java.net.ConnectException: Connection timed out: connect

今天启动tomcat之后，发现报错：

com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: ** BEGIN NESTED EXCEPTION ** java.net.ConnectExceptionMESSAGE: Connection timed out: connectSTACKTRACE:java.net.ConnectException: Connection timed out: connectat java.net.PlainSocketImpl.socketConnect(Native Method)at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)at java.net.Socket.connect(Socket.java:519)at java.net.Socket.connect(Socket.java:469)at java.net.Socket.<init>(Socket.java:366)at java.net.Socket.<init>(Socket.java:209)at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:173)at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:268)at com.mysql.jdbc.Connection.createNewIO(Connection.java:2745)at com.mysql.jdbc.Connection.<init>(Connection.java:1553)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 19 ms ago.at com.mysql.jdbc.Connection.createNewIO(Connection.java:2820)at com.mysql.jdbc.Connection.<init>(Connection.java:1553)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$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)[2015-11-12 09:46:22,476 DEBUG] [com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0] com.mchange.v2.resourcepool.BasicResourcePool - An exception occurred while acquiring a poolable resource. Will retry.com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: ** BEGIN NESTED EXCEPTION ** java.net.ConnectExceptionMESSAGE: Connection timed out: connectSTACKTRACE:java.net.ConnectException: Connection timed out: connectat java.net.PlainSocketImpl.socketConnect(Native Method)at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)at java.net.Socket.connect(Socket.java:519)at java.net.Socket.connect(Socket.java:469)at java.net.Socket.<init>(Socket.java:366)at java.net.Socket.<init>(Socket.java:209)at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:173)at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:268)at com.mysql.jdbc.Connection.createNewIO(Connection.java:2745)at com.mysql.jdbc.Connection.<init>(Connection.java:1553)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 19 ms ago.at com.mysql.jdbc.Connection.createNewIO(Connection.java:2820)at com.mysql.jdbc.Connection.<init>(Connection.java:1553)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$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)[2015-11-12 09:46:22,476 DEBUG] [com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1] com.mchange.v2.resourcepool.BasicResourcePool - An exception occurred while acquiring a poolable resource. Will retry.com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: ** BEGIN NESTED EXCEPTION ** java.net.ConnectExceptionMESSAGE: Connection timed out: connectSTACKTRACE:java.net.ConnectException: Connection timed out: connectat java.net.PlainSocketImpl.socketConnect(Native Method)at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)at java.net.Socket.connect(Socket.java:519)at java.net.Socket.connect(Socket.java:469)at java.net.Socket.<init>(Socket.java:366)at java.net.Socket.<init>(Socket.java:209)at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:173)at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:268)at com.mysql.jdbc.Connection.createNewIO(Connection.java:2745)at com.mysql.jdbc.Connection.<init>(Connection.java:1553)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 19 ms ago.at com.mysql.jdbc.Connection.createNewIO(Connection.java:2820)at com.mysql.jdbc.Connection.<init>(Connection.java:1553)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$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)[2015-11-12 09:46:44,491 DEBUG] [com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0] com.mchange.v2.resourcepool.BasicResourcePool - An exception occurred while acquiring a poolable resource. Will retry.com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: ** BEGIN NESTED EXCEPTION ** java.net.ConnectException MESSAGE: Connection timed out: connectSTACKTRACE:java.net.ConnectException: Connection timed out: connectat java.net.PlainSocketImpl.socketConnect(Native Method)at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)at java.net.Socket.connect(Socket.java:519)at java.net.Socket.connect(Socket.java:469)at java.net.Socket.<init>(Socket.java:366)at java.net.Socket.<init>(Socket.java:209)at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:173)at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:268)at com.mysql.jdbc.Connection.createNewIO(Connection.java:2745)at com.mysql.jdbc.Connection.<init>(Connection.java:1553)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:2820)at com.mysql.jdbc.Connection.<init>(Connection.java:1553)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$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)[2015-11-12 09:46:44,492 DEBUG] [com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1] com.mchange.v2.resourcepool.BasicResourcePool - An exception occurred while acquiring a poolable resource. Will retry.com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: ** BEGIN NESTED EXCEPTION ** java.net.ConnectExceptionMESSAGE: Connection timed out: connectSTACKTRACE:java.net.ConnectException: Connection timed out: connectat java.net.PlainSocketImpl.socketConnect(Native Method)at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)at java.net.Socket.connect(Socket.java:519)at java.net.Socket.connect(Socket.java:469)at java.net.Socket.<init>(Socket.java:366)at java.net.Socket.<init>(Socket.java:209)at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:173)at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:268)at com.mysql.jdbc.Connection.createNewIO(Connection.java:2745)at com.mysql.jdbc.Connection.<init>(Connection.java:1553)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 1 ms ago.at com.mysql.jdbc.Connection.createNewIO(Connection.java:2820)at com.mysql.jdbc.Connection.<init>(Connection.java:1553)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$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)[2015-11-12 09:46:44,492 DEBUG] [com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2] com.mchange.v2.resourcepool.BasicResourcePool - An exception occurred while acquiring a poolable resource. Will retry.com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: ** BEGIN NESTED EXCEPTION ** java.net.ConnectExceptionMESSAGE: Connection timed out: connectSTACKTRACE:java.net.ConnectException: Connection timed out: connectat java.net.PlainSocketImpl.socketConnect(Native Method)at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)at java.net.Socket.connect(Socket.java:519)at java.net.Socket.connect(Socket.java:469)at java.net.Socket.<init>(Socket.java:366)at java.net.Socket.<init>(Socket.java:209)at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:173)at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:268)at com.mysql.jdbc.Connection.createNewIO(Connection.java:2745)at com.mysql.jdbc.Connection.<init>(Connection.java:1553)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:2820)at com.mysql.jdbc.Connection.<init>(Connection.java:1553)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)

这个其实就是数据库方面的问题：

1、数据库连接不正确

2、数据库服务没有开启