/*
* Copyright 2009-2012 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.apache.ibatis.datasource.pooled;
import java.io.PrintWriter;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Proxy;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
import java.util.logging.Logger;
import javax.sql.DataSource;
import org.apache.ibatis.datasource.unpooled.UnpooledDataSource;
import org.apache.ibatis.logging.Log;
import org.apache.ibatis.logging.LogFactory;
/**
* This is a simple, synchronous, thread-safe database connection pool.
*
* @author Clinton Begin
*/
/**
* 有连接池的数据源
* 这个是mybatis自己实行了一个连接池
* 其他还有诸如C3P0的com.mchange.v2.c3p0.ComboPooledDataSource
* DBCP 等等
* 还有一些人喜欢自己用apache commons pool写一个连接池
*/
public class PooledDataSource implements DataSource {
private static final Log log = LogFactory.getLog(PooledDataSource.class);
//有一个池状态
private final PoolState state = new PoolState(this);
//里面有一个UnpooledDataSource
private final UnpooledDataSource dataSource;
// OPTIONAL CONFIGURATION FIELDS
//正在使用连接的数量
protected int poolMaximumActiveConnections = 10;
//空闲连接数
protected int poolMaximumIdleConnections = 5;
//在被强制返回之前,池中连接被检查的时间
protected int poolMaximumCheckoutTime = 20000;
//这是给连接池一个打印日志状态机会的低层次设置,还有重新 尝试获得连接, 这些情况下往往需要很长时间 为了避免连接池没有配置时静默失 败)。
protected int poolTimeToWait = 20000;
//发送到数据的侦测查询,用来验证连接是否正常工作,并且准备 接受请求。默认是“NO PING QUERY SET” ,这会引起许多数据库驱动连接由一 个错误信息而导致失败
protected String poolPingQuery = "NO PING QUERY SET";
//开启或禁用侦测查询
protected boolean poolPingEnabled = false;
//用来配置 poolPingQuery 多次时间被用一次
protected int poolPingConnectionsNotUsedFor = 0;
private int expectedConnectionTypeCode;
public PooledDataSource() {
dataSource = new UnpooledDataSource();
}
public PooledDataSource(String driver, String url, String username, String password) {
dataSource = new UnpooledDataSource(driver, url, username, password);
expectedConnectionTypeCode = assembleConnectionTypeCode(dataSource.getUrl(), dataSource.getUsername(), dataSource.getPassword());
}
public PooledDataSource(String driver, String url, Properties driverProperties) {
dataSource = new UnpooledDataSource(driver, url, driverProperties);
expectedConnectionTypeCode = assembleConnectionTypeCode(dataSource.getUrl(), dataSource.getUsername(), dataSource.getPassword());
}
public PooledDataSource(ClassLoader driverClassLoader, String driver, String url, String username, String password) {
dataSource = new UnpooledDataSource(driverClassLoader, driver, url, username, password);
expectedConnectionTypeCode = assembleConnectionTypeCode(dataSource.getUrl(), dataSource.getUsername(), dataSource.getPassword());
}
public PooledDataSource(ClassLoader driverClassLoader, String driver, String url, Properties driverProperties) {
dataSource = new UnpooledDataSource(driverClassLoader, driver, url, driverProperties);
expectedConnectionTypeCode = assembleConnectionTypeCode(dataSource.getUrl(), dataSource.getUsername(), dataSource.getPassword());
}
@Override
public Connection getConnection() throws SQLException {
//覆盖了DataSource.getConnection方法，每次都是pop一个Connection，即从池中取出一个来
return popConnection(dataSource.getUsername(), dataSource.getPassword()).getProxyConnection();
}
@Override
public Connection getConnection(String username, String password) throws SQLException {
return popConnection(username, password).getProxyConnection();
}
@Override
public void setLoginTimeout(int loginTimeout) throws SQLException {
DriverManager.setLoginTimeout(loginTimeout);
}
@Override
public int getLoginTimeout() throws SQLException {
return DriverManager.getLoginTimeout();
}
@Override
public void setLogWriter(PrintWriter logWriter) throws SQLException {
DriverManager.setLogWriter(logWriter);
}
@Override
public PrintWriter getLogWriter() throws SQLException {
return DriverManager.getLogWriter();
}
public void setDriver(String driver) {
dataSource.setDriver(driver);
forceCloseAll();
}
public void setUrl(String url) {
dataSource.setUrl(url);
forceCloseAll();
}
public void setUsername(String username) {
dataSource.setUsername(username);
forceCloseAll();
}
public void setPassword(String password) {
dataSource.setPassword(password);
forceCloseAll();
}
public void setDefaultAutoCommit(boolean defaultAutoCommit) {
dataSource.setAutoCommit(defaultAutoCommit);
forceCloseAll();
}
public void setDefaultTransactionIsolationLevel(Integer defaultTransactionIsolationLevel) {
dataSource.setDefaultTransactionIsolationLevel(defaultTransactionIsolationLevel);
forceCloseAll();
}
public void setDriverProperties(Properties driverProps) {
dataSource.setDriverProperties(driverProps);
forceCloseAll();
}
/*
* The maximum number of active connections
*
* @param poolMaximumActiveConnections The maximum number of active connections
*/
public void setPoolMaximumActiveConnections(int poolMaximumActiveConnections) {
this.poolMaximumActiveConnections = poolMaximumActiveConnections;
forceCloseAll();
}
/*
* The maximum number of idle connections
*
* @param poolMaximumIdleConnections The maximum number of idle connections
*/
public void setPoolMaximumIdleConnections(int poolMaximumIdleConnections) {
this.poolMaximumIdleConnections = poolMaximumIdleConnections;
forceCloseAll();
}
/*
* The maximum time a connection can be used before it *may* be
* given away again.
