IntelliJ IDEA 2017版 spring-boot基础补充,原理详解

一、Spring发展史

1、Spring1.x

版本一时代主要是通过XML文件配置bean，在java和xml中不断切换，在学习java web 初期的时候经常使用

2、Spring2.x

版本二可以支持注解模式，这样大大简化开发，减少XML文件配置

注意：

IOC推荐用注解方式实现，AOP推荐用配置方式实现

2.0版本时候的问题，到底采用注解还是文本配置

最后结论最佳实践：

（1）应用的基本配置用xml，比如：数据源、资源文件等；
（2）业务开发用注解，比如：Service中注入bean等；

3、Spring3.X到Spring4.X

从版本三开始启用通过java代码配置取代XML,可以更好的理解Bean

二、Spring的java配置

版本三提出，版本四极力推荐使用。完全替代XML配置

1、最基本的两个java配置

（1）@Configuration 作用于类上，相当于一个xml配置文件；

（2）@Bean 作用于方法上，相当于xml配置中的<bean>；

2、实战演练

（1）创建Spring项目，详见http://www.cnblogs.com/liuyangfirst/p/8298588.html

(2) 创建目录,如图所示:

(3)POJO源码

 package com.springboot.exersize.pojo;

 /**

  * Created by liuya

  * User: liuya

  * Date: 2018/3/24

  * Time:  21:35

  * projectName:20180324versionone

  */

 public class User {

     private String userName;

     private String passWord;

     private Integer age;

     public String getUserName() {

         return userName;

     }

     public void setUserName(String userName) {

         this.userName = userName;

     }

     public String getPassWord() {

         return passWord;

     }

     public void setPassWord(String passWord) {

         this.passWord = passWord;

     }

     public Integer getAge() {

         return age;

     }

     public void setAge(Integer age) {

         this.age = age;

     }

 }

) Dao源码

 package com.springboot.exersize.dao;

 import com.springboot.exersize.pojo.User;

 import java.util.ArrayList;

 import java.util.List;

 /**

  * Created by liuya

  * User: liuya

  * Date: 2018/3/24

  * Time:  22:00

  * projectName:20180324versionone

  */

 public class UserDao {

     public List<User> userList() {

         List<User> userList = new ArrayList<>();

         for (int i = 0; i < 10; i++) {

             User user = new User();

             user.setUserName("username_" + i);

             user.setPassWord("password_" + i);

             user.setAge(i + 1);

             userList.add(user);

         }

         return userList;

     }

 }

(5)Service源码

 package com.springboot.exersize.service;

 import com.springboot.exersize.dao.UserDao;

 import com.springboot.exersize.pojo.User;

 import org.springframework.beans.factory.annotation.Autowired;

 import org.springframework.stereotype.Service;

 import java.util.List;

 /**

  * Created by liuya

  * User: liuya

  * Date: 2018/3/24

  * Time:  22:04

  * projectName:20180324versionone

  */

 @Service

 public class UserService {

     @Autowired

     private UserDao userDao;

     public List<User> userList() {

         return this.userDao.userList();

     }

 }

(6) Java配置文档

 package com.springboot.exersize.config;

 import com.springboot.exersize.dao.UserDao;

 import org.springframework.context.annotation.Bean;

 import org.springframework.context.annotation.ComponentScan;

 import org.springframework.context.annotation.Configuration;

 /**

  * Created by liuya

  * User: liuya

  * Date: 2018/3/24

  * Time:  22:06

  * projectName:20180324versionone

  */

 @Configuration

 @ComponentScan(basePackages = "com.springboot.exersize.service")

 public class SpringConf {

     @Bean

     public UserDao getUserDao() {

         return new UserDao();

     }

 }

(7)测试代码

 package com.liuyangfirst.test;

 import com.liuyangfirst.conf.SpringConf;

 import com.liuyangfirst.pojo.User;

 import com.liuyangfirst.service.UserService;

 import org.springframework.context.annotation.AnnotationConfigApplicationContext;

 import java.util.List;

 /**

  * Created by liuya

  * User: liuya

  * Date: 2018/3/24

  * Time:  22:10

  * projectName:20180324versionone

  */

 public class Test {

     public static void main(String[] args) {

         // 通过Java配置来实例化Spring容器

         AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(SpringConf.class);

         // 在Spring容器中获取Bean对象

         UserService userService = context.getBean(UserService.class);

         // 调用对象中的方法

         List<User> list = userService.userList();

         for (User user : list) {

             System.out.println(user.getUserName() + ", " + user.getPassWord() + ", " + user.getPassWord());

         }

         // 销毁该容器

         context.destroy();

     }

 }

(8)成功运行

(9)原理图解

巴特西

IntelliJ IDEA 2017版 spring-boot基础补充,原理详解

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