Spring 注解开发定义Bean与纯注解开发_纯注解创建spring bean-优快云博客

package com.itheima.dao.impl;

import com.itheima.dao.BookDao;
import org.springframework.stereotype.Component;

@Component("bookDao")
public class BookDaoImpl implements BookDao {

    public void save() {
        System.out.println("bookDao save ...");
    }
}

2.若注解以这个形式@Component的话，则就以文件类型作为id（没有括号也没有括号内的配置信息）

package com.itheima.service.impl;

import com.itheima.dao.BookDao;
import com.itheima.service.BookService;
import org.springframework.stereotype.Component;

@Component
public class BookServiceImpl implements BookService {

    private BookDao bookDao;

    public BookServiceImpl(BookDao bookDao) {
        this.bookDao = bookDao;
    }

    @Override
    public void save() {
        System.out.println("Service save...");
    }
}

3.main方法实现的写法（有ID，无ID）

package com.itheima;

import com.itheima.dao.BookDao;
import com.itheima.service.BookService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;


public class AppForLifeCycle {
    public static void main(String[] args) {

        ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
        BookDao bookDao = (BookDao) ctx.getBean("bookDao");
        BookService bookService = (BookService) ctx.getBean(BookService.class);
        System.out.println(bookService);
        System.out.println(bookDao);

    }
}

4.核心配置文件中通过组件扫描加载Bean

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd">

    <context:component-scan base-package="com.itheima"/>
</beans>

二.衍生注解

1.Spring提供了@Component注解的三个衍生注解（功能一样，便于理解）

@Controller：用于表现层的bean定义

@Service：用于业务层的bean定义

@Repository：用于数据层的bean定义

@Component：常用于工具类的bean定义

纯注解开发

Spring3.0中升级了纯注解开发模式，使用Java类代替配置文件，开启了Spring快速开发时代

1.Java类代替了Spring核心配置文件的具体内容

1.@Configuration注解用于设定当前类为配置类

2.@ComponentScan("com.itheima")注解用于设定扫描路径，此注解只能添加一个，多个数据请求数组格式（有些bean是不能乱加载的，所以还是详细一些比较好，详细些好）
@ComponentScan({"com.itheima.service","com.itheima.dao"}) 

2.读取Spring核心配置文件初始化容器对象切换为读取Java配置类初始化容器对象

package com.itheima;

import com.itheima.config.SpringConfig;
import com.itheima.dao.BookDao;
import com.itheima.service.BookService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class App2 {
    public static void main(String[] args) {
        
        //1.加载配置类
        ApplicationContext ctx = new AnnotationConfigApplicationContext(SpringConfig.class);

        //2.获取bean
        BookDao bookDao = (BookDao) ctx.getBean("bookDao");
        BookService bookService = (BookService) ctx.getBean(BookService.class);

        //输出bean
        System.out.println(bookDao);
        System.out.println(bookService);


    }
}