Integration von Hibernate in die OSGi Service Architektur

package org.hibernate.osgi;

import org.hibernate.Session;

/**
 * Service responsible for creating and releasing of sessions in a given Context
 * 
 * @author Christoph Läubrich
 * 
 */
public interface SessionContext {

	/**
	 * Creates and returns a session in this context. Be sure to release this
	 * session some time later even if an exception occurs! To safely access a
	 * session object without the need to take care about sessions and releasing
	 * it, use the # {@link #accessSession(SessionAccess)} method
	 * 
	 * @return the freshly created session
	 */
	public Session getSession();

	/**
	 * Releases a session back to the context. Each session obtained from the
	 * context should be released after usage. If the session has an open
	 * transaction, this one is rolled back. If the session is open, it will be
	 * closed
	 * 
	 * @param session
	 */
	public void releaseSession(Session session);

	/**
	 * 
	 * @return an ID describing this context, in most cases a combination of
	 *         host, port and schema
	 */
	public String getID();

	/**
	 * Provides a way of save accessing a session. This means, a session is
	 * obtained from the context, passed to the access object, and then is
	 * automatically released afterwards even if an exception occurs.
	 * 
	 * @param <T>
	 * @param access
	 * @return
	 */
	public <T> T accessSession(SessionAccess<T> access);

}

package org.hibernate.osgi;

import org.hibernate.Session;
import org.hibernate.Transaction;

/**
 * Access Interface to access a session
 * 
 * @author Christoph Läubrich
 * @param <T>
 */
public interface SessionAccess<T> {
    /**
     * Provides a session for accession data object. The transaction for this
     * session is already started. To commit changes call
     * {@link Session#getTransaction()}{@link Transaction#commit()} otherwhise
     * it will be rolled back automatically
     * 
     * @param session
     * @return
     */
    public T access(Session session);

}

Thread thread = Thread.currentThread();
ClassLoader contextClassLoader = thread.getContextClassLoader();
ClassLoader loader = new ClassLoader(contextClassLoader) {

    /* (non-Javadoc)
     * @see java.lang.ClassLoader#findClass(java.lang.String)
     */
    @Override
    protected Class<?> findClass(String name) throws ClassNotFoundException {
        return SessionHandler.class.getClassLoader().loadClass(name);
    }

};
thread.setContextClassLoader(loader);
factory = configuration.buildSessionFactory();
thread.setContextClassLoader(contextClassLoader);

package de.laeubisoft.hibernatetest.data;

import java.io.Serializable;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;

/**
 * @author Christoph Läubrich
 */
@Entity
@Table(name = "test", schema = "test")
public class TestDAO implements Serializable {

    private static final long serialVersionUID = 7827517804260638035L;

    @Id
    @Column(name = "id")
    private long              id;

    @Column(name = "text")
    private String            text;

    public void setId(long id) {
        this.id = id;
    }

    public long getId() {
        return id;
    }

    public void setText(String text) {
        this.text = text;
    }

    public String getText() {
        return text;
    }

    /* (non-Javadoc)
     * @see java.lang.Object#toString()
     */
    @Override
    public String toString() {
        return "(" + id + ") " + text;
    }
}

final Map<String, Class<?>> mappedClasses = new Hashtable<String, Class<?>>();

...

Thread thread = Thread.currentThread();
ClassLoader contextClassLoader = thread.getContextClassLoader();
ClassLoader loader = new ClassLoader(contextClassLoader) {

    /* (non-Javadoc)
     * @see java.lang.ClassLoader#findClass(java.lang.String)
     */
    @Override
    protected Class<?> findClass(String name) throws ClassNotFoundException {
        if (mappedClasses.containsKey(name)) {
            Class<?> daoClass = mappedClasses.get(name);
            if (daoClass != null) {
                return daoClass;
            }
        }
        if (OSGiConnectionProvider.class.getName().equals(name)) {
            return SessionHandler.class.getClassLoader().loadClass(name);
        }
        return super.findClass(name);
    }

};
thread.setContextClassLoader(loader);
LOG.trace("[{}] build session factory for configuration with delegation contextloader {}", id, contextClassLoader);
factory = configuration.buildSessionFactory();
thread.setContextClassLoader(contextClassLoader);