SpringBoot+Mybatis分页插件PageHelper实现分页效果

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我是靠谱客的博主奋斗蜡烛，最近开发中收集的这篇文章主要介绍SpringBoot+Mybatis分页插件PageHelper实现分页效果，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

一、项目结构

按照controller,service,mapper(也叫dao)来建立项目，utils里面是两个自己写的分页工具类。看前

端需要什么分页参数，你方便添加。并能返回给他

二、插件引入

1.pom.xml。引入PageHelper插件

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.5.6</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.simons</groupId>
    <artifactId>SimonsStudio</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>SimonsStudio</name>
    <description>SimonsStudio</description>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!--Mybatis框架-->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.2.0</version>
        </dependency>
 
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <!--pageHelper分页插件-->
        <dependency>
            <groupId>com.github.pagehelper</groupId>
            <artifactId>pagehelper-spring-boot-starter</artifactId>
            <version>1.2.3</version>
        </dependency>
    </dependencies>
 
    <build>
 
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
 
</project>

2.application.xml配置。我的*maper.xml都是放在resource文件夹里面的。这里有个 mapper-locations一定要配你项目的，不懂的看我的项目结构。PageHelper照着配置就行了。

server:
  port: 8080
 
spring:
    datasource:
        name: test
        url: jdbc:mysql://127.0.0.1:3306/simonsdb
        username: root
        password: root
        driver-class-name: com.mysql.jdbc.Driver
 
mybatis:
  mapper-locations: classpath:mapper/*.xml  #注意了！这个是mapper.xml的路径。要按照目录文件夹来命名。
  type-aliases-package: com.smions.entity  #实体类的文件夹
pagehelper: #
  helperDialect: mysql
  reasonable: true
  supportMethodsArguments: true
  params: count=countSql

三、代码

1.mapper。习惯上从dao层写起来。@Mapper@Component两个注解要写上，不然后面springboot启动的时候扫描不到。在Mybatis中。mapper相当于dao层。只有接口。selectPage这个是我们要做的分页，这个名字和Maper.xml里面的id对应。要写对了。

package com.simons.mapper;
 
import com.simons.entity.Student;
import org.apache.ibatis.annotations.Mapper;
import org.springframework.stereotype.Component;
import java.util.List;
import java.util.Map;
 
@Mapper
@Component
public interface StudentMapper {
    /**
     * 查询全部用户
     * @return
     */
    List<Map<String,Object>> selectAll();
 
    /**
     * 分页查询用户
     * @return
     */
    List<Student> selectPage();
}

2.*mapper.xml。namespace对应Java中的mapper类。id = "Base_Column_List"，是你要查询的表里面的所有字段。记得username不要写成name.这个我踩过好多坑。运行的时候一直报mapper找不到对应的方法。原因是name会被识别为关键字！！不要取名sql或者java的关键字，不然你会哭的！！

<?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.simons.mapper.StudentMapper" >
    <sql id="Base_Column_List" >
        id,
        username,
        password
    </sql>
    <select id="selectAll" resultType="map">
        SELECT
        <include refid="Base_Column_List" />
        FROM student
    </select>
 
 
    <select id="selectPage" resultType="map">
        SELECT
        <include refid="Base_Column_List" />
        FROM student
    </select>
 
 
</mapper>

3.service.java。getPageInfo方法是重点。PageHelper的核心代码就只有一句:

PageHelper.startPage(pageNum,pageSize);//开始分页
List<Student> students = studentMapper.selectPage();//查询数据库返回数据
PageInfo<Student> pageInfo = new PageInfo<>(students);//得到数据，里面还带有分页的各个参数

很简单是不是。接下来介绍一下pageInfo自带的分页参数:

pageNum=5, //查询的页数(第5页)
pageSize=3, //每页的大小
size=3,
startRow=13,
endRow=15,
total=22,//总数
pages=8, //总页数：22/3=8
list=Page{count=true, pageNum=5, pageSize=3, startRow=12, endRow=15, total=22, pages=8, reasonable=true, pageSizeZero=false},
prePage=4, //前一页
nextPage=6, //后一页
isFirstPage=false, //是否是第一页
isLastPage=false, //是否是最后一页
hasPreviousPage=true, //是否有上一页
hasNextPage=true, //是否有下一页
navigatePages=8, //导航总页数
navigateFirstPage=1, //导航第一页
navigateLastPage=8, //导航最后一页
navigatepageNums=[1, 2, 3, 4, 5, 6, 7, 8]//页数码

