Spring Boot 教程(2) - Mybatis

1. 什么是Mybatis?

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。

2. Spring Boot 整合 Mybatis

• 2.1 引入maven坐标

  <!--springboot父工程-->
      <parent>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-starter-parent</artifactId>
          <version>2.2.2.RELEASE</version>
          <relativePath/> <!-- lookup parent from repository -->
      </parent>
  
      <dependencies>
          <!--springboot框架web组件-->
          <dependency>
              <groupId>org.springframework.boot</groupId>
              <artifactId>spring-boot-starter-web</artifactId>
              <version>2.2.2.RELEASE</version>
          </dependency>
          <!--mybatis整合springboot组件-->
          <dependency>
              <groupId>org.mybatis.spring.boot</groupId>
              <artifactId>mybatis-spring-boot-starter</artifactId>
              <version>2.1.0</version>
          </dependency>
          <!--mysql数据库连接驱动-->
          <dependency>
              <groupId>mysql</groupId>
              <artifactId>mysql-connector-java</artifactId>
              <version>8.0.18</version>
          </dependency>
          <!--lombok组件-->
          <dependency>
              <groupId>org.projectlombok</groupId>
              <artifactId>lombok</artifactId>
              <version>1.18.10</version>
          </dependency>
      </dependencies>
  
      <build>
          <!--springboot的maven插件-->
          <plugins>
              <plugin>
                  <groupId>org.springframework.boot</groupId>
                  <artifactId>spring-boot-maven-plugin</artifactId>
              </plugin>
              <plugin>
                  <groupId>org.apache.maven.plugins</groupId>
                  <artifactId>maven-compiler-plugin</artifactId>
                  <configuration>
                      <compilerArgs>
                          <arg>-parameters</arg>
                      </compilerArgs>
                  </configuration>
              </plugin>
          </plugins>
      </build>
  

• 2.2 编写代码

  • 2.2.1 创建如图所示的目录结构

    

    记得两个mapper文件的路径要一致，在编译之后mybatis的映射文件和接口文件才会在同一个目录下。

  • 2.2.2 代码编写

    • 2.2.2.1 创建配置文件和启动类

      application.yml：

      butterflytri:
        databaseurl-port: 127.0.0.1:3306 # 数据库端口
        database-name: student_db # 数据库名
      server:
        port: 8080 # 应用端口
        servlet:
          context-path: /butterflytri # 应用映射
      spring:
        application:
          name: mybatis # 应用名称
        datasource:
          url: jdbc:mysql://${butterflytri.databaseurl-port}/${butterflytri.database-name}?useUnicode=true&characterEncoding=UTF-8&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC
          driver-class-name: com.mysql.jdbc.Driver
          username: root
          password: root
      mybatis:
        type-aliases-package: org.wjf.entity # entity别名
        mapper-locations: classpath:org/wjf/mapper/*Mapper.xml # mapper映射包扫描
      

      启动类MybatisApplication.java：

      package org.butterflytri;
      
      import org.springframework.boot.SpringApplication;
      import org.springframework.boot.autoconfigure.SpringBootApplication;
      
      /**
       * @author: WJF
       * @date: 2020/5/16
       * @description: MybatisApplication
       */
      @SpringBootApplication
      public class MybatisApplication {
      
          public static void main(String[] args) {
              SpringApplication.run(MybatisApplication.class,args);
          }
      
      }
      

    • 2.2.2.2 创建实体类Student

      在entity包下创建Student.java实体类。

      package org.butterflytri.entity;
      
      import lombok.Getter;
      import lombok.Setter;
      import lombok.ToString;
      
      import java.io.Serializable;
      
      /**
       * @author: WJF
       * @date: 2020/5/16
       * @description: Student
       */
      
      @ToString
      @Getter
      @Setter
      public class Student implements Serializable {
      
          private Long id;
      
          private String studentName;
      
          private String studentNo;
      
          private String sex;
      
          private Integer age;
      
      }
      

    • 2.2.2.3 编写mybatis接口文件

      在mapper包下创建StudentMapper.java接口。

      package org.butterflytri.mapper;
      
      import org.apache.ibatis.annotations.Mapper;
      import org.butterflytri.entity.Student;
      
      import java.util.List;
      
      /**
       * @author: WJF
       * @date: 2020/5/16
       * @description:
       */
      @Mapper
      public interface StudentMapper {
      
          /**
           * 查询所有学生信息
           * @return List<Student>
           */
          List<Student> findAll();
      
          /**
           * 通过id查询学生信息
           * @param id
           * @return Student
           */
          Student findOne(Long id);
      
          /**
           * 通过学号查询学生信息
           * @param studentNo
           * @return Student
           */
          Student findByStudentNo(String studentNo);
      
      }
      

    • 2.2.2.4 创建mybatis映射文件

      在mapper包下创建StudentMapper.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="org.butterflytri.mapper.StudentMapper">
          <sql id="propertyMapper">
              `ID` AS id,
              `STUDENT_NAME` AS studentName,
              `STUDENT_NO` AS studentNo,
              `SEX` AS sex,
              `AGE` AS age
          </sql>
          <select id="findAll" resultType="org.butterflytri.entity.Student">
              SELECT
                  <include refid="propertyMapper"></include>
              FROM
                  `t_student`
          </select>
          <select id="findOne" parameterType="java.lang.Long" resultType="org.butterflytri.entity.Student">
              SELECT
                  <include refid="propertyMapper"></include>
              FROM
                  `t_student`
              WHERE
                  `ID` = #{id}
          </select>
          <select id="findByStudentNo" parameterType="java.lang.String" resultType="org.butterflytri.entity.Student">
              SELECT
                  <include refid="propertyMapper"></include>
              FROM
                  `t_student`
              WHERE
                  `STUDENT_NO` = #{studentNo}
          </select>
      </mapper>
      

    • 2.2.2.5 Service层

      在service包下创建StudentService.java接口，在impl包下创建StudentServiceImpl.Java类并继承StudentService.Java接口。

      StudentService.java：

      package org.butterflytri.service;
      
      import org.butterflytri.entity.Student;
      
      import java.util.List;
      
      /**
       * @author: WJF
       * @date: 2020/5/16
       * @description: StudentService
       */
      
      public interface StudentService {
      
          public List<Student> findAll();
      
          public Student findOne(Long id);
      
          public Student findByStudentNo(String studentNo);
      }
      
      

      StudentServiceImpl.java：

      package org.butterflytri.service.impl;
      
      import org.butterflytri.entity.Student;
      import org.butterflytri.mapper.StudentMapper;
      import org.butterflytri.service.StudentService;
      import org.springframework.stereotype.Service;
      
      import javax.annotation.Resource;
      import java.util.List;
      
      /**
       * @author: WJF
       * @date: 2020/5/16
       * @description: StudentServiceImpl
       */
      @Service
      public class StudentServiceImpl implements StudentService {
      
          @Resource
          private StudentMapper studentMapper;
      
          @Override
          public List<Student> findAll() {
              return studentMapper.findAll();
          }
      
          @Override
          public Student findOne(Long id) {
              return studentMapper.findOne(id);
          }
      
          @Override
          public Student findByStudentNo(String studentNo) {
              return studentMapper.findByStudentNo(studentNo);
          }
      }
      

    • 2.2.2.6 Controller层

      在controller包下创建StudentController.java控制器类。

      package org.butterflytri.controller;
      
      import org.butterflytri.entity.Student;
      import org.butterflytri.service.StudentService;
      import org.springframework.web.bind.annotation.RequestMapping;
      import org.springframework.web.bind.annotation.RestController;
      
      import javax.annotation.Resource;
      import java.util.List;
      
      /**
       * @author: WJF
       * @date: 2020/5/16
       * @description: StudentController
       */
      @RestController
      @RequestMapping("/student")
      public class StudentController {
      
          @Resource
          private StudentService studentService;
      
          @RequestMapping("/findAll")
          public List<Student> findAll() {
              return studentService.findAll();
          }
      
          @RequestMapping("/findOne")
          public Student findOne(Long id) {
              return studentService.findOne(id);
          }
      
          @RequestMapping("/findByStudentNo")
          public Student findByStudentNo(String studentNo) {
              return studentService.findByStudentNo(studentNo);
          }
      
      }
      

    • 2.2.2.7 启动工程，访问路径

      启动工程，访问三个接口：

      findAll：

      

      findOne：

      

      findByStudentNo：

      

3. 项目地址

本项目传送门：spring-boot-mybatis

此教程会一直更新下去，觉得博主写的可以的话，关注一下，也可以更方便下次来学习。