使用spring注解——定义bean和自动注入

今天药忘吃喽~ 2023-06-02 05:25 1阅读 0赞

对于java bean的定义和依赖配置，使用xml文件真心是不方便。

今天学习如何用注解，解决bean的定义和注入。

**常用注解：**

1、自动注入：@Resources，@Autowired

2、Bean定义：@Component、@Repository、@Service 和 @Constroller

@Component是个泛化概念，可以用在任何层次。如果是web开发，尽量用@Repository、@Service 和 @Constroller

**Demo：**

以丁磊养猪为例，Pig和DingLei两个类

1、Pig类，以@Component定义为bean

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@Component
    public class Pig {
    
        private Double weight;
        private String color;
        public Pig(){
            this.weight = 55.8;
            this.color = "black";
        }
        public Double getWeight() {
            return weight;
        }
        public void setWeight(Double weight) {
            this.weight = weight;
        }
        public String getColor() {
            return color;
        }
        public void setColor(String color) {
            this.color = color;
        }
        public String toString(){
            return  weight + " kg " + color + " pig!";
        }
    }

2、DingLei类，以@Component定义为bean，同时用@Autowired注入依赖pig

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@Component
    public class DingLei {
    
        @Autowired
        private Pig pig;
        
        public Pig getPig() {
            return pig;
        }
        public void setPig(Pig pig) {
            this.pig = pig;
        }
        
        public String toString(){
            return "Dinglei has a " + pig.toString();
        }
    }

3、bean.xml文件中，配置包扫描，注解才生效

<context:annotation-config/> :启用注释驱动自动注入

<context:component-scan/>：对类包进行扫描以实施注释驱动 Bean 定义，同时隐式启用注释驱动自动注入。因此，配置这个就可以

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<?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-3.0.xsd">
            
           
           <context:component-scan base-package="anotation"/>
    </beans>

4、测试类

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public class TestAnotation {
        @SuppressWarnings("resource")
        public static void main(String[] arg) {
            ApplicationContext context = new ClassPathXmlApplicationContext("bean.xml");
            DingLei dingLei = (DingLei) context.getBean("dingLei");
            System.out.println( dingLei.toString() );        
        }
    }

5、运行测试类，可以看到输出。说明注解成功定义bean，并成功完成注入

信息: Loading XML bean definitions from class path resource [bean.xml]
    Dinglei has a 55.8 kg black pig!

参考：

谢谢无私分享的伙伴，写的非常详细的一篇：[Spring注解详解][Spring]

转载于:https://www.cnblogs.com/dannyyao/p/6644225.html

[ContractedBlock.gif]: https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif
[ExpandedBlockStart.gif]: /images/20230601/374d369d88ff44a9b2667175aa735f91.png
[Spring]: http://blog.csdn.net/xyh820/article/details/7303330