idea启动，mysql连接超时错误

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.)
    at org.apache.tomcat.dbcp.dbcp.BasicDataSource.createPoolableConnectionFactory(BasicDataSource.java:1549) ~[tomcat-dbcp.jar:7.0.79]
    at org.apache.tomcat.dbcp.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1388) ~[tomcat-dbcp.jar:7.0.79]
    at org.apache.tomcat.dbcp.dbcp.BasicDataSource.getConnection(BasicDataSource.java:1044) ~[tomcat-dbcp.jar:7.0.79]
    at org.springframework.jdbc.datasource.DataSourceTransactionManager.doBegin(DataSourceTransactionManager.java:203) ~[spring-jdbc-3.2.3.RELEASE.jar:3.2.3.RELEASE]
    ... 77 common frames omitted
Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.7.0_45]
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57) ~[na:1.7.0_45]
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.7.0_45]
    at java.lang.reflect.Constructor.newInstance(Constructor.java:526) ~[na:1.7.0_45]
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:411) ~[mysql-connector-java-5.1.26.jar:na]
    at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1121) ~[mysql-connector-java-5.1.26.jar:na]
    at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:357) ~[mysql-connector-java-5.1.26.jar:na]
    at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2482) ~[mysql-connector-java-5.1.26.jar:na]
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2519) ~[mysql-connector-java-5.1.26.jar:na]
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2304) ~[mysql-connector-java-5.1.26.jar:na]
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:834) ~[mysql-connector-java-5.1.26.jar:na]
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47) ~[mysql-connector-java-5.1.26.jar:na]
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.7.0_45]
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57) ~[na:1.7.0_45]
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.7.0_45]
    at java.lang.reflect.Constructor.newInstance(Constructor.java:526) ~[na:1.7.0_45]
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:411) ~[mysql-connector-java-5.1.26.jar:na]
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:416) ~[mysql-connector-java-5.1.26.jar:na]
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:346) ~[mysql-connector-java-5.1.26.jar:na]
    at org.apache.tomcat.dbcp.dbcp.DriverConnectionFactory.createConnection(DriverConnectionFactory.java:38) ~[tomcat-dbcp.jar:7.0.79]
    at org.apache.tomcat.dbcp.dbcp.PoolableConnectionFactory.makeObject(PoolableConnectionFactory.java:582) ~[tomcat-dbcp.jar:7.0.79]
    at org.apache.tomcat.dbcp.dbcp.BasicDataSource.validateConnectionFactory(BasicDataSource.java:1556) ~[tomcat-dbcp.jar:7.0.79]
    at org.apache.tomcat.dbcp.dbcp.BasicDataSource.createPoolableConnectionFactory(BasicDataSource.java:1545) ~[tomcat-dbcp.jar:7.0.79]
    ... 80 common frames omitted
Caused by: java.net.ConnectException: Connection timed out: connect
    at java.net.DualStackPlainSocketImpl.connect0(Native Method) ~[na:1.7.0_45]
    at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:79) ~[na:1.7.0_45]
    at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339) ~[na:1.7.0_45]
    at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200) ~[na:1.7.0_45]
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182) ~[na:1.7.0_45]
    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172) ~[na:1.7.0_45]
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[na:1.7.0_45]
    at java.net.Socket.connect(Socket.java:579) ~[na:1.7.0_45]
    at java.net.Socket.connect(Socket.java:528) ~[na:1.7.0_45]
    at java.net.Socket.<init>(Socket.java:425) ~[na:1.7.0_45]
    at java.net.Socket.<init>(Socket.java:241) ~[na:1.7.0_45]
    at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:259) ~[mysql-connector-java-5.1.26.jar:na]
    at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:307) ~[mysql-connector-java-5.1.26.jar:na]
    ... 96 common frames omitted
2018-04-25 10:26:18,388 [RMI TCP Connection(3)-127.0.0.1] DEBUG org.activiti.engine.impl.interceptor.LogInterceptor - --- SchemaOperationsProcessEngineBuild finished --------------------------------------------------------
2018-04-25 10:26:18,389 [RMI TCP Connection(3)-127.0.0.1] DEBUG org.activiti.engine.impl.interceptor.LogInterceptor -

报错原因：

因为idea切换分支前，设置了另外一个项目的数据库配置，切换分支后，未更改数据库配置，前者需要连接VPN才能访问，所以报数据库连接超时错误。

生活点滴，记录下。