Could not resolve placeholder

翻译过来的意思就是“无法解析占位符”

我遇到了一个问题，便是如此

常出现在myeclipse中Spring的初始化的过程中，是加载property配置文件的错误信息

信息如下

org.springframework.beans.factory.BeanDefinitionStoreException:

和

Invalid bean definition with name ‘xxxx’ defined in class path resource [Spring/applicationContext.xml]:

和

Could not resolve placeholder ‘xxxx’ in string value “${xxxx}”

我遇到问题的详细错误信息
严重: Exception sending context initialized event to listener instance of class org.springframework.web.context.ContextLoaderListener
org.springframework.beans.factory.BeanDefinitionStoreException: Invalid bean definition with name 'dataSource' defined in class path resource [Spring/applicationContext.xml]: Could not resolve placeholder 'jdbc.driverClass ' in string value "${jdbc.driverClass }"
at org.springframework.beans.factory.config.PlaceholderConfigurerSupport.doProcessProperties(PlaceholderConfigurerSupport.java:209)
at org.springframework.context.support.PropertySourcesPlaceholderConfigurer.processProperties(PropertySourcesPlaceholderConfigurer.java:174)
at org.springframework.context.support.PropertySourcesPlaceholderConfigurer.postProcessBeanFactory(PropertySourcesPlaceholderConfigurer.java:151)
at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:694)
at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:669)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:461)
at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:383)
at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:283)
at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:112)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4745)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5207)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.StandardContext.reload(StandardContext.java:3800)
at org.apache.catalina.startup.HostConfig.reload(HostConfig.java:1377)
at org.apache.catalina.startup.HostConfig.checkResources(HostConfig.java:1350)
at org.apache.catalina.startup.HostConfig.check(HostConfig.java:1586)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:280)
at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:94)
at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1164)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1388)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1392)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1360)
at java.lang.Thread.run(Thread.java:745)

通常可能的情况

• 文件路径错误
• 使用了多个 PropertyPlaceholderConfigurer
• 重复使用了 <context:property-placeholder>

解决方法

对于重复来说是添加ignore-unresolvable="true"属性
如：

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

而我所遇到的问题的不是以上，而是拼写错误——空格

<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
<property name="driverClass" value="${jdbc.driverClass }"></property>
.......

在value里的表达式里多了一个空格

${jdbc.driverClass }
更改后
${jdbc.driverClass}

问题解决了