Question

with my RCP program I have the problem that I want to have more than one copy running on my PC. The first instance runs very good.
If I start the second instance, everything is fine until I want to access the database.

Using this code:

..    
Map properties = new HashMap();
            properties.put("javax.persistence.jdbc.driver", dbDriver);
            properties.put("javax.persistence.jdbc.url", dbUrl);
            properties.put("javax.persistence.jdbc.user", dbUser);
            properties.put("javax.persistence.jdbc.password", dbPass);
            try {
                factory = Persistence.createEntityManagerFactory(
                        PERSISTENCE_UNIT_NAME, properties);
            } catch (Exception e) {
                System.out.println(e);
            }
            em=factory.createEntityManager(); // the second instance stops here
    ...

with an persistence.xml of

<?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="default">
        <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider> 

        <class>myclasshere</class>


        <properties>
            <property name="eclipselink.ddl-generation" value="create-tables" />
            <property name="eclipselink.ddl-generation.output-mode" value="database" />     

            <property name="eclipselink.jdbc.read-connections.min" value="1" />
            <property name="eclipselink.jdbc.write-connections.min" value="1" />
            <property name="eclipselink.jdbc.batch-writing" value="JDBC" />
            <property name="eclipselink.logging.level" value="SEVERE" />
            <property name="eclipselink.logging.timestamp" value="false" />
            <property name="eclipselink.logging.session" value="false" />
            <property name="eclipselink.logging.thread" value="false" />    
        </properties>
    </persistence-unit>
</persistence>

The program stalls / does not continue in the second instance beyond this step:

em=factory.createEntityManager();

Debugging the program step by step showed me, that nothing happens at this point. Perhaps the program runs into a timeout. I havent been wainting for more than 1 minute….

Do you have any clues what might cause this stall might?

Answer 1

In the debugger, stop all threads (select the application and click the pause button) and then check which thread hangs in Object.wait(). One of them must be related to your problem. Check the stack traces for instances of EclipseLink to find out which one. That might give you a clue what is going on.