Spring的<context:property-placeholder.../>在junit中不起作用，失效，解决方法

大家都知道，我们使用spring框架的时候喜欢把可以配置的变量放入一个properties配置文件中，然后在spring的applicationContext.xml配置文件中加入配置：

<context:property-placeholder location="classpath:*.properties" ignore-unresolvable="true"/>

最后就可以在applicationContext.xml中愉快的使用${attributeName}来获取properties中的值了，屡试不爽。获取方式如下：

这种配置在正常启动项目的时候工作的很好，并且很简洁，我肥肠的稀饭，然而，我今天做练习junit测试的时候，居然报错！如下：

java.lang.IllegalStateException: Failed to load ApplicationContext

    at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:124)
    at org.springframework.test.context.support.DefaultTestContext.getApplicationContext(DefaultTestContext.java:83)
    at org.springframework.test.context.web.ServletTestExecutionListener.setUpRequestContextIfNecessary(ServletTestExecutionListener.java:183)
    at org.springframework.test.context.web.ServletTestExecutionListener.prepareTestInstance(ServletTestExecutionListener.java:123)
    at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:228)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTest(SpringJUnit4ClassRunner.java:230)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner$1.runReflectiveCall(SpringJUnit4ClassRunner.java:289)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.methodBlock(SpringJUnit4ClassRunner.java:291)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:249)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:89)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:193)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:117)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:42)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:262)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:84)
    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 com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSource' defined in class path resource [context-mybatis.xml]: Invocation of init method failed; nested exception is java.sql.SQLException: ${driverClassName}
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1583)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:553)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:778)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:843)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:541)
    at org.springframework.test.context.web.AbstractGenericWebContextLoader.loadContext(AbstractGenericWebContextLoader.java:133)
    at org.springframework.test.context.web.AbstractGenericWebContextLoader.loadContext(AbstractGenericWebContextLoader.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.cache.DefaultCacheAwareContextLoaderDelegate.loadContextInternal(DefaultCacheAwareContextLoaderDelegate.java:98)
    at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:116)
    ... 29 more
Caused by: java.sql.SQLException: ${driverClassName}
    at com.alibaba.druid.util.JdbcUtils.createDriver(JdbcUtils.java:570)
    at com.alibaba.druid.pool.DruidDataSource.init(DruidDataSource.java:697)
    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:1713)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1650)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1579)
    ... 44 more
Caused by: java.lang.ClassNotFoundException: ${driverClassName}
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:264)
    at com.alibaba.druid.util.JdbcUtils.createDriver(JdbcUtils.java:568)
    ... 52 more

诸如此类吧，反正就是找不到我properties中配置的变量。

我的配置文件：

driverClassName=com.mysql.jdbc.Driver
jdbc_url=jdbc:mysql://localhost:3306/***-demo?useUnicode=true&characterEncoding=UTF-8
jdbc_username=root
jdbc_password=root

经过各种挣扎，各种调换位置，铩羽而归！but 楼主不抛弃，不放弃，最后还是完美的解决了问题。方案如下：

1. 直接写死（废话），这种方式肯定可以解决，但是这不符合我广大程序猿的传统美德。
2. 　　采用如下配置替换<context:property-placeholder...

   <bean id="propertyPlaceHolderConfigurer"
             class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
           <property name="locations">
               <list>
                   <value>classpath:dbconfig.properties</value>
                   <value>classpath:system-config.properties</value>
               </list>
           </property>
       </bean>

   最后重新启动junit测试，诱人的小绿条蠢蠢欲动。至此问题解决，特此记下，下面送上junit的测试代码样子：

   /**
    * 测试使用SqlSessionTemplate
    * Created by ascend on 2017/6/7 14:27.
    */
   @RunWith(SpringJUnit4ClassRunner.class)
   @WebAppConfiguration
   //配置了@ContextConfiguration注解并使用该注解的locations属性指明spring和配置文件
   @ContextConfiguration(locations = {"classpath:context-mybatis.xml", "classpath:context-spring.xml", "classpath:context-springmvc.xml"})　　//也可以用“classpath:context-*.xml”取代
   public class SqlSessionTest {
   
       @Autowired
       private SqlSession sqlSession;
   
       @Test
       public void testSqlSession(){
           System.out.println("sqlSession = " + sqlSession);
           TestStudentPO studentPO = sqlSession.selectOne("com.***.manage.gen.dao.mapper.TestStudentPOMapper.selectByPrimaryKey", 1L);
           System.out.println("studentPO = " + studentPO);
       }
   }

   结果：

   studentPO = TestStudentPO [Hash = 1934908288, id=1, name=张三, age=24]

作者原创，转载请注明：http://www.cnblogs.com/adeng/p/6957463.html