MyBatis-Plus多表查询分页实现(注解方式)

Mybatis-Plus 多表实现分页(注解方式)

1、准备阶段

  1. 构建一个Springboot项目

  2. 引入需要依赖

    
    <dependency>
        <groupId>org.springframework.bootgroupId>
        <artifactId>spring-boot-starter-webartifactId>
        <version>2.7.6version>
    dependency>
    
    
    <dependency>
        <groupId>com.baomidougroupId>
        <artifactId>mybatis-plus-boot-starterartifactId>
        <version>3.5.1version>
    dependency>
    
    
    <dependency>
        <groupId>mysqlgroupId>
        <artifactId>mysql-connector-javaartifactId>
        <version>8.0.26version>
    dependency>
    
  3. 创建数据表

    student:学生表

    在这里插入图片描述

    student_class:班级表

    在这里插入图片描述

  4. 配置 Mybatis-plus 分页插件

    @Configuration
    public class MybatisConfig {
        /**
         * 分页插件
         * @return
         */
        @Bean
        public MybatisPlusInterceptor mybatisPlusInterceptor() {
            MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
            interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
            return interceptor;
        }
    }
    
  5. 配置全局返回类

    
    public class R extends HashMap<String, Object> {
        /**
         * 状态码
         */
        public static final String CODE_TAG = "code";
    
        /**
         * 返回内容
         */
        public static final String MSG_TAG = "msg";
    
        /**
         * 数据对象
         */
        public static final String DATA_TAG = "data";
    
        public R() {
    
        }
    
        public R(Integer code, String msg, Object data) {
            super.put(CODE_TAG, code);
            super.put(MSG_TAG, msg);
            if (data != null) {
                super.put(DATA_TAG, data);
            }
        }
    
        public static R ok() {
            return R.ok(200, "操作成功");
        }
    
        public static R ok(Integer code, String msg) {
            return new R(code, msg, null);
        }
    
    
        public static R error() {
            return R.ok(500, "系统错误");
        }
    
        public static R error(Integer code, String msg) {
            return new R(code, msg, null);
        }
    
        public static R ok(Object data) {
            return new R(200, "操作成功", data);
        }
    }
    
  6. 配置 application.yml

    server:
      port: 8888
    
    spring:
      datasource:
        driver-class-name: com.mysql.jdbc.Driver
        url: jdbc:mysql://localhost:3306/test?useSSL=false&useUnicode=true&characterEncoding=utf8&serverTimezone=GMT%2B8&autoReconnect=true
        username: root
        password: 123456
    
    logging:
      level:
        com:
          zhang: debug
    

2、开始实现

(1)、单表分页

实体类


@TableName("student")
public class Student implements Serializable {

    private static final long serialVersionUID = 1L;

    @TableId(value = "id", type = IdType.AUTO)
    private Integer id;

    /**
     * 学生名称
     */
    private String name;

    /**
     * 年龄
     */
    private Integer age;

    /**
     * 班级id
     */
    private Integer classId;
	
    // ... get  set 方法
}

Controller 层

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

    @Autowired
    private IStudentService studentService;


    @GetMapping("/list")
    public R selectList() {
       return R.ok(studentService.selectList());
    }

}

Service 层

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

    public Object selectList() {
        return this.baseMapper.selectPage(new Page<Student>(1, 10), null);
    }
}

Mapper 层

public interface StudentMapper extends BaseMapper<Student> {}

测试:

MyBatis-Plus多表查询分页实现(注解方式)_第1张图片

(2) 多表查询

编写Vo类,用于传输请求参数和返回参数

请求参数Vo类

public class RequestStudentVo {

    // 学生名称
    private String name;

    // 开始年龄
    private Integer startAge;
    // 结束年龄
    private Integer endAge;
    // 班级名称
    private String className;

    private Integer page;
    private Integer pageSize;

    //  ... get set方法
}

返回数据 Vo类


public class ResponseStudentVo {


    private Integer id;
    private String name;
    private Integer age;
    private String className;
	// ... get  set方法
}

Controller 层

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

    @Autowired
    private IStudentService studentService;


    @GetMapping("/list")
    public R selectList() {
       return R.ok(studentService.selectList());
    }

    @GetMapping("/selectPage")
    public R selectStudentPage(RequestStudentVo vo){
        return R.ok(studentService.selectStudentPage(vo));
    }

}

Servicet 层

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


    @Autowired
    private StudentMapper studentMapper;

    public Object selectList() {
        return this.baseMapper.selectPage(new Page<Student>(1, 10), null);
    }


    public Object selectStudentPage(RequestStudentVo vo) {
        QueryWrapper<ResponseStudentVo> warpper = getWarpper(vo);
        IPage<ResponseStudentVo> page = getPage(vo);
        IPage<ResponseStudentVo> pageList = studentMapper.selectStudentPage(page, warpper);
        return pageList;
    }


    /**
     * 构建分页
     *
     * @param vo
     * @param 
     * @return
     */
    private <T> IPage<T> getPage(RequestStudentVo vo) {
        Integer page = vo.getPage() == null || vo.getPage() < 0 || vo.getPage() > 1000 ? 1 : vo.getPage();
        Integer pageSize = vo.getPageSize() == null || vo.getPageSize() < 0 || vo.getPageSize() > 1000 ? 1 : vo.getPageSize();
        return new Page<T>(page, pageSize);
    }

    /**
     * 构建 warpper
     *
     * @param vo
     * @param 
     * @return
     */
    private <T> QueryWrapper<T> getWarpper(RequestStudentVo vo) {
        QueryWrapper<T> queryWrapper = new QueryWrapper<T>();

        if (!StringUtils.isEmpty(vo.getName())) {
            queryWrapper.like("s.name", vo.getName());
        }

        if (!ObjectUtils.isEmpty(vo.getStartAge()) && !ObjectUtils.isEmpty(vo.getEndAge())) {
            queryWrapper.between("s.age", vo.getStartAge(), vo.getEndAge());
        }

        if (!ObjectUtils.isEmpty(vo.getClassName())) {
            queryWrapper.like("ss.class_name", vo.getClassName());
        }

        return queryWrapper;
    }

}

Mapper 层

public interface StudentMapper extends BaseMapper<Student> {

    @Select("select s.id,s.`name`,s.age,ss.class_name from student s\n" +
            "INNER JOIN student_class ss\n" +
            "ON ss.id = s.class_id ${ew.customSqlSegment}")
    IPage<ResponseStudentVo> selectStudentPage(IPage<ResponseStudentVo> page, @Param(Constants.WRAPPER) QueryWrapper<ResponseStudentVo> warpper);
}

说明:

${ew.customSqlSegment}:拼接 where 后的语句(在动态sql中请勿处于 标签内)

${ew.sqlSelect} :拼接 select SQL 主体

${ew.sqlSet} :拼接 update 主体

${ew.sqlSegment} : 拼接 where 后的语句

Mysql 原始sql:

select s.id,s.`name`,s.age,ss.class_name from student s
INNER JOIN student_class ss
ON ss.id = s.class_id
where s.name like '%李%'
and s.age BETWEEN 11 and 20
and ss.class_name like '%二%'

测试:

MyBatis-Plus多表查询分页实现(注解方式)_第2张图片

日志查看:

: ==>  Preparing: select s.id,s.`name`,s.age,ss.class_name from student s INNER JOIN student_class ss ON ss.id = s.class_id WHERE (s.name LIKE ? AND s.age BETWEEN ? AND ? AND ss.class_name LIKE ?)
 : ==> Parameters: %李%(String), 11(Integer), 20(Integer), %二%
 : <==      Total: 1

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