*
* @param poolMaximumCheckoutTime The maximum time
*/
public void setPoolMaximumCheckoutTime(int poolMaximumCheckoutTime) {
this.poolMaximumCheckoutTime = poolMaximumCheckoutTime;
forceCloseAll();
}
/*
* The time to wait before retrying to get a connection
*
* @param poolTimeToWait The time to wait
*/
public void setPoolTimeToWait(int poolTimeToWait) {
this.poolTimeToWait = poolTimeToWait;
forceCloseAll();
}
/*
* The query to be used to check a connection
*
* @param poolPingQuery The query
*/
public void setPoolPingQuery(String poolPingQuery) {
this.poolPingQuery = poolPingQuery;
forceCloseAll();
}
/*
* Determines if the ping query should be used.
*
* @param poolPingEnabled True if we need to check a connection before using it
*/
public void setPoolPingEnabled(boolean poolPingEnabled) {
this.poolPingEnabled = poolPingEnabled;
forceCloseAll();
}
/*
* If a connection has not been used in this many milliseconds, ping the
* database to make sure the connection is still good.
*
* @param milliseconds the number of milliseconds of inactivity that will trigger a ping
*/
public void setPoolPingConnectionsNotUsedFor(int milliseconds) {
this.poolPingConnectionsNotUsedFor = milliseconds;
forceCloseAll();
}
public String getDriver() {
return dataSource.getDriver();
}
public String getUrl() {
return dataSource.getUrl();
}
public String getUsername() {
return dataSource.getUsername();
}
public String getPassword() {
return dataSource.getPassword();
}
public boolean isAutoCommit() {
return dataSource.isAutoCommit();
}
public Integer getDefaultTransactionIsolationLevel() {
return dataSource.getDefaultTransactionIsolationLevel();
}
public Properties getDriverProperties() {
return dataSource.getDriverProperties();
}
public int getPoolMaximumActiveConnections() {
return poolMaximumActiveConnections;
}
public int getPoolMaximumIdleConnections() {
return poolMaximumIdleConnections;
}
public int getPoolMaximumCheckoutTime() {
return poolMaximumCheckoutTime;
}
public int getPoolTimeToWait() {
return poolTimeToWait;
}
public String getPoolPingQuery() {
return poolPingQuery;
}
public boolean isPoolPingEnabled() {
return poolPingEnabled;
}
public int getPoolPingConnectionsNotUsedFor() {
return poolPingConnectionsNotUsedFor;
}
/*
* Closes all active and idle connections in the pool
*/
public void forceCloseAll() {
synchronized (state) {
expectedConnectionTypeCode = assembleConnectionTypeCode(dataSource.getUrl(), dataSource.getUsername(), dataSource.getPassword());
//关闭所有的activeConnections和idleConnections
for (int i = state.activeConnections.size(); i > 0; i--) {
try {
PooledConnection conn = state.activeConnections.remove(i - 1);
conn.invalidate();
Connection realConn = conn.getRealConnection();
if (!realConn.getAutoCommit()) {
realConn.rollback();
}
realConn.close();
} catch (Exception e) {
// ignore
}
}
for (int i = state.idleConnections.size(); i > 0; i--) {
try {
PooledConnection conn = state.idleConnections.remove(i - 1);
conn.invalidate();
Connection realConn = conn.getRealConnection();
if (!realConn.getAutoCommit()) {
realConn.rollback();
}
realConn.close();
} catch (Exception e) {
// ignore
}
}
}
if (log.isDebugEnabled()) {
log.debug("PooledDataSource forcefully closed/removed all connections.");
}
}
public PoolState getPoolState() {
return state;
}
private int assembleConnectionTypeCode(String url, String username, String password) {
return ("" + url + username + password).hashCode();
}
protected void pushConnection(PooledConnection conn) throws SQLException {
synchronized (state) {
//先从activeConnections中删除此connection
state.activeConnections.remove(conn);
