Java之Spring注解开发案例详解

<? xml version = "1.0" encoding = "UTF-8" ?>

< beans xmlns = "http://HdhCmsTestspringframework.org/schema/beans"

        xmlns:xsi = "http://HdhCmsTestw3.org/2001/XMLSchema-instance"

        xmlns:context = "http://HdhCmsTestspringframework.org/schema/context"

        xsi:schemaLocation="http://HdhCmsTestspringframework.org/schema/beans

        https://HdhCmsTestspringframework.org/schema/beans/spring-beans.xsd

                            http://HdhCmsTestspringframework.org/schema/context

        https://HdhCmsTestspringframework.org/schema/context/spring-context.xsd">

     <!--指定要扫描的包，这个包下的注解就会生效-->

     < context:component-scan base-package = "com.example.springannotation" />

     < context:annotation-config ></ context:annotation-config >

     <!-- <bean id="cat" class="com.example.springannotation.dao.Cat"/>

     <bean id="people" class="com.example.springannotation.dao.People"/>-->

</ beans >

//@Component 等价于<bean id="pepople" class="com.example.springannotation.dao.People" />

@Component

public class People {

     @Autowired (required = false )

     @Value ( "1235" ) //相当<property name="id " value="1235"/>

     private int id;

     @Autowired (required = false )

     private String name = "ming" ;

     @Value ( "qing" ) //相当<property name="name " value="qing"/>

     public void setName( @Nullable String name) {

         this .name = name;

     }

}

@Scope ( "singleton" ) //singleton：标识单例模式，prototype：标识原型模式 、request：标识请求模式、session：标识会话模式

<!--指定要扫描的包，这个包下的注解就会生效-->

     < context:component-scan base-package = "com.example.springannotation" />

     < context:annotation-config ></ context:annotation-config >

// 配置类 代替 beans.xml

import com.example.springannotation.dao.Cat;

import com.example.springannotation.dao.People;

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.ComponentScan;

import org.springframework.context.annotation.Configuration;

import org.springframework.context.annotation.Import;

@Configuration

@ComponentScan ( "com.example.springannotation" )

@Import (WwConfig. class )  //引入第二个配置

public class AppConfig {

     //注朋一个bean 相当于当于我们之前写的一个bean标签

     //这个方法的名字，就相当于bean标签中的id属性

     //这个方法的返回价，就和当了bean标签中的class属性

     @Bean

     public People getPeople(){

         return new People();

     }

     @Bean

     public Cat getCat(){

         return new Cat();

     }

}

import org.springframework.context.annotation.Configuration;

@Configuration

public class WwConfig {

}

//测试类

import com.example.springannotation.config.AppConfig;

import com.example.springannotation.dao.People;

import org.junit.jupiter.api.Test;

import org.springframework.boot.test.context.SpringBootTest;

import org.springframework.context.ApplicationContext;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

@SpringBootTest

class SpringannotationApplicationTests {

     @Test

     void contextLoads() {

         如果完全使用了配置类方式做，

         // 我们就只能通过 AnnotationConfig 上下文来获取容器，通过配置类的class对象加载!

         ApplicationContext context = new AnnotationConfigApplicationContext(AppConfig. class );

         People people = (People) context.getBean( "getPeople" );

         System.out.println(people.toString());

     }

}