Spring xml中加载properties文件

一、 两个文件

1. applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
    <property name="driverClass" value="com.mysql.jdbc.Driver"></property>
    <property name="jdbcUrl" value="jdbc:mysql://localhost:3306/test"></property>
    <property name="user" value="root"></property>
    <property name="password" value="root"></property>
</beans>

2. jdbc.properties

jdbc.driverClassName=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/test
jdbc.username=root
jdbc.password=root

二、 将jdbc.properties文件加载到applicationContext.xml中，替换四个value

1.在beans标签属性中添加下边这段代码

xmlns:context="http://www.springframework.org/schema/context"

注：xmlns是XML Namespace的缩写，可译为“XML命名空间”

注：因为需要添加context:property-placeholder标签，而这个标签在http://www.springframework.org/schema/context命令空间中（即context命令空间），所以添加这行代码

2.在beans标签xsi:schemaLocation属性中添加新的位置

http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd

注：约束路径

3.加入标签context:property-placeholder

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

注：location=“jdbc.properties” 中 jdbc.properties为我们想要加载的properties文件全名

4.将4个value的key替换

<property name="driverClass" value="${jdbc.driverClassName}"></property>
<property name="jdbcUrl" value="${jdbc.url}"></property>
<property name="user" value="${jdbc.username}"></property>
<property name="password" value="${jdbc.password}"></property>

注：格式：value=“${key}”，key为jdbc.properties中的key

5.改完后的applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
                            http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">
	<!--加载外部properties文件-->
    <context:property-placeholder location="jdbc.properties"></context:property-placeholder>
    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
        <property name="driverClass" value="${jdbc.driverClassName}"></property>
        <property name="jdbcUrl" value="${jdbc.url}"></property>
        <property name="user" value="${jdbc.username}"></property>
        <property name="password" value="${jdbc.password}"></property>
    </bean>
</beans>

图文解析