Mybatis-plus的介绍及优缺点，这里不再详细说明，需要的朋友到官网支详细了解
下面就用一个springboot项目mybatis-plus 的基础操作
第一步：数据库准备
CREATE TABLE `data0917`.`student` ( `id` int(11) NOT NULL AUTO_INCREMENT, `name` varchar(30) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL, `sex` char(1) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL DEFAULT '男', `blood` varchar(2) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '血型', PRIMARY KEY (`id`) USING BTREE ) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;
第二步：核心依赖
<dependency> <groupId>com.baomidou</groupId> <artifactId>mybatis-plus-boot-starter</artifactId> <version>3.5.1</version> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <scope>runtime</scope> </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>
这些是核心依赖，用到了mysql驱动、lombok。集成mybatis-plus要把mybatis、mybatis-spring去掉，避免冲突；lombok是一个工具，添加了这个依赖，就可以使用它的简化功能，最常用的用法就是在实体类中使用它的@Data注解，这样实体类就不用写set、get、toString等方法了。
第三步：application.yml配置
mybatis-plus: configuration: log-impl: org.apache.ibatis.logging.stdout.StdOutImpl #开启sql日志 map-underscore-to-camel-case: true # 该配置就是将带有下划线的表字段映射为驼峰格式的实体类属性 spring: datasource: driver-class-name: com.mysql.cj.jdbc.Driver url: jdbc:mysql://localhost:3306/data0917?serverTimezone=GMT%2B8&useUnicode=true&characterEncoding=UTF-8 username: root password: root
第四步：实体类Student.java
import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableId;
import lombok.Data;
@Data
public class Student {
@TableId(value = "id", type = IdType.AUTO)//指定自增策略
private Integer id;
private String name;
private String sex;
private String blood;
}第五步：StudentMapper.java
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.example.springbootmybatisplus.entity.Student;
import org.apache.ibatis.annotations.Mapper;
@Mapper
//表明这是一个Mapper，也可以在启动类上加上包扫描
//Mapper 继承该接口后，无需编写 mapper.xml 文件，即可获得CRUD功能
public interface StudentMapper extends BaseMapper<Student> {
}这样就完成了mybatis-plus与springboot的整合。把mybatis和mybatis-spring依赖换成mybatis-plus的依赖，最后mapper继承BaseMapper即可。
第六步：Mybatis分页插件配置
import com.baomidou.mybatisplus.annotation.DbType;
import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class MyBatisPlusPager {
/**
* 分页插件
*
* @return 分页插件的实例
*/
@Bean
public MybatisPlusInterceptor mybatisPlusInterceptor() {
MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
//指定数据库类型是 MySQL
interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
return interceptor;
}
}第七步：StudentService.java
import com.example.springbootmybatisplus.entity.Student;
import com.example.springbootmybatisplus.mapper.StudentMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.List;
@Service
public class StudentService {
@Autowired
private StudentMapper studentMapper;
//查询全部
public List<Student> selectAll() {
return studentMapper.selectList(null);
}
//添加一条数据
public int add(Student student) {
return studentMapper.insert(student);
}
public Student queryById(Student student) {
return studentMapper.selectById(student.getId());
}
//多条件判断判断查询 及 分页
//当姓名，性别，血型不为空时， 进行条件查询
public Page<Student> queryWhere(Student student,Page studentPage){
QueryWrapper<Student> wrapper = new QueryWrapper<>();
wrapper.like("".equals(student.getName()) == false && student.getName() != null, "name",student.getName())
.eq("".equals(student.getSex()) == false && student.getSex() != null, "sex",student.getSex())
.eq("".equals(student.getBlood()) == false && student.getBlood() != null, "blood",student.getBlood());
return studentMapper.selectPage(studentPage,wrapper);
}
}第八步：测试类
import com.example.springbootmybatisplus.entity.Student;
import com.example.springbootmybatisplus.service.StudentService;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
@SpringBootTest
public class StudentCURDTest {
@Autowired
private StudentService studentService;
@Test
public void queryAll() {
studentService.selectAll().forEach(System.out::println);
}
@Test
public void addOne(){
Student student = new Student();
student.setName("小小雨");
student.setSex("男");
student.setBlood("A");
System.out.println(studentService.add(student));
}
@Test void queryOne(){
Student student = new Student();
student.setId(1);
System.out.println(studentService.queryById(student));
}
@Test void queryWhere(){
Page<Student> studentPage = new Page<Student>(1L, 2L);
Student student = new Student();
student.setName("小");
//student.setBlood("A");
Page<Student> studentPage1 =studentService.queryWhere(student,studentPage);
System.out.println("pages"+ studentPage1.getPages());
System.out.println("total:"+studentPage1.getTotal());
System.out.println("size:"+studentPage1.getSize());
studentPage1.getRecords().forEach(System.out::println);
}
}Mybatis-plus之IService的使用(以上面的内容为基础), 简单列具两个实例
第一步：创建StuService.java接口, 继承IService
import com.baomidou.mybatisplus.extension.service.IService;
import com.example.springbootmybatisplus.entity.Student;
public interface StuService extends IService<Student> {
}第二步： 定义实现类StuServiceImpl.java
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.example.springbootmybatisplus.entity.Student;
import com.example.springbootmybatisplus.mapper.StudentMapper;
import org.springframework.stereotype.Service;
@Service
public class StuServiceImpl extends ServiceImpl<StudentMapper, Student> implements StuService{
}第三步：测试调用
@Test void iServiceSaveTest(){
Student student = new Student();
student.setName("小小雨");
student.setSex("男");
student.setBlood("A");
System.out.println(stuService.save(student));
}
//IPage分页及多条件查询
@Test void iServiceIPageTest(){
IPage<Student> studentPage = new Page<>(1l,2l);
Student student = new Student();
student.setName("小小雨");
student.setSex("男");
student.setBlood("A");
QueryWrapper<Student> wrapper = new QueryWrapper<>();
wrapper.like("".equals(student.getName()) == false && student.getName() != null, "name",student.getName())
.eq("".equals(student.getSex()) == false && student.getSex() != null, "sex",student.getSex())
.eq("".equals(student.getBlood()) == false && student.getBlood() != null, "blood",student.getBlood());
IPage<Student> studentPage1 =stuService.page(studentPage,wrapper);
System.out.println("pages"+ studentPage1.getPages());
System.out.println("total:"+studentPage1.getTotal());
System.out.println("size:"+studentPage1.getSize());
studentPage1.getRecords().forEach(System.out::println);
}