1：net.sf.hibernate.connection
此包中的類為提供數(shù)據(jù)源連接池的類，其中用到了C3P0，DBCP，DriverManager等第三方連接池插件；
其中ConnectionProvider為一致對(duì)外接口；所有的功能類都實(shí)現(xiàn)的他的接口；
/**
???????? * Initialize the connection provider from given properties.
???????? * @param props <tt>SessionFactory</tt> properties
???????? */
public void configure(Properties props) throws HibernateException;
????????/**
???????? * Grab a connection
???????? * @return a JDBC connection
???????? * @throws SQLException
???????? */
????????public Connection getConnection() throws SQLException;
????????/**
???????? * Dispose of a used connection.
???????? * @param conn a JDBC connection
???????? * @throws SQLException
???????? */
????????public void closeConnection(Connection conn) throws SQLException;
????????
????????/**
???????? * Release all resources held by this provider. JavaDoc requires a second sentence.
???????? * @throws HibernateException
???????? */
????????public void close() throws HibernateException;
源碼中的注釋把方法功能描述的很具體，我再次就不再加介紹了，現(xiàn)在具體的拿出兩個(gè)實(shí)現(xiàn)類來具體看一下他的功能；
1.1????????C3P0ConnectionProvider implements ConnectionProvider
public void configure(Properties props) throws HibernateException {
//獲取數(shù)據(jù)庫的驅(qū)程和URL;
????????????????String jdbcDriverClass = props.getProperty(Environment.DRIVER);
????????????????String jdbcUrl = props.getProperty(Environment.URL);
????????//對(duì)第三方插件所需要的屬性進(jìn)行定制包裝；
????????????????Properties connectionProps = ConnectionProviderFactory.getConnectionProperties(props);
????????????????
????????????????log.info("C3P0 using driver: " + jdbcDriverClass + " at URL: " + jdbcUrl);
????????????????log.info("Connection properties: " + connectionProps);
????????????????//加載數(shù)據(jù)庫驅(qū)動(dòng)程序
????????????????if (jdbcDriverClass==null) {
????????????????????????log.warn("No JDBC Driver class was specified by property " + Environment.DRIVER);
????????????????}
????????????????else {
????????????????????????try {
????????????????????????????????Class.forName(jdbcDriverClass);
????????????????????????}
????????????????????????catch (ClassNotFoundException cnfe) {
????????????????????????????????String msg = "JDBC Driver class not found: " + jdbcDriverClass;
????????????????????????????????log.fatal(msg);
????????????????????????????????throw new HibernateException(msg);
????????????????????????}
????????????????}
????????????????
????????????????try {
????????//加載配置文件中的properties;????????????????
????????int minPoolSize = PropertiesHelper.getInt(Environment.C3P0_MIN_SIZE, props, 1);
????????int maxPoolSize = PropertiesHelper.getInt(Environment.C3P0_MAX_SIZE, props, 100);
????????int maxIdleTime = PropertiesHelper.getInt(Environment.C3P0_TIMEOUT, props, 0);
????????int maxStatements = PropertiesHelper.getInt(Environment.C3P0_MAX_STATEMENTS, props, 0);
????????int acquireIncrement = PropertiesHelper.getInt(Environment.C3P0_ACQUIRE_INCREMENT, props, 1);
????????int idleTestPeriod = PropertiesHelper.getInt(Environment.C3P0_IDLE_TEST_PERIOD, props, 0);
????????boolean validateConnection = PropertiesHelper.getBoolean(Environment.C3P0_VALIDATE_CONNECTION, props);
????????????????????????//有C3P0的連接池接口來設(shè)置第三方插件所需要的屬性
????????????此處為與第三方插件的結(jié)合點(diǎn)；
????????????????????????PoolConfig pcfg = new PoolConfig();
????????????????????????pcfg.setInitialPoolSize(minPoolSize);
????????????????????????pcfg.setMinPoolSize(minPoolSize);
????????????????????????pcfg.setMaxPoolSize(maxPoolSize);
????????????????????????pcfg.setAcquireIncrement(acquireIncrement);
????????????????????????pcfg.setMaxIdleTime(maxIdleTime);
????????????????????????pcfg.setMaxStatements(maxStatements);
????????????????????????pcfg.setTestConnectionOnCheckout(validateConnection);
????????????????????????pcfg.setIdleConnectionTestPeriod(idleTestPeriod);
????????????????????????
?????????? //用第三方插件來初始化連接池，并向程序返回了JDBC的DataSource接口，使得任何第三方插件的上層程序都不必去引入相應(yīng)具體的第三方的類庫，實(shí)現(xiàn)的低耦合；
????????????????????????/*DataSource unpooled = DataSources.unpooledDataSource(
????????????????????????????????jdbcUrl, props.getProperty(Environment.USER), props.getProperty(Environment.PASS)
????????????????????????);*/
????????????????????????DataSource unpooled = DataSources.unpooledDataSource(jdbcUrl, connectionProps);
????????????????????????ds = DataSources.pooledDataSource(unpooled, pcfg);
????????????????????????
????????????????}
????????????????catch (Exception e) {
????????????????????????log.fatal("could not instantiate C3P0 connection pool", e);
????????????????????????throw new HibernateException("Could not instantiate C3P0 connection pool", e);
????????????????}
????????????????
????????????????String i = props.getProperty(Environment.ISOLATION);
????????????????if (i==null) {
????????????????????????isolation=null;
????????????????}
????????????????else {
????????????????????????isolation = new Integer(i);
????????????????????????log.info( "JDBC isolation level: " + Environment.isolationLevelToString( isolation.intValue() ) );
????????????????}
????????????????
