mybatis中数据库连接池源代码
MyBatis-Plus是一个增强版的MyBatis框架，它在不影响MyBatis现有功能的情况下，实现了对MyBatis的功能增强。MyBatis-Plus的主要原理是遵循开闭原则，即在扩展功能时，不需要修改原有代码。它通过在实体类中与数据库表进行映射，简化了CRUD操作，无需编写SQL语句。MyBatis-Plus还内置了通用Mapper、通用Service，通过少量配置即可实现单表大部分CRUD操作。
MyBatis-Plus还支持Lambda形式调用，方便的编写各类查询条件。同时，它支持主键自动生成，支持多达4种主键策略（内含分布式唯一ID生成器-Sequence），可自由配置，完美解决主键问题。
此外，MyBatis-Plus还支持ActiveRecord模式，实体类只需继承Model类即可进行强大的CRUD操作。同时，它还支持自定义全局通用操作，支持全局通用方法注入（Write once, use anywhere）。
MyBatis-Plus内置了代码生成器，可快速生成Mapper、Model、Service、Controller层代码。它还内置了分页插件，基于MyBatis物理分页，开发者无需关心具体操作，配置好插件之后，写分页等同于普通List查询。
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 FIELDS
protected 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());
}
@Override
public Connection getConnection() throws SQLException {
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) {
DriverManager.setLoginTimeout(loginTimeout);
}
@Override
public int getLoginTimeout() {
return DriverManager.getLoginTimeout();
}
@Override
public void setLogWriter(PrintWriter logWriter) {
DriverManager.setLogWriter(logWriter);
}
@Override
public 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 connection
conn = state.idleConnections.remove(0);
if (log.isDebugEnabled()) {
log.debug("Checked out connection " + conn.getRealHashCode() + " from pool.");
}
} else {
// Pool does not have available connection
if (state.activeConnections.size() < poolMaximumActiveConnections) {
// Can create new connection
conn = new PooledConnection(dataSource.getConnection(), this);
if (log.isDebugEnabled()) {
log.debug("Created connection " + conn.getRealHashCode() + ".");
}
} else {
// Cannot create new connection
PooledConnection oldestActiveConnection = state.activeConnections.get(0);
long longestCheckoutTime = oldestActiveConnection.getCheckoutTime();
if (longestCheckoutTime > poolMaximumCheckoutTime) {
// Can claim overdue connection
state.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 following
statement like nothing happened.
Wrap the bad connection with a new PooledConnection, this will help
to not interrupt current executing thread and give current thread a
chance to join the next competition for another valid/good database
connection. 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 wait
try {
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 not
if (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;
}
@Override
protected void finalize() throws Throwable {
forceCloseAll();
super.finalize();
}
@Override
public <T> T unwrap(Class<T> iface) throws SQLException {
throw new SQLException(getClass().getName() + " is not a wrapper.");
}
@Override
public boolean isWrapperFor(Class<?> iface) {
return false;
}
@Override
public Logger getParentLogger() {
return Logger.getLogger(Logger.GLOBAL_LOGGER_NAME);
}
}在MyBatis-Plus中实现分页插件，需要先创建一个分页插件类，然后配置分页插件。
以下是一个简单的分页插件实现示例：
import com.baomidou.mybatisplus.extension.plugins.PaginationInterceptor;
import org.springframework.stereotype.Component;
@Component
public class MyBatisPlusPaginationInterceptor extends PaginationInterceptor {
@Override
public void intercept(Chain chain) throws Exception {
// 获取分页参数
Page<?> page = (Page<?>) chain.getArgs()[0];
// 获取SQL片段
String sql = chain.getSql();
// 拼接分页SQL片段
String paginationSql = buildPaginationSql(sql, page);
// 替换原SQL片段
chain.setSql(paginationSql);
super.intercept(chain);
}
private String buildPaginationSql(String sql, Page<?> page) {
// 根据分页参数拼接分页SQL片段，这里只是一个示例，实际情况下需要根据具体的分页参数和SQL语句来拼接。
return sql + " LIMIT " + (page.getCurrent() - 1) * page.getSize() + ", " + page.getSize();
}
}
在上面的示例中，我们创建了一个名为MyBatisPlusPaginationInterceptor的分页插件类，它继承了PaginationInterceptor类。在intercept方法中，我们获取了分页参数和原始SQL语句，然后根据分页参数拼接了分页SQL片段，最后将原始SQL语句替换为分页SQL片段。
接下来，我们需要在Spring配置文件中配置这个分页插件：
@Configuration
public class MyBatisPlusConfig {
@Bean
public MyBatisPlusPaginationInterceptor myBatisPlusPaginationInterceptor() {
return new MyBatisPlusPaginationInterceptor();
}
}