if (conn.isValid()) {
if (state.idleConnections.size() < poolMaximumIdleConnections && conn.getConnectionTypeCode() == expectedConnectionTypeCode) {
//如果空闲的连接太少，
state.accumulatedCheckoutTime += conn.getCheckoutTime();
if (!conn.getRealConnection().getAutoCommit()) {
conn.getRealConnection().rollback();
}
//new一个新的Connection，加入到idle列表
PooledConnection newConn = new PooledConnection(conn.getRealConnection(), this);
state.idleConnections.add(newConn);
newConn.setCreatedTimestamp(conn.getCreatedTimestamp());
newConn.setLastUsedTimestamp(conn.getLastUsedTimestamp());
conn.invalidate();
if (log.isDebugEnabled()) {
log.debug("Returned connection " + newConn.getRealHashCode() + " to pool.");
}
//通知其他线程可以来抢connection了
state.notifyAll();
} else {
//否则，即空闲的连接已经足够了
state.accumulatedCheckoutTime += conn.getCheckoutTime();
if (!conn.getRealConnection().getAutoCommit()) {
conn.getRealConnection().rollback();
}
//那就将connection关闭就可以了
conn.getRealConnection().close();
if (log.isDebugEnabled()) {
log.debug("Closed connection " + conn.getRealHashCode() + ".");
}
conn.invalidate();
}
} else {
if (log.isDebugEnabled()) {
log.debug("A bad connection (" + conn.getRealHashCode() + ") attempted to return to the pool, discarding connection.");
}
state.badConnectionCount++;
}
}
}
private PooledConnection popConnection(String username, String password) throws SQLException {
boolean countedWait = false;
PooledConnection conn = null;
long t = System.currentTimeMillis();
int localBadConnectionCount = 0;
//最外面是while死循环，如果一直拿不到connection，则不断尝试
while (conn == null) {
synchronized (state) {
if (!state.idleConnections.isEmpty()) {
//如果有空闲的连接的话
// Pool has available connection
//删除空闲列表里第一个，返回
conn = state.idleConnections.remove(0);
if (log.isDebugEnabled()) {
log.debug("Checked out connection " + conn.getRealHashCode() + " from pool.");
}
} else {
//如果没有空闲的连接
// Pool does not have available connection
if (state.activeConnections.size() < poolMaximumActiveConnections) {
//如果activeConnections太少,那就new一个PooledConnection
// Can create new connection
conn = new PooledConnection(dataSource.getConnection(), this);
if (log.isDebugEnabled()) {
log.debug("Created connection " + conn.getRealHashCode() + ".");
}
} else {
//如果activeConnections已经很多了，那不能再new了
// Cannot create new connection
//取得activeConnections列表的第一个（最老的）
PooledConnection oldestActiveConnection = state.activeConnections.get(0);
long longestCheckoutTime = oldestActiveConnection.getCheckoutTime();
if (longestCheckoutTime > poolMaximumCheckoutTime) {
//如果checkout时间过长，则这个connection标记为overdue（过期）
// Can claim overdue connection
state.claimedOverdueConnectionCount++;
state.accumulatedCheckoutTimeOfOverdueConnections += longestCheckoutTime;
state.accumulatedCheckoutTime += longestCheckoutTime;
state.activeConnections.remove(oldestActiveConnection);
if (!oldestActiveConnection.getRealConnection().getAutoCommit()) {
oldestActiveConnection.getRealConnection().rollback();
}
//删掉最老的连接，然后再new一个新连接
conn = new PooledConnection(oldestActiveConnection.getRealConnection(), this);
oldestActiveConnection.invalidate();
if (log.isDebugEnabled()) {
log.debug("Claimed overdue connection " + conn.getRealHashCode() + ".");
}
} else {
//如果checkout时间不够长，等待吧
// Must wait
try {
if (!countedWait) {
//统计信息：等待+1
state.hadToWaitCount++;
countedWait = true;
}
if (log.isDebugEnabled()) {
log.debug("Waiting as long as " + poolTimeToWait + " milliseconds for connection.");
}
long wt = System.currentTimeMillis();
//睡一会儿吧
state.wait(poolTimeToWait);
state.accumulatedWaitTime += System.currentTimeMillis() - wt;
} catch (InterruptedException e) {
