之前一直都是使用了mybatis-plus，因为项目的需要突然要使用mybatis进行整合，就写篇文章温习一下！

技术栈及工具:

mysql 8
mybatis
sping boot
Java 8
IDEA

构建项目

创建一个空工程，方便以后学习其它框架，不用东一个项目右一个项目


创建好之后会弹出来Project Structure窗口点击+号创建项目架构


项目名称见名之意随便起，但是在真实的项目中都是以公司的名称倒过来进行编写

勾选依赖

pom.xml

<?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>2.5.4</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.guhaoqaun</groupId>
	<artifactId>01-springboot-myabtis</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>01-springboot-myabtis</name>
	<description>Spring Boot集成Mybatis</description>
	<properties>
		<java.version>1.8</java.version>
	</properties>
	<dependencies>
		<!--	jdbc	-->
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-jdbc</artifactId>
		</dependency>

		<!--	web，可以理解成controller层的请求映射	-->
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>

		<!--	mysql	-->
		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
			<scope>runtime</scope>
		</dependency>

		<!--	lombok插件，用于生成get,set方法或有参无参构造	-->
		<dependency>
			<groupId>org.projectlombok</groupId>
			<artifactId>lombok</artifactId>
			<optional>true</optional>
		</dependency>

		<!-- 	mybatis	-->
		<dependency>
			<groupId>org.mybatis.spring.boot</groupId>
			<artifactId>mybatis-spring-boot-starter</artifactId>
			<version>2.2.0</version>
		</dependency>

		<!--	测试,不用,留在这为了好看	-->
		<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>

编写配置

选中生成的application.properties文件ctrl + F6重命名

application中的数据库url 三条///表示为本地 localhost == ///

#端口号
server:
  port: 8080
  servlet:
  #前缀
    context-path: /

#数据库名及时区
spring:
  datasource:
    url: jdbc:mysql:///test?serverTimezone=GMT%2B8&characterEncoding=utf8
    username: root
    password: root
mybatis:
  configuration:
    default-statement-timeout: 30
    map-underscore-to-camel-case: true
  mapper-locations:
    - classpath:/mapper/*.xml
#日志
logging:
  level:
    com.guhaoquan: debug

数据库表

实现使用mybatis进行CRUD

实体类

package com.guhaoqaun.entity;

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

/**
 * 生成的实体类尽量与数据库字段一一对应
 * @Data    生成get set方法
 * @NoArgsConstructor   无参构造
 * @AllArgsConstructor  有参构造
 */
@Data
@NoArgsConstructor
@AllArgsConstructor
public class Student {
    private Integer id; //用户id
    private String name;//用户名称
    private Integer age;    //用户年龄
    private String email;   //用户邮箱
}

统一返回值类型

这个可以拿来直接在项目中使用，现在很多公司命名为R(具体看业务需要)

package com.guhaoqaun.utils;

import lombok.Data;

import java.io.Serializable;

@Data
public class JsonResult implements Serializable {
    private static final long serialVersionUID = -7075739518556671717L; //序例化
    private int state = 1;//状态码
    private String message = "ok";//1：表示SUCCESS,0:ERROR
    private Object data;//正确数据
    public JsonResult(){}
    public JsonResult(String message){
        this.message=message;
    }
    //一般查询时调用。用于封装数据
    public JsonResult(Object data){
        this.data=data;
    }
    //出现异常时调用
    public JsonResult(Throwable t){
        this.state=0;
        this.message=t.getMessage();
    }
}

自定义异常

package com.guhaoqaun.utils;

public class ServiceException extends RuntimeException{
    private static final long serialVersionUID = -5614175354004336252L;
    public ServiceException(){
        super();
    }
    public ServiceException(String message){
        super(message);
    }

    public ServiceException(Throwable cause){
        super(cause);
    }
}

查询数据表中的所有数据

dao

package com.guhaoqaun.dao;

import com.guhaoqaun.entity.Student;
import org.apache.ibatis.annotations.Mapper;
import java.util.List;

@Mapper //mybatis注解，声明这是一个接口对应类
public interface StudentDao {

    /**
     * 使用List集合封装所有的数据
     * @return  从数据库中查询到的数据
     */
    List<Student> selectStudent();
}

Mapper.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.guhaoqaun.dao.StudentDao">
    <!--    namespace：必须有值，自定义的唯一字符串推荐使用：dao 接口的全限定名称 -->

    <!--
        <select>: 查询数据， 标签中必须是 select 语句
        id: sql 语句的自定义名称，推荐使用 dao 接口中方法名称， 
        使用名称表示要执行的 sql 语句
        resultType: 查询语句的返回结果数据类型，使用全限定类名 
     -->
    <!--   sql语句，查询所有数据,实际项目中不能用*，把字段写出来 -->
    <select id="selectStudent" resultType="com.guhaoqaun.entity.Student">
        select id,name,age,email from t_student
    </select>
</mapper>

service

package com.guhaoqaun.service;

import com.guhaoqaun.entity.Student;

import java.util.List;

public interface StudentService {

    /**
     * 用户访问的方法
     * @return
     */
    List<Student> selectStudentList();
}

serviceImpl

package com.guhaoqaun.service.impl;

import com.guhaoqaun.dao.StudentDao;
import com.guhaoqaun.entity.Student;
import com.guhaoqaun.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class StudentServiceImpl implements StudentService {

    /* 引入dao层的方法接口 */
    @Autowired
    private StudentDao studentDao;

    /**
     * 实现业务逻辑
     * @return
     */
    @Override
    public List<Student> selectStudentList() {
        List<Student> list = studentDao.selectStudent();    //调用dao层的方法，返回List集合，dao与service层的返回类型须统一
        return list;
    }
}

controller

package com.guhaoqaun.controller;

import com.guhaoqaun.service.StudentService;
import com.guhaoqaun.utils.JsonResult;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RequestMapping("student")
@RestController
public class StudentController {

    /*  引入service */
    @Autowired
    private StudentService studentService;

    /**
     * 查询列表
     * @return
     */
    @RequestMapping("list")
    public JsonResult list(){
        return new JsonResult(studentService.selectStudentList());
    }
}

测试

localhost:8080/student/list
当前后端分离时可以把这个路径给到前端即可

新增数据

dao

    /**
     * 返回值使用int,如新增成功返回新增条数，失败则返回0
     * @param entity
     * @return
     */
    int insertStudent(Student entity);

mapper.xml

    <insert id="insertStudent">
        insert into t_student(id,name,age,email)
        values
        (#{id},#{name},#{age},#{email})
    </insert>

service

    /**
     * 用户访问新增方法
     * @param entity
     * @return
     */
    int insertStudents(Student entity);

serviceimpl

    @Override
    public int insertStudents(Student entity) {
        if (entity == null)
            throw new ServiceException("保存对象不能为空");
        if (StringUtils.isEmpty(entity.getEmail()))
            throw new ServiceException("保存对象名称不能为空");
        int insertStudent = studentDao.insertStudent(entity);
        return insertStudent;
    }

controller

    /**
     * 用户新增
     * @param entity
     * @return
     */
    @RequestMapping("save")
    @ResponseBody
    public JsonResult save(Student entity){
        studentService.insertStudents(entity);
        return new JsonResult("保存成功");
    }

测试

localhost:8080/student/save?name=bbbb&age=21&[email protected]

查看数据库

修改数据库中的方法

dao

    /**
     * 修改用户数据,如成功返回条数，失败则返回0
     * @param entity
     * @return
     */
    int updatestudent(Student entity);

mapper.xml

    <update id="updatestudent">
        update t_student set
        name=#{name},
        age=#{age},
        email=#{email}
        where id=#{id}
    </update>

service

    /**
     * 用户访问修改方法
     * @param entity
     * @return
     */
    int updatestudent(Student entity);

serviceImpl

    @Override
    public int updatestudent(Student entity) {
    	//参数校验
        if (entity.getId() == null || entity.getId() < 0)
            throw new ServiceException("请选择一条记录进行修改");
        int updatestudent = studentDao.updatestudent(entity);
        if (updatestudent < 0)
            throw new ServiceException("修改失败，请填写相关参数");
        return updatestudent;
    }

controller

    @RequestMapping("update")
    public JsonResult update(Student entity){
        studentService.updatestudent(entity);
        return new JsonResult("修改成功");
    }

测试

localhost:8080/student/update?id=7&name=bccb&age=21&[email protected]

删除用户数据

dao

    /**
     * 删除用户数据
     * @param id
     * @return
     */
    int deleteStudent(Integer id);

mapper.xml

    <delete id="deleteStudent">
        delete from t_student where id=#{id}
    </delete>

service

    /**
     * 用户访问删除方法
     * @param id
     * @return
     */
    int deleteStudent(Integer id);

serviceImpl

    @Override
    public int deleteStudent(Integer id) {
        if (id == null || id < 0)
            throw new ServiceException("请选择一条数据进行删除");
        int student = studentDao.deleteStudent(id);
        if (student == 0)
            throw new ServiceException("此记录可能已经不存在了");
        return student;
    }

controller

    @RequestMapping("delete")
    public JsonResult delete(Integer id){
        studentService.deleteStudent(id);
        return new JsonResult("删除成功");
    }

测试

http://localhost:8080/student/delete?id=7