关于系统中使用多个PropertyPlaceholderConfigurer的配置

Spring中PropertyPlaceholderConfigurer这个类，它是用来解析Java Properties属性文件值，并提供在spring配置期间替换使用属性值。接下来让我们逐渐的深入其配置。

基本的使用方法是：(1)

<bean id="propertyConfigurerForAnalysis" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="location">
        <value>classpath:/spring/include/dbQuery.properties</value>
    </property>
</bean>

其中classpath是引用src目录下的文件写法。

当存在多个Properties文件时，配置就需使用locations了：(2)

<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="locations">
       <list>
          <value>classpath:/spring/include/jdbc-parms.properties</value>
          <value>classpath:/spring/include/base-config.properties</value>
        </list>
    </property>
</bean>

接下来我们要使用多个PropertyPlaceholderConfigurer来分散配置，达到整合多工程下的多个分散的Properties文件，其配置如下：(3)

<bean id="propertyConfigurerForProject1" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="order" value="1" />
    <property name="ignoreUnresolvablePlaceholders" value="true" />
    <property name="location">
       <value>classpath:/spring/include/dbQuery.properties</value>
    </property>
</bean>

<bean id="propertyConfigurerForProject2" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="order" value="2" />
    <property name="ignoreUnresolvablePlaceholders" value="true" />
    <property name="locations">
      <list>
        <value>classpath:/spring/include/jdbc-parms.properties</value>
        <value>classpath:/spring/include/base-config.properties</value>
      </list>
    </property>
</bean>

其中order属性代表其加载顺序，而ignoreUnresolvablePlaceholders为是否忽略不可解析的Placeholder，如配置了多个PropertyPlaceholderConfigurer，则需设置为true