4------自动装配

自动装配

1. 自动装配是使用spring满足bean依赖的一种方法
2. spring会在应用上下文为某个bean寻找其依赖的bean。

方式种类

1. 在xml中显示配置；前面的博客讲过了！
2. 在java中显示配置；通过注解实现的
3. 隐式的bean发现机制和自动装配

重点讲第三种：隐式的bean发现机制和自动装配

component scanning（组件扫描）：spring会自动发现应用上下文所创建的bean

自动装配（autowiring）：spring自动满足bean之间的依赖，也就是我们说的IOC/DI

正常的：

<?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="dog" class="com.kuang.pojo.Dog"/>
   <bean id="cat" class="com.kuang.pojo.Cat"/>

   <bean id="user" class="com.kuang.pojo.User">
       <property name="cat" ref="cat"/>
       <property name="dog" ref="dog"/>
       <property name="str" value="qinjiang"/>
   </bean>
</beans>

使用第三种方法：

通过名字：

 

 

 通过类型：

 

 来吧 ，小小的使用注解，任性一次吧

添加头文件

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

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

实体类

package demo1.com.sicheng.entity;


import org.springframework.beans.factory.annotation.Autowired;

import java.util.List;

public class Hello {

    private String name;

    @Autowired
    private List<Person> person;

    public String getName() {
        return name;
    }

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

    public List<Person> getPerson() {
        return person;
    }

    public void setPerson(List<Person> person) {
        this.person = person;
    }

    public Hello(String name, List<Person> person) {
        this.name = name;
        this.person = person;
    }

    public Hello() {
    }

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

package demo1.com.sicheng.entity;

public class Person {

    private int age;

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public Person(int age) {
        this.age = age;
    }

    public Person() {
    }

    @Override
    public String toString() {
        return "Person{" +
                "age=" + age +
                '}';
    }
}

 

 

 xml文件

<?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:annotation-config/>
    <bean id="person" class="demo1.com.sicheng.entity.Person">
        <property name="age" value="10"/>
    </bean>
    
    <bean id="hello" class="demo1.com.sicheng.entity.Hello"/>
</beans>

测试文件

import demo1.com.sicheng.entity.Hello;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SpringTest {

    @Test
    public void HelloTest(){
        ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
        Hello hello = (Hello)context.getBean("hello");
        System.out.println(hello.toString());
    }
}