Mybatis核心源码赏析（五）

mybatis中数据库连接池源代码

默认参数配置

protected int poolMaximumActiveConnections = 10;
protected int poolMaximumIdleConnections = 5;
protected int poolMaximumCheckoutTime = 20000;
protected int poolTimeToWait = 20000;
protected int poolMaximumLocalBadConnectionTolerance = 3;

默认最大连接数10，最小连接数5

连接池核心代码：

public void forceCloseAll() {
synchronized (state) {
expectedConnectionTypeCode = assembleConnectionTypeCode(dataSource.getUrl(), dataSource.getUsername(), dataSource.getPassword());
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.");
}
}

/***    Copyright 2009-2020 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**       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.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*/
public class PooledDataSource implements DataSource {private static final Log log = LogFactory.getLog(PooledDataSource.class);private final PoolState state = new PoolState(this);private final UnpooledDataSource dataSource;// OPTIONAL CONFIGURATION FIELDSprotected int poolMaximumActiveConnections = 10;protected int poolMaximumIdleConnections = 5;protected int poolMaximumCheckoutTime = 20000;protected int poolTimeToWait = 20000;protected int poolMaximumLocalBadConnectionTolerance = 3;protected String poolPingQuery = "NO PING QUERY SET";protected boolean poolPingEnabled;protected int poolPingConnectionsNotUsedFor;private int expectedConnectionTypeCode;public PooledDataSource() {dataSource = new UnpooledDataSource();}public PooledDataSource(UnpooledDataSource dataSource) {this.dataSource = dataSource;}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());}@Overridepublic Connection getConnection() throws SQLException {return popConnection(dataSource.getUsername(), dataSource.getPassword()).getProxyConnection();}@Overridepublic Connection getConnection(String username, String password) throws SQLException {return popConnection(username, password).getProxyConnection();}@Overridepublic void setLoginTimeout(int loginTimeout) {DriverManager.setLoginTimeout(loginTimeout);}@Overridepublic int getLoginTimeout() {return DriverManager.getLoginTimeout();}@Overridepublic void setLogWriter(PrintWriter logWriter) {DriverManager.setLogWriter(logWriter);}@Overridepublic PrintWriter getLogWriter() {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();}/*** Sets the default network timeout value to wait for the database operation to complete. See {@link Connection#setNetworkTimeout(java.util.concurrent.Executor, int)}** @param milliseconds*          The time in milliseconds to wait for the database operation to complete.* @since 3.5.2*/public void setDefaultNetworkTimeout(Integer milliseconds) {dataSource.setDefaultNetworkTimeout(milliseconds);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 number of tolerance for bad connection happens in one thread* which are applying for new {@link PooledConnection}.** @param poolMaximumLocalBadConnectionTolerance*          max tolerance for bad connection happens in one thread** @since 3.4.5*/public void setPoolMaximumLocalBadConnectionTolerance(int poolMaximumLocalBadConnectionTolerance) {this.poolMaximumLocalBadConnectionTolerance = poolMaximumLocalBadConnectionTolerance;}/*** 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();}/*** Gets the default network timeout.** @return the default network timeout* @since 3.5.2*/public Integer getDefaultNetworkTimeout() {return dataSource.getDefaultNetworkTimeout();}public int getPoolMaximumActiveConnections() {return poolMaximumActiveConnections;}public int getPoolMaximumIdleConnections() {return poolMaximumIdleConnections;}public int getPoolMaximumLocalBadConnectionTolerance() {return poolMaximumLocalBadConnectionTolerance;}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());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) {state.activeConnections.remove(conn);if (conn.isValid()) {if (state.idleConnections.size() < poolMaximumIdleConnections && conn.getConnectionTypeCode() == expectedConnectionTypeCode) {state.accumulatedCheckoutTime += conn.getCheckoutTime();if (!conn.getRealConnection().getAutoCommit()) {conn.getRealConnection().rollback();}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.");}state.notifyAll();} else {state.accumulatedCheckoutTime += conn.getCheckoutTime();if (!conn.getRealConnection().getAutoCommit()) {conn.getRealConnection().rollback();}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;while (conn == null) {synchronized (state) {if (!state.idleConnections.isEmpty()) {// Pool has available connectionconn = state.idleConnections.remove(0);if (log.isDebugEnabled()) {log.debug("Checked out connection " + conn.getRealHashCode() + " from pool.");}} else {// Pool does not have available connectionif (state.activeConnections.size() < poolMaximumActiveConnections) {// Can create new connectionconn = new PooledConnection(dataSource.getConnection(), this);if (log.isDebugEnabled()) {log.debug("Created connection " + conn.getRealHashCode() + ".");}} else {// Cannot create new connectionPooledConnection oldestActiveConnection = state.activeConnections.get(0);long longestCheckoutTime = oldestActiveConnection.getCheckoutTime();if (longestCheckoutTime > poolMaximumCheckoutTime) {// Can claim overdue connectionstate.claimedOverdueConnectionCount++;state.accumulatedCheckoutTimeOfOverdueConnections += longestCheckoutTime;state.accumulatedCheckoutTime += longestCheckoutTime;state.activeConnections.remove(oldestActiveConnection);if (!oldestActiveConnection.getRealConnection().getAutoCommit()) {try {oldestActiveConnection.getRealConnection().rollback();} catch (SQLException e) {/*Just log a message for debug and continue to execute the followingstatement like nothing happened.Wrap the bad connection with a new PooledConnection, this will helpto not interrupt current executing thread and give current thread achance to join the next competition for another valid/good databaseconnection. At the end of this loop, bad {@link @conn} will be set as null.*/log.debug("Bad connection. Could not roll back");}}conn = new PooledConnection(oldestActiveConnection.getRealConnection(), this);conn.setCreatedTimestamp(oldestActiveConnection.getCreatedTimestamp());conn.setLastUsedTimestamp(oldestActiveConnection.getLastUsedTimestamp());oldestActiveConnection.invalidate();if (log.isDebugEnabled()) {log.debug("Claimed overdue connection " + conn.getRealHashCode() + ".");}} else {// Must waittry {if (!countedWait) {state.hadToWaitCount++;countedWait = true;}if (log.isDebugEnabled()) {log.debug("Waiting as long as " + poolTimeToWait + " milliseconds for connection.");}long wt = System.currentTimeMillis();state.wait(poolTimeToWait);state.accumulatedWaitTime += System.currentTimeMillis() - wt;} catch (InterruptedException e) {break;}}}}if (conn != null) {// ping to server and check the connection is valid or notif (conn.isValid()) {if (!conn.getRealConnection().getAutoCommit()) {conn.getRealConnection().rollback();}conn.setConnectionTypeCode(assembleConnectionTypeCode(dataSource.getUrl(), username, password));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.");}state.badConnectionCount++;localBadConnectionCount++;conn = null;if (localBadConnectionCount > (poolMaximumIdleConnections + poolMaximumLocalBadConnectionTolerance)) {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 && poolPingEnabled && poolPingConnectionsNotUsedFor >= 0&& conn.getTimeElapsedSinceLastUse() > poolPingConnectionsNotUsedFor) {try {if (log.isDebugEnabled()) {log.debug("Testing connection " + conn.getRealHashCode() + " ...");}Connection realConn = conn.getRealConnection();try (Statement statement = realConn.createStatement()) {statement.executeQuery(poolPingQuery).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;}@Overrideprotected void finalize() throws Throwable {forceCloseAll();super.finalize();}@Overridepublic <T> T unwrap(Class<T> iface) throws SQLException {throw new SQLException(getClass().getName() + " is not a wrapper.");}@Overridepublic boolean isWrapperFor(Class<?> iface) {return false;}@Overridepublic Logger getParentLogger() {return Logger.getLogger(Logger.GLOBAL_LOGGER_NAME);}}

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