springDI构造方法、set方法先后顺序和命名空间

构造方法和set方法的执行顺序

1. 配置文件配置如下：

    <bean id="computer" class="domain.Computer"></bean>

    <bean id="room" class="domain.Room">
        <property name="name" value="001"></property>
        <constructor-arg name="name" value="guanyu"></constructor-arg>
        <constructor-arg name="computer" ref="computer"></constructor-arg>
    </bean>

2.实体类：

public class Room {

    private String name;
    private Computer computer; //类与类关系 has a

    public Room(String name, Computer computer) {
        this.name = name;
        this.computer = computer;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Computer getComputer() {
        return computer;
    }

    public void setComputer(Computer computer) {
        this.computer = computer;
    }


    @Override
    public String toString() {
        return "Room{" +
                "name='" + name + '\'' +
                ", computer=" + computer +
                '}';
    }
}

3.测试代码

        Room room = (Room) factory1.getBean("room");
        System.out.println(room);

4.运行结果，展示的是set方法中的值

Room{name='001', computer=Computer{brand='null', name='null', price=null}}

5.原理：因为构造方法先执行，构造方法将值赋值为guanyu后，set方法又再次给name属性赋值一次，将guanyu改为001

命名空间

• 本质上就是配置文件的一种简写
• property p:
• constructor-arg c:
  举例：原来写法

<bean id="room" class="domain.Room">
      <property name="name" value="001"></property>
 </bean>

简写

<bean p:name="001"></bean>

1.配置文件中的头部配置文件需要配置
xmlns:c="http://www.springframework.org/schema/c"

原来写法
    <bean id="room" class="domain.Room">
        <constructor-arg name="name" value="guanyu"></constructor-arg>
        <constructor-arg name="computer" ref="computer"></constructor-arg>
    </bean>
简写
    <bean id="room" class="domain.Room" c:name="guanyu" c:computer-ref="computer">

    </bean>

3.测试代码

        Room room = (Room) factory1.getBean("room");
        System.out.println(room);

4.运行结果，展示的是set方法中的值

Room{name='guanyu', computer=Computer{brand='null', name='null', price=null}}