SpringBoot MyBatis 实现分页查询数据【SpringBoot系列4】

待我称王封你为后i 2023-10-08 20:04 8阅读 0赞

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##### 1 项目准备 #####

[创建SpringBoot基础项目][SpringBoot]  
[SpringBoot项目集成mybatis][SpringBoot_mybatis]  
[SpringBoot 集成 Druid 数据源【SpringBoot系列3】][SpringBoot _ Druid _SpringBoot_3]

##### 2 分页插件 #####

pagehelper是一个mybatis的分页插件，首先在 pom.xml 文件中添加分页插件依赖包。

<dependency>
        <groupId>com.github.pagehelper</groupId>
        <artifactId>pagehelper-spring-boot-starter</artifactId>
        <version>1.4.6</version>
    </dependency>

然后在 application.yml 配置文件中添加分页插件有关的配置。

pagehelper:
      helperDialect: mysql
      reasonable: true
      supportMethodsArguments: true
      params: count=countSql

##### 3 PageResult 与 PageRequest 、PageUtils #####

定义分页请求体，主要是用于当前请求的是第几页数据以及每页数据加载多少条

import lombok.AllArgsConstructor;
    import lombok.Data;
    import lombok.NoArgsConstructor;
    import lombok.ToString;
    
    /**
     * 分页请求
     */
    @Data
    @ToString
    @AllArgsConstructor
    @NoArgsConstructor
    public class PageRequest {
        
        /**
         * 当前页码
         */
        private int pageNum;
        /**
         * 每页数量
         */
        private int pageSize;
    
    }

定义分页返回结果集 PageResult

import lombok.AllArgsConstructor;
    import lombok.Data;
    import lombok.NoArgsConstructor;
    import lombok.ToString;
    
    import java.util.List;
    /**
     * 分页返回结果
     */
    
    @Data
    @ToString
    @AllArgsConstructor
    @NoArgsConstructor
    public class PageResult {
        
        /**
         * 当前页码
         */
        private int pageNum;
        /**
         * 每页数量
         */
        private int pageSize;
        /**
         * 记录总数
         */
        private long totalSize;
        /**
         * 页码总数
         */
        private int totalPages;
        /**
         * 数据模型
         */
        private List<?> content;
      
    }

PageUtils 将分页信息封装到统一的接口

import com.github.pagehelper.PageInfo;
    
    public class PageUtils {
        
    
        public static PageResult getPageResult(PageRequest pageRequest, PageInfo<?> pageInfo) {
        
            PageResult pageResult = new PageResult();
            pageResult.setPageNum(pageInfo.getPageNum());
            pageResult.setPageSize(pageInfo.getPageSize());
            pageResult.setTotalSize(pageInfo.getTotal());
            pageResult.setTotalPages(pageInfo.getPages());
            pageResult.setContent(pageInfo.getList());
            return pageResult;
        }
    }

##### 4 实现分页请求 #####

首先是 UserController 中

@Api(tags="用户模块")
    @RestController
    @RequestMapping("user")
    public class UserController {
        
        @Resource
        private UserService userService;
     
        @PostMapping(value="/findPage")
        @ApiOperation(value = "分页查询")
        public Object findPage(@RequestBody PageRequest pageQuery) {
        
            return userService.findPage(pageQuery);
        }
    }

UserService.java

public interface UserService {
        
        PageResult findPage(PageRequest pageRequest);
    }

UserServiceImpl.java

@Service
    public class UserServiceImpl implements UserService {
        
        @Resource
        private UserMapper userMapper;
     
        @Override
        public PageResult findPage(PageRequest pageRequest) {
        
            return PageUtils.getPageResult(pageRequest, getPageInfo(pageRequest));
        }
    
        /**
         * 调用分页插件完成分页
         * @return
         */
        private PageInfo<UserInfo> getPageInfo(PageRequest pageRequest) {
        
            int pageNum = pageRequest.getPageNum();
            int pageSize = pageRequest.getPageSize();
            PageHelper.startPage(pageNum, pageSize);
            List<UserInfo> userInfoList = userMapper.selectPage();
            return new PageInfo<UserInfo>(userInfoList);
        }
    }

UserMapper.java

public interface UserMapper {
        
        List<UserInfo> selectList();
    
    
    
        /**
         * 分页查询用户
         * @return
         */
        List<UserInfo> selectPage();
    }

UserMapper.xml

<?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.biglead.demo.mapper.UserMapper">
        <resultMap id="BaseResultMap" type="com.biglead.demo.pojo.UserInfo">
            <id column="id" jdbcType="BIGINT" property="userId"/>
            <result column="create_time" property="createTime"/>
            <result column="user_name" property="userName"/>
            <result column="user_age" property="userAge"/>
        </resultMap>
    
        <select id="selectList" resultMap="BaseResultMap">
            select id, user_name, user_age, create_time
            from t_user
        </select>
    
        <select id="selectPage" resultMap="BaseResultMap">
            select id, user_name, user_age, create_time
            from t_user
        </select>
    
    </mapper>

然后在 postman 中执行请求，已可以实现分页请求  
![在这里插入图片描述][c89f8eab6ddb42f398d7a77095e98526.png]

项目源码在这里 ：[https://gitee.com/android.long/spring-boot-study/tree/master/biglead-api-04-pagehelper][https_gitee.com_android.long_spring-boot-study_tree_master_biglead-api-04-pagehelper]  
有兴趣可以关注一下公众号：biglead

[SpringBoot]: https://biglead.blog.csdn.net/article/details/129510825
[SpringBoot_mybatis]: https://biglead.blog.csdn.net/article/details/129394530
[SpringBoot _ Druid _SpringBoot_3]: https://biglead.blog.csdn.net/article/details/129535296
[c89f8eab6ddb42f398d7a77095e98526.png]: https://img-blog.csdnimg.cn/c89f8eab6ddb42f398d7a77095e98526.png
[https_gitee.com_android.long_spring-boot-study_tree_master_biglead-api-04-pagehelper]: https://gitee.com/android.long/spring-boot-study/tree/master/biglead-api-04-pagehelper