mysql数据库C3P0连接池Acquisition Attempt Failed错误每2分钟发一次警告

Question

2010-11-17 2:02:32 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask run警告: com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@fc84f2 -- Acquisition Attempt Failed!!! Clearing pending acquires. While trying to acquire a needed new resource, we failed to succeed more than the maximum number of allowed acquisition attempts (30). Last acquisition attempt exception: 
com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: ** BEGIN NESTED EXCEPTION ** java.lang.NullPointerExceptionSTACKTRACE:java.lang.NullPointerException
at com.mysql.jdbc.Connection.checkTransactionIsolationLevel(Connection.java:2044)
at com.mysql.jdbc.Connection.initializePropsFromServer(Connection.java:4094)
at com.mysql.jdbc.Connection.createNewIO(Connection.java:2789)
at com.mysql.jdbc.Connection.<init>(Connection.java:1555)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:135)
at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:182)
at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:171)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137)
at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014)
at com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32)
at com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810)
at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
** END NESTED EXCEPTION **Last packet sent to the server was 0 ms ago.
at com.mysql.jdbc.Connection.createNewIO(Connection.java:2847)
at com.mysql.jdbc.Connection.<init>(Connection.java:1555)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:135)
at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:182)
at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:171)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137)
at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014)
at com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32)
at com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810)
at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)c3p0的连接池 直接在程序里配置的=======================================================================
  private ConnectionManager() throws SQLException, PropertyVetoException {
        dataSource = new ComboPooledDataSource();        dataSource.setUser("");
        dataSource.setPassword("");
        dataSource.setJdbcUrl("");
        dataSource.setDriverClass("");
        dataSource.setInitialPoolSize(5);
        dataSource.setMinPoolSize(1);
        dataSource.setMaxPoolSize(10);
        dataSource.setMaxStatements(50);
        dataSource.setMaxIdleTime(600);
        dataSource.setAutoCommitOnClose(true); 
    }    public static final ConnectionManager getInstance() {
        if (instance == null) {
            try {
                instance = new ConnectionManager();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
       
        return instance;
    }    public synchronized final Connection getConnection() {
        Connection conn = null;
        try {
        
            conn = dataSource.getConnection();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return conn;
    }
    protected void finalize() throws Throwable {
       DataSources.destroy(dataSource); //关闭datasource
       super.finalize();
      }