maven+springmvc+mybatis项目从properties读数据库连接属性时拿不到连接，的研究与解决方案

初学过程中遇到的问题，记录并分享一下，如果文中有错误，望指正，谢谢~

那么现在进入正题：

运行环境：

win8 mysql jdk1.8

maven+springmvc+mybatis

c3p0(druid)

最近在看慕课网一个秒杀课程的视频

跟着老师敲啊敲，当运行到第一个junit测试时，偏偏他运行就可以我运行就错了。

无独有偶的发现身边，windows的同事就可我一样报错，mac的就没事（我就是windows，视频中老师就是mac）

那么具体是什么情况呢？

spring-dao.xml配置完数据库连接池属性后（错误代码）

<context:property-placeholder location="classpath:jdbc.properties"/>
<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
<!-- 配置连接池属性 -->
<property name="driverClass" value="${driver}"/>
<property name="jdbcUrl" value="${url}"/>
<property name="user" value="${username}"/>
<property name="password" value="${password}"/>

<!-- c3p0连接池的私有属性 -->
<property name="maxPoolSize" value="30"/>
<property name="minPoolSize" value="10"/>
<!-- 关闭连接后不自动commit -->
<property name="autoCommitOnClose" value="false"/>
<!-- 获取连接超时时间 -->
<property name="checkoutTimeout" value="1000"/>
<!-- 当获取链接失败重试次数 -->
<property name="acquireRetryAttempts" value="2"/>
</bean>

又填写了一个properties（错误代码）

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://127.0.0.1:3306/seckill?useUnicode=true&characterEncoding=utf8
username=root
password=root

但是当运行测试的手死活也拿不到链接，c3p0、druid数据库连接池都试过就是拿不到连接。

（详细异常见文章最后）

各种报

An attempt by a client to checkout a Connection has timed out.

Access denied for user ‘zilong’@’localhost’ (using password: YES)

基本上就是连不上数据库的意思

解决方案

（有些是网上找的，是这个病的现象，但不是我这个病的病理）

1. 填写连接池配置时value作为了标签且带了换行如：

<property name="driverClass">
<value>
${driver}
</value>
</property>
建议改为
<property name="driverClass" value="${driver}"/>

2.注意是不是这两段配置，书写时不小心多敲空格了，据说也会出现这种情况，基本上遇上一个问题属于一类（当然嘛，拿不到连接肯定也就这四个值的问题，多了空格回车肯定不行）

3.当然也有说，数据库版本与驱动版本不配的（我增加、减少版本都试了，不好使，可能是我没遇到这个病理，大家可以试试）

4.还有说与连接池的 max min init maxwait这些值有关，修改相关值试试。（教学视频的，练习demo的，一般不会是这个原因，毕竟现在就我一个线程测试。如果是实际项目开发中或者是之前可以后来突然不可以了的，可以试试这个。）

5.因为教学视频中用的c3p0，朋友说你试试druid呢。so，我试了，也不行。

6.最后发现把properties里的driver、url等等，都加上jdbc.，并在引用的地方也加上就好了，如：

xml中

<property name="driverClass" value="${jdbc.driver}"/>
<property name="jdbcUrl" value="${jdbc.url}"/>
<property name="user" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>

propert中

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306/seckill?useUnicode=true&characterEncoding=utf8
jdbc.username=root
jdbc.password=root

使用c3p0时所报异常

org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException:
### Error querying database.  Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is java.sql.SQLException: An attempt by a client to checkout a Connection has timed out.
### The error may exist in file [E:\workspace\seckill\target\classes\mapper\SeckillDao.xml]
### The error may involve org.seckill.dao.SeckillDao.queryById
### The error occurred while executing a query
### Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is java.sql.SQLException: An attempt by a client to checkout a Connection has timed out.

at org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:76)
at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:399)
at com.sun.proxy.$Proxy13.selectOne(Unknown Source)
at org.mybatis.spring.SqlSessionTemplate.selectOne(SqlSessionTemplate.java:165)
at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:69)
at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:53)
at com.sun.proxy.$Proxy14.queryById(Unknown Source)
at org.seckill.dao.SeckillDaoTest.queryById(SeckillDaoTest.java:37)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:73)
at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:82)
at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:73)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:224)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:83)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:68)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:163)
at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:119)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:42)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:234)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:74)

Caused by: org.apache.ibatis.exceptions.PersistenceException:

### Error querying database. Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is java.sql.SQLException: An attempt by a client to checkout a Connection has timed out.

