1.新建一个project

新建项目时选择Spring Initializer。

2.创建项目文件结构、选择jdk版本

一般选择Java version8，不会创建的可以多试几次，就会熟练了。

3.选择项目需要的依赖

首先点击web选择spring web，再点击SQL选择MySQL driver 等，然后再一路next到新建完成

新建立好的项目结构如下：

4. 新建完成项目后，查看pom.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.7.3</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.lucky</groupId>
    <artifactId>springboot-mybatis-01</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>springboot-mybatis-01</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.2.2</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
    </dependencies>

    <build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                    <include>**/*.yml</include>
                </includes>
                <filtering>true</filtering>
            </resource>

        </resources>

        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

5.修改相关配置文件src/main/resources

配置文件application.properties

server.port=8080
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.url=jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf-8&useSSL=true&serverTimezone=UTC
spring.datasource.driver-class-name= com.mysql.cj.jdbc.Driver

6.该项目的文件结构

在com.lucky包下分别创建包controller、entity、mapper、service。在resources下创建mapper/UserMapper.xml文件夹。具体的代码结构如下图所示：

7. 建立数据库

CREATE TABLE `user` (
`id` int(32) NOT NULL AUTO_INCREMENT,
`userName` varchar(32) NOT NULL,
`passWord` varchar(50) NOT NULL,
`realName` varchar(32) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;

8. 开始编码操作

先在pom.xml加入以下代码导入所需的maven

<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</dependency>

在entity包中新建User.java，使之与数据库中的字段一一对应

package com.lucky.entity;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
    private Integer id;
    private String userName;
    private String passWord;
    private String realName;
}

在mapper包中新建UserMapper接口

package com.lucky.mapper;

import com.lucky.entity.User;
import org.apache.ibatis.annotations.Mapper;
import org.springframework.stereotype.Repository;

import java.util.List;

@Mapper
@Repository
public interface UserMapper {

// 根据id 查询用户信息
    User getUserInfo(int id);

// 新增用户
    int save (User user);

// 更新用户信息
    int update (User user);

// 根据id删除
    int deleteById (int id);

// 查询所有用户信息
    List<User> selectAll ();

}

在service包中新建实现类UserService.java

package com.lucky.service;

import com.lucky.entity.User;
import com.lucky.mapper.UserMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class UserService {

    @Autowired
    private UserMapper userMapper;

    public User getUserInfo(int id) {
        return userMapper.getUserInfo(id);
    }


    public int deleteById(int id) {
        return userMapper.deleteById(id);
    }

    public int Update(User user) {
        return userMapper.update(user);
    }

    public User save(User user) {
        int save = userMapper.save(user);
        return user;
    }

    public List<User> selectAll() {
        return userMapper.selectAll();
    }

}

在controller包中新建访问类UserController.java

package com.lucky.controller;

import com.lucky.entity.User;
import com.lucky.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("/api")
public class UserController {

    @Autowired
    private UserService userService;

    // 通过用户id获取用户所有信息
    @RequestMapping(value = "getUser/{id}",method = RequestMethod.GET)
    public String GetUser(@PathVariable int id){
        return userService.getUserInfo(id).toString();
    }

    @GetMapping("/delete")
    public String delete(int id){
        int result = userService.deleteById(id);
        if (result>=1){
            return "删除成功";
        }else{
            return "删除失败";
        }
    }

    //根据用户id更新用户信息
    //http://localhost:8080/testBoot/update?id=2&userName=波波&passWord=123456&realName=lalala
    @RequestMapping(value = "/update", method = RequestMethod.POST)
    public String update(User user) {
        int result = userService.Update(user);
        if (result >= 1) {
            return "修改成功";
        } else {
            return "修改失败";
        }
    }
    //插入新用户
    //    http://localhost:8080/testBoot/insert?id=100&userName=波波&passWord=123456&realName=lalala
    @RequestMapping(value = "/insert", method = RequestMethod.POST)
    public User insert(User user) {
        return userService.save(user);
    }
    //打印所有用户信息
    //    http://localhost:8080/testBoot/selectAll
    @RequestMapping("/selectAll")
    @ResponseBody
    public List<User> ListUser() {
        return userService.selectAll();
    }

}

在src/main/resources/mapping文件夹下新建Mapper的映射文件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">
<mapper namespace="com.lucky.mapper.UserMapper">

    <!--查询用户信息-->
    <select id="getUserInfo" resultType="User">
        select * from user where id = #{id}
    </select>
    <!--删除用户信息-->
    <delete id="deleteById" parameterType="int">
        delete from user where id=#{id}
    </delete>
    <!--返回所有用户信息-->
    <select id="selectAll"  resultType="User">
        select * from user
    </select>

    <!--增加用户信息-->
    <insert id="save" parameterType="User" >
        insert into user
        <trim prefix="(" suffix=")" suffixOverrides="," >
            <if test="id != null" >
                id,
            </if>
            <if test="userName != null" >
                userName,
            </if>
            <if test="passWord != null" >
                passWord,
            </if>

            <if test="realName != null" >
                realName,
            </if>
        </trim>
        <trim prefix="values (" suffix=")" suffixOverrides="," >
            <if test="id != null" >
                #{id,jdbcType=INTEGER},
            </if>
            <if test="userName != null" >
                #{userName,jdbcType=VARCHAR},
            </if>
            <if test="passWord != null" >
                #{passWord,jdbcType=VARCHAR},
            </if>
            <if test="realName != null" >
                #{realName,jdbcType=VARCHAR},
            </if>
        </trim>
    </insert>

    <!--根据id更改用户信息-->
    <update id="update" parameterType="User">
        update user
        <set >
            <if test="userName != null" >
                userName = #{userName,jdbcType=VARCHAR},
            </if>
            <if test="passWord != null" >
                passWord = #{passWord,jdbcType=VARCHAR},
            </if>
            <if test="realName != null" >
                realName = #{realName,jdbcType=VARCHAR},
            </if>
        </set>
        where id = #{id,jdbcType=INTEGER}
    </update>
</mapper>

最后整合一下mybatis，配置文件application.properties

加上如下代码：

// 整合mybatis
mybatis.type-aliases-package=com.lucky.entity
mybatis.mapper-locations=classpath:mapper/*.xml

9. 验证

到这里就完成了增删改查操作，接下来我们对上面的代码在Postman中进行验证

9.1通过用户id获取用户信息：

http://localhost:8080/api/getUser/1

(此处1为要获取的id）