spring 加载配置文件的相关配置总结

PropertyPlaceholderConfigurer
      注意： Spring容器仅允许最多定义一个PropertyPlaceholderConfigurer(或<context:property-placeholder/>)，其余的会被Spring忽略掉。
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）。

一：配置单个Properties文件

<bean id="deployProperties" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
      <property name="location">
          <value>classpath:config/sysconfig/sysconfig.properties</value>
      </property>
  </bean>

<bean id="deployProperties" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
      <property name="location" value="classpath:config/sysconfig/sysconfig.properties"/>
 </bean>

二：配置多个Properties文件

<bean id="deployProperties" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
      <property name="locations">
       <list>
        <value>classpath:config/dbconfig/database.properties</value>
        <value>classpath:config/sysconfig/sysconfig.properties</value>
        <value>file:/opt/demo/config/demo-mq.properties</value>
    </list>
     </property>
   </bean>

三：简化操作
为简化PropertyPlaceholderConfigurer的使用，Spring提供了<context:property-placeholder/>元素。下面给出了配置示例，启用它后，开发者便不用配置PropertyPlaceholderConfigurer对象了。

<context:property-placeholder location="classpath:jdbc.properties"/>

四：参考用例

1.

1. applicationContext.xml
<bean id="deployProperties" class="org.springframework.beans.factory.config.PropertiesFactoryBean">
        <property name="locations" >
        <list>
            <value>classpath:config/dbconfig/database.properties</value>
            <value>classpath:config/sysconfig/sysconfig.properties</value>
        </list>
        </property>
    </bean>
 // 其中classpath是引用src目录下的文件写法

<import resource="classpath:config/spring/spring-data.xml" /> 

spring-data.xml
<context:property-placeholder  properties-ref="deployProperties" />

2.

applicationContext.xml
<context:property-placeholder location="classpath:config/*config/*.properties"/>   

3.

applicationContext.xml
 <bean id="deployProperties" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
      <property name="locations">
       <list>
        <value>classpath:config/dbconfig/database.properties</value>
        <value>classpath:config/sysconfig/sysconfig.properties</value>
        <value>file:/opt/demo/config/demo-mq.properties</value>
    </list>
     </property>
   </bean>

4.

applicationContext.xml
   <bean   class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="order" value="1" />
        <property name="ignoreUnresolvablePlaceholders" value="true" />
        <property name="location" value="classpath:config/dbconfig/database.properties"/>
    </bean>
    <bean   class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="order" value="2" />
        <property name="ignoreUnresolvablePlaceholders" value="true" />
        <property name="location" value="classpath:config/sysconfig/sysconfig.properties"/>
    </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

5.

applicationContext.xml
  <bean id="dbResources" class="java.util.ArrayList">
        <constructor-arg>
        <list>
            <value>classpath:config/dbconfig/database.properties</value>
            <value>classpath:config/sysconfig/sysconfig.properties</value>
        </list>
        </constructor-arg>
    </bean> 

<bean id="deployProperties" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
      <property name="locations" ref="dbResources">

     </property>
   </bean>

6.

applicationContext.xml
    <bean id="configproperties" class="org.springframework.beans.factory.config.PropertiesFactoryBean">
        <property name="locations" >
        <list>
            <value>classpath:config/dbconfig/database.properties</value>
            <value>classpath:config/sysconfig/sysconfig.properties</value>
        </list>
        </property>
   </bean>
   <bean id="deployProperties" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
       <property name="properties" ref="configproperties">
       </property>
   </bean>  

7.context 标签和PropertyPlaceholderConfigurer 混合在一起要加ignoreUnresolvablePlaceholders

<context:property-placeholder location="classpath:config/*config/database.properties"/>

 <bean   class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="order" value="2" />
        <property name="ignoreUnresolvablePlaceholders" value="true" />
        <property name="location" value="classpath:config/sysconfig/sysconfig.properties"/>
    </bean>

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