JPAModule.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 org.apache.ode.di.guice.jpa;

import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;
import java.util.logging.Level;
import java.util.logging.Logger;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.PersistenceContext;
import javax.persistence.PersistenceUnit;

import com.google.inject.AbstractModule;
import com.google.inject.MembersInjector;
import com.google.inject.TypeLiteral;
import com.google.inject.matcher.Matchers;
import com.google.inject.spi.TypeEncounter;
import com.google.inject.spi.TypeListener;

public class JPAModule extends AbstractModule {

	public static Logger log = Logger.getLogger(JPAModule.class.getName());

	protected void configure() {

		bindListener(Matchers.any(), new JPATypeListener());
	}

	public static class JPATypeListener implements TypeListener {

		Map<String, EntityManagerFactory> pus = new HashMap<String, EntityManagerFactory>();

		public <T> void hear(TypeLiteral<T> typeLiteral, TypeEncounter<T> typeEncounter) {
			for (Field field : typeLiteral.getRawType().getDeclaredFields()) {
				if (field.getType() == EntityManager.class || field.getType() == EntityManagerFactory.class) {
					String unitName = null;
					if (field.isAnnotationPresent(PersistenceContext.class)) {
						PersistenceContext pc = field.getAnnotation(PersistenceContext.class);
						unitName = pc.unitName();
					} else if (field.isAnnotationPresent(PersistenceUnit.class)) {
						PersistenceUnit pc = field.getAnnotation(PersistenceUnit.class);
						unitName = pc.unitName();
					}
					if (unitName != null) {
						EntityManagerFactory emf = pus.get(unitName);
						if (emf == null) {
							emf = Persistence.createEntityManagerFactory(unitName);
							pus.put(unitName, emf);
						}
						typeEncounter.register(new JPASessionMembersInjector(field, emf));
					}

				}

			}
		}
	}

	public static class JPASessionMembersInjector<T> implements MembersInjector<T> {
		private final Field field;
		private final EntityManagerFactory emf;

		JPASessionMembersInjector(Field field, EntityManagerFactory emf) {
			this.field = field;
			this.emf = emf;
			field.setAccessible(true);
		}

		public void injectMembers(T t) {
			try {
				if (field.getType() == EntityManager.class) {
					field.set(t, emf.createEntityManager());
					//TODO How will the entity manager.close() method be invoked on disposal?
				} else if (field.getType() == EntityManagerFactory.class) {
					field.set(t, emf);
				} else {
					throw new Exception(String.format("Unexpected type %s", field.getType().getName()));
				}
			} catch (Throwable e) {
				log.log(Level.SEVERE, "", e);
				throw new RuntimeException(e);
			}
		}
	}

}