Could not resolve placeholder 'jdbc.url' in string value "${jdbc.url}"

报错信息：

<span style="font-family:Microsoft YaHei;font-size:14px;"><span style="font-family:Microsoft YaHei;font-size:14px;">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 file [G:\Computer\Java\MyObject\taotao\taotao-manager\taotao-manager-web\target\classes\spring\applicationContext-dao.xml]: Could not resolve placeholder 'jdbc.url' in string value "${jdbc.url}"; nested exception is java.lang.IllegalArgumentException: Could not resolve placeholder 'jdbc.url' in string value "${jdbc.url}"
at org.springframework.beans.factory.config.PlaceholderConfigurerSupport.doProcessProperties(PlaceholderConfigurerSupport.java:211)
at org.springframework.context.support.PropertySourcesPlaceholderConfigurer.processProperties(PropertySourcesPlaceholderConfigurer.java:180)
at org.springframework.context.support.PropertySourcesPlaceholderConfigurer.postProcessBeanFactory(PropertySourcesPlaceholderConfigurer.java:155)
at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:265)
at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:162)
at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:606)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:462)
at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:403)
at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:306)
at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:106)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4939)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5434)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1559)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1549)
at java.util.concurrent.FutureTask.run(FutureTask.java:262)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:744)</span></span>

这个Bug，一般的都会说，你的*.properties 属性文件是否存在，文件中，名称是否与applicationcontext.xml 中的文件名称是否一致，一开始，我也是天真的这么认为的，然后还认认真真的对比了半天，没毛病啊。

下边是properties 属性文件

<span style="font-family:Microsoft YaHei;font-size:14px;">jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://192.168.25.134:3306/SCTest?characterEncoding=utf-8
jdbc.username=root
jdbc.password=root</span>

对比一下，正确。而且工程的jar包中也包含JDBC的。

后来，找了半天，经过大神的指导，找到了原因：

Could not resolve placeholder就是eclipse在运行过程中要加在properties文件中的jdbc.url这个配置项，由于没有找到无法加在，就会报这个错。

解决方法：

在Spring 3中可以用如下方式解决，增加ignore-unresolvable="true"属性，注意必须都要加上

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

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

在Spring 2.5中，<context:property-placeholder>没有ignore-unresolvable属性，此时可以改用PropertyPlaceholderConfigurer。其实<context:property-placeholder location="xxx.properties" ignore-unresolvable="true" />与下面的配置是等价的

<bean id="XX" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"> 

<property name="location" value="xxx.properties" /> 

<property name="ignoreUnresolvablePlaceholders" value="true" /> 

</bean>

OK，可以了。