Mybatis-plus实现数据库的增删改查操作
目录
1、MybatisPlus简介
2、MybatisPlus注解介绍
3、常用方法
4、SpringBoot整合MybatisPlus实现增删改查的一个简单Demo
5、参考资料
1、MybatisPlus简介
Mybatis和MybatisPlus都是非常流行的持久层框架。mybatis可以直接在xml或注解中通过SQL语句操作数据库，很是灵活。但是其操作都要通过SQL语句进行，就必须写大量的xml文件或者注解sql语句，很是麻烦。而mybatis-plus就很好的解决了这个问题。
Mybatis-Plus（简称MP）是 Mybatis 的增强工具，在 Mybatis 的基础上只做增强不做改变，为简化开发、提高效率而生。关于mybatis-plus的更多介绍及特性，可以参考mybatis-plus官网。
mybatis-plus已经封装好了一些crud方法，我们不需要再写SQL语句了，直接调用这些方法就行
2、MybatisPlus注解介绍
- @TableId 关联主键，可以通过type属性指定是否自增
- @TableName 通过value属性关联表名，当类名与表名一致时，value属性可省写
- @TableField 关联表字段，如果属性名称与字段名称一致则此注解可以省写（包含驼峰规则）
3、常用方法
MybatisPlus常用方法可以去看BaseMapper这个接口。BaseMapper这个接口里面封装了一些常用的sql。
public interface BaseMapper extends Mapper {
int insert(T entity);
int deleteById(Serializable id);
int deleteByMap(@Param("cm") Map columnMap);
int delete(@Param("ew") Wrapper wrapper);
int deleteBatchIds(@Param("coll") Collection idList);
int updateById(@Param("et") T entity);
int update(@Param("et") T entity, @Param("ew") Wrapper updateWrapper);
T selectById(Serializable id);
List selectBatchIds(@Param("coll") Collection idList);
List selectByMap(@Param("cm") Map columnMap);
T selectOne(@Param("ew") Wrapper queryWrapper);
Integer selectCount(@Param("ew") Wrapper queryWrapper);
List selectList(@Param("ew") Wrapper queryWrapper);
List> selectMaps(@Param("ew") Wrapper queryWrapper);
List Wrapper为条件查询构造器，QueryWrapper为Wrapper的一个实现方法。主要是用来进行多个where条件的拼接。
例如：
QueryWrapper queryWrapper = new QueryWrapper<>();
queryWrapper.gt("age", 10).eq("sex", "女"); //年龄大于10且性别为“女" | Wrapper中的方法 | 含义 |
| ge | |
| gt | |
| le | |
| lt | |
| eq | |
| ne | |
| between | |
4、SpringBoot整合MybatisPlus实现增删改查的一个简单Demo
源码：https://gitee.com/wulinchun/mybatis-plus.git (dev分支)
4.1、目录结构
4.2、代码
4.2.1、xml&yml配置
pom.xml
4.0.0
org.springframework.boot
spring-boot-starter-parent
2.2.2.RELEASE
org.example
mybatis-plus
1.0-SNAPSHOT
8
8
org.springframework.boot
spring-boot-starter-web
org.springframework.boot
spring-boot-starter-test
test
com.baomidou
mybatis-plus-boot-starter
3.4.0
com.baomidou
mybatis-plus-generator
3.4.0
org.projectlombok
lombok
1.18.20
provided
com.microsoft.sqlserver
mssql-jdbc
mysql
mysql-connector-java
5.1.26
org.springframework.boot
spring-boot-maven-plugin
true
application.yml
server:
port: 8080
spring:
profiles:
active: dev #使用application-dev.yml里面的配置
application-dev.yml
server:
port: 8080
spring:
datasource:
name: mybatis_plus
url: jdbc:mysql://localhost:3306/mydb?serverTimezone=UTC&characterEncoding=utf8
username: root
password: 123456
driver-class-name: com.mysql.jdbc.Driver
mybatis:
mapper-locations: classpath:mapper/*.xml #注意：一定要对应mapper映射xml文件的所在路径
type-aliases-package: com.mybatisplus.entity # 注意：对应实体类的路径
mybatis-plus:
configuration:
log-impl: org.apache.ibatis.logging.stdout.StdOutImpl #打印mybatis-plus的sql语句
ScoreMapper.xml
StudentMapper.xml
4.2.2、实体类
Score.java
package com.mybatisplus.entity;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
/**
* @author: wu linchun
* @time: 2021/6/6 11:34
* @description:
*/
@Data
@TableName("t_score")
@NoArgsConstructor
@AllArgsConstructor
public class Score {
@TableField("sno")
private int sno;
@TableField("subject")
private String subject;
@TableField("score")
private int score;
}
Student.java
package com.mybatisplus.entity;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import java.io.Serializable;
/**
* @author: Wu Linchun
* @date: 2021/06/04/10:25
* @Description:
**/
@Data
@TableName("t_student")
@NoArgsConstructor
@AllArgsConstructor
public class Student implements Serializable {
@TableId
@TableField("sno")
