Too many connections 错误

Question

这个错误一般什么情况下发生，如何处理呢。16:45:51,703  WARN JDBCExceptionReporter:71 - SQL Error: 1040, SQLState: 08004
16:45:51,703 ERROR JDBCExceptionReporter:72 - Data source rejected establishment of connection,  message from server: "Too many connections"
16:45:51,718  WARN JDBCExceptionReporter:71 - SQL Error: 1040, SQLState: 08004
16:45:51,718 ERROR JDBCExceptionReporter:72 - Data source rejected establishment of connection,  message from server: "Too many connections"
16:45:51,718  INFO DefaultLoadEventListener:95 - Error performing load command
org.hibernate.exception.JDBCConnectionException: Cannot open connection
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:74)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:29)
at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:420)
at org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:144)
at org.hibernate.jdbc.AbstractBatcher.prepareQueryStatement(AbstractBatcher.java:105)
at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1561)
at org.hibernate.loader.Loader.doQuery(Loader.java:661)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:224)
at org.hibernate.loader.Loader.loadEntity(Loader.java:1785)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:47)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:41)
at org.hibernate.persister.entity.AbstractEntityPersister.load(AbstractEntityPersister.java:2730)
at org.hibernate.event.def.DefaultLoadEventListener.loadFromDatasource(DefaultLoadEventListener.java:365)
at org.hibernate.event.def.DefaultLoadEventListener.doLoad(DefaultLoadEventListener.java:346)
at org.hibernate.event.def.DefaultLoadEventListener.load(DefaultLoadEventListener.java:123)
at org.hibernate.event.def.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:177)
at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:87)
at org.hibernate.impl.SessionImpl.fireLoad(SessionImpl.java:862)
at org.hibernate.impl.SessionImpl.get(SessionImpl.java:799)
at org.springframework.orm.hibernate3.HibernateTemplate$2.doInHibernate(HibernateTemplate.java:489)
at org.springframework.orm.hibernate3.HibernateTemplate.execute(HibernateTemplate.java:372)
at org.springframework.orm.hibernate3.HibernateTemplate.get(HibernateTemplate.java:483)
at org.springframework.orm.hibernate3.HibernateTemplate.get(HibernateTemplate.java:477)
at model.CibprojectDAO.findById(CibprojectDAO.java:67)
at busdao.XiangmuobjectDAOImpl.saveXiangMuData(XiangmuobjectDAOImpl.java:38)
at autorun.ReadTxt2DB.ReadDataDBWrite(ReadTxt2DB.java:146)
at autorun.ReadTxt2DB.init(ReadTxt2DB.java:211)
at autorun.MyTask.run(MyTask.java:12)
at java.util.TimerThread.mainLoop(Timer.java:512)
at java.util.TimerThread.run(Timer.java:462)
Caused by: com.mysql.jdbc.exceptions.MySQLNonTransientConnectionException: Data source rejected establishment of connection,  message from server: "Too many connections"
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:921)
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1053)
at com.mysql.jdbc.Connection.createNewIO(Connection.java:2743)
at com.mysql.jdbc.Connection.<init>(Connection.java:1553)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:266)
at org.apache.commons.dbcp.DriverConnectionFactory.createConnection(DriverConnectionFactory.java:38)
at org.apache.commons.dbcp.PoolableConnectionFactory.makeObject(PoolableConnectionFactory.java:294)
at org.apache.commons.pool.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:771)
at org.apache.commons.dbcp.PoolingDataSource.getConnection(PoolingDataSource.java:96)
at org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDataSource.java:880)
at org.springframework.orm.hibernate3.LocalDataSourceConnectionProvider.getConnection(LocalDataSourceConnectionProvider.java:81)
at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:417)
... 27 more
16:45:51,718 ERROR CibprojectDAO:71 - get failed
org.springframework.dao.DataAccessResourceFailureException: Cannot open connection; nested exception is org.hibernate.exception.JDBCConnectionException: Cannot open connection
Caused by: 

