Spring / Toplink / MySQL set up

28th August 2008

Spring / Toplink / MySQL set up

Spring is an amazing framework in Java. However, the set up pain was really huge for a Tomcat / Toplink / MySQL set up. Here's how I finally managed to do it.

According the Spring documentation, here's how you're supposed to do it.

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:context="http://www.springframework.org/schema/context"
  xmlns:p="http://www.springframework.org/schema/p"
  xmlns:tx="http://www.springframework.org/schema/tx"
  xsi:schemaLocation="http://www.springframework.org/schema/beans
  http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
  http://www.springframework.org/schema/context
  http://www.springframework.org/schema/context/spring-context-2.5.xsd
  http://www.springframework.org/schema/tx
  http://www.springframework.org/schema/tx/spring-tx-2.0.xsd" >

 <bean 
class="org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor"/>
 <bean id="entityManagerFactory" 
class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
 <property name="dataSource" ref="dataSource"/>
 <property name="jpaVendorAdapter">
 <bean class="org.springframework.orm.jpa.vendor.TopLinkJpaVendorAdapter">
  <property name="showSql" value="true"/>
  <property name="generateDdl" value="false"/>
  <property name="databasePlatform" 
value="oracle.toplink.essentials.platform.database.MySQL4Platform"/>
 </bean>
</property>
<property name="loadTimeWeaver">
<bean class="org.springframework.instrument.classloading.SimpleLoadTimeWeaver"/>
</property>
</bean>
<bean id="dataSource"
  class="org.springframework.jdbc.datasource.DriverManagerDataSource">
 <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
 <property name="url" value="jdbc:mysql://localhost:3306/mydatabase"/>
 <property name="username" value="myuser"/>
 <property name="password" value="mypass"/>
</bean>
 <bean id="transactionManager" 
class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="entityManagerFactory"/>
 </bean>
</beans>

The advantage of using the Spring set up is that you can use Spring to inject an entityManager into your data access objects. Unfortunately, although I fiddled and tried many times, it just didn't work over Tomcat. I got it working fine for my unit tests so I ended up having a seperate Spring/Toplink config file.

First I established a javax.sql.DataSource datasource connection in Tomcat. I did this by sticking it in the /META-INF/context.xml file

<Resource
    auth="Container"
    name="jdbc/mycon"
    type="javax.sql.DataSource"
    password="mypass"
    driverClassName="com.mysql.jdbc.Driver"
    maxIdle="2"
    maxWait="5000"
    username="myuser"
    url="jdbc:mysql://localhost:3306/mydatabase?characterEncoding=UTF-8"
    maxActive="4"/>

The characterEncoding proved necessary as I've outlined here

Next, I set up a persistence file in /WEB-INF/classes/META-INF/persistence.xml

<?xml version="1.0" encoding="UTF-8"?>

  <persistence 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"

  version="1.0">

<persistence-unit name="mypersistence" transaction-type="RESOURCE_LOCAL">

 <provider>oracle.toplink.essentials.ejb.cmp3.EntityManagerFactoryProvider</provider>

  <non-jta-data-source>java:comp/env/jdbc/mycon</non-jta-data-source>

 <class>com.yourclass</class>
<properties>

  <property name="toplink.weaving" value="true"/>

  <property name="toplink.cache.type.default" value="Full"/>

  <property name="toplink.cache.size.default" value="1"/>
  <property name="toplink.logging.level" value="FINE"/>

  <property name="toplink.session.customizer" 
value="classes.ToplinkSessionCustomiser"/>

</properties>
 </persistence-unit>
</persistence>

To get Toplink to pick up the DataSource, I had to use the toplink.session.customizer property. Here's the class

import oracle.toplink.essentials.tools.sessionconfiguration.SessionCustomizer;

import oracle.toplink.essentials.sessions.Session;

import oracle.toplink.essentials.jndi.JNDIConnector;
/**
  * This is what is needed to get a JNDI database connection
  * http://forums.oracle.com/forums/thread.jspa?threadID=519351&tstart=105
  */

  public class ToplinkSessionCustomiser implements SessionCustomizer {

    public ToplinkSessionCustomiser() {  }
     public void customize(Session session) throws Exception {

       JNDIConnector connector = (JNDIConnector) session.getLogin().getConnector();

       connector.setLookupType(JNDIConnector.STRING_LOOKUP);
     }

  }
  

Next I put together an EntityManager

import javax.persistence.Persistence;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityManager;
public class PersistenceUtil {

  private static EntityManagerFactory emf;

  private static String entity_name = "mypersistence";

private PersistenceUtil() {  }
 public static EntityManagerFactory getEMF() {
   return getEMF();
 }
 public static EntityManager getManager() {
   return getEMF().createEntityManager();
 }


 public static EntityManagerFactory getEMF() {
  if (emf == null) {
  emf = Persistence.createEntityManagerFactory(entity_name);
  }
  return emf;
  }
}

I had to put spring-tomcat-weaver.jar into my /tomcat/common/lib folder

Finally, I was able to write some code to stuff to and from the database

import javax.persistence.Query;
/**
  * @author Kevin Saunders, saunderswebsolutions.com
  */
@NamedQuery(
  name = "userById",
  query = "SELECT t FROM MyUserClass t WHERE t.userid = :userid"
  )
  public class EmailService {

  private EntityManager em;
public final EntityManager getEntityManager() {

  if (em == null) {
  return em = PersistenceUtil.getManager();
  }
  return em;
  }
 public MyUserClass getEmail(Integer userid) {

  Query query = getEntityManager().createNamedQuery("userById");
  query.setParameter("userid", userid);
  return query.getSingleResult();
  }

  }
 

I hope this helps someone to cut down on the set up time needed to get Spring working with Tomcat.

If you are having problems getting MySQL to maintain a connection to Toplink, click here