看完后，是不是一个很完美的插件(狗头)。相关的分页参数都是很齐全的。

service代码。这里我先用getInfo拿到PageInfo。再把相关的参数和list数据拿出来。返回给controller即可。

package com.simons.service;
 
import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;
import com.simons.entity.Student;
import com.simons.mapper.StudentMapper;
import com.simons.util.PageRequest;
import com.simons.util.PageResult;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
 
import java.util.List;
import java.util.Map;
 
@Service
public class StudentService{
    @Autowired
    private StudentMapper studentMapper;
 
    public List<Map<String,Object>> findAll() {
//        List<Student> students =
        List<Map<String,Object>>  map = studentMapper.selectAll();
        return map;
    }
 
    public PageResult findPage(PageRequest pageRequest) {
        PageInfo<Student> pageInfo = getPageInfo(pageRequest);
        PageResult pageResult = new PageResult();
        pageResult.setPageNum(pageInfo.getPageNum());
        pageResult.setPageSize(pageInfo.getPageSize());
        pageResult.setTotalPages(pageInfo.getPages());
        pageResult.setContent(pageInfo.getList());
        return pageResult;
    }
    
    /**
     * 调用分页插件完成分页
     *
     */
    public PageInfo<Student> getPageInfo(PageRequest pageRequest) {
        int pageNum = pageRequest.getPageNum();
        int pageSize = pageRequest.getPageSize();
        PageHelper.startPage(pageNum,pageSize);//核心代码:pageHelper查询分页
        List<Student> students = studentMapper.selectPage();
        PageInfo<Student> pageInfo = new PageInfo<>(students);
        return pageInfo;
    }
}

4.controller层。findpage方法。查找分页的方案。因为分页往往带有查询参数。这边没写。

package com.simons.controller;
 
import com.simons.service.StudentService;
import com.simons.util.PageRequest;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;
 
import java.util.List;
import java.util.Map;
 
//@RestController
//@RequestMapping("/student")
 
@Controller
@RequestMapping(value = {"/student"})
public class StudentController {
    @Autowired
    private StudentService studentService;
    @ResponseBody
    @RequestMapping(value="/findAll")
    public List<Map<String,Object>> findAll() {
        return studentService.findAll();
    }
 
    @ResponseBody
    @RequestMapping(value = {"/findPage"})
    public Object findPage(@RequestParam(name = "pageNum")String pageNum , @RequestParam(name = "pageSize") String pageSize) {
        PageRequest pageQuery = new PageRequest();
        pageQuery.setPageNum(Integer.parseInt(pageNum));
        pageQuery.setPageSize(Integer.parseInt(pageSize));
        return studentService.findPage(pageQuery);
    }
//    @PostMapping(value="/findPage")
//    public Object findPage(@RequestBody PageRequest pageQuery) {
//        return studentService.findPage(pageQuery);
//    }
}

5.utils类。一个是pageRequest请求分页，一个是pageResult返回分页的实体类

package com.simons.util;
 
 
import java.util.List;
/**
 * 分页返回结果
 */
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;
    public int getPageNum() {
        return pageNum;
    }
    public void setPageNum(int pageNum) {
        this.pageNum = pageNum;
    }
    public int getPageSize() {
        return pageSize;
    }
    public void setPageSize(int pageSize) {
        this.pageSize = pageSize;
    }
    public long getTotalSize() {
        return totalSize;
    }
    public void setTotalSize(long totalSize) {
        this.totalSize = totalSize;
    }
    public int getTotalPages() {
        return totalPages;
    }
    public void setTotalPages(int totalPages) {
        this.totalPages = totalPages;
    }
    public List<?> getContent() {
        return content;
    }
    public void setContent(List<?> content) {
        this.content = content;
    }
}

package com.simons.util;
 
public class PageRequest {
    /**
     * 当前页码
     */
    private int pageNum;
    /**
     * 每页数量
     */
    private int pageSize;
 
    public int getPageNum() {
        return pageNum;
    }
    public void setPageNum(int pageNum) {
        this.pageNum = pageNum;
    }
    public int getPageSize() {
        return pageSize;
    }
    public void setPageSize(int pageSize) {
        this.pageSize = pageSize;
    }
}

6.spring项目启动 application.java

package com.simons;
 
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;
 
@SpringBootApplication
@MapperScan("com.simons.mapper")
//@ComponentScan(basePackages={"com.simons.*"})
public class SimonsStudioApplication {
 
    public static void main(String[] args) {
        SpringApplication.run(SimonsStudioApplication.class, args);
    }
 
}