????????}
public Connection getConnection() throws SQLException {
????????????????final Connection c = ds.getConnection();
????????//設(shè)置事務(wù)的隔離級(jí)別；
????????????????if (isolation!=null) c.setTransactionIsolation( isolation.intValue() );
????????????????if ( c.getAutoCommit() ) c.setAutoCommit(false);
????????????????return c;
????????}
public void closeConnection(Connection conn) throws SQLException {
????????????????conn.close();
????????}
public void close() {
????????????????try {
????????????????????????DataSources.destroy(ds);
????????????????}
????????????????catch (SQLException sqle) {
????????????????????????log.warn("could not destroy C3P0 connection pool", sqle);
????????????????}
????????}
1.2????????class DriverManagerConnectionProvider implements ConnectionProvider
public void configure(Properties props) throws HibernateException {
????????????????
????????????????String driverClass = props.getProperty(Environment.DRIVER);
????????????????
????????????????poolSize = PropertiesHelper.getInt(Environment.POOL_SIZE, props, 20); //default pool size 20
????????????????log.info("Using Hibernate built-in connection pool (not for production use!)");
????????????????log.info("Hibernate connection pool size: " + poolSize);
????????????????
????????????????isolation = PropertiesHelper.getInteger(Environment.ISOLATION, props);
????????????????if (isolation!=null)
????????????????log.info( "JDBC isolation level: " + Environment.isolationLevelToString( isolation.intValue() ) );
????????????????
????????????????if (driverClass==null) {
????????????????????????log.warn("no JDBC Driver class was specified by property " + Environment.DRIVER);
????????????????}
????????????????else {
????????????????????????try {
????????????????????????????????// trying via forName() first to be as close to DriverManager's semantics
????????????????????????????????Class.forName(driverClass);????????????????????????????????????????????????????????????????
????????????????????????}
????????????????????????catch (ClassNotFoundException cnfe) {
????????????????????????????????try {
????????????????????????????????????????ReflectHelper.classForName(driverClass);
????????????????????????????????} catch (ClassNotFoundException e) {
????????????????????????????????String msg = "JDBC Driver class not found: " + driverClass;
????????????????????????????????log.fatal(msg);
????????????????????????????????throw new HibernateException(msg);
????????????????????????????????}
????????????????????????}
????????????????}
????????????????
????????????????url = props.getProperty(Environment.URL);
????????????????if (url==null) {
????????????????????????String msg = "JDBC URL was not specified by property " + Environment.URL;
????????????????????????log.fatal(msg);
????????????????????????throw new HibernateException(msg);
????????????????}
????????????????
????????????????connectionProps = ConnectionProviderFactory.getConnectionProperties(props);
????????????????
????????????????log.info( "using driver: " + driverClass + " at URL: " + url );
????????????????log.info("connection properties: " + connectionProps);
????????????????
????????}
??
????????public Connection getConnection() throws SQLException {
????????????????
????????????????if ( log.isTraceEnabled() ) log.trace( "total checked-out connections: " + checkedOut );
????????????????//鎖死連接池，只需一個(gè)線程訪問，池中有連接就提供，沒有在新建一個(gè)；
????????????????synchronized (pool) {
????????????????????????if ( !pool.isEmpty() ) {
????????????????????????????????int last = pool.size() - 1;
????????????????????????????????if ( log.isTraceEnabled() ) {
????????????????????????????????????????log.trace("using pooled JDBC connection, pool size: " + last);
????????????????????????????????????????checkedOut++;
????????????????????????????????}
????????????????????????????????Connection pooled = (Connection) pool.remove(last);
????????????????????????????????if (isolation!=null) pooled.setTransactionIsolation( isolation.intValue() );
????????????????????????????????if ( pooled.getAutoCommit() ) pooled.setAutoCommit(false);
????????????????????????????????return pooled;
????????????????????????}
????????????????}
????????????????
????????????????log.debug("opening new JDBC connection");
????????????????Connection conn = DriverManager.getConnection(url, connectionProps);
????????????????if (isolation!=null) conn.setTransactionIsolation( isolation.intValue() );
????????????????if ( conn.getAutoCommit() ) conn.setAutoCommit(false);
????????????????if ( log.isDebugEnabled() ) {
????????????????????????log.debug( "created connection to: " + url + ", Isolation Level: " + conn.getTransactionIsolation() );
????????????????}
????????????????if ( log.isTraceEnabled() ) checkedOut++;
????????????????
????????????????return conn;
????????}
public void closeConnection(Connection conn) throws SQLException {
????????????????
????????????????if ( log.isDebugEnabled() ) checkedOut--;
????????????????//如果池中連接已滿就釋放連接，否則就加到連接池中；
????????????????synchronized (pool) {
????????????????????????int currentSize = pool.size();
????????????????????????if ( currentSize < poolSize ) {
????????????????????????????????if ( log.isTraceEnabled() ) log.trace("returning connection to pool, pool size: " + (currentSize + 1) );
????????????????????????????????pool.add(conn);
????????????????????????????????return;
????????????????????????}
????????????????}
????????????????
????????????????log.debug("closing JDBC connection");
????????????????
????????????????try {
????????????????????????conn.close();
????????????????}
????????????????catch (SQLException sqle) {
????????????????????????JDBCExceptionReporter.logExceptions(sqle);
????????????????????????throw sqle;
????????????????}
????????}
public void close() {
????????????????//清空連接池；
????????????????log.info("cleaning up connection pool: " + url);
????????????????
????????????????Iterator iter = pool.iterator();
????????????????while ( iter.hasNext() ) {
????????????????????????try {
????????????????????????????????( (Connection) iter.next() ).close();
????????????????????????}
????????????????????????catch (SQLException sqle) {
????????????????????????????????log.warn("problem closing pooled connection", sqle);
????????????????????????}
????????????????}
????????????????pool.clear();
????????????????
????????}