Spring系列：注解方式注册Bean的三种方式

目录

​​基础​​

​​@Component​​

​​@Import​​

​​@Bean 内部​​

---

基础

​​IOC依赖注入（根据类型查找）实例​​

@Component

package com.test;

import com.test.pojo.User;
import org.springframework.beans.factory.ListableBeanFactory;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Import;
import org.springframework.stereotype.Component;

import java.util.Map;

//@Import(IOCDemo2.innerIOCClass.class )
public class IOCDemo2 {


    public static void main(String[] args) {
        AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext();
        applicationContext.register( InnerIOCClass.class) ;
        applicationContext.refresh() ;
        lookupBeans(applicationContext);
    }

    private static void lookupBeans(AnnotationConfigApplicationContext beanFactory) {
        if(beanFactory instanceof ListableBeanFactory){
            Map<String,User> users =  beanFactory.getBeansOfType(User.class);
            System.out.println(users);
        }
    }

    @Component
    public static class InnerIOCClass {
        @Bean
        public User user() {
            User u = new User();
            u.setId(1);
            u.setName("NIO");
            return u;
        }
    }

}

@Import

package com.test;

import com.test.pojo.User;
import org.springframework.beans.factory.ListableBeanFactory;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Import;
import org.springframework.stereotype.Component;

import java.util.Map;

@Import(IOCDemo2.InnerIOCClass.class )
public class IOCDemo2 {


    public static void main(String[] args) {
        AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext();
        applicationContext.register( InnerIOCClass.class) ;
        applicationContext.refresh() ;
        lookupBeans(applicationContext);
    }

    private static void lookupBeans(AnnotationConfigApplicationContext beanFactory) {
        if(beanFactory instanceof ListableBeanFactory){
            Map<String,User> users =  beanFactory.getBeansOfType(User.class);
            System.out.println(users);
        }
    }

//    @Component
    public static class InnerIOCClass {
        @Bean
        public User user() {
            User u = new User();
            u.setId(1);
            u.setName("NIO");
            return u;
        }
    }

}

@Bean 内部

package com.test;

import com.test.pojo.User;
import org.springframework.beans.factory.ListableBeanFactory;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Import;
import org.springframework.stereotype.Component;

import java.util.Map;

public class IOCDemo2 {


    public static void main(String[] args) {
        AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext();
        applicationContext.register( IOCDemo2.class) ;
        applicationContext.refresh() ;
        lookupBeans(applicationContext);
    }

    private static void lookupBeans(AnnotationConfigApplicationContext beanFactory) {
        if(beanFactory instanceof ListableBeanFactory){
            Map<String,User> users =  beanFactory.getBeansOfType(User.class);
            System.out.println(users);
        }
    }

    @Bean
    public User user() {
        User u = new User();
        u.setId(1);
        u.setName("NIO");
        return u;
    }



}