/*
* Copyright 2002-2010 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.jdbc.datasource;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;
import javax.sql.DataSource;
import org.springframework.transaction.support.TransactionSynchronizationManager;
import org.springframework.util.Assert;
/**
* Proxy for a target JDBC {@link javax.sql.DataSource}, adding awareness of
* Spring-managed transactions. Similar to a transactional JNDI DataSource
* as provided by a J2EE server.
*
* <p>Data access code that should remain unaware of Spring's data access support
* can work with this proxy to seamlessly participate in Spring-managed transactions.
* Note that the transaction manager, for example {@link DataSourceTransactionManager},
* still needs to work with the underlying DataSource, <i>not</i> with this proxy.
*
* <p><b>Make sure that TransactionAwareDataSourceProxy is the outermost DataSource
* of a chain of DataSource proxies/adapters.</b> TransactionAwareDataSourceProxy
* can delegate either directly to the target connection pool or to some
* intermediary proxy/adapter like {@link LazyConnectionDataSourceProxy} or
* {@link UserCredentialsDataSourceAdapter}.
*
* <p>Delegates to {@link DataSourceUtils} for automatically participating in
* thread-bound transactions, for example managed by {@link DataSourceTransactionManager}.
* <code>getConnection</code> calls and <code>close</code> calls on returned Connections
* will behave properly within a transaction, i.e. always operate on the transactional
* Connection. If not within a transaction, normal DataSource behavior applies.
*
* <p>This proxy allows data access code to work with the plain JDBC API and still
* participate in Spring-managed transactions, similar to JDBC code in a J2EE/JTA
* environment. However, if possible, use Spring's DataSourceUtils, JdbcTemplate or
* JDBC operation objects to get transaction participation even without a proxy for
* the target DataSource, avoiding the need to define such a proxy in the first place.
*
* <p>As a further effect, using a transaction-aware DataSource will apply remaining
* transaction timeouts to all created JDBC (Prepared/Callable)Statement. This means
* that all operations performed through standard JDBC will automatically participate
* in Spring-managed transaction timeouts.
*
* <p><b>NOTE:</b> This DataSource proxy needs to return wrapped Connections
* (which implement the {@link ConnectionProxy} interface) in order to handle
* close calls properly. Therefore, the returned Connections cannot be cast
* to a native JDBC Connection type like OracleConnection or to a connection
* pool implementation type. Use a corresponding
* {@link org.springframework.jdbc.support.nativejdbc.NativeJdbcExtractor}
* to retrieve the native JDBC Connection.
*
* @author Juergen Hoeller
* @since 1.1
* @see javax.sql.DataSource#getConnection()
* @see java.sql.Connection#close()
* @see DataSourceUtils#doGetConnection
* @see DataSourceUtils#applyTransactionTimeout
* @see DataSourceUtils#doReleaseConnection
*/
public class TransactionAwareDataSourceProxy extends DelegatingDataSource {
private boolean reobtainTransactionalConnections = false;
/**
* Create a new TransactionAwareDataSourceProxy.
* @see #setTargetDataSource
*/
public TransactionAwareDataSourceProxy() {
}
/**
* Create a new TransactionAwareDataSourceProxy.
* @param targetDataSource the target DataSource
*/
public TransactionAwareDataSourceProxy(DataSource targetDataSource) {
super(targetDataSource);
}
/**
* Specify whether to reobtain the target Connection for each operation
* performed within a transaction.
* <p>The default is "false". Specify "true" to reobtain transactional
* Connections for every call on the Connection proxy; this is advisable
* on JBoss if you hold on to a Connection handle across transaction boundaries.
* <p>The effect of this setting is similar to the
* "hibernate.connection.release_mode" value "after_statement".
*/
public void setReobtainTransactionalConnections(boolean reobtainTransactionalConnections) {
this.reobtainTransactionalConnections = reobtainTransactionalConnections;
}
/**
* Delegates to DataSourceUtils for automatically participating in Spring-managed
* transactions. Throws the original SQLException, if any.
* <p>The returned Connection handle implements the ConnectionProxy interface,
* allowing to retrieve the underlying target Connection.
* @return a transactional Connection if any, a new one else
* @see DataSourceUtils#doGetConnection
* @see ConnectionProxy#getTargetConnection
*/
public Connection getConnection() throws SQLException {
DataSource ds = getTargetDataSource();
Assert.state(ds != null, "'targetDataSource' is required");
return getTransactionAwareConnectionProxy(ds);
}
/**
* Wraps the given Connection with a proxy that delegates every method call to it
* but delegates <code>close()</code> calls to DataSourceUtils.
* @param targetDataSource DataSource that the Connection came from
* @return the wrapped Connection
* @see java.sql.Connection#close()
* @see DataSourceUtils#doReleaseConnection
*/
protected Connection getTransactionAwareConnectionProxy(DataSource targetDataSource) {
return (Connection) Proxy.newProxyInstance(
ConnectionProxy.class.getClassLoader(),
new Class[] {ConnectionProxy.class},
new TransactionAwareInvocationHandler(targetDataSource));
}
/**
* Determine whether to obtain a fixed target Connection for the proxy
* or to reobtain the target Connection for each operation.
* <p>The default implementation returns <code>true</code> for all
* standard cases. This can be overridden through the
* {@link #setReobtainTransactionalConnections "reobtainTransactionalConnections"}
* flag, which enforces a non-fixed target Connection within an active transaction.
* Note that non-transactional access will always use a fixed Connection.
* @param targetDataSource the target DataSource
*/
protected boolean shouldObtainFixedConnection(DataSource targetDataSource) {
return (!TransactionSynchronizationManager.isSynchronizationActive() ||
!this.reobtainTransactionalConnections);
}
/**
* Invocation handler that delegates close calls on JDBC Connections
* to DataSourceUtils for being aware of thread-bound transactions.
*/
private class TransactionAwareInvocationHandler implements InvocationHandler {
private final DataSource targetDataSource;
private Connection target;
private boolean closed = false;
public TransactionAwareInvocationHandler(DataSource targetDataSource) {
this.targetDataSource = targetDataSource;
}
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
// Invocation on ConnectionProxy interface coming in...
if (method.getName().equals("equals")) {
// Only considered as 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(System.identityHashCode(proxy));
}
else if (method.getName().equals("toString")) {
// Allow for differentiating between the proxy and the raw Connection.
StringBuffer buf = new StringBuffer("Transaction-aware proxy for target Connection ");
if (this.target != null) {
buf.append("[").append(this.target.toString()).append("]");
}
else {
buf.append(" from DataSource [").append(this.targetDataSource).append("]");
}
return buf.toString();
}
else if (method.getName().equals("close")) {
// Handle close method: only close if not within a transaction.
DataSourceUtils.doReleaseConnection(this.target, this.targetDataSource);
this.closed = true;
return null;
}
if (this.target == null) {
if (this.closed) {
throw new SQLException("Connection handle already closed");
}
if (shouldObtainFixedConnection(this.targetDataSource)) {
this.target = DataSourceUtils.doGetConnection(this.targetDataSource);
}
}
Connection actualTarget = this.target;
if (actualTarget == null) {
actualTarget = DataSourceUtils.doGetConnection(this.targetDataSource);
}
if (method.getName().equals("getTargetConnection")) {
// Handle getTargetConnection method: return underlying Connection.
return actualTarget;
}
// Invoke method on target Connection.
try {
Object retVal = method.invoke(actualTarget, args);
// If return value is a Statement, apply transaction timeout.
// Applies to createStatement, prepareStatement, prepareCall.
if (retVal instanceof Statement) {
DataSourceUtils.applyTransactionTimeout((Statement) retVal, this.targetDataSource);
}
return retVal;
}
catch (InvocationTargetException ex) {
throw ex.getTargetException();
}
finally {
if (actualTarget != this.target) {
DataSourceUtils.doReleaseConnection(actualTarget, this.targetDataSource);
}
}
}
}
}