Springboot连接数据库及查询数据完整流程

# 增加数据库连接

spring.datasource.url=jdbc:mysql: //127.0.0.1:3306/spring?serverTimezone=Asia/Shanghai&useUnicode=true&characterEncoding=utf8&useSSL=false

spring.datasource.username=root

spring.datasource.password=lvxingchen

spring.datasource.driver- class -name=com.mysql.cj.jdbc.Driver

package com.lxc.springboot.domain;

public class User {

     private int id;

     private String user;

     private String name;

     private int age;

     private String password;

     @Override

     public String toString() {

         return "User{" +

                 "id=" + id +

                 ", user='" + user + '\ '' +

                 ", name='" + name + '\ '' +

                 ", age=" + age +

                 ", password='" + password + '\ '' +

                 '}' ;

     }

     public int getId() {

         return id;

     }

     public void setId( int id) {

         this .id = id;

     }

     public String getUser() {

         return user;

     }

     public void setUser(String user) {

         this .user = user;

     }

     public String getName() {

         return name;

     }

     public void setName(String name) {

         this .name = name;

     }

     public int getAge() {

         return age;

     }

     public void setAge( int age) {

         this .age = age;

     }

     public String getPassword() {

         return password;

     }

     public void setPassword(String password) {

         this .password = password;

     }

}

package com.lxc.springboot.mapper;

import com.lxc.springboot.domain.User;

import java.util.List;

public interface UserMapper {

     public List<User> getUserList();

}

@ComponentScan ( "com.lxc.springboot" )

@SpringBootApplication

@MapperScan ( "com.lxc.springboot.mapper" ) // 让springboot知道mapper是这个项目的持久层

public class BootAndVueProjectApplication {

     private static final Logger LOG = LoggerFactory.getLogger(BootAndVueProjectApplication. class );

     public static void main(String[] args) {

         SpringApplication app = new SpringApplication(BootAndVueProjectApplication. class );

         //  SpringApplication.run(BootAndVueProjectApplication.class, args);

         Environment env = app.run(args).getEnvironment();

         LOG.info( "启动成功!" );

         LOG.info( "地址：\thttp://127.0.0.1:{}" , env.getProperty( "server.port" ));

     }

}

<?xml version= "1.0" encoding= "UTF-8" ?>

<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >

<!--接口-->

<!--

namespace:对应接口的全路径；

id：对应接口的方法；

resultType：结果类型。

-->

<mapper namespace= "com.lxc.springboot.mapper.UserMapper" >

     <select id= "getUserList" resultType= "com.lxc.springboot.domain.User" >

         select id, user, name, age, password from user

     </select>

</mapper>

# 配置mybatis所有的Mapper.xml所在的路径

mybatis.mapper-locations=classpath:/mapper /**/ *.xml

package com.lxc.springboot.service;

import com.lxc.springboot.domain.User;

import com.lxc.springboot.mapper.UserMapper;

import org.springframework.stereotype.Service;

import javax.annotation.Resource;

import java.util.List;

/**

  * service层调用持久层

  * @Service // 让spring扫描到这个包

  *

  * @Autowired和@Resource

  * 两个注解都可以把一个类注入进来（相当于import）

  * Resource JDK自带的

  * Autowired spring自带的

  */

@Service // 让spring扫描到这个包

public class UserService {

     @Resource

     public UserMapper userMapper;

     public List<User> getList() {

         return userMapper.getUserList();

     }

}

package com.lxc.springboot.controller;

import com.lxc.springboot测试数据monResponse.ComResponse;

import com.lxc.springboot.service.UserService;

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

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.RequestMethod;

import org.springframework.web.bind.annotation.RestController;

import javax.annotation.Resource;

@RestController // 通常返回一个json或 字符串

//@Controller // 一般是返回一个页面

public class TestController {

     @Resource // 把service层userService注入进来

     private UserService userService;

     // 调用service层

     @RequestMapping (value = "/service" )

     public ComResponse getService() {

         ComResponse<List<User>> objComResponse = new ComResponse<>();

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

         objComResponse.setData(userList);

         objComResponse.setMsg( "返回成功" )

         return objComResponse;

     }

}

package com.lxc.springboot测试数据monResponse;

/**

  *

  * @param <T>

  *     ComResponse 是一个泛型类，返回的是一个泛型，外界可以传入任何类型的值

  *     理解泛型：

  *     有点像js方法，你给它传任何类型都可以,但是最后返回的类型是setData时候传的对象！！！

  */

public class ComResponse<T> {

     private String msg = "返回成功" ;

     private int code = 200 ;

     private T data;

     public String getMsg() {

         return msg;

     }

     public void setMsg(String msg) {

         this .msg = msg;

     }

     public int getCode() {

         return code;

     }

     public void setCode( int code) {

         this .code = code;

     }

     public T getData() {

         return data;

     }

     public void setData(T data) {

         this .data = data;

     }

}