private int sno;
@TableField("sname")
private String sname;
@TableField("age")
private int age;
@TableField("sex")
private String sex;
@TableField("sclass")
private String sclass;
}
StudentScoreVO.java 注:该实体类为映射t_student表和t_score表联合查询的结果package com.mybatisplus.entity.vo;
import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import java.io.Serializable;
/**
* @author: wu linchun
* @time: 2021/6/6 11:42
* @description:
*/
@Data
@NoArgsConstructor
@AllArgsConstructor
public class StudentScoreVO implements Serializable {
@TableField("sno")
private int sno;
@TableField("sname")
private String sname;
@TableField("subject")
private String subject;
@TableField("score")
private int score;
}
4.2.3、接口&实现类
IScoreMapper.javapackage com.mybatisplus.mapper;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.mybatisplus.entity.Student;
import com.mybatisplus.entity.vo.StudentScoreVO;
import javafx.scene.control.Pagination;
import org.apache.ibatis.annotations.Select;
import org.springframework.stereotype.Component;
import java.util.List;
/**
* @description:
* @author: wu linchun
* @time: 2021/6/6 11:49
*/
@Component("iScoreMapper")
public interface IScoreMapper extends BaseMapper {
/**
* 获取学生成绩并分页显示
* @return
*/
@Select("select tst.sno,tst.sname,tsc.subject,tsc.score from t_student tst,t_score tsc where tst.sno=tsc.sno")
List getScore();
/**
* 分页显示学生成绩
* @param
* @return
*/
@Select("select tst.sno,tst.sname,tsc.subject,tsc.score from t_student tst,t_score tsc where tst.sno=tsc.sno")
IPage getByPage(Page studentScoreVOPage,QueryWrapper queryWrapper);
@Select("select count(*) from t_student tst,t_score tsc where tst.sno=tsc.sno")
int getCount();
}
IStudentMapper.javapackage com.mybatisplus.mapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.mybatisplus.entity.Student;
import org.apache.ibatis.annotations.Mapper;
import org.springframework.stereotype.Component;
/**
* @author: Wu Linchun
* @date: 2021/06/04/14:48
* @Description:
**/
@Component("iStudentMapper")
public interface IStudentMapper extends BaseMapper {
}
IScoreService.javapackage com.mybatisplus.service;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.mybatisplus.entity.vo.StudentScoreVO;
import javafx.scene.control.Pagination;
import java.util.List;
/**
* @description:
* @author: wu linchun
* @time: 2021/6/6 11:55
*/
public interface IScoreService {
/**
*
* @return
*/
List getScore();
/**
*分页显示
* @param
* @return
*/
IPage getByPage(Page studentScoreVOPage, QueryWrapper queryWrapper);
/**
*
* @return
*/
int getCount();
}
IStudentService.javapackage com.mybatisplus.service;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.mybatisplus.entity.Student;
import org.apache.ibatis.annotations.Mapper;
import org.springframework.stereotype.Repository;
import java.util.List;
/**
* @author: Wu Linchun
* @date: 2021/06/04/14:02
* @Description:
**/
public interface IStudentService {
/**
* 根据唯一性主键进行查询 sno是唯一性主键
*
* @param sno
* @return
*/
Student getBySno(int sno);
/**
* 查询全部
*
* @return
*/
List getAll();
/**
* 根据性别和年龄查询
*
* @param sex
* @param age
* @return
*/
List getBySexAge(String sex, int age);
/**
* 范围&多条件查询
*
* @param age
* @return
*/
List getStudentsByScope(int age);
/**
* 添加学生
*
* @param student
* @return
*/
int insertStudent(Student student);
/**
* 根据指定条件删除
*
* @param sno
* @return
*/
int deleteBySno(int sno);
/**
* 根据多个指定条件删除
*
* @param sclass
* @param sex
* @return
*/
int deleteBySclass_sex(String sclass, String sex);
/**
* 更新
*
* @param student
* @return
*/
int updateStudent(Student student);
/**
* 获取表中总记录数
* @return
*/
int getCount();
