spring5入门（八）：基于xml配置管理bean，自动装配、外部属性文件

自动装配

• 自动装配定义

根据指定装配规则（属性名称或者属性类型），Spring 自动将匹配的属性值进行注入

• 实现代码1：​​byName根据属性名称注入 ，注入值bean的id值和类属性名称一样​​

# 部门实体
public class Dept {

    @Override
    public String toString() {
        return "Dept{}";
    }

}

# 员工实体
public class Emp {

    private Dept dept;

    public void setDept(Dept dept) {
        this.dept = dept;
    }

    @Override
    public String toString() {
        return "Emp{" +
                "dept=" + dept +
                '}';
    }

    public void test() {
        System.out.println(dept);
    }

}

# 配置bean.xml
    <bean id="emp" class="com.ychen.spring.autowire.Emp" autowire="byName">
    </bean>

    <bean id="dept" class="com.ychen.spring.autowire.Dept"></bean>

# 测试方法
    @Test
    public void test4() {
        ApplicationContext context =
                new ClassPathXmlApplicationContext("bean3.xml");
        Emp emp = context.getBean("emp", Emp.class);
        System.out.println(emp);
    }

# 控制台
Emp{dept=Dept{}}

Process finished with exit code 0

• 实现代码2：​​byType根据属性类型注入​​

# 部门实体
public class Dept {

    @Override
    public String toString() {
        return "Dept{}";
    }

}

# 员工实体
public class Emp {

    private Dept dept;

    public void setDept(Dept dept) {
        this.dept = dept;
    }

    @Override
    public String toString() {
        return "Emp{" +
                "dept=" + dept +
                '}';
    }

    public void test() {
        System.out.println(dept);
    }

}

# 配置bean.xml
    <bean id="emp" class="com.ychen.spring.autowire.Emp" autowire="byType">
    </bean>

    <bean id="dept" class="com.ychen.spring.autowire.Dept"></bean>

# 测试方法
    @Test
    public void test4() {
        ApplicationContext context =
                new ClassPathXmlApplicationContext("bean3.xml");
        Emp emp = context.getBean("emp", Emp.class);
        System.out.println(emp);
    }

# 控制台
Emp{dept=Dept{}}

Process finished with exit code 0

• ​​byType缺陷：bean.xml中有2个bean时会报错​​



• 
  

外部属性文件

• 导入依赖



• 直接配置

<bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource">
    <property name="driverClassName" value="com.mysql.jdbc.Driver"></property>
    <property name="url" value="jdbc:mysql://localhost:3306/dbtest"></property>
    <property name="username" value="root"></property>
    <property name="password" value="123456"></property>
</bean>

• ​​使用context 名称空间​​
• src目录下创建jdbc.properties

prop.driverClass=com.mysql.jdbc.Driver
prop.url=jdbc:mysql://localhost:3306/userDb
prop.userName=root
prop.password=root

• bean.xml中添加：xmlns:context="​​http://www.springframework.org/schema/context​​​"​​http://www.springframework.org/schema/context​​​​http://www.springframework.org/schema/context/spring-context.xsd​​

<?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">

    <!--引入外部属性文件-->
    <context:property-placeholder location="classpath:jdbc.properties"/>

    <!--配置连接池-->
    <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource">
        <property name="driverClassName" value="${prop.driverClass}"></property>
        <property name="url" value="${prop.url}"></property>
        <property name="username" value="${prop.userName}"></property>
        <property name="password" value="${prop.password}"></property>
    </bean>

</beans>