### The error may exist in file [E:\workspace\seckill\target\classes\mapper\SeckillDao.xml]

### The error may involve org.seckill.dao.SeckillDao.queryById

### The error occurred while executing a query

### Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is java.sql.SQLException: An attempt by a client to checkout a Connection has timed out.

at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)

at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:122)

at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:113)

at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:73)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

at java.lang.reflect.Method.invoke(Method.java:498)

at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:386)

… 34 more

Caused by: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is java.sql.SQLException: An attempt by a client to checkout a Connection has timed out.

at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:80)

at org.mybatis.spring.transaction.SpringManagedTransaction.openConnection(SpringManagedTransaction.java:82)

at org.mybatis.spring.transaction.SpringManagedTransaction.getConnection(SpringManagedTransaction.java:68)

at org.apache.ibatis.executor.BaseExecutor.getConnection(BaseExecutor.java:315)

at org.apache.ibatis.executor.SimpleExecutor.prepareStatement(SimpleExecutor.java:75)

at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:61)

at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:303)

at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:154)

at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:102)

at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:82)

at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:120)

… 41 more

Caused by: java.sql.SQLException: An attempt by a client to checkout a Connection has timed out.

at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:106)

at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:65)

at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:527)

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)

… 51 more

Caused by: com.mchange.v2.resourcepool.TimeoutException: A client timed out while waiting to acquire a resource from com.mchange.v2.resourcepool.BasicResourcePool@d78795 – timeout at awaitAvailable()

at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:1317)

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)

… 54 more

使用druid时所报异常

java.lang.IllegalStateException: Failed to load ApplicationContext

at org.springframework.test.context.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:94)
at org.springframework.test.context.DefaultTestContext.getApplicationContext(DefaultTestContext.java:72)
at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.injectDependencies(DependencyInjectionTestExecutionListener.java:117)
at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.prepareTestInstance(DependencyInjectionTestExecutionListener.java:83)
at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:212)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTest(SpringJUnit4ClassRunner.java:200)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner$1.runReflectiveCall(SpringJUnit4ClassRunner.java:259)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.methodBlock(SpringJUnit4ClassRunner.java:261)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:219)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:83)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:68)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:163)
at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:119)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:42)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:234)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:74)
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSource' defined in class path resource [spring/spring-dao.xml]: Invocation of init method failed; nested exception is java.sql.SQLException: Access denied for user 'zilong'@'localhost' (using password: YES)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1574)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:539)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:303)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:299)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:755)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:757)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:480)
at org.springframework.test.context.support.AbstractGenericContextLoader.loadContext(AbstractGenericContextLoader.java:125)
at org.springframework.test.context.support.AbstractGenericContextLoader.loadContext(AbstractGenericContextLoader.java:60)
at org.springframework.test.context.support.AbstractDelegatingSmartContextLoader.delegateLoading(AbstractDelegatingSmartContextLoader.java:109)
at org.springframework.test.context.support.AbstractDelegatingSmartContextLoader.loadContext(AbstractDelegatingSmartContextLoader.java:261)
at org.springframework.test.context.DefaultCacheAwareContextLoaderDelegate.loadContextInternal(DefaultCacheAwareContextLoaderDelegate.java:68)
at org.springframework.test.context.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:86)
... 24 more
Caused by: java.sql.SQLException: Access denied for user 'zilong'@'localhost' (using password: YES)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:998)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3835)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3771)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:870)
at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:1659)
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1206)
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2239)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2270)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2069)
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:794)
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:44)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:389)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:399)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:325)
at com.alibaba.druid.filter.FilterChainImpl.connection_connect(FilterChainImpl.java:148)
at com.alibaba.druid.filter.stat.StatFilter.connection_connect(StatFilter.java:211)
at com.alibaba.druid.filter.FilterChainImpl.connection_connect(FilterChainImpl.java:142)
at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1410)
at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1464)
at com.alibaba.druid.pool.DruidDataSource.init(DruidDataSource.java:684)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeCustomInitMethod(AbstractAutowireCapableBeanFactory.java:1702)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1641)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1570)
... 39 more