}
ScoreServiceImpl.javapackage com.mybatisplus.service.impl;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.mybatisplus.entity.vo.StudentScoreVO;
import com.mybatisplus.mapper.IScoreMapper;
import com.mybatisplus.service.IScoreService;
import javafx.scene.control.Pagination;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Service;
import java.util.List;
/**
* @author: wu linchun
* @time: 2021/6/6 11:56
* @description:
*/
@Service
public class ScoreServiceImpl implements IScoreService {
@Autowired
@Qualifier("iScoreMapper")
private IScoreMapper iScoreMapper;
@Override
public List getScore() {
return iScoreMapper.getScore();
}
@Override
public IPage getByPage(Page studentScoreVOPage, QueryWrapper queryWrapper) {
return iScoreMapper.getByPage(studentScoreVOPage, queryWrapper);
}
@Override
public int getCount() {
return iScoreMapper.getCount();
}
}
StudentServiceImpl.javapackage com.mybatisplus.service.impl;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.mybatisplus.entity.Student;
import com.mybatisplus.mapper.IStudentMapper;
import com.mybatisplus.service.IStudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Service;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* @author: Wu Linchun
* @date: 2021/06/04/14:55
* @Description:
**/
@Service
public class StudentServiceImpl implements IStudentService {
@Autowired
@Qualifier("iStudentMapper")
private IStudentMapper iStudentMapper;
@Override
public Student getBySno(int sno) {
return iStudentMapper.selectById(sno);
}
@Override
public List getAll() {
return iStudentMapper.selectList(null);
}
@Override
public List getBySexAge(String sex, int age) {
Map map = new HashMap<>();
map.put("sex", sex);
map.put("age", age);
return iStudentMapper.selectByMap(map);
}
@Override
public List getStudentsByScope(int age) {
QueryWrapper queryWrapper = new QueryWrapper<>();
//ge表示大于等于、gt表示大于、le表示小于等于、lt表示小于
//eq等于、ne不等于
//between范围 between("age",20,30); 年龄范围20~30
//查询年龄20-30范围 1.代表字段 2.代表开始值 3.代表结束值
/* queryWrapper.gt("age",age);
queryWrapper.gt("age",10); //年龄大于10
queryWrapper.ge("age",10); //年龄大于等于10
queryWrapper.le("age",10); //年龄小于等于10
queryWrapper.lt("age",10); //年龄小于10
queryWrapper.eq("age",10); //年龄等于10
queryWrapper.ne("age",10); //年龄不等于10
queryWrapper.between("age",20,30); //年龄介于20~30之间*/
queryWrapper.gt("age", 10).eq("sex", "女"); //年龄大于10且性别为“女"
return iStudentMapper.selectList(queryWrapper);
}
@Override
public int insertStudent(Student student) {
return iStudentMapper.insert(student);
}
@Override
public int deleteBySno(int sno) {
QueryWrapper queryWrapper = new QueryWrapper<>();
queryWrapper.eq("sno", sno);
return iStudentMapper.delete(queryWrapper);
}
/**
* 根据班级和性别删除
*
* @param sclass
* @param sex
* @return
*/
@Override
public int deleteBySclass_sex(String sclass, String sex) {
Map map = new HashMap<>();
map.put("sclass", sclass);
map.put("sex", sex);
return iStudentMapper.deleteByMap(map);
}
@Override
public int updateStudent(Student student) {
QueryWrapper queryWrapper = new QueryWrapper<>();
queryWrapper.eq("sno", student.getSno());
return iStudentMapper.update(student, queryWrapper);
}
@Override
public int getCount() {
QueryWrapper queryWrapper=new QueryWrapper<>();
queryWrapper.eq("sex","男");
// return iStudentMapper.selectCount(null); //null为获取表中总记录数
return iStudentMapper.selectCount(queryWrapper); //获取指定条件的记录数
}
}
4.2.4、配置类
MybatisPlusConfig.javapackage com.mybatisplus.config;
import com.baomidou.mybatisplus.annotation.DbType;
import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.PaginationInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
