ProxyFactory.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.netxilia.spi.impl.storage.sql;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Proxy;
import java.sql.CallableStatement;
import java.sql.Connection;
import java.sql.Driver;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;

/**
 * Creates proxy implementations of JDBC interfaces. This avoids incompatibilities between the JDBC 2 and JDBC 3
 * interfaces. This class is thread safe.
 * 
 * @see java.lang.reflect.Proxy
 * @see java.lang.reflect.InvocationHandler
 */
public class ProxyFactory {

	/**
	 * The Singleton instance of this class.
	 */
	private static final ProxyFactory instance = new ProxyFactory();

	/**
	 * Returns the Singleton instance of this class.
	 * 
	 * @return singleton instance
	 */
	public static ProxyFactory instance() {
		return instance;
	}

	/**
	 * Protected constructor for ProxyFactory subclasses to use.
	 */
	protected ProxyFactory() {
		super();
	}

	/**
	 * Convenience method to generate a single-interface proxy using the handler's classloader
	 * 
	 * @param <T>
	 *            The type of object to proxy
	 * @param type
	 *            The type of object to proxy
	 * @param handler
	 *            The handler that intercepts/overrides method calls.
	 * @return proxied object
	 */
	public <T> T newProxyInstance(Class<T> type, InvocationHandler handler) {
		return type.cast(Proxy.newProxyInstance(handler.getClass().getClassLoader(), new Class<?>[] { type }, handler));
	}

	/**
	 * Creates a new proxy <code>CallableStatement</code> object.
	 * 
	 * @param handler
	 *            The handler that intercepts/overrides method calls.
	 * @return proxied CallableStatement
	 */
	public CallableStatement createCallableStatement(InvocationHandler handler) {
		return newProxyInstance(CallableStatement.class, handler);
	}

	/**
	 * Creates a new proxy <code>Connection</code> object.
	 * 
	 * @param handler
	 *            The handler that intercepts/overrides method calls.
	 * @return proxied Connection
	 */
	public Connection createConnection(InvocationHandler handler) {
		return newProxyInstance(Connection.class, handler);
	}

	/**
	 * Creates a new proxy <code>Driver</code> object.
	 * 
	 * @param handler
	 *            The handler that intercepts/overrides method calls.
	 * @return proxied Driver
	 */
	public Driver createDriver(InvocationHandler handler) {
		return newProxyInstance(Driver.class, handler);
	}

	/**
	 * Creates a new proxy <code>PreparedStatement</code> object.
	 * 
	 * @param handler
	 *            The handler that intercepts/overrides method calls.
	 * @return proxied PreparedStatement
	 */
	public PreparedStatement createPreparedStatement(InvocationHandler handler) {
		return newProxyInstance(PreparedStatement.class, handler);
	}

	/**
	 * Creates a new proxy <code>ResultSet</code> object.
	 * 
	 * @param handler
	 *            The handler that intercepts/overrides method calls.
	 * @return proxied ResultSet
	 */
	public ResultSet createResultSet(InvocationHandler handler) {
		return newProxyInstance(ResultSet.class, handler);
	}

	/**
	 * Creates a new proxy <code>ResultSetMetaData</code> object.
	 * 
	 * @param handler
	 *            The handler that intercepts/overrides method calls.
	 * @return proxied ResultSetMetaData
	 */
	public ResultSetMetaData createResultSetMetaData(InvocationHandler handler) {
		return newProxyInstance(ResultSetMetaData.class, handler);
	}

	/**
	 * Creates a new proxy <code>Statement</code> object.
	 * 
	 * @param handler
	 *            The handler that intercepts/overrides method calls.
	 * @return proxied Statement
	 */
	public Statement createStatement(InvocationHandler handler) {
		return newProxyInstance(Statement.class, handler);
	}

}