Spring Framework example source code file (SingleConnectionFactory.java)

This example Spring Framework source code file (SingleConnectionFactory.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Spring Framework tags/keywords

cci, closesuppressinginvocationhandler, connection, connection, connectionspec, disposablebean, object, object, reflection, resourceexception, resourceexception, singleconnectionfactory, singleconnectionfactory, target, throwable

The Spring Framework SingleConnectionFactory.java source code

/*
 * Copyright 2002-2006 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.jca.cci.connection;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

import javax.resource.NotSupportedException;
import javax.resource.ResourceException;
import javax.resource.cci.Connection;
import javax.resource.cci.ConnectionFactory;
import javax.resource.cci.ConnectionSpec;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.factory.DisposableBean;
import org.springframework.util.Assert;

/**
 * A CCI ConnectionFactory adapter that returns the same Connection on all
 * <code>getConnection calls, and ignores calls to
 * <code>Connection.close().
 *
 * <p>Useful for testing and standalone environments, to keep using the same
 * Connection for multiple CciTemplate calls, without having a pooling
 * ConnectionFactory, also spanning any number of transactions.
 *
 * <p>You can either pass in a CCI Connection directly, or let this
 * factory lazily create a Connection via a given target ConnectionFactory.
 *
 * @author Juergen Hoeller
 * @since 1.2
 * @see #getConnection()
 * @see javax.resource.cci.Connection#close()
 * @see org.springframework.jca.cci.core.CciTemplate
 */
public class SingleConnectionFactory extends DelegatingConnectionFactory implements DisposableBean {

	protected final Log logger = LogFactory.getLog(getClass());

	/** Wrapped Connection */
	private Connection target;

	/** Proxy Connection */
	private Connection connection;

	/** Synchronization monitor for the shared Connection */
	private final Object connectionMonitor = new Object();


	/**
	 * Create a new SingleConnectionFactory for bean-style usage.
	 * @see #setTargetConnectionFactory
	 */
	public SingleConnectionFactory() {
	}

	/**
	 * Create a new SingleConnectionFactory that always returns the
	 * given Connection.
	 * @param target the single Connection
	 */
	public SingleConnectionFactory(Connection target) {
		Assert.notNull(target, "Target Connection must not be null");
		this.target = target;
		this.connection = getCloseSuppressingConnectionProxy(target);
	}

	/**
	 * Create a new SingleConnectionFactory that always returns a single
	 * Connection that it will lazily create via the given target
	 * ConnectionFactory.
	 * @param targetConnectionFactory the target ConnectionFactory
	 */
	public SingleConnectionFactory(ConnectionFactory targetConnectionFactory) {
		Assert.notNull(targetConnectionFactory, "Target ConnectionFactory must not be null");
		setTargetConnectionFactory(targetConnectionFactory);
	}

	/**
	 * Make sure a Connection or ConnectionFactory has been set.
	 */
	public void afterPropertiesSet() {
		if (this.connection == null && getTargetConnectionFactory() == null) {
			throw new IllegalArgumentException("Connection or targetConnectionFactory is required");
		}
	}


	public Connection getConnection() throws ResourceException {
		synchronized (this.connectionMonitor) {
			if (this.connection == null) {
				initConnection();
			}
			return this.connection;
		}
	}

	public Connection getConnection(ConnectionSpec connectionSpec) throws ResourceException {
		throw new NotSupportedException(
				"SingleConnectionFactory does not support custom ConnectionSpec");
	}

	/**
	 * Close the underlying Connection.
	 * The provider of this ConnectionFactory needs to care for proper shutdown.
	 * <p>As this bean implements DisposableBean, a bean factory will
	 * automatically invoke this on destruction of its cached singletons.
	 */
	public void destroy() {
		resetConnection();
	}


	/**
	 * Initialize the single underlying Connection.
	 * <p>Closes and reinitializes the Connection if an underlying
	 * Connection is present already.
	 * @throws javax.resource.ResourceException if thrown by CCI API methods
	 */
	public void initConnection() throws ResourceException {
		if (getTargetConnectionFactory() == null) {
			throw new IllegalStateException("targetConnectionFactory is required for lazily initializing a Connection");
		}
		synchronized (this.connectionMonitor) {
			if (this.target != null) {
				closeConnection(this.target);
			}
			this.target = doCreateConnection();
			prepareConnection(this.target);
			if (logger.isInfoEnabled()) {
				logger.info("Established shared CCI Connection: " + this.target);
			}
			this.connection = getCloseSuppressingConnectionProxy(this.target);
		}
	}

	/**
	 * Reset the underlying shared Connection, to be reinitialized on next access.
	 */
	public void resetConnection() {
		synchronized (this.connectionMonitor) {
			if (this.target != null) {
				closeConnection(this.target);
			}
			this.target = null;
			this.connection = null;
		}
	}

	/**
	 * Create a CCI Connection via this template's ConnectionFactory.
	 * @return the new CCI Connection
	 * @throws javax.resource.ResourceException if thrown by CCI API methods
	 */
	protected Connection doCreateConnection() throws ResourceException {
		return getTargetConnectionFactory().getConnection();
	}

	/**
	 * Prepare the given Connection before it is exposed.
	 * <p>The default implementation is empty. Can be overridden in subclasses.
	 * @param con the Connection to prepare
	 */
	protected void prepareConnection(Connection con) throws ResourceException {
	}

	/**
	 * Close the given Connection.
	 * @param con the Connection to close
	 */
	protected void closeConnection(Connection con) {
		try {
			con.close();
		}
		catch (Throwable ex) {
			logger.warn("Could not close shared CCI Connection", ex);
		}
	}

	/**
	 * Wrap the given Connection with a proxy that delegates every method call to it
	 * but suppresses close calls. This is useful for allowing application code to
	 * handle a special framework Connection just like an ordinary Connection from a
	 * CCI ConnectionFactory.
	 * @param target the original Connection to wrap
	 * @return the wrapped Connection
	 */
	protected Connection getCloseSuppressingConnectionProxy(Connection target) {
		return (Connection) Proxy.newProxyInstance(
				Connection.class.getClassLoader(),
				new Class[] {Connection.class},
				new CloseSuppressingInvocationHandler(target));
	}


	/**
	 * Invocation handler that suppresses close calls on CCI Connections.
	 */
	private static class CloseSuppressingInvocationHandler implements InvocationHandler {

		private final Connection target;

		private CloseSuppressingInvocationHandler(Connection target) {
			this.target = target;
		}

		public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
			if (method.getName().equals("equals")) {
				// Only consider equal when proxies are identical.
				return (proxy == args[0] ? Boolean.TRUE : Boolean.FALSE);
			}
			else if (method.getName().equals("hashCode")) {
				// Use hashCode of Connection proxy.
				return new Integer(hashCode());
			}
			else if (method.getName().equals("close")) {
				// Handle close method: don't pass the call on.
				return null;
			}
			try {
				return method.invoke(this.target, args);
			}
			catch (InvocationTargetException ex) {
				throw ex.getTargetException();
			}
		}
	}

}