/**
* @author: wu linchun
* @time: 2021/6/6 12:13
* @description: mybatis-plus分页插件配置
*/
@Configuration
public class MybatisPlusConfig {
@Bean
public PaginationInterceptor paginationInterceptor() {
return new PaginationInterceptor();
}
}
4.2.5、测试类
MyControllerTest.javapackage com.mybatisplus.test;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.mybatisplus.entity.Student;
import com.mybatisplus.entity.vo.StudentScoreVO;
import com.mybatisplus.service.IStudentService;
import com.mybatisplus.service.impl.ScoreServiceImpl;
import com.mybatisplus.service.impl.StudentServiceImpl;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.test.context.web.WebAppConfiguration;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
/**
* @author: wu linchun
* @time: 2021/6/5 20:31
* @description:
*/
@RunWith(SpringRunner.class)
@SpringBootTest
//由于是Web项目，Junit需要模拟ServletContext，因此我们需要给我们的测试类加上@WebAppConfiguration。
@WebAppConfiguration
public class MyControllerTest {
@Autowired
@Qualifier("studentServiceImpl")
private StudentServiceImpl studentServiceImpl;
@Autowired
@Qualifier("scoreServiceImpl")
private ScoreServiceImpl scoreServiceImpl;
@Test
public void testAdd() {
int sno = 20160001;
for (int i = 0; i < 10; i++) {
Student student = new Student(sno++, "张三", 20, "男", "2016222");
if (studentServiceImpl.insertStudent(student) == 1) {
System.out.println("添加成功");
} else {
System.out.println("添加失败");
}
}
}
@Test
public void testDeleteBySno() {
if (studentServiceImpl.deleteBySno(20160009) == 1) {
System.out.println("删除成功");
} else {
System.out.println("删除失败");
}
}
@Test
public void testDeleteBySclass_sex() {
if (studentServiceImpl.deleteBySclass_sex("2016221", "男") == 1) {
System.out.println("删除成功");
} else {
System.out.println("删除失败");
}
}
@Test
public void testGetAll() {
List studentList = new ArrayList();
studentList = studentServiceImpl.getAll();
for (Student student : studentList) {
System.out.println(studentList.toString());
}
}
@Test
public void testGetStudentsByScope() {
List studentList = studentServiceImpl.getStudentsByScope(10);
for (Student student : studentList) {
System.out.println(studentList.toString());
}
}
@Test
public void testUpdateStudent() {
Student student = new Student(20160010, "HHH", 20, "男", "2016222");
if (studentServiceImpl.updateStudent(student) == 1) {
System.out.println("更新成功");
} else {
System.out.println("更新失败");
}
}
@Test
public void testGetBySno() {
Student student = studentServiceImpl.getBySno(20160003);
System.out.println(student.toString());
}
@Test
public void testGetCount() {
System.out.println(studentServiceImpl.getCount());
}
@Test
public void testGetScore() {
List studentScoreVOList = scoreServiceImpl.getScore();
for (StudentScoreVO studentScoreVO : studentScoreVOList) {
System.out.println(studentScoreVO.toString());
}
}
@Test
public void testGetByPage() {
int curr = 0, size = 3;
while (curr <= scoreServiceImpl.getCount() / 3 + 1) {
Page page = new Page<>(curr, size);
System.out.println(curr + " " + size);
scoreServiceImpl.getByPage(page, null).getRecords().forEach(System.out::println);
curr++;
System.out.println("------------------------------------------------");
}
}
}
由于在yml中增加了打印MybatisPlus的sql配置，因此执行时可以在控制台看到输出的MybatisPlus封装的sql语句。
5、参考资料
MyBatis Plus 简单介绍 - 知乎 (zhihu.com)
mybatis plus实现某种条件查询 - 谢世林 - 博客园 (cnblogs.com)
mybatis-plus的sql语句打印问题_猿,码的博客-CSDN博客_mybatisplus打印sql语句
mybatis-plus实现多表联查 - 白衣风云 - 博客园 (cnblogs.com)
MyBatis-Plus_分页查询_Gblfy_Blog-CSDN博客_mybatis-plus分页查询
Mybatis-plus中sql语句LT、LE、EQ、NE、GE、GT的意思 - 潘向福 - 博客园 (cnblogs.com)