PersistenceEnvBuilder.java

/**
 * Licensed to The Apereo Foundation under one or more contributor license
 * agreements. See the NOTICE file distributed with this work for additional
 * information regarding copyright ownership.
 *
 *
 * The Apereo Foundation licenses this file to you under the Educational
 * Community 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://opensource.org/licenses/ecl2.txt
 *
 * 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.opencastproject.util.persistence;

import static org.opencastproject.util.data.Collections.map;

import org.opencastproject.util.data.Function0;
import org.opencastproject.util.data.Lazy;

import java.util.Map;

import javax.persistence.spi.PersistenceProvider;

/**
 * Builder for persistence environments.
 * Useful in OSGi bound services where required properties are injected by the OSGi environment.
 */
public final class PersistenceEnvBuilder {
  private Map<String, Object> persistenceProperties = map();
  private PersistenceProvider persistenceProvider;
  private String persistenceUnit;
  private Lazy<PersistenceEnv> penv = Lazy.lazy(new Function0<PersistenceEnv>() {
    @Override public PersistenceEnv apply() {
      if (persistenceProvider == null) {
        throw new IllegalStateException("Persistence provider has not been set yet");
      }
      if (persistenceUnit == null) {
        throw new IllegalStateException("Persistence unit has not been set yet");
      }
      return PersistenceEnvs.persistenceEnvironment(persistenceProvider, persistenceUnit, persistenceProperties);
    }
  });

  public PersistenceEnvBuilder() {
  }

  public PersistenceEnvBuilder(String persistenceUnit) {
    this.persistenceUnit = persistenceUnit;
  }

  /** Set the mandatory name of the persistence unit. */
  public void setPersistenceUnit(String name) {
    this.persistenceUnit = name;
  }

  /** Set the optional persistence properties. */
  public void setPersistenceProperties(Map<String, Object> properties) {
    this.persistenceProperties = properties;
  }

  /** Set the mandatory persistence provider. */
  public void setPersistenceProvider(PersistenceProvider provider) {
    this.persistenceProvider = provider;
  }

  /** Builds the persistence env. Always returns the same environment so it may be safely called multiple times. */
  public PersistenceEnv buildOrGet() {
    return penv.value();
  }
}