【Spring框架】IoC注解方式实现注入

一. 概述：

      基于Annotation装配，在和Spring IoC有关的配置技巧，这些技巧都是基于XML形式的配置文件进行的。在Spring中，尽管使用XML配置文件实现Bean的装配工作，但如果应用中有很多Bean时，则会导致XML配置文件过于臃肿，给后续的维护和升级工作带来了一定的困难。为此，从Spring2.0版本开始引入注解的配置方式，将Bean的配置和Bean实现类结合在一起，可进一步减少配置文件的代码量。

二.  常用的IoC注解 

三. 两种方式注入

(一)、 @Configuration和@Bean

文件目录如下，一个GoodsHandler接口对应着它的两个实现类GoodsHandlerImpl类和OthergoodsHandlerImpl类, 还有一个配置类AnnotationConfig和测试类RunTest4

1. GoodsHandler接口：

public interface GoodsHandler {
    public void showInfo();
}

2. GoodsHandlerImpl.java

public class GoodsHandlerImpl implements GoodsHandler{
    @Override
    public void showInfo() {
        System.out.println("show goods information");
    }
}

3. OthergoodsHandlerImpl.java 

public class OtherGoodsHandlerImpl implements GoodsHandler{
    @Override
    public void showInfo() {
        System.out.println("other information");
    }
}

4. GoodsHandlerApp.java

public class GoodsHandlerApp {
    @Value("GoodsHandlerApp---description")
    private String description;
    private GoodsHandler goodsHandler;
    public GoodsHandlerApp(GoodsHandler goodsHandler){
        this.goodsHandler = goodsHandler;
    }
    public void goodsHandler(){
        this.goodsHandler.showInfo();
        System.out.println(this.description);
    }

}

 5. AnnotationConfig.java

@Configuration
public class AnnotationConfig {
    @Bean
    public GoodsHandlerImpl goodsHandlerimpl(){return new GoodsHandlerImpl();}
    @Bean
    public OtherGoodsHandlerImpl othergoodsHandlerimpl(){return new OtherGoodsHandlerImpl();}
    @Bean
    public GoodsHandlerApp goodsHandlerApp(GoodsHandler goodsHandlerimpl){return new GoodsHandlerApp(goodsHandlerimpl);}

}

  

 6. RunTest4.java

public class RunTest4 {
    public static void main(String[] args){
        ApplicationContext apc = new AnnotationConfigApplicationContext(AnnotationConfig.class);
        GoodsHandlerApp goodsHandlerApp = apc.getBean(GoodsHandlerApp.class);
        goodsHandlerApp.goodsHandler();
    }
}

输出：

 

 (二)、 @Configuration，@ComponentScan和@Component

1.  接口和测试类没有发生改变

2. GoodsHandlerImpl.java

@Component("goodsHandlerImpl")
public class GoodsHandlerImpl implements GoodsHandler{
    @Override
    public void showInfo() {
        System.out.println("show goods information");
    }
}

3. OthergoodsHandlerImpl.java 

@Component("otherGoodsHandlerImpl")
public class OtherGoodsHandlerImpl implements GoodsHandler{
    @Override
    public void showInfo() {
        System.out.println("other information");
    }
}

 4. GoodsHandlerApp.java

@Component
public class GoodsHandlerApp {
    @Value("GoodsHandlerApp---description")
     private String description;
     private GoodsHandler goodsHandler;

     public GoodsHandlerApp(@Qualifier(value = "goodsHandlerImpl")GoodsHandler goodsHandler){
         this.goodsHandler = goodsHandler;
     }

     public void goodsHandler(){
        this.goodsHandler.showInfo();
        System.out.println(this.description);
    }

}

 5. AnnotationConfig.java

@Configuration
@ComponentScan(basePackages = "org.example.anno")
public class AnnotationConfig {

}

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 输出：