/*
 * Copyright 2002-2008 the original author or authors.
 *
 * Licensed 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.springframework.orm.jdo;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.Collection;
import java.util.Map;

import javax.jdo.JDOException;
import javax.jdo.PersistenceManager;
import javax.jdo.PersistenceManagerFactory;
import javax.jdo.Query;

import org.springframework.dao.DataAccessException;
import org.springframework.dao.InvalidDataAccessApiUsageException;
import org.springframework.transaction.support.TransactionSynchronizationManager;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;

/**
 * Helper class that simplifies JDO data access code, and converts
 * JDOExceptions into Spring DataAccessExceptions, following the
 * <code>org.springframework.dao</code> exception hierarchy.
 *
 * <p>The central method is <code>execute</code>, supporting JDO access code
 * implementing the {@link JdoCallback} interface. It provides JDO PersistenceManager
 * handling such that neither the JdoCallback implementation nor the calling
 * code needs to explicitly care about retrieving/closing PersistenceManagers,
 * or handling JDO lifecycle exceptions.
 *
 * <p>Typically used to implement data access or business logic services that
 * use JDO within their implementation but are JDO-agnostic in their interface.
 * The latter or code calling the latter only have to deal with business
 * objects, query objects, and <code>org.springframework.dao</code> exceptions.
 *
 * <p>Can be used within a service implementation via direct instantiation
 * with a PersistenceManagerFactory reference, or get prepared in an
 * application context and given to services as bean reference.
 * Note: The PersistenceManagerFactory should always be configured as bean in
 * the application context, in the first case given to the service directly,
 * in the second case to the prepared template.
 *
 * <p>This class can be considered as direct alternative to working with the
 * raw JDO PersistenceManager API (through
 * <code>PersistenceManagerFactoryUtils.getPersistenceManager()</code>).
 * The major advantage is its automatic conversion to DataAccessExceptions, the
 * major disadvantage that no checked application exceptions can get thrown from
 * within data access code. Corresponding checks and the actual throwing of such
 * exceptions can often be deferred to after callback execution, though.
 *
 * <p>{@link LocalPersistenceManagerFactoryBean} is the preferred way of obtaining
 * a reference to a specific PersistenceManagerFactory, at least in a non-EJB
 * environment. The Spring application context will manage its lifecycle,
 * initializing and shutting down the factory as part of the application.
 *
 * <p>Note that lazy loading will just work with an open JDO PersistenceManager,
 * either within a Spring-driven transaction (with JdoTransactionManager or
 * JtaTransactionManager) or within OpenPersistenceManagerInViewFilter/Interceptor.
 * Furthermore, some operations just make sense within transactions,
 * for example: <code>evict</code>, <code>evictAll</code>, <code>flush</code>.
 *
 * <p><b>NOTE: This class requires JDO 2.0 or higher, as of Spring 2.5.</b>
 *
 * @author Juergen Hoeller
 * @since 03.06.2003
 * @see #setPersistenceManagerFactory
 * @see JdoCallback
 * @see javax.jdo.PersistenceManager
 * @see LocalPersistenceManagerFactoryBean
 * @see JdoTransactionManager
 * @see org.springframework.transaction.jta.JtaTransactionManager
 * @see org.springframework.orm.jdo.support.OpenPersistenceManagerInViewFilter
 * @see org.springframework.orm.jdo.support.OpenPersistenceManagerInViewInterceptor
 */
public class JdoTemplate extends JdoAccessor implements JdoOperations {

	private boolean allowCreate = true;

	private boolean exposeNativePersistenceManager = false;


	/**
	 * Create a new JdoTemplate instance.
	 */
	public JdoTemplate() {
	}

	/**
	 * Create a new JdoTemplate instance.
	 * @param pmf PersistenceManagerFactory to create PersistenceManagers
	 */
	public JdoTemplate(PersistenceManagerFactory pmf) {
		setPersistenceManagerFactory(pmf);
		afterPropertiesSet();
	}

	/**
	 * Create a new JdoTemplate instance.
	 * @param pmf PersistenceManagerFactory to create PersistenceManagers
	 * @param allowCreate if a non-transactional PersistenceManager should be created
	 * when no transactional PersistenceManager can be found for the current thread
	 */
	public JdoTemplate(PersistenceManagerFactory pmf, boolean allowCreate) {
		setPersistenceManagerFactory(pmf);
		setAllowCreate(allowCreate);
		afterPropertiesSet();
	}

	/**
	 * Set if a new PersistenceManager should be created when no transactional
	 * PersistenceManager can be found for the current thread.
	 * <p>JdoTemplate is aware of a corresponding PersistenceManager bound to the
	 * current thread, for example when using JdoTransactionManager.
	 * If allowCreate is true, a new non-transactional PersistenceManager will be
	 * created if none found, which needs to be closed at the end of the operation.
	 * If false, an IllegalStateException will get thrown in this case.
	 * @see PersistenceManagerFactoryUtils#getPersistenceManager(javax.jdo.PersistenceManagerFactory, boolean)
	 */
	public void setAllowCreate(boolean allowCreate) {
		this.allowCreate = allowCreate;
	}

	/**
	 * Return if a new PersistenceManager should be created if no thread-bound found.
	 */
	public boolean isAllowCreate() {
		return this.allowCreate;
	}

	/**
	 * Set whether to expose the native JDO PersistenceManager to JdoCallback
	 * code. Default is "false": a PersistenceManager proxy will be returned,
	 * suppressing <code>close</code> calls and automatically applying transaction
	 * timeouts (if any).
	 * <p>As there is often a need to cast to a provider-specific PersistenceManager
	 * class in DAOs that use provider-specific functionality, the exposed proxy
	 * implements all interfaces implemented by the original PersistenceManager.
	 * If this is not sufficient, turn this flag to "true".
	 * @see JdoCallback
	 * @see javax.jdo.PersistenceManager
	 * @see #prepareQuery
	 */
	public void setExposeNativePersistenceManager(boolean exposeNativePersistenceManager) {
		this.exposeNativePersistenceManager = exposeNativePersistenceManager;
	}

