Spring bean自动装配的属性值注入的个人见解

来源：互联网发布：eia数据美国公布时间编辑：程序博客网时间：2024/06/12 20:59

Spring框架是现在开发使用比较流行的框架，主要的核心思想就是依赖注入(DI)和面向界面(AOP)，依赖注入使得对频繁对象的创建,使用、销毁等步骤脱离出来，统一放入Spring的IOC容器，由Spring的IOC容器统一管理项目中常用的类，从而将程序员从繁琐的对象关系处理中解放出来，下面分享一下个人学习的Spring的部分心得，希望对各位学习spring的同学有所启发，关于AOP和DI的源码实现后续下次给大家分享......

House类：只有一个People属性，验证引用的ref引用bean的set方法注入方式

package com.zhiwei.autowire;

public class House {

   private People people;

   public People getPeople() {
       return people;
   }

   public void setPeople(People people){
       this.people=people;
   }

   @Override
   public String toString() {
       return "House [people=" + people + "]";
   }
}

People类：存在一个name和Dog属性，主要时验证普通的set方法的值注入

package com.zhiwei.autowire;
/**People类：属性:name,dog*/
public class People {

   private String name;
   private Dog dog;

   public String getName() {
       return name;
   }
   public void setName(String name) {
       System.out.println("People is running setting.......");
       this.name = name;
   }
   public Dog getDog() {
       return dog;
   }
   public void setDog(Dog dog) {
       this.dog = dog;
   }

   @Override
   public String toString() {
       return "People [name=" + name + ", dog=" + dog + "]";
   }
}

dog:一个属性：dogName:测试构造方法属性值的注入

package com.zhiwei.autowire;

public class Dog {

   private String dogName;

   public String getDogName() {
       return dogName;
   }

   public void setDogName(String dogName) {
       this.dogName = dogName;
   }

   public Dog(String dogName) {
       System.out.println("Dog is initting by coustructor..........");
       this.dogName = dogName;
   }

   @Override
   public String toString() {
       return "Dog [dogName=" + dogName + "]";
   }
}

Spring的配置文件：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"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
               http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd
               http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd">
               


<bean id="dog" class="com.zhiwei.autowire.Dog">
<constructor-arg index="0" value="xiaohua"/>
</bean>


<bean id="people" class="com.zhiwei.autowire.People" autowire="byName">
<property name="name" value="squirrel"/>
</bean>


<bean id="house" class="com.zhiwei.autowire.House">
<property name="people" ref="people"></property>
</bean>
</beans>

测试类;测试Spring装配的结果

package com.zhiwei.autowire;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
* Spring装配：创建IOC容器中bean的写作关系的行为称为装配wiring
* bean注入的方式：
*   1: property:直接属性注入(set)
*   2：constructor-arg:构造函数注入：index 表示参数的序列号
* 注意：使用ref关联外部bean的javabean不能包含构造方法，否则报错,ref关联属性只能通过set进行属性注入
* 构造方法顺序：默认构造方法注入---->set属性注入
* bean初始化顺序：实例化bean按照applicationContext.xml配置顺序实例化
*
* 装配类型：
*    @resource：byName-->byType，匹配不上报错
*    @autowired:byType:匹配不上报错
*
*    byName:IOC容器中的bean初始化时未找到初始化对象则根据属性名和IOC容器中id相同的bean关联,注意最后是通过构造函数注入对象
*    byType:Bean初始化时未指定默认的属性值，则更具属性类型一致的其他bean关联
*    constructor:将关联的对象作为构造函数的参数装配进当前bean
*    autodetect:自动检测当前的byType和constuctor装配方式，不行则报错
*    default：beans设置的默认装配方式：default-autowire="autodetect"
*    no:无默认配置方式
*
* IOC容器：ApplicationContext和SessionFactory
*/
public class MainTest {

   public static void main(String[] args) {

       //初始化IOC容器
       ApplicationContext ac=new ClassPathXmlApplicationContext("com/zhiwei/autowire/applicationContext.xml");

        House house=(House) ac.getBean("house");
        System.out.println("house:"+house);

        People people=(People) ac.getBean("people");
        System.out.println("people:"+people);
   }
}

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