Spring Ioc 依赖查找

Spring ioc 有依赖查找和依赖注入，之前不太明白依赖查找是什么意思，翻了一大堆博客看了好多定义也不太清楚 ，后来看了小马哥视频，他通过代码演示，清楚地讲解了什么是 依赖查找以及几种依赖查找的方法，本文结合代码浅析一下Spring ioc的依赖查找，通过代码来更加形象的理解依赖查找。

1.根据bean名称查找：

• 实时查找

• 延时查找

1.配置xml文件

 <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
       ">
     <!--实时查找-->
     <bean id="User" class="thinking.in.spring.ioc.overview.domain.User">
         <property name="id" value="1"/>
         <property name="name" value="小明"/>
     </bean>
     <!--延时查找-->
     <bean id="objectFactory" class="org.springframework.beans.factory.config.ObjectFactoryCreatingFactoryBean">
         <property name="targetBeanName" value="User"/>
     </bean>
 </beans>

　

2.启动spring应用上下文

 public class DenpendencyLookupDemo {
     public static void main(String[] args) {
         BeanFactory beanFactory=new ClassPathXmlApplicationContext("META-INF/dependency-Lookup-context.xml");
       //时实查找
         User user=(User) beanFactory.getBean("User");
         System.out.println("实时查找"+user.toString());
         //延时查找
       ObjectFactory<User>  objectFactory= (ObjectFactory<User>)beanFactory.getBean("objectFactory");
       User user1=objectFactory.getObject();
         System.out.println("延时查找"+user1.toString());
     }
 }

输出：

2.通过类型查找

• 单个Bean对象

• 集合Bean对象

 /**
      * 根据类型查找单个bean
      * @param beanFactory
      */
     private static void lookupSingleByType(BeanFactory beanFactory){

         User user2 = beanFactory.getBean(User.class);
         System.out.println("根据类型时实查找单一" + user2.toString());
     }
     /**
      * 查找多个bean
      */
     private static void lookupCollectionBtType (BeanFactory beanFactory){
         if (beanFactory instanceof ListableBeanFactory) {
             ListableBeanFactory listableBeanFactory = (ListableBeanFactory) beanFactory;
             Map<String, User> users = listableBeanFactory.getBeansOfType(User.class);
             System.out.println("查找多个bean" + users);
         }
     }

输出：

3.通过注解查找

 <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
       ">
     <!--实时查找-->
     <bean id="User" class="thinking.in.spring.ioc.overview.domain.User">
         <property name="id" value="1"/>
         <property name="name" value="小明"/>
     </bean>
     <!--延时查找-->
     <bean id="objectFactory" class="org.springframework.beans.factory.config.ObjectFactoryCreatingFactoryBean">
         <property name="targetBeanName" value="User"/>
     </bean>
     <bean id="superUser" class="thinking.in.spring.ioc.overview.domain.SuperUser" parent="User" primary="true">
         <property name="number" value="1"/>
     </bean>
 </beans>

@Super注解

@Target({ElementType.TYPE}) @Retention(RetentionPolicy.RUNTIME) public @interface Super { }

SuperUser类

@Super
public class SuperUser extends User{
    private String number;

    public String getNumber() {
        return number;

    }

    public void setNumber(String number) {
        this.number = number;
    }

    @Override
    public String toString() {
        return "SuperUser{" +
                "number='" + number + '\'' +
                "} " + super.toString();
    }
}

用法

 /**
      * 通过注解查找
      * @param beanFactory
      */
     private static  void lookupByAnnotatonType(BeanFactory beanFactory){
         if(beanFactory instanceof ListableBeanFactory){
             ListableBeanFactory listableBeanFactory=(ListableBeanFactory)beanFactory;
                       //根据注解查找
             Map<String,User> users=( Map)listableBeanFactory.getBeansWithAnnotation(Super.class);
             System.out.println("查找标注@Super 所有的User集合对象"+users);
         }
     }

输出：

只查找出标注了@Super注解且是User类型的Bean