Mybatis-Plus使用page类实现分页查询

1. pom.xml

注意当前使用的mybatis plus的版本，版本过高会需要额外引入jsqlparser包，才有PaginationInnerInterceptor类。

<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.5.10</version>
</dependency>
<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-jsqlparser</artifactId>
    <version>3.5.10</version> <!-- 确保版本和 MyBatis Plus 主包一致 -->
</dependency>

2. 配置类

package com.whl.info.config;

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 MybatisPlusConfig {

    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        // 添加分页插件
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL)); // 数据库类型
        return interceptor;
    }

}

注意，config类如果是在别的模块下，需要在该服务下的主启动类中配置能扫描到config类的路径名@ComponentScan(basePackages = {"com.example.a","com.example.a"})
比如，模块目录如下：

- module-a
  - src
    - main
      - java
        - com
          - example
            - a
              - MyBatisConfig.java
- module-b
  - src
    - main
      - java
        - com
          - example
            - b
              - ApplicationB.java

那么在模块B中的主启动类ApplicationB.java示例如下：

@SpringBootApplication
@ComponentScan(basePackages = {"com.example.a", "com.example.b"})
public class ApplicationB {
    public static void main(String[] args) {
        SpringApplication.run(ApplicationB.class, args);
    }
}

或者直接将config放在B模块目录下，但是如果其他模块也有分页操作，需要写重复的代码，不便于维护，最好是将config都放在同一个模块下，别的模块在依赖中引用即可。
如，在 B 模块的 pom.xml 中添加对 A 模块的依赖：

<dependency>
    <groupId>com.example</groupId>
    <artifactId>module-a</artifactId>
    <version>1.0.0</version>
</dependency>

3. 业务代码

只需要给定pageNum（分页当前页）和pageSize（总页数）即可。

1. controller层：

   package com.whl.info.controller;
   
   import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
   import com.whl.entity.result.Result;
   import com.whl.info.entity.dto.ArticleDto;
   import com.whl.info.entity.dto.ArticlePageDto;
   import com.whl.info.entity.vo.ArticleVo;
   import com.whl.info.service.ArticleService;
   import org.springframework.beans.factory.annotation.Autowired;
   import org.springframework.web.bind.annotation.*;
   
   import java.util.List;
   
   @RestController
   @RequestMapping("/article/")
   public class ArticleController {
   
       @Autowired
       private ArticleService articleService;
   
       /**
        * 分页查询文章列表
        * @param articlePageDto
        * @return
        */
       @PostMapping("articleListPage")
       public Result<Page<ArticleVo>> getArticleListByPage(@RequestBody ArticlePageDto articlePageDto){
           Page<ArticleVo> articleVoPage = articleService.getArticleListByPage(articlePageDto);
           return Result.success(articleVoPage);
       }
   }
   

2. service层：

   public interface ArticleService {
       Page<ArticleVo> getArticleListByPage(ArticlePageDto articlePageDto);
   }
   
   

   package com.whl.info.service.impl;
   
   import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
   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.mysql.cj.util.StringUtils;
   import com.whl.info.entity.dto.ArticleDto;
   import com.whl.info.entity.dto.ArticlePageDto;
   import com.whl.info.entity.vo.ArticleVo;
   import com.whl.info.mapper.ArticleMapper;
   import com.whl.info.service.ArticleService;
   import org.springframework.beans.factory.annotation.Autowired;
   import org.springframework.stereotype.Service;
   
   import java.util.List;
   
   @Service
   public class ArticleServiceImpl implements ArticleService {
   
       @Autowired
       private ArticleMapper articleMapper;
   
       @Override
       public Page<ArticleVo> getArticleListByPage(ArticlePageDto articlePageDto) {
           //1. 分页对象
           Page<ArticleVo> articleVoPage = new Page<>(articlePageDto.getPageNum(), articlePageDto.getPageSize());
   
           //2. 查询条件
           LambdaQueryWrapper<ArticleVo> queryWrapper = new LambdaQueryWrapper<>();
           //校验入参，条件查询
           if (!StringUtils.isNullOrEmpty(articlePageDto.getArticleName())){
               queryWrapper.like(ArticleVo::getArticleTitle, articlePageDto.getArticleName());
           }
           if (!StringUtils.isNullOrEmpty(articlePageDto.getStartTime()) && !StringUtils.isNullOrEmpty(articlePageDto.getEndTime())){
               queryWrapper.between(ArticleVo::getPublishTime,articlePageDto.getStartTime(), articlePageDto.getEndTime());
           }else if (!StringUtils.isNullOrEmpty(articlePageDto.getStartTime())){
               queryWrapper.ge(ArticleVo::getPublishTime, articlePageDto.getStartTime());
           }else if (!StringUtils.isNullOrEmpty(articlePageDto.getEndTime())){
               queryWrapper.le(ArticleVo::getPublishTime, articlePageDto.getEndTime());
           }
           if (articlePageDto.getArticleCategory() != null){
               queryWrapper.eq(ArticleVo::getArticleCategory, articlePageDto.getArticleCategory());
           }
   
           //3. 执行查询
           Page<ArticleVo> voPage = articleMapper.selectPage(articleVoPage, queryWrapper);
   
           return voPage;
       }
   }
   

3. mapper层：

   @Mapper
   public interface ArticleMapper extends BaseMapper<ArticleVo> {
   }
   

   <?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.whl.info.mapper.ArticleMapper">
   
   
   </mapper>
   

4. 实体类

1. dto代表传参

   package com.whl.info.entity.dto;
   
   import com.whl.entity.page.PageVo;
   import lombok.AllArgsConstructor;
   import lombok.Data;
   import lombok.NoArgsConstructor;
   
   @Data
   @AllArgsConstructor
   @NoArgsConstructor
   public class ArticlePageDto {
       /**
        * 文章名称
        */
       private String articleName;
   
       /**
        * 开始时间
        */
       private String startTime;
   
       /**
        * 结束时间
        */
       private String endTime;
   
       /**
        * 文章类型
        */
       private Integer articleCategory;
   
       /**
        * 当前页
        */
       private Integer pageNum;
   
       /**
        * 每页大小
        */
       private Integer pageSize;
   }
   

2. vo代表回参

   package com.whl.info.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;
   
   @Data
   @AllArgsConstructor
   @NoArgsConstructor
   @TableName("article_info")
   public class ArticleVo {
   
       /**
        * 主键自增
        */
       @TableId(type = IdType.AUTO)
       private Integer id;
   
       /**
        * 文章封面
        */
       @TableField("article_pic_url")
       private String articlePicUrl;
   
       /**
        * 文章标题
        */
       @TableField("article_title")
       private String articleTitle;
   
       /**
        * 文章分类
        */
       @TableField("article_category")
       private Integer articleCategory;
   
       /**
        * 发布时间
        */
       @TableField("publish_time")
       private String publishTime;
   
       /**
        * 置顶
        */
       @TableField("on_head")
       private Integer onHead;
   
       /**
        * 创建时间
        */
       @TableField("create_time")
       private String createTime;
   
       /**
        * 是否删除
        */
       @TableField("is_delete")
       private Integer isDelete;
   }
   

总结

1. 引入依赖，注意版本问题
2. 写好config配置类，注意扫描配置类的路径配置
3. 传参pageNum和pageSize给定

以上为个人学习分享，如有问题，欢迎指出：）