c3p0 连接mysql 时错误信息

错误信息

com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database server. Attempted reconnect 3 times. Giving up.
    at sun.reflect.GeneratedConstructorAccessor165.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)
    at com.mysql.jdbc.Util.getInstance(Util.java:408)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:918)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:897)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:886)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:860)
    at com.mysql.jdbc.ConnectionImpl.connectWithRetries(ConnectionImpl.java:2104)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2029)
    at com.mysql.jdbc.ConnectionImpl.(ConnectionImpl.java:779)
    at com.mysql.jdbc.JDBC4Connection.(JDBC4Connection.java:47)
    at sun.reflect.GeneratedConstructorAccessor163.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:389)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:330)
    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)
Caused by: java.sql.SQLException: Access denied for user 'Administrator'@'192.168.0.104' (using password: YES)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:964)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3973)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3909)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:873)
    at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:1710)
    at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1226)
    at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2198)
    at com.mysql.jdbc.ConnectionImpl.connectWithRetries(ConnectionImpl.java:2045)
    ... 17 more

c3p0 连接mysql 时出错

    ### The error may exist in file [D:\软件\apache-tomcat-8.0.9\webapps\websocket-s\WEB-INF\classes\co\cn\test\mapper\User.xml]
### The error may involve co.cn.test.dao.IUserDao.getUser
### The error occurred while executing a query
### Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is java.sql.SQLException: Connections could not be acquired from the underlying da
tabase!] with root cause
com.mchange.v2.resourcepool.CannotAcquireResourceException: A ResourcePool could not acquire a resource from its primary factory or source.
    at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:1319)
    at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:557)
    at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:477)
    at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:525)
    at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:128)
    at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils.java:111)
    at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:77)
    at org.mybatis.spring.transaction.SpringManagedTransaction.openConnection(SpringManagedTransaction.java:84)
    at org.mybatis.spring.transaction.SpringManagedTransaction.getConnection(SpringManagedTransaction.java:70)
    at org.apache.ibatis.executor.BaseExecutor.getConnection(BaseExecutor.java:271)
    at org.apache.ibatis.executor.SimpleExecutor.prepareStatement(SimpleExecutor.java:69)
    at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:56)
    at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:259)
    at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:132)
    at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:105)
    at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:81)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.apache.ibatis.plugin.Invocation.proceed(Invocation.java:46)
    at com.github.pagehelper.SqlUtil._processPage(SqlUtil.java:401)
    at com.github.pagehelper.SqlUtil.processPage(SqlUtil.java:374)
    at com.github.pagehelper.PageHelper.intercept(PageHelper.java:255)
    at org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:57)
    at com.sun.proxy.$Proxy30.query(Unknown Source)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:104)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:98)

错误原因：

　　在系统中也有个username属性，这时系统变量覆盖了Properties中的值，这时取得username的值为系统的用户名Administrator，密码为properties中的password去查询数据库，此时用户名名和密码并不匹配就会报错。在Spring完成注入时是用 “${..}” 方式获取值完成注入的。而通过这种表达式也能直接获取到JVM系统属性……….

解决方案：

　　方案一：将properties文件中的username换成user或其他就字符串就可以成功获取连接访问数据库。建议：username时敏感词汇，为了安全起见还是尽量不要使用username。

　　方案二：在Spring配置文件中修改成：

　　　　　　添加一个system-properties-mode属性

　　　　　　该属性有三个值：FALLBACK　　— 默认值，不存在时覆盖

　　　　　　　　　　　　　　NEVER　　　 — 不覆盖

　　　　　　　　　　　　　　OVERRIDE　　— 覆盖