Code example

• BookDao.java

package com.kevin.spring.demo1.dao;

/**
 * Book data access interface
 */
public interface BookDao {

    /**
     * Add books
     *
     * @param bookName
     * @return
     */
    String addBook(String bookName);
}

• BookDaoImpl.java

/**
 * Interface implementation class
 */
@Repository
public class BookDaoImpl implements BookDao {
    /**
     * Add book interface
     *
     * @param bookName
     * @return
     */
    public String addBook(String bookName) {
        return "Add book<" + bookName + ">Success";
    }
}

• BookService.java

@Service
public class BookService {
    @Resource
    BookDaoImpl bookDao;

    public void storeBook(String bookName){
        String result = bookDao.addBook(bookName);
        System.out.println(result);
    }

}

• User.java

package com.kevin.spring.demo1.entity;

import org.springframework.stereotype.Component;

@Component
public class User {

    public User() {
        System.out.println("Establish User object");
    }

    public User(String msg) {
        System.out.println("Establish User object" + msg);
    }

    public void show() {
        System.out.println("A student object!");
    }
}

• ApplicationConfig.java

package com.kevin.spring.demo1.config;

import com.kevin.spring.demo1.entity.User;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@ComponentScan(basePackages = "com.kevin.spring.demo1")
public class ApplicationConfig {

    @Bean
    public User getUser(){
        return new User("Success");
    }
}

Test class

    @org.junit.Test
    public void testBook(){
        ApplicationContext ctx = new AnnotationConfigApplicationContext(ApplicationConfig.class);
        BookService bookService = ctx.getBean(BookService.class);
        bookService.storeBook("Jay Chou");
        User user = ctx.getBean("getUser",User.class);
        user.show();
    }

Operation result

Create User object
 User object created successfully
 Add the book Jay Chou successfully
 A student object!

@Configuration

@Configuration is equivalent to < beans / >

@ComponentScan

@Component scan is equivalent to the context: component scan in the configuration file

@Bean

@Bean is equivalent to < bean / > and can only be annotated on methods and annotations. It is generally used on methods
Method name is equivalent to id

@Value get properties configuration

• Create a new dev.properties file

boy.name = kevin
boy.age = 20

• BoyUtil.java

package com.kevin.spring.demo1.util;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.PropertySource;
import org.springframework.stereotype.Component;

@Component
@PropertySource("classpath:dev.properties")
public class BoyUtil {

    @Value("${boy.name}")
    private String name;
    @Value("${boy.age}")
    private String age;

    @Override
    public String toString() {
        return "BoyUtil{" +
                "name='" + name + '\'' +
                ", age='" + age + '\'' +
                '}';
    }
    //get and set methods omitted
}

test

    @org.junit.Test
    public void testBoyUtil(){
        ApplicationContext ctx = new AnnotationConfigApplicationContext(ApplicationConfig.class);
        BoyUtil boyUtil = ctx.getBean(BoyUtil.class);
        System.out.println(boyUtil);
    }

Output result

Create User object
 User object created successfully
BoyUtil{name='kevin', age='20'}

OK, the spring IOC foundation will come to an end for the time being. Have fun
Code: https://github.com/runzhenghengbin/spring-study
Reference resources: https://www.cnblogs.com/best/p/5727935.html#_label3