Answer 1

org.hibernate.exception.JDBCConnectionException: Cannot open connection
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:74)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:29)
at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:420)
at org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:144)
at org.hibernate.jdbc.AbstractBatcher.prepareQueryStatement(AbstractBatcher.java:105)
at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1561)
at org.hibernate.loader.Loader.doQuery(Loader.java:661)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:224)
at org.hibernate.loader.Loader.loadEntity(Loader.java:1785)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:47)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:41)
at org.hibernate.persister.entity.AbstractEntityPersister.load(AbstractEntityPersister.java:2730)
at org.hibernate.event.def.DefaultLoadEventListener.loadFromDatasource(DefaultLoadEventListener.java:365)
at org.hibernate.event.def.DefaultLoadEventListener.doLoad(DefaultLoadEventListener.java:346)
at org.hibernate.event.def.DefaultLoadEventListener.load(DefaultLoadEventListener.java:123)
at org.hibernate.event.def.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:177)
at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:87)
at org.hibernate.impl.SessionImpl.fireLoad(SessionImpl.java:862)
at org.hibernate.impl.SessionImpl.get(SessionImpl.java:799)
at org.springframework.orm.hibernate3.HibernateTemplate$2.doInHibernate(HibernateTemplate.java:489)
at org.springframework.orm.hibernate3.HibernateTemplate.execute(HibernateTemplate.java:372)
at org.springframework.orm.hibernate3.HibernateTemplate.get(HibernateTemplate.java:483)
at org.springframework.orm.hibernate3.HibernateTemplate.get(HibernateTemplate.java:477)
at model.CibprojectDAO.findById(CibprojectDAO.java:67)
at busdao.XiangmuobjectDAOImpl.saveXiangMuData(XiangmuobjectDAOImpl.java:38)
at autorun.ReadTxt2DB.ReadDataDBWrite(ReadTxt2DB.java:146)
at autorun.ReadTxt2DB.init(ReadTxt2DB.java:211)
at autorun.MyTask.run(MyTask.java:12)
at java.util.TimerThread.mainLoop(Timer.java:512)
at java.util.TimerThread.run(Timer.java:462)
Caused by: com.mysql.jdbc.exceptions.MySQLNonTransientConnectionException: Data source rejected establishment of connection,  message from server: "Too many connections"
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:921)
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1053)
at com.mysql.jdbc.Connection.createNewIO(Connection.java:2743)
at com.mysql.jdbc.Connection.<init>(Connection.java:1553)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:266)
at org.apache.commons.dbcp.DriverConnectionFactory.createConnection(DriverConnectionFactory.java:38)
at org.apache.commons.dbcp.PoolableConnectionFactory.makeObject(PoolableConnectionFactory.java:294)
at org.apache.commons.pool.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:771)
at org.apache.commons.dbcp.PoolingDataSource.getConnection(PoolingDataSource.java:96)
at org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDataSource.java:880)
at org.springframework.orm.hibernate3.LocalDataSourceConnectionProvider.getConnection(LocalDataSourceConnectionProvider.java:81)
at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:417)
... 27 more
Exception in thread "Timer-0" org.springframework.dao.DataAccessResourceFailureException: Cannot open connection; nested exception is org.hibernate.exception.JDBCConnectionException: Cannot open connection
Caused by: org.hibernate.exception.JDBCConnectionException: Cannot open connection
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:74)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:29)
at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:420)
at org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:144)
at org.hibernate.jdbc.AbstractBatcher.prepareQueryStatement(AbstractBatcher.java:105)
at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1561)
at org.hibernate.loader.Loader.doQuery(Loader.java:661)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:224)
at org.hibernate.loader.Loader.loadEntity(Loader.java:1785)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:47)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:41)
at org.hibernate.persister.entity.AbstractEntityPersister.load(AbstractEntityPersister.java:2730)
at org.hibernate.event.def.DefaultLoadEventListener.loadFromDatasource(DefaultLoadEventListener.java:365)
at org.hibernate.event.def.DefaultLoadEventListener.doLoad(DefaultLoadEventListener.java:346)
at org.hibernate.event.def.DefaultLoadEventListener.load(DefaultLoadEventListener.java:123)
at org.hibernate.event.def.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:177)
at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:87)
at org.hibernate.impl.SessionImpl.fireLoad(SessionImpl.java:862)
at org.hibernate.impl.SessionImpl.get(SessionImpl.java:799)
at org.springframework.orm.hibernate3.HibernateTemplate$2.doInHibernate(HibernateTemplate.java:489)
at org.springframework.orm.hibernate3.HibernateTemplate.execute(HibernateTemplate.java:372)
at org.springframework.orm.hibernate3.HibernateTemplate.get(HibernateTemplate.java:483)
at org.springframework.orm.hibernate3.HibernateTemplate.get(HibernateTemplate.java:477)
at model.CibprojectDAO.findById(CibprojectDAO.java:67)
at busdao.XiangmuobjectDAOImpl.saveXiangMuData(XiangmuobjectDAOImpl.java:38)
at autorun.ReadTxt2DB.ReadDataDBWrite(ReadTxt2DB.java:146)
at autorun.ReadTxt2DB.init(ReadTxt2DB.java:211)
at autorun.MyTask.run(MyTask.java:12)
at java.util.TimerThread.mainLoop(Timer.java:512)
at java.util.TimerThread.run(Timer.java:462)
Caused by: com.mysql.jdbc.exceptions.MySQLNonTransientConnectionException: Data source rejected establishment of connection,  message from server: "Too many connections"
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:921)
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1053)
at com.mysql.jdbc.Connection.createNewIO(Connection.java:2743)
at com.mysql.jdbc.Connection.<init>(Connection.java:1553)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:266)
at org.apache.commons.dbcp.DriverConnectionFactory.createConnection(DriverConnectionFactory.java:38)
at org.apache.commons.dbcp.PoolableConnectionFactory.makeObject(PoolableConnectionFactory.java:294)
at org.apache.commons.pool.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:771)
at org.apache.commons.dbcp.PoolingDataSource.getConnection(PoolingDataSource.java:96)
at org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDataSource.java:880)
at org.springframework.orm.hibernate3.LocalDataSourceConnectionProvider.getConnection(LocalDataSourceConnectionProvider.java:81)
at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:417)
... 27 more

Answer 2

九成九是因为前面的程序打开了连接没有关闭对数据库的操作应该要这样写：Connection conn = null;try{
    conn = DriverManager.getConnection(......);
    // ......
}catch(Exception ex){
    // ......
}finally{
    if(conn != null){
         try{ conn.close(); }catch(Throwable ex1){}
    }
}虽然没有 finally 程序也可以运行，但是它没有释放数据库的连接

Answer 3

如果是用 hibernate，就必须关闭 hibernate 的 Session:Session session = null;try{
    session = HibernateSessionFactory.getCurrentSession();
    //......
}catch(......){
}finally{
    if(session != null){
        try{ session.close(); }catch(Throwable ex){}
    }
}