	/**
	 * Return whether to expose the native JDO PersistenceManager to JdoCallback
	 * code, or rather a PersistenceManager proxy.
	 */
	public boolean isExposeNativePersistenceManager() {
		return this.exposeNativePersistenceManager;
	}


	public Object execute(JdoCallback action) throws DataAccessException {
		return execute(action, isExposeNativePersistenceManager());
	}

	public Collection executeFind(JdoCallback action) throws DataAccessException {
		Object result = execute(action, isExposeNativePersistenceManager());
		if (result != null && !(result instanceof Collection)) {
			throw new InvalidDataAccessApiUsageException(
					"Result object returned from JdoCallback isn't a Collection: [" + result + "]");
		}
		return (Collection) result;
	}

	/**
	 * Execute the action specified by the given action object within a
	 * PersistenceManager.
	 * @param action callback object that specifies the JDO action
	 * @param exposeNativePersistenceManager whether to expose the native
	 * JDO persistence manager to callback code
	 * @return a result object returned by the action, or <code>null</code>
	 * @throws org.springframework.dao.DataAccessException in case of JDO errors
	 */
	public Object execute(JdoCallback action, boolean exposeNativePersistenceManager) throws DataAccessException {
		Assert.notNull(action, "Callback object must not be null");

		PersistenceManager pm = PersistenceManagerFactoryUtils.getPersistenceManager(
		    getPersistenceManagerFactory(), isAllowCreate());
		boolean existingTransaction =
		    TransactionSynchronizationManager.hasResource(getPersistenceManagerFactory());
		try {
			PersistenceManager pmToExpose = (exposeNativePersistenceManager ? pm : createPersistenceManagerProxy(pm));
			Object result = action.doInJdo(pmToExpose);
			flushIfNecessary(pm, existingTransaction);
			return postProcessResult(result, pm, existingTransaction);
		}
		catch (JDOException ex) {
			throw convertJdoAccessException(ex);
		}
		catch (RuntimeException ex) {
			// callback code threw application exception
			throw ex;
		}
		finally {
			PersistenceManagerFactoryUtils.releasePersistenceManager(pm, getPersistenceManagerFactory());
		}
	}

	/**
	 * Create a close-suppressing proxy for the given JDO PersistenceManager.
	 * Called by the <code>execute</code> method.
	 * <p>The proxy also prepares returned JDO Query objects.
	 * @param pm the JDO PersistenceManager to create a proxy for
	 * @return the PersistenceManager proxy, implementing all interfaces
	 * implemented by the passed-in PersistenceManager object (that is,
	 * also implementing all provider-specific extension interfaces)
	 * @see javax.jdo.PersistenceManager#close()
	 * @see #execute(JdoCallback, boolean)
	 * @see #prepareQuery
	 */
	protected PersistenceManager createPersistenceManagerProxy(PersistenceManager pm) {
		Class[] ifcs = ClassUtils.getAllInterfacesForClass(pm.getClass(), getClass().getClassLoader());
		return (PersistenceManager) Proxy.newProxyInstance(
				getClass().getClassLoader(), ifcs, new CloseSuppressingInvocationHandler(pm));
	}

	/**
	 * Post-process the given result object, which might be a Collection.
	 * Called by the <code>execute</code> method.
	 * <p>Default implementation always returns the passed-in Object as-is.
	 * Subclasses might override this to automatically detach result
	 * collections or even single result objects.
	 * @param pm the current JDO PersistenceManager
	 * @param result the result object (might be a Collection)
	 * @param existingTransaction if executing within an existing transaction
	 * (within an existing JDO PersistenceManager that won't be closed immediately)
	 * @return the post-processed result object (can be simply be the passed-in object)
	 * @see #execute(JdoCallback, boolean)
	 */
	protected Object postProcessResult(Object result, PersistenceManager pm, boolean existingTransaction) {
		return result;
	}


	//-------------------------------------------------------------------------
	// Convenience methods for load, save, delete
	//-------------------------------------------------------------------------

	public Object getObjectById(final Object objectId) throws DataAccessException {
		return execute(new JdoCallback() {
			public Object doInJdo(PersistenceManager pm) throws JDOException {
				return pm.getObjectById(objectId, true);
			}
		}, true);
	}

	public Object getObjectById(final Class entityClass, final Object idValue) throws DataAccessException {
		return execute(new JdoCallback() {
			public Object doInJdo(PersistenceManager pm) throws JDOException {
				return pm.getObjectById(entityClass, idValue);
			}
		}, true);
	}

	public void evict(final Object entity) throws DataAccessException {
		execute(new JdoCallback() {
			public Object doInJdo(PersistenceManager pm) throws JDOException {
				pm.evict(entity);
				return null;
			}
		}, true);
	}

	public void evictAll(final Collection entities) throws DataAccessException {
		execute(new JdoCallback() {
			public Object doInJdo(PersistenceManager pm) throws JDOException {
				pm.evictAll(entities);
				return null;
			}
		}, true);
	}

	public void evictAll() throws DataAccessException {
		execute(new JdoCallback() {
			public Object doInJdo(PersistenceManager pm) throws JDOException {
				pm.evictAll();
				return null;
			}
		}, true);
	}

	public void refresh(final Object entity) throws DataAccessException {
		execute(new JdoCallback() {
			public Object doInJdo(PersistenceManager pm) throws JDOException {
				pm.refresh(entity);
				return null;
			}
		}, true);
	}