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[JPA 2] Adding support to WebLogic 10.3.5 for JPA 2

March 1st, 2013 No comments

WebLogic 10.3.5 is JAVA EE 5 certified. However JPA 2 is not part of the JAVA EE 5 (2006) specifications, it is part of the JAVA EE 6 (2009) specifications.
So since WebLogic Server implements the Java EE 5 specification, it is not required to support JPA 2. However it is possible to add support to WebLogic 10.3.5 for JPA 2. Look no further, the answer is of course on Oracle WebLogic website: Using Oracle TopLink with Oracle WebLogic Server

A default WebLogic installation already contains the files needed :

javax.persistence_1.0.0.0_2-0-0.jar
com.oracle.jpa2support_1.0.0.0_2-0.jar

So if you make the choice to configure things manually then you do not need to install a patch.
It is just a matter of declaring a PRE_CLASSPATH environment variable in the file commEnv.cmd (Windows) or commEnv.sh (Linux) located in the WL_HOME/common/bin/ folder.

Under Windows :

@rem JPA 2 activation

set PRE_CLASSPATH=%BEA_HOME%\modules\javax.persistence_1.0.0.0_2-0-0.jar;%BEA_HOME%\modules\com.oracle.jpa2support_1.0.0.0_2-0.jar

Under Linux :

PRE_CLASSPATH=${BEA_HOME}/modules/javax.persistence_1.0.0.0_2-0-0.jar:${BEA_HOME}/modules/com.oracle.jpa2support_1.0.0.0_2-0.jar
export PRE_CLASSPATH

If you do not configure WebLogic 10.3.5 to support JPA 2 you will get an error message like this one :

nested exception is:
	javax.ejb.EJBException: what do i do: seems an odd quirk of the EJB spec.
  The exception is:java.lang.NoSuchMethodError: javax.persistence.EntityManager.createQuery(Ljava/lang/String;Ljava/lang/Class;)Ljavax/persistence/TypedQuery;;
nested exception is: javax.ejb.EJBException: what do i do: seems an odd quirk of the EJB spec.
The exception is:java.lang.NoSuchMethodError: javax.persistence.EntityManager.createQuery(Ljava/lang/String;Ljava/lang/Class;)Ljavax/persistence/TypedQuery;

javax.ejb.EJBException: what do i do: seems an odd quirk of the EJB spec.
 The exception is:java.lang.NoSuchMethodError: javax.persistence.EntityManager.createQuery(Ljava/lang/String;Ljava/lang/Class;)Ljavax/persistence/TypedQuery;

There is no need to edit the file weblogic-application.xml and to add some additional prefered application package. That one for instance works :

<?xml version="1.0" encoding="UTF-8" ?>
<weblogic-application xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns:wls="http://www.bea.com/ns/weblogic/90"
	xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/j2ee_1_4.xsd http://www.bea.com/ns/weblogic/90 http://www.bea.com/ns/weblogic/90/weblogic-application.xsd">
	<prefer-application-packages>
		<package-name>org.apache.commons.lang.*</package-name>
		<package-name>org.eclipse.persistence.*</package-name>
	</prefer-application-packages>
	<application-param>
		<param-name>webapp.encoding.default</param-name>
		<param-value>UTF-8</param-value>
	</application-param>
	<session-descriptor>
		<persistent-store-type>replicated_if_clustered</persistent-store-type>
	</session-descriptor>
</weblogic-application>


Categories: Criteria, JPA, JPQL, WebLogic Server Tags:

[JPA 2] Criteria API and MetaModel

September 12th, 2012 No comments

I want to mention the Criteria API, a very cool API which in my opinion is not used as much as it should be. The developers who implement the specification (JSR 317: Java Persistence 2.0) do an impressive work. Thanks to them we have an API that makes it possible to write type safe queries in an object oriented way.
Usually Java developers write queries using JPQL or they write native queries. The fact is that the API Criteria has a (small) learning curve : you have to explore the API and study some basic queries examples before writing your own queries. The first time you use it, it does not seem as intuitive as JPQL.

The Criteria API is particularly convenient when writing queries which do not have a static where clause. For instance in the case of a web page where the user can make a research based on optional criterias. Then the generated query is not always the same.

The Criteria API has its advantages and its disadvantages : it produces typesafe queries that can be checked at compile time but on the other hand queries can be a bit hard to read (apparently unlike QueryDSL or EasyCriteria).
Another advantage is that it can help to avoid SQL injection since the user input is validated or escaped by the JDBC driver (which is not the case with native queries).

To create typesafe queries, one uses the canonical metamodel class associated to an entity (an idea originally proposed by Gavin King, as far as i know). A possible definition of a metamodel class could be that one : it is a class that provides meta information about a managed entity. By default, it has the same name as the entity plus an underscore. For instance if an entity is called Employee then the metamodel class is called Employee_. It is annotated with the annotation javax.persistence.StaticMetamodel.
Fortunately you do not have to write them, you can generate them using an annotation processor, through Eclipse or a Maven plugin for instance.
I chose to generate the metamodel classes with the help of the Hibernate Metamodel Generator (an annotation processor) and the maven-processor-plugin maven plugin, at each build so that they are updated whenever the entities are modified. It is a good way to keep the metamodel classes up to date.

<plugin>
<groupId>org.bsc.maven</groupId>
<artifactId>maven-processor-plugin</artifactId>
<version>2.0.5</version>
<dependencies>
<!-- Annotation processor to generate the JPA 2.0 metamodel classes for typesafe criteria queries -->
  <dependency>
    <groupId>org.hibernate</groupId>
    <artifactId>hibernate-jpamodelgen</artifactId>
    <version>1.2.0.Final</version>
  </dependency>
</dependencies>
<executions>
  <execution>
    <id>process</id>
    <goals>
      <goal>process</goal>
    </goals>
    <phase>generate-sources</phase>
    <configuration>
      <outputDirectory>${project.basedir}/src/main/.metamodel/</outputDirectory>
      <processors>
        <processor>org.hibernate.jpamodelgen.JPAMetaModelEntityProcessor</processor>
      </processors>
    </configuration>
  </execution>
</executions>
</plugin>

<!--  add sources (classes generated inside the .metamodel folder) to the build -->
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>build-helper-maven-plugin</artifactId>
<version>1.7</version>
<executions>
  <execution>
    <id>add-source</id>
    <phase>generate-sources</phase>
    <goals>
      <goal>add-source</goal>
    </goals>
    <configuration>
      <sources>
        <source>${basedir}/src/main/.metamodel</source>
      </sources>
    </configuration>
  </execution>
</executions>
</plugin>

And here is the kind of dynamic query one can create :
Read more…

Categories: Criteria, Java, Java EE, JPA, JPQL Tags:

My book on EJB 3 is now on sale

July 3rd, 2010 No comments

I received an email from the editor informing me that the book is now printed and will be available in bookstores next week (from July 5th, 2010).

It is already available for sale on Amazon and ENI.

An online version is also available.

Here is the cover of the book :

SO3EJB_max

Autocomplete with jQuery, Struts 2, EJB 3 and JPQL

April 8th, 2010 No comments

If you are looking for a way to fill a field and perform a live search, in an asynchronous way, look no further.
jQuery autocompleter is a jQuery plugin that performs real-time autocompletion of a text-field.

You need jQuery and the jQuery plugin autocomplete of course.

Read more…

Categories: Ajax, EJB 3.0, JPQL, jQuery, Struts 2 Tags: