SpringBoot配置Mybatis：详细易懂

喜欢ヅ旅行 2023-05-21 10:23 92阅读 0赞

### 文章目录 ###

*   *  SpringBoot配置Mybatis：详细易懂
     *   *  前期准备工作
         *  Mybatis相应配置
         *  编写相应代码
         *  文件结构和结果
         *  增删查改
         *  Mybatis 动态SQL
         *  参考文章

## SpringBoot配置Mybatis：详细易懂 ##

> Mybatis作为后端持久层框架，在互联网大厂中应用广泛，所以掌握Mybatis，可谓是必备的。最近准备系统得复习一下Mybatis框架，所以博客会更几期关于Mybatis得文章，如果觉得看完有收获，希望收藏、点赞。如果觉得写得不好，欢迎评论区指正。

### 前期准备工作 ###

*  **安装mysql**，可以参考 [安装MySQL][MySQL]
    
    mysql记得给远程用户分配权限，参考[mysql 8 设置允许远程连接 You are not allowed to create a user with GRANT][mysql 8 _ You are not allowed to create a user with GRANT]
 *  配置SpringBoot开发环境,参考[VS Code打造一个完美的Springboot开发环境][VS Code_Springboot]
 *  创建一个学生表(终端, 代码动态创建均可)
    
        create table(Sno int(10) primary key, Sname varchar(10), Sage int(5));

### Mybatis相应配置 ###

**修改pom.xml，获取Mybatis、MySQL相关依赖**

<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>2.1.2</version>
        <scope>compile</scope>
    </dependency>

**在`application.properties`文件中配置Mybatis连接环境**

mybatis.type-aliases-package=com.test.demo
    #mysql驱动
    spring.datasource.driver-class-name=com.mysql.jdbc.Driver
    #远程数据库链接 serverTimezone不可少
    spring.datasource.url=jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf-8&serverTimezone=UTC
    #MySQL数据库用户名、密码
    spring.datasource.username=root
    spring.datasource.password=xxxxx
    #xml格式的mapper文件位置
    mybatis.mapper-locations=classpath:/mapper/*.xml

### 编写相应代码 ###

**添加bean类(对应与数据库属性列)**

package com.test.demo;
    
    public class Student { 
        public int sNo;
        public String sName;
        public int sAge;
        public Student(int sNo, String sName, int sAge) { 
            this.sNo = sNo;
            this.sName = sName;
            this.sAge = sAge;
        }
        //Getter、Setter方法,我省略了，你在代码中别省略
    }

**添加mapper接口代码**

package com.test.demo.mapper;
    
    import com.test.demo.Student;
    
    public interface StudentMapper { 
        void insert(Student student);
    }

**添加mapper接口对应的xml格式文件**

**一定注意路径对应，com.test.demo.mapper.StudentMapper**。

> 这里只写了插入，下文会补充删除、更新、查询

**最后的controller代码文件**

package com.test.demo.controller;
    import org.springframework.web.bind.annotation.RestController;
    import com.test.demo.Student;
    import com.test.demo.mapper.StudentMapper;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.RequestMapping;
    @RestController
    public class HomeController { 
        @Autowired
        private StudentMapper  studentMapper;
        @RequestMapping("/")
        public String index() throws Exception { 
            studentMapper.insert(new Student(1, "天宇", 24));
            return "OK";
        }
    }

### 文件结构和结果 ###

![format_png][]

![format_png 1][]

### 增删查改 ###

**mapper接口**

package com.test.demo.mapper;
    import com.test.demo.Student;
    
    public interface StudentMapper { 
        void insert(Student student);
        void delete(String sNo);
        Student selectByNumber(Integer sNo);
        void updateName(Student student);
    }

**对应xml文件**

**参数的类型一定是完整的包名，参数名写ben类的属性名**

<?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.test.demo.mapper.StudentMapper">
    	
        <insert id="insert" parameterType="com.test.demo.Student" >
            INSERT INTO student (Sno,Sname,Sage) VALUES (#{sNo},#{sName},#{sAge})
        </insert> 
        
        
        <delete id="delete" parameterType="java.lang.String">
            DELETE FROM student where Sno = #{sNo};
        </delete>
    
        
        <select id="selectByNumber" parameterType="java.lang.Integer" resultType="com.test.demo.Student">
            SELECT * FROM student where Sno = #{sNo}
        </select>
    
        
        <update id="updateName" parameterType="com.test.demo.Student">
            UPDATE student SET Sname = #{sName} where Sno = #{sNo}
        </update>
    </mapper>

### Mybatis 动态SQL ###

在实际应用开发过程中，我们往往需要写复杂的 SQL 语句，需要拼接，而拼接SQL语句又稍微不注意，由于引号，空格等缺失可能都会导致错误。Mybatis提供了动态SQL，也就是可以根据用户提供的参数，动态决定查询语句依赖的查询条件或SQL语句的内容。

**if、foreach关键字用法**

mapper接口

public interface StudentMapper { 
        List<Student> findByCondition(String sName, Integer sAge);
        List<Student> selectByNumberList(List<Integer> list);
    }

对应的xml格式mapper文件

<select id="findByCondition" resultType="com.test.demo.Student" parameterType="map">
            select * from student
            
            
    		<where>
                <if test="sName!=null">
                    and Sname = #{sName}
                </if>
                <if test="sAge!=null">
                    and Sage < #{sAge}
                </if>
    		</where>
        </select>
        <select id="selectByNumberList" resultType="com.test.demo.Student" parameterType="list">
            select * from student
            <where>
                Sno in
                <foreach item="item" collection="list" separator="," open="(" close=")" index="">
                    #{item}
                </foreach>
            </where>
        </select>

### 参考文章 ###

[简单，Spring boot 配置mybatis][Spring boot _mybatis]

[Mybatis入门看这一篇就够了][Mybatis]

[MySQL]: https://www.runoob.com/mysql/mysql-install.html
[mysql 8 _ You are not allowed to create a user with GRANT]: https://blog.csdn.net/mxskymx/article/details/88765072
[VS Code_Springboot]: https://blog.csdn.net/xiaocy66/article/details/82875770
[format_png]: /images/20230521/eac8a6a226794aac91e66ab0e08d7469.png
[format_png 1]: /images/20230521/0544ea4c4d1b4be6ace8ccd427c8510a.png
[Spring boot _mybatis]: https://blog.csdn.net/zhoujiyu123/article/details/79786847
[Mybatis]: https://juejin.im/post/5aa5c6fb5188255587232e5a