org.springframework.jdbc.datasource.SingleConnectionDataSource Maven / Gradle / Ivy
/*
* Copyright 2002-2020 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
*
* https://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 org.springframework.beans.factory.DisposableBean;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ObjectUtils;
/**
* Implementation of {@link SmartDataSource} that wraps a single JDBC Connection
* which is not closed after use. Obviously, this is not multi-threading capable.
*
* Note that at shutdown, someone should close the underlying Connection
* via the {@code close()} method. Client code will never call close
* on the Connection handle if it is SmartDataSource-aware (e.g. uses
* {@code DataSourceUtils.releaseConnection}).
*
*
If client code will call {@code close()} in the assumption of a pooled
* Connection, like when using persistence tools, set "suppressClose" to "true".
* This will return a close-suppressing proxy instead of the physical Connection.
*
*
This is primarily intended for testing. For example, it enables easy testing
* outside an application server, for code that expects to work on a DataSource.
* In contrast to {@link DriverManagerDataSource}, it reuses the same Connection
* all the time, avoiding excessive creation of physical Connections.
*
* @author Rod Johnson
* @author Juergen Hoeller
* @see #getConnection()
* @see java.sql.Connection#close()
* @see DataSourceUtils#releaseConnection
*/
public class SingleConnectionDataSource extends DriverManagerDataSource implements SmartDataSource, DisposableBean {
/** Create a close-suppressing proxy?. */
private boolean suppressClose;
/** Override auto-commit state?. */
@Nullable
private Boolean autoCommit;
/** Wrapped Connection. */
@Nullable
private Connection target;
/** Proxy Connection. */
@Nullable
private Connection connection;
/** Synchronization monitor for the shared Connection. */
private final Object connectionMonitor = new Object();
/**
* Constructor for bean-style configuration.
*/
public SingleConnectionDataSource() {
}
/**
* Create a new SingleConnectionDataSource with the given standard
* DriverManager parameters.
* @param url the JDBC URL to use for accessing the DriverManager
* @param username the JDBC username to use for accessing the DriverManager
* @param password the JDBC password to use for accessing the DriverManager
* @param suppressClose if the returned Connection should be a
* close-suppressing proxy or the physical Connection
* @see java.sql.DriverManager#getConnection(String, String, String)
*/
public SingleConnectionDataSource(String url, String username, String password, boolean suppressClose) {
super(url, username, password);
this.suppressClose = suppressClose;
}
/**
* Create a new SingleConnectionDataSource with the given standard
* DriverManager parameters.
* @param url the JDBC URL to use for accessing the DriverManager
* @param suppressClose if the returned Connection should be a
* close-suppressing proxy or the physical Connection
* @see java.sql.DriverManager#getConnection(String, String, String)
*/
public SingleConnectionDataSource(String url, boolean suppressClose) {
super(url);
this.suppressClose = suppressClose;
}
/**
* Create a new SingleConnectionDataSource with a given Connection.
* @param target underlying target Connection
* @param suppressClose if the Connection should be wrapped with a Connection that
* suppresses {@code close()} calls (to allow for normal {@code close()}
* usage in applications that expect a pooled Connection but do not know our
* SmartDataSource interface)
*/
public SingleConnectionDataSource(Connection target, boolean suppressClose) {
Assert.notNull(target, "Connection must not be null");
this.target = target;
this.suppressClose = suppressClose;
this.connection = (suppressClose ? getCloseSuppressingConnectionProxy(target) : target);
}
/**
* Set whether the returned Connection should be a close-suppressing proxy
* or the physical Connection.
*/
public void setSuppressClose(boolean suppressClose) {
this.suppressClose = suppressClose;
}
/**
* Return whether the returned Connection will be a close-suppressing proxy
* or the physical Connection.
*/
protected boolean isSuppressClose() {
return this.suppressClose;
}
/**
* Set whether the returned Connection's "autoCommit" setting should be overridden.
*/
public void setAutoCommit(boolean autoCommit) {
this.autoCommit = (autoCommit);
}
/**
* Return whether the returned Connection's "autoCommit" setting should be overridden.