break;
}
}
}
}
if (conn != null) {
//如果已经拿到connection，则返回
if (conn.isValid()) {
if (!conn.getRealConnection().getAutoCommit()) {
conn.getRealConnection().rollback();
}
conn.setConnectionTypeCode(assembleConnectionTypeCode(dataSource.getUrl(), username, password));
//记录checkout时间
conn.setCheckoutTimestamp(System.currentTimeMillis());
conn.setLastUsedTimestamp(System.currentTimeMillis());
state.activeConnections.add(conn);
state.requestCount++;
state.accumulatedRequestTime += System.currentTimeMillis() - t;
} else {
if (log.isDebugEnabled()) {
log.debug("A bad connection (" + conn.getRealHashCode() + ") was returned from the pool, getting another connection.");
}
//如果没拿到，统计信息：坏连接+1
state.badConnectionCount++;
localBadConnectionCount++;
conn = null;
if (localBadConnectionCount > (poolMaximumIdleConnections + 3)) {
//如果好几次都拿不到，就放弃了，抛出异常
if (log.isDebugEnabled()) {
log.debug("PooledDataSource: Could not get a good connection to the database.");
}
throw new SQLException("PooledDataSource: Could not get a good connection to the database.");
}
}
}
}
}
if (conn == null) {
if (log.isDebugEnabled()) {
log.debug("PooledDataSource: Unknown severe error condition. The connection pool returned a null connection.");
}
throw new SQLException("PooledDataSource: Unknown severe error condition. The connection pool returned a null connection.");
}
return conn;
}
/*
* Method to check to see if a connection is still usable
*
* @param conn - the connection to check
* @return True if the connection is still usable
*/
protected boolean pingConnection(PooledConnection conn) {
boolean result = true;
try {
result = !conn.getRealConnection().isClosed();
} catch (SQLException e) {
if (log.isDebugEnabled()) {
log.debug("Connection " + conn.getRealHashCode() + " is BAD: " + e.getMessage());
}
result = false;
}
if (result) {
if (poolPingEnabled) {
if (poolPingConnectionsNotUsedFor >= 0 && conn.getTimeElapsedSinceLastUse() > poolPingConnectionsNotUsedFor) {
try {
if (log.isDebugEnabled()) {
log.debug("Testing connection " + conn.getRealHashCode() + " ...");
}
Connection realConn = conn.getRealConnection();
Statement statement = realConn.createStatement();
ResultSet rs = statement.executeQuery(poolPingQuery);
rs.close();
statement.close();
if (!realConn.getAutoCommit()) {
realConn.rollback();
}
result = true;
if (log.isDebugEnabled()) {
log.debug("Connection " + conn.getRealHashCode() + " is GOOD!");
}
} catch (Exception e) {
log.warn("Execution of ping query '" + poolPingQuery + "' failed: " + e.getMessage());
try {
conn.getRealConnection().close();
} catch (Exception e2) {
//ignore
}
result = false;
if (log.isDebugEnabled()) {
log.debug("Connection " + conn.getRealHashCode() + " is BAD: " + e.getMessage());
}
}
}
}
}
return result;
}
/*
* Unwraps a pooled connection to get to the 'real' connection
*
* @param conn - the pooled connection to unwrap
* @return The 'real' connection
*/
public static Connection unwrapConnection(Connection conn) {
if (Proxy.isProxyClass(conn.getClass())) {
InvocationHandler handler = Proxy.getInvocationHandler(conn);
if (handler instanceof PooledConnection) {
return ((PooledConnection) handler).getRealConnection();
}
}
return conn;
}
protected void finalize() throws Throwable {
forceCloseAll();
super.finalize();
}
public <T> T unwrap(Class<T> iface) throws SQLException {
throw new SQLException(getClass().getName() + " is not a wrapper.");
}
public boolean isWrapperFor(Class<?> iface) throws SQLException {
return false;
}
public Logger getParentLogger() {
return Logger.getLogger(Logger.GLOBAL_LOGGER_NAME); // requires JDK version 1.6
}
}