Spring学习笔记——getBean方法

Spring帮助我们创建对象

package hello;

import org.springframework.stereotype.Component;

/**
 * 获取消息
 *
 * @author ChenHanlu at 2019-12-08
 */
/*这个类不需要new关键字创建，可以由Spring管理，自动加载*/
@Component
public class MessageService {

    public MessageService() {
        super();
        System.out.println("初始化MessageService！");
    }

    public String getMessage() {
        return "Hello word!";
    }
}

package hello;

import org.springframework.stereotype.Component;

/**
 * 打印功能
 */
@Component
public class MessagePrinter {

    public MessagePrinter() {
        super();
        System.out.println("初始化MessagePrinter！");
    }

    /*初始化服务*/
    private MessageService service;

    /**
     * 设置服务
     */
    public void setService(MessageService service) {
        this.service = service;
    }

    /*打印功能*/
    public void printMessage() {
        System.out.println(this.service.getMessage());
    }
}

package hello;

import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.ComponentScan;

/*组建扫描Component，扫描到之后，自动创建到Spring容器中
* Spring容器所在的位置就是，ComponentScan类所在的位置
* */
@ComponentScan
public class ApplicationSpring {
    public static void main(String[] args) {
        /*初始化Spring容器，
        Spring中所有的Compent也会被初始化出来*/
        ApplicationContext context = new AnnotationConfigApplicationContext(ApplicationSpring.class);
        /* 初始化Bean对象*/
        MessagePrinter printer = context.getBean(MessagePrinter.class);
        MessageService service = context.getBean(MessageService.class);
        /* 调用函数*/
        printer.setService(service);
        printer.printMessage();
    }
}