenceProviderImpl
> </provider>
>
>
> <!-- We must enumerate each entity in the persistence unit -->
> <class>hellojpa.Message</class>
>
> <properties>
> <property name="openjpa.ConnectionURL"
>
> value="jdbc:derby:C:/DerbyDatabases/hellojpa-database5;create=true" />
> <property name="openjpa.ConnectionDriverName"
> value="org.apache.derby.jdbc.EmbeddedDriver" />
> <property name="openjpa.ConnectionUserName" value="" />
> <property name="openjpa.ConnectionPassword" value="" />
>
> <!--
> Tell OpenJPA to automatically create tables in the
> database
> for entities. Note that this should be disabled when
> running against a production database, since you
> probably
> don't want to be altering the schema at runtime.
> -->
> <property name="openjpa.jdbc.SynchronizeMappings"
> value="buildSchema" />
>
> </properties>
> </persistence-unit>
>
> </persistence>
>
>
> -----------Main.java
>
> /*
> * Licensed to the Apache Software Foundation (ASF) under one
> * or more contributor license agreements. See the NOTICE file
> * distributed with this work for additional information
> * regarding copyright ownership. The ASF licenses this file
> * to you under the Apache License, Version 2.0 (the
> * "License"); you may not use this file except in compliance
> * with the License. You may obtain a copy of the License at
> *
> * http://www.apache.org/licenses/LICENSE-2.0
> *
> * Unless required by applicable law or agreed to in writing,
> * software distributed under the License is distributed on an
> * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
> * KIND, either express or implied. See the License for the
> * specific language governing permissions and limitations
> * under the License.
> */
> package hellojpa;
>
> import java.util.*;
> import javax.persistence.*;
>
>
> /**
> * A very simple, stand-alone program that stores a new entity in the
> * database and then performs a query to retrieve it.
> */
> public class Main {
>
> @SuppressWarnings("unchecked")
> public static void main(String[] args) {
> System.out.println(System.getProperty("java.class.path"));
> // Create a new EntityManagerFactory using the System
> properties.
> // The "hellojpa" name will be used to configure based on the
> // corresponding name in the META-INF/persistence.xml file
> EntityManagerFactory factory = Persistence.
> createEntityManagerFactory("hellojpa",
> System.getProperties());
>
> // Create a new EntityManager from the EntityManagerFactory. The
> // EntityManager is the main object in the persistence API, and
> is
> // used to create, delete, and query objects, as well as access
> // the current transaction
> EntityManager em = factory.createEntityManager();
>
> // Begin a new local transaction so that we can persist a new
> entity
> em.getTransaction().begin();
>
> // Create and persist a new Message entity
> em.persist(new Message("Hello Persistence!"));
>
> // Commit the transaction, which will cause the entity to
> // be stored in the database
> em.getTransaction().commit();
>
> // It is always good practice to close the EntityManager so that
> // resources are conserved.
> em.close();
>
> // Create a fresh, new EntityManager
> EntityManager em2 = factory.createEntityManager();
>
> // Perform a simple query for all the Message entities
> Query q = em2.createQuery("select m from Message m");
>
> // Go through each of the entities and print out each of their
> // messages, as well as the date on which it was created
> for (Message m : (List<Message>) q.getResultList()) {
> System.out.println(m.getMessage()
> + " (created on: " + m.getCreated() + ")");
> }
>
> // Again, it is always good to clean up after ourselves
> em2.close();
> factory.close();
> }
> }
>
> -----------
>
RE: JPA - Null pointer exception
Posted by "Addanki, Venkatesh" <Ve...@aquilent.com>.
Lars,
One obvious difference between your code and the out of box sample is
the way the driver class and its properties are specified. build.xml vs
persistence.xml. It looks like the org.apache.derby.jdbc.EmbeddedDriver
class from your persistence.xml is not being found or the connection url
is not getting through.
Regards
V
-----Original Message-----
From: Lars Vogel [mailto:lars.vogel@googlemail.com]
Sent: Wednesday, March 12, 2008 9:22 AM
To: users@openjpa.apache.org
Subject: JPA - Null pointer exception
Hi,
I trying to make JPA work for me. The delivered example works without
problems, I can also successfully modify this example. The example was
based on http://openjpa.apache.org/quick-start.html.
