【c3p0】报错：Initializing c3p0 pool... com.mchange.v2.c3p0.ComboPooledDataSource [ acquireIncrement...

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按照书上的指导配置c3p0，但是运行不成功

一开始运行：

信息: Initializing c3p0 pool... com.mchange.v2.c3p0.ComboPooledDataSource [ acquireIncrement -> 3, acquireRetryAttempts -> 30, acquireRetryDelay -> 1000, autoCommitOnClose -> false, automaticTestTable -> null, breakAfterAcquireFailure -> false, checkoutTimeout -> 0, connectionCustomizerClassName -> null, connectionTesterClassName -> com.mchange.v2.c3p0.impl.DefaultConnectionTester, dataSourceName -> 1hgeby99n2wpirj7phm07|69847c5d, debugUnreturnedConnectionStackTraces -> false, description -> null, driverClass -> com.mysql.jdbc.Driver, factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, identityToken -> 1hgeby99n2wpirj7phm07|69847c5d, idleConnectionTestPeriod ->

然后我刷新了十几次，报如下异常了：

com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Data source rejected establishment of connection, message from server: "Too many connections"

先来看看我配置数据库连接池的代码：

public static Connection getConnection() throws PropertyVetoException, SQLException{//c3p0连接池ComboPooledDataSource cpds = new ComboPooledDataSource();try {cpds.setDriverClass(DriverURL);} catch (PropertyVetoException e) {// TODO Auto-generated catch blocke.printStackTrace();}cpds.setJdbcUrl(ConURL);cpds.setUser(username);cpds.setPassword(passwoed);cpds.setMaxPoolSize(30);cpds.setMinPoolSize(2);cpds.setInitialPoolSize(10);cpds.setMaxStatements(180);return cpds.getConnection();}

结合异常声明："Too many connections"，才知道原来出错的地方就在这里：

ComboPooledDataSource cpds = new ComboPooledDataSource();

每次getConnection都会创建一个ComboPooledDataSource类，ComboPooledDataSource是重量级类，创建比较耗费资源，当然会报错

用单例模式来创建ComboPooledDataSource类即可解决问题：

private static ComboPooledDataSource ds;static{ds = new ComboPooledDataSource();try {ds.setDriverClass(DriverURL);} catch (PropertyVetoException e) {// TODO Auto-generated catch blocke.printStackTrace();}ds.setJdbcUrl(ConURL);ds.setUser(username);ds.setPassword(passwoed);ds.setMaxPoolSize(30);ds.setMinPoolSize(2);ds.setInitialPoolSize(10);ds.setMaxStatements(180);}

我是用饿汉式，然后对getConnection方法进行修改：

public static Connection getConnection() throws PropertyVetoException, SQLException{//用连接池return ds.getConnection();}

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