springBoot学习笔记（2）—— 整合mybatis

一、引入jar包和配置文件

1. 引入jar包

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>1.3.1</version>
        </dependency>

2.完整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>2.6.2</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>springboot-mybatis</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>springboot-mybatis</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-thymeleaf</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>1.3.1</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

3. application.yml配置文件内容

spring:
  datasource:
    #   数据源基本配置
    username: root
    password: 123456
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://101.34.49.127:3306/springBootAll?useUnicode=true&characterEncoding=utf8&serverTimezone=GMT%2B8&useSSL=false
mybatis:
  mapper-locations: classpath:mybatis/mapper/*.xml #配置mapper文件的映射位置
server:
  port: 8082 # 配置项目启动端口

二、具体代码内容

1.创建表格

DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
  `id` int NOT NULL,
  `user_name` varchar(255) NOT NULL,
  `idCardNumber` varchar(255) NOT NULL,
  `phone_number` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb3;

2.创建实体类

@Data
public class User {
    /**
     * 主键id
     */
    private  Long  id;
    /**
     * 用户名
     */
    private String userName;
    /**
     * 身份证号码
     */
    private String idCardNumber;
    /**
     * 手机号码
     */
    private String phoneNumber;
}

说明:

此处的@Data注解使用的是lombok需要下载lombok插件才不会报错，作用是在编译项目是自动生成get，set方法。

3.Controller控制层方法

@RestController
@RequestMapping("userController")
public class UserController {
    @Resource
    UserService userService;
    /***
     * description: 通过用户id查询用户数据集
     * version: 1.0 ->
     * date: 2021/12/28 14:42
     * author: xiaYZ
     * iteration: 迭代说明
     * @param userId
     * @return com.example.springbootmybatis.entity.User
     */
    @ResponseBody
    @RequestMapping("findUserById")
    public String findUserById(Long userId){
        User user = new User();
        try{
           user = userService.findUserById(userId);
        }catch (Exception e){
            e.printStackTrace();
            System.out.println("查询用户错误");
            return "查询用户错误";
        }
        return user.toString();
    }
}

4.service服务层方法

@Service
@Mapper
public interface UserDao {
    /**
     * description: 通过用户id查询用户信息
     * version: 1.0
     * date: 2021/12/28 14:36
     * author: xiaYZ
     * iteration: 迭代说明
     * @param userId
     * @return
     */
    User findUserById(Long userId);
}

5.dao持久层方法

@Mapper
public interface UserDao {
    /**
     * description: 通过用户id查询用户信息
     * version: 1.0
     * date: 2021/12/28 14:36
     * author: xiaYZ
     * iteration: 迭代说明
     * @param userId
     * @return
     */
    User findUserById(Long userId);
}

说明：

@Mapper注解是说明此类为一个持久层接口，如果没有这个注解的话SpringBoot项目会扫码不到接口方法报错
当然你也可以选择在SpringBoot项目的main方法上面加一个@MapperScan(value = “com.example.springbootmybatis.dao”)，两个方法任选其一即可。

6.mapper方法

<?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.example.springbootmybatis.dao.UserDao">
    <select id="findUserById" resultType="com.example.springbootmybatis.entity.User">
        select id, user_name userName, idcardNumber, phone_number phoneNumber
        from user
        where id = #{userId}
    </select>
</mapper>

可也使用@select注解在接口上面写sql语句，如：

   @Select("select * from user where id = #{userId}")
    User findUserById(Long userId);

两张方法任选其一即可，不过当sql语句十分复杂时建议使用第一种方法。

7运行截图

2. 整合mybatis - 图1