* @return the "autoCommit" value, or {@code null} if none to be applied
*/
@Nullable
protected Boolean getAutoCommitValue() {
return this.autoCommit;
}
@Override
public Connection getConnection() throws SQLException {
synchronized (this.connectionMonitor) {
if (this.connection == null) {
// No underlying Connection -> lazy init via DriverManager.
initConnection();
}
if (this.connection.isClosed()) {
throw new SQLException(
"Connection was closed in SingleConnectionDataSource. Check that user code checks " +
"shouldClose() before closing Connections, or set 'suppressClose' to 'true'");
}
return this.connection;
}
}
/**
* Specifying a custom username and password doesn't make sense
* with a single Connection. Returns the single Connection if given
* the same username and password; throws an SQLException else.
*/
@Override
public Connection getConnection(String username, String password) throws SQLException {
if (ObjectUtils.nullSafeEquals(username, getUsername()) &&
ObjectUtils.nullSafeEquals(password, getPassword())) {
return getConnection();
}
else {
throw new SQLException("SingleConnectionDataSource does not support custom username and password");
}
}
/**
* This is a single Connection: Do not close it when returning to the "pool".
*/
@Override
public boolean shouldClose(Connection con) {
synchronized (this.connectionMonitor) {
return (con != this.connection && con != this.target);
}
}
/**
* Close the underlying Connection.
* The provider of this DataSource needs to care for proper shutdown.
*
As this bean implements DisposableBean, a bean factory will
* automatically invoke this on destruction of its cached singletons.
*/
@Override
public void destroy() {
synchronized (this.connectionMonitor) {
closeConnection();
}
}
/**
* Initialize the underlying Connection via the DriverManager.
*/
public void initConnection() throws SQLException {
if (getUrl() == null) {
throw new IllegalStateException("'url' property is required for lazily initializing a Connection");
}
synchronized (this.connectionMonitor) {
closeConnection();
this.target = getConnectionFromDriver(getUsername(), getPassword());
prepareConnection(this.target);
if (logger.isDebugEnabled()) {
logger.debug("Established shared JDBC Connection: " + this.target);
}
this.connection = (isSuppressClose() ? getCloseSuppressingConnectionProxy(this.target) : this.target);
}
}
/**
* Reset the underlying shared Connection, to be reinitialized on next access.
*/
public void resetConnection() {
synchronized (this.connectionMonitor) {
closeConnection();
this.target = null;
this.connection = null;
}
}
/**
* Prepare the given Connection before it is exposed.
*
The default implementation applies the auto-commit flag, if necessary.
* Can be overridden in subclasses.
* @param con the Connection to prepare
* @see #setAutoCommit
*/
protected void prepareConnection(Connection con) throws SQLException {
Boolean autoCommit = getAutoCommitValue();
if (autoCommit != null && con.getAutoCommit() != autoCommit) {
con.setAutoCommit(autoCommit);
}
}
/**
* Close the underlying shared Connection.
*/
private void closeConnection() {
if (this.target != null) {
try {
this.target.close();
}
catch (Throwable ex) {
logger.info("Could not close shared JDBC Connection", ex);
}
}
}
/**
* Wrap the given Connection with a proxy that delegates every method call to it
* but suppresses close calls.
* @param target the original Connection to wrap
* @return the wrapped Connection
*/
protected Connection getCloseSuppressingConnectionProxy(Connection target) {
return (Connection) Proxy.newProxyInstance(
ConnectionProxy.class.getClassLoader(),
new Class[] {ConnectionProxy.class},
new CloseSuppressingInvocationHandler(target));
}
/**
* Invocation handler that suppresses close calls on JDBC Connections.
*/
private static class CloseSuppressingInvocationHandler implements InvocationHandler {
private final Connection target;
public CloseSuppressingInvocationHandler(Connection target) {
this.target = target;
}
@Override
@Nullable
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
// Invocation on ConnectionProxy interface coming in...
switch (method.getName()) {
case "equals":
// Only consider equal when proxies are identical.
return (proxy == args[0]);
case "hashCode":
// Use hashCode of Connection proxy.
return System.identityHashCode(proxy);
case "close":
// Handle close method: don't pass the call on.
return null;
case "isClosed":
return this.target.isClosed();
case "getTargetConnection":
// Handle getTargetConnection method: return underlying Connection.
return this.target;
case "unwrap":
return (((Class) args[0]).isInstance(proxy) ? proxy : this.target.unwrap((Class) args[0]));
case "isWrapperFor":
return (((Class) args[0]).isInstance(proxy) || this.target.isWrapperFor((Class) args[0]));
}
// Invoke method on target Connection.
try {
return method.invoke(this.target, args);
}
catch (InvocationTargetException ex) {
throw ex.getTargetException();
}
}
}
}