spring加载不到.properties中属性问题(spring中类：PropertyPlaceholderConfigurer出现多次)

spring在加载properties时出现的问题

在spring.xml中将redis.properties

Exception in thread "main" org.springframework.beans.factory.BeanDefinitionStoreException: Invalid bean definition with name 'dsd' defined in class path resource [spring-mybatis.xml]: Could not resolve placeholder 'redis.time' in string value "${redis.time}"; nested exception is java.lang.IllegalArgumentException: Could not resolve placeholder 'redis.time' in string value "${redis.time}"

at org.springframework.beans.factory.config.PlaceholderConfigurerSupport.doProcessProperties(PlaceholderConfigurerSupport.java:223)
at org.springframework.beans.factory.config.PropertyPlaceholderConfigurer.processProperties(PropertyPlaceholderConfigurer.java:222)
at org.springframework.beans.factory.config.PropertyResourceConfigurer.postProcessBeanFactory(PropertyResourceConfigurer.java:86)
at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:284)
at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:166)
at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:681)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:523)
at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:93)
at com.groupds.provider.Provider.main(Provider.java:18)
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:144)
Caused by: java.lang.IllegalArgumentException: Could not resolve placeholder 'redis.time' in string value "${redis.time}"
at org.springframework.util.PropertyPlaceholderHelper.parseStringValue(PropertyPlaceholderHelper.java:174)
at org.springframework.util.PropertyPlaceholderHelper.replacePlaceholders(PropertyPlaceholderHelper.java:126)
at org.springframework.beans.factory.config.PropertyPlaceholderConfigurer$PlaceholderResolvingStringValueResolver.resolveStringValue(PropertyPlaceholderConfigurer.java:258)
at org.springframework.beans.factory.config.BeanDefinitionVisitor.resolveStringValue(BeanDefinitionVisitor.java:282)
at org.springframework.beans.factory.config.BeanDefinitionVisitor.resolveValue(BeanDefinitionVisitor.java:204)
at org.springframework.beans.factory.config.BeanDefinitionVisitor.visitPropertyValues(BeanDefinitionVisitor.java:141)
at org.springframework.beans.factory.config.BeanDefinitionVisitor.visitBeanDefinition(BeanDefinitionVisitor.java:82)
at org.springframework.beans.factory.config.PlaceholderConfigurerSupport.doProcessProperties(PlaceholderConfigurerSupport.java:220)

... 14 more

在spring中如果出现类似的错误，

那么出现异常信息的可能性有三种

（1）location中的属性文件配置错误

（2）location中定义的配置文件里面没有对应的placeholder值

（3）第三种就比较麻烦点，可能是Spring容器的配置问题

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Spring容器采用反射扫描的发现机制，在探测到Spring容器中有一个org.springframework.beans.factory.config.PropertyPlaceholderConfigurer的Bean就会停止对剩余PropertyPlaceholderConfigurer的扫描（Spring 3.1已经使用PropertySourcesPlaceholderConfigurer替代PropertyPlaceholderConfigurer了）。 

而这个基于命名空间的配置，其实内部就是创建一个PropertyPlaceholderConfigurer Bean而已。换句话说，即Spring容器仅允许最多定义一个PropertyPlaceholderConfigurer(或)，其余的会被Spring忽略掉（其实Spring如果提供一个警告就好了）。

<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="locations">
        <list>
            <value>classpath:jdbc.properties</value>
            <!--<value>classpath:redis.properties</value>-->
        </list>
    </property>
</bean>

总结：这个类在一个项目的spring.xml中配置一次1就够了。