Com.mysql.jdbc.exceptions.jdbc4.CommunicationsException:Communications link Failure

When you start Tomcat, the following exception occurs:

DEBUG Resourcepool. Basicresourcepool-an exception occurred while acquiring a poolable resource. Would retry. Com.mysql.jdbc.exceptions.jdbc4.CommunicationsException:Communications link Failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has no received any packets from the server.  at Sun.reflect.NativeConstructorAccessorImpl.newInstance0 (Native Method)  at Sun.reflect.NativeConstructorAccessorImpl.newInstance (nativeconstructoraccessorimpl.java:57)  at Sun.reflect.DelegatingConstructorAccessorImpl.newInstance (delegatingconstructoraccessorimpl.java:45)  at Java.lang.reflect.Constructor.newInstance (constructor.java:525)  at com.mysql.jdbc.Util.handleNewInstance ( util.java:411)  at com.mysql.jdbc.SQLError.createCommunicationsException (sqlerror.java:1129)  at Com.mysql.jdbc.mysqlio.<init> (mysqlio.java:358)  at Com.mysql.jdbc.ConnectionImpl.coreConnect ( connectionimpl.java:2489)  at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly (connectionimpl.java:2526)  at Com.mysql.jdbc.ConnectionImpl.createNewIO (connectionimpl.java:2311)  at Com.mysql.jdbc.connectionimpl.<init> (Connectionimpl.java:834)  at com.mysql.jdbc.jdbc4connection.<init> (jdbc4connection.java:47)  at Sun.reflect.NativeConstructorAccessorImpl.newInstance0 (Native Method)  at Sun.reflect.NativeConstructorAccessorImpl.newInstance (nativeconstructoraccessorimpl.java:57)  at Sun.reflect.DelegatingConstructorAccessorImpl.newInstance (delegatingconstructoraccessorimpl.java:45)  at Java.lang.reflect.Constructor.newInstance (constructor.java:525)  at com.mysql.jdbc.Util.handleNewInstance ( util.java:411)  at com.mysql.jdbc.ConnectionImpl.getInstance (connectionimpl.java:416)  at Com.mysql.jdbc.NonRegisteringDriver.connect (nonregisteringdriver.java:347)  at Com.mchange.v2.c3p0.DriverManagerDataSource.getConnection (drivermanagerdatasource.java:134)  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) Caused By:java.net.ConnectException:Connection refused:connect  at java.net.DualStackPlainSocketImpl.connect0 ( Native Method)  at java.net.DualStackPlainSocketImpl.socketConnect (dualstackplainsocketimpl.java:69)  at Java.net.AbstractPlainSocketImpl.doConnect (abstractplainsocketimpl.java:339)  at Java.net.AbstractPlainSocketImpl.connectToAddress (abstractplainsocketimpl.java:200)  at Java.net.AbstraCtplainsocketimpl.connect (abstractplainsocketimpl.java:182)  at Java.net.PlainSocketImpl.connect ( plainsocketimpl.java:157)  at java.net.SocksSocketImpl.connect (sockssocketimpl.java:391)  at Java.net.Socket.connect (socket.java:579)  at java.net.Socket.connect (socket.java:528)  at Java.net.socket.<init> (socket.java:425)  at java.net.socket.<init> (Socket.java:241)  at Com.mysql.jdbc.StandardSocketFactory.connect (standardsocketfactory.java:256)  at Com.mysql.jdbc.MysqlIO. <init> (mysqlio.java:308) &nbsp ... More

Abnormal:

Finally find out why:

Because it is a boot directly start the project, forget to open the database service, so reported connectionexception, open the database service immediately.

Com.mysql.jdbc.exceptions.jdbc4.CommunicationsException:Communications link Failure