@Autowired自动装配,@Bean注入@Primary,@Qualifier优先级讲解

<groupId>com.MySpring</groupId> <artifactId>demo</artifactId> 

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.MySpring</groupId>
    <artifactId>demo</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.0.6.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
</project>

package com.MySpring.demo.controller;
import com.MySpring.demo.service.TestService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
@Controller
public class TestController {
    @Autowired
    private TestService testService;
}

package com.MySpring.demo.dao;
import org.springframework.stereotype.Repository;
@Repository
public class TestDao {
    public String getMessage( ) {
        return message;
    }
    public void setMessage( String message ) {
        this.message = message;
    }
    private  String message ="1";
    @Override
    public String toString( ) {
        return "TestDao{" +
                "message='" + message + '\'' +
                '}';
    }
}

package com.MySpring.demo.service;
import com.MySpring.demo.dao.TestDao;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class TestService {
    @Autowired
    private TestDao testDao;
    public void print(){
        System.out.printf( "[%s] from testService.\n" ,testDao);
    }
}

package com.MySpring.demo;
import com.MySpring.demo.dao.TestDao;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
@Configuration
@ComponentScan({"com.MySpring.demo.controller","com.MySpring.demo.service","com.MySpring.demo.dao",})
public class AppConfig {
    @Bean
    public TestDao testDao(){
        TestDao dao = new TestDao();
        dao.setMessage( "2" );
        return dao;
    }
}

package com.MySpring.demo;
import com.MySpring.demo.dao.TestDao;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
@Configuration
@ComponentScan({"com.MySpring.demo.controller","com.MySpring.demo.service","com.MySpring.demo.dao",})
public class AppConfig {
    @Bean
    public TestDao testDao(){
        TestDao dao = new TestDao();
        dao.setMessage( "2" );
        return dao;
    }
}

public @interface Autowired {
	/**
	 * Declares whether the annotated dependency is required.
	 * <p>Defaults to {@code true}.
	 */
	boolean required() default true;
}