java-spring 通过配置文件获取bean

1、druid.properties

# mysql连接参数
jdbc.driver-class-name=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/wangdb?useUnicode=true&characterEncoding=utf8&serverTimezone=GMT%2B8&useSSL=false&&useServerPrepStmts=true
jdbc.username=admin
jdbc.password=Admin@123
jdbc.initialSize=5
jdbc.minIdle=5
jdbc.maxActive=20

2、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
">
    <context:property-placeholder location="druid.properties"/>
   <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource">
       <property name="driverClassName" value="${jdbc.driver-class-name}"/>
       <property name="url" value="${jdbc.url}"/>
       <property name="username" value="${jdbc.username}"/>
       <property name="password" value="${jdbc.password}"/>
       <property name="maxActive" value="${jdbc.maxActive}"/>
       <property name="minIdle" value="${jdbc.minIdle}"/>
       <property name="initialSize" value="${jdbc.initialSize}"/>
   </bean>
    <bean id="userDao" class="cn.tjhis.dao.impl.UserDaoImpl">
        <property name="dataSource" ref="dataSource"/>
    </bean>
<!--    <beans id="UserDaoImplrDao" class="cn.tjhis.factory.UserDaoFactoryBean" />-->
    <bean id="userService" class="cn.tjhis.service.impl.UserServiceImpl" init-method="init" destroy-method="destroy">
<!--        <constructor-arg name="userDao" ref="userDao" />-->
<!--        <constructor-arg name="name" value="我"/>-->
        <property name="userDao" ref="userDao"/>
    </bean>
</beans>

推荐写法

• classpath*:表示不仅仅加载当前路径的，也包含依赖包中的配置文件
• system-properties-mode：表示系统属性的模式 never 不用系统属性，防止重名被覆盖掉

 <context:property-placeholder location="classpath*:*.properties" system-properties-mode="NEVER"/>