But if I create a new project the Entity Manager returns only a NULL
value.
Error:
Exception in thread "main" java.lang.NullPointerException
at hellojpa.Main.main(Main.java:44)
I use the same files as in the working example. All jars are included in
the build path. I assume that the persistence.xml is not found but to my
knowledge the classpath is correctly maintained. The path .../bin
contains the directory META-INF and here the file persistence.xml.
Any advice? I must be missing something very simple but cannot figure it
out. For example coding please see below.
Best regards, Lars
File structure:
src
- hellojpa
- Main.java
- Message.java
- META-INF
- persistence.xml
Same structure in the bin directory.
-----------persistence.xml..............
<?xml version="1.0" encoding="UTF-8"?>
<!--
Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements. See the NOTICE file
distributed with this work for additional information
regarding copyright ownership. The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied. See the License for the
specific language governing permissions and limitations
under the License.
-->
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="1.0">
<!--
A persistence unit is a set of listed persistent entities as
well
the configuration of an EntityManagerFactory. We configure each
example in a separate persistence-unit.
-->
<persistence-unit name="hellojpa"
transaction-type="RESOURCE_LOCAL">
<!--
The default provider can be OpenJPA, or some other product.
This element is optional if OpenJPA is the only JPA provider
in the current classloading environment, but can be
specified
in cases where there are multiple JPA implementations
available.
-->
<provider>
org.apache.openjpa.persistence.PersistenceProviderImpl
</provider>
<!-- We must enumerate each entity in the persistence unit -->
<class>hellojpa.Message</class>
<properties>
<property name="openjpa.ConnectionURL"
value="jdbc:derby:C:/DerbyDatabases/hellojpa-database5;create=true" />
<property name="openjpa.ConnectionDriverName"
value="org.apache.derby.jdbc.EmbeddedDriver" />
<property name="openjpa.ConnectionUserName" value="" />
<property name="openjpa.ConnectionPassword" value="" />
<!--
Tell OpenJPA to automatically create tables in the
database
for entities. Note that this should be disabled when
running against a production database, since you
probably
don't want to be altering the schema at runtime.
-->
<property name="openjpa.jdbc.SynchronizeMappings"
value="buildSchema" />
</properties>
</persistence-unit>
</persistence>
-----------Main.java
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package hellojpa;
import java.util.*;
import javax.persistence.*;
/**
* A very simple, stand-alone program that stores a new entity in the
* database and then performs a query to retrieve it.
*/
public class Main {
@SuppressWarnings("unchecked")
public static void main(String[] args) {
System.out.println(System.getProperty("java.class.path"));
// Create a new EntityManagerFactory using the System
properties.
// The "hellojpa" name will be used to configure based on the
// corresponding name in the META-INF/persistence.xml file
EntityManagerFactory factory = Persistence.
createEntityManagerFactory("hellojpa",
System.getProperties());
// Create a new EntityManager from the EntityManagerFactory. The
// EntityManager is the main object in the persistence API, and
is
// used to create, delete, and query objects, as well as access
// the current transaction
EntityManager em = factory.createEntityManager();
// Begin a new local transaction so that we can persist a new
entity
em.getTransaction().begin();
// Create and persist a new Message entity
em.persist(new Message("Hello Persistence!"));
// Commit the transaction, which will cause the entity to
// be stored in the database
em.getTransaction().commit();
// It is always good practice to close the EntityManager so that
// resources are conserved.
em.close();
// Create a fresh, new EntityManager
EntityManager em2 = factory.createEntityManager();
// Perform a simple query for all the Message entities
Query q = em2.createQuery("select m from Message m");
// Go through each of the entities and print out each of their
// messages, as well as the date on which it was created
for (Message m : (List<Message>) q.getResultList()) {
System.out.println(m.getMessage()
+ " (created on: " + m.getCreated() + ")");
}
// Again, it is always good to clean up after ourselves
em2.close();
factory.close();
}
}
-----------