SpringBoot MyBatis怎么快速入门

一、MyBatis简介

MyBatis 是一款优秀的持久层框架，它支持自定义 SQL、存储过程以及高级映射。MyBatis 免除了几乎所有的 JDBC 代码以及设置参数和获取结果集的工作。MyBatis 可以通过简单的 XML 或注解来配置和映射原始类型、接口和 Java POJO（Plain Old Java Objects，普通老式 Java 对象）为数据库中的记录。

二、MyBatis使用步骤

 1、MyBatis工程总体目录结构

2、创建简单的SpringBoot工程

3、添加MyBatis依赖

  <!--MyBatis-->

        <dependency>

            <groupId>mysql</groupId>

            <artifactId>mysql-connector-java</artifactId>

            <version>5.1.32</version>

        </dependency>

        <dependency>

            <groupId>org.mybatis</groupId>

            <artifactId>mybatis</artifactId>

            <version>3.4.6</version>

        </dependency>

4、在数据库创建USER表

CREATE TABLE `user` (

  `id` int(11) NOT NULL AUTO_INCREMENT,

  `username` varchar(20) NOT NULL  DEFAULT "" COMMENT "用户名",

  `password` varchar(50) NOT NULL DEFAULT "" COMMENT "密码",

  PRIMARY KEY (`id`) USING BTREE

) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 ROW_FORMAT=DYNAMIC;

5、在application.properties配置数据库连接信息

#数据库相关配置

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

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

spring.datasource.username=root

spring.datasource.password=QQ796413



#mybaits配置

#mapper加载路径

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

#实体包位置

mybatis.type-aliases-package= com.example.mybatisdemo.entity

#myatbis配置文件

mybatis.config-location= classpath:mybatis-config.xml

6、创建USER表对应的实体类

package com.example.mybatisdemo.entity;



public class User {

    private int id;

    private String username;

    private String password;



    public int getId() {

        return id;

    }



    public void setId(int id) {

        this.id = id;

    }



    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;

    }



    @Override

    public String toString() {

        return "User{" +

                "id=" + id +

                ", username="" + username + """ +

                ", password="" + password + """ +

                "}";

    }

7、在mapper/UserMapper创建UserMapper.java

package com.example.mybatisdemo.mapper;



import com.example.mybatisdemo.entity.User;

import org.apache.ibatis.annotations.Mapper;



@Mapper

public interface UserMapper{



     User findUserById(Integer id);

}

8、在service/UserService新建UserService.java

package com.example.mybatisdemo.service;



import com.example.mybatisdemo.entity.User;



public interface UserService {

    User findUserById(Integer id);

}

9、在service/impl/UserServiceImpl 创建UserServiceImpl.java

package com.example.mybatisdemo.service.impl;



import com.example.mybatisdemo.entity.User;

import com.example.mybatisdemo.mapper.UserMapper;

import com.example.mybatisdemo.service.UserService;

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

import org.springframework.stereotype.Service;



@Service

public class UserServiceImpl implements UserService {

        @Autowired

        private UserMapper userMapper;



        @Override

        public User findUserById(Integer id) {

            return userMapper.findUserById(id);

        }

}

10、在resources下新建mybatis-conf.xml

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

<!DOCTYPE configuration

        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"

        "http://mybatis.org/dtd/mybatis-3-config.dtd">



<configuration>

    <settings>

        <!--开启日志-->

        <setting name="logImpl" value="STDOUT_LOGGING"/>

        <!--开启驼峰命名法-->

        <setting name="mapUnderscoreToCamelCase" value="true"/>

        <!--开启全局延迟加载-->

        <setting name="lazyLoadingEnabled" value="true"/>

        <!-- 集合为空时强制返回空集合实例而不是null -->

        <setting name="returnInstanceForEmptyRow" value="true"/>

        <!-- 结果集中value为空时保留key -->

        <setting name="callSettersOnNulls" value="true"/>

    </settings>

</configuration>

11、在resources下mapper文件下创建UserMapper.xml

<?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">

<!--注意：1.这里的namespace要是你usermapper的位置-->

<mapper namespace="com.example.mybatisdemo.mapper.UserMapper">

    <!--注意这里的返回类型-->

    <resultMap id="BaseResultMap" type="com.example.mybatisdemo.entity.User">

        <result column="id" property="id"/>

        <result column="username" property="username"/>

        <result column="password" property="password"/>

    </resultMap>



    <!--2.id和你的方法名一样，resultMap为上面的id名一致-->

    <select id="findUserById" resultMap="BaseResultMap">

        select

             id,

             username,

             password

        from

             user

        where

             id= #{id,jdbcType=INTEGER}

    </select>

</mapper>

12、创建UserController.java

package com.example.mybatisdemo.controller;



import com.example.mybatisdemo.entity.User;

import com.example.mybatisdemo.service.UserService;

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

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

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

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



@RestController

public class UserController {



    @Autowired

    UserService userService;



    @GetMapping("/findUserById")

    public User findUserById(@RequestParam Integer id){

       return userService.findUserById(1);

    }

}

13、测试