xml形式配置DataSource
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd"> <configuration> <properties resource="/com/cn/cs/config.properties"/> <environments default="development"> <environment id="development"> <transactionManager type="JDBC"/> <dataSource type="POOLED"> <property name="driver" value="${oracle.driver}"/> <property name="url" value="${oracle.url}"/> <property name="username" value="${oracle.username}"/> <property name="password" value="${oracle.password}"/> <property name="poolMaximumActiveConnections" value="10"/> <!--最大活跃连接数 --> <property name="poolMaximumIdleConnections" value="5"/> <!--最大空闲连接数--> <property name="poolTimeToWait" value="20000"/> <!--创建连接时最大等待时间20s--> </dataSource> </environment> </environments> <mappers> <mapper resource="/com/cn/cs/mapping/UserCsMapper.xml"/> </mappers>
</configuration>
mybatis中DataSource节点有一个 type属性. 有三个可选值: pooled(连接池), unpooled(非连接池), jndi
mybatis内部定义了一个DataSourceFactory接口
public interface DataSourceFactory { void setProperties(Properties props); DataSource getDataSource(); }
根据type 属性值分别对应实现类.
pooled --> PooledDataSourceFactory
unpooled --> UnpooledDataSourceFactory
jndi--> JndiDataSourceFactory
这三个实现类都实现了 DataSourceFactory 的 DataSource getDataSource()方法.
PooledDataSourceFactory.getDataSource() 返回 PooledDataSource.
UnpooledDataSourceFactory.getDataSource() 返回 UnpooledDataSource
JndiDataSourceFactory.getDataSource() 返回 环境中的 DataSource
DataSource 将会保存在Environment 的静态内部类Builder中.
连接池的初始化
dataSource 此时只会保存好配置信息.连接池此时并没有创建好连接.只有当程序在调用操作数据库的方法时,才会出示化连接.
管理连接池的类为PooledDateSource 这个类中有一个获取连接的方法.
这个方法会先判断是否有空闲连接,有的话会直接将连接取出来.如果没有则判断当前活跃的连接是否大于最大空闲连接数.如果小于则创建一个新的连接.
否则将旧的连接删掉一个,并创建一个新的连接.
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; }
原文地址:https://www.cnblogs.com/ldspeace/p/10854422.html