[Java知识库]mybatis plus配置以及controller层增删改查、分页

一、新建一个spring boot项目

如何在idea中创建一个SpringBoot项目（超详细教学）_我是老伯的博客-CSDN博客

二、建立分层包

添加依赖

<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.4.2</version>
</dependency>

1. config层 MybatisPlusConfig.java ??

集成完毕分页插件之后，可去掉PageHelper 分页插件

@Configuration
public class MybatisPlusConfig {
    // 最新版
    @Bean  // <bean id=""/>
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
        return interceptor;
    }
}

2. entity层 Student.java

@Data
public class Student {
    private Long id;
    private String name;
    private String number;

}

3.mapper层 StudentMapper.java

public interface StudentMapper extends BaseMapper<Student> {
}

4.service层 Impl包下StudentServiceImpl.java

@Service
public class StudentServiceImpl extends ServiceImpl<StudentMapper, Student> implements StudentService {
}

StudentService.java

public interface StudentService extends IService<Student> {

}

mybatis plus配置

application.yaml

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/qcby_db?useUnicode=true&characterEncoding=utf-8&serverTimezone=CTT
    username: root
    password: 密码
    driver-class-name: com.mysql.cj.jdbc.Driver
# mybatis-plus配置
mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
  typeAliasesPackage: com.qcby.zsgc.entity
  mapperLocations: classpath:mapper/*.xml
  #  全局配置id自增
  global-config:
    db-config:
      id-type: auto

pagehelper:
  helperDialect: mysql
  reasonable: true # 修改默认值

5. controller层 Studentcontroller.java

@RestController
@RequestMapping("/student")
public class StudentController {
    @Autowired
    private StudentService studentService;

    @RequestMapping("save")
    public void save(Student student){
        studentService.save(student);
    }
    @RequestMapping("update")
    public void update(Student student) {
        studentService.updateById(student);
    }
    @RequestMapping("saveOrUpdate")
    public void saveOrUpdate(Student student){
        studentService.saveOrUpdate(student);
    }
    @RequestMapping("removeById")
    public void removeById(Long id) {
      studentService.removeById(id);
    }
    @RequestMapping("list")
    public List<Student> list(Long id) {
       return studentService.list();
    }

    /**
     * 查询条件 =》name得模糊查询 和 number精确匹配  可选的
     * @param pageNo
     * @param pageSize
     * @return
     */
    @RequestMapping("listPage")
    public Page<Student> listPage(Integer pageNo,Integer pageSize){
        Page<Student> page =new Page(pageNo,pageSize);
        return studentService.page(page);
    }
}

?添加模糊查询和精确查询

@RequestMapping("listPage")
    public Page<Student> listPage(Integer pageNo,Integer pageSize,Student student){
        //处理分页
        Page<Student> page =new Page(pageNo,pageSize);
        //帮助我们拼接where
        QueryWrapper<Student> queryWrapper = new QueryWrapper();
        if(!StringUtils.isEmpty(student.getName())){
            queryWrapper.like("name",student.getName());
        }
        if (!StringUtils.isEmpty(student.getNumber())) {
            queryWrapper.eq("numner",student.getNumber());
        }
            //添加分页 和查询条件
        return studentService.page(page,queryWrapper);
    }