JavaWeb（SpringBoot3+vue3）开发+教学管理系统项目实战之PageHelper分页插件

package com.zidiu.controller;

import com.zidiu.pojo.Emp;
import com.zidiu.pojo.PageResult;
import com.zidiu.pojo.Result;
import com.zidiu.service.EmpService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RequestMapping("/emps")
@Slf4j
@RestController
public class EmpController {
    @Autowired
    private EmpService empService;

    /**
     * 查询员工列表带分页
     */
    @GetMapping
    public Result page(@RequestParam(defaultValue = "1") Integer page, @RequestParam(defaultValue = "5") Integer pageSize) {
        log.info("查询员工信息,页码page: {}, 每页记录数pageSize: {}", page, pageSize);
        PageResult<Emp> pageResult = empService.page(page, pageSize);
        return Result.success(pageResult);
    }
}
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package com.zidiu.service;

import com.zidiu.pojo.Emp;
import com.zidiu.pojo.PageResult;

import java.util.List;

public interface EmpService {
      /**
     * 分页查询
     * @param page 页码
     * @param pageSize 每页记录数
     */
    PageResult<Emp> page(Integer page, Integer pageSize);
}
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package com.zidiu.service.impl;

import com.zidiu.mapper.EmpMapper;
import com.zidiu.pojo.Emp;
import com.zidiu.pojo.PageResult;
import com.zidiu.service.EmpService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class EmpServiceImpl implements EmpService {
    @Autowired
    private EmpMapper empMapper;

    /**
     * 查询员工列表
     */
    @Override
    public PageResult<Emp> page(Integer page, Integer pageSize) {
        // 1，获取总记录数
        Long total = empMapper.count();
        // 2，获取分页查询结果列表
        int start = (page - 1) * pageSize;
        List<Emp> rows = empMapper.list(start, pageSize);
        // 3，封装PageResult并返回
        return new PageResult<Emp>(total, rows);
    }
}
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package com.zidiu.mapper;

import com.zidiu.pojo.Emp;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Select;

import java.util.List;

@Mapper
public interface EmpMapper {
    /**
     * 查询所有员工信息
     */
    @Select("select e.*, d.name as deptName from emp e left join dept d on e.dept_id = d.id limit #{start}, #{pageSize}")
    List<Emp> list(int start, int pageSize);

    /**
     * 查询员工总数
     */
    @Select("select count(*) from emp e left join dept d on e.dept_id = d.id")
    Long count();
}
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<!--分页插件PageHelper-->
<dependency>
    <groupId>com.github.pagehelper</groupId>
    <artifactId>pagehelper-spring-boot-starter</artifactId>
    <version>2.1.1</version>
</dependency>
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package com.zidiu.mapper;

import com.zidiu.pojo.Emp;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Select;

import java.util.List;

@Mapper
public interface EmpMapper {
    /**
     * 查询所有员工信息
     */
    /**
     * 查询所有的员工及其对应的部门名称
     */
    @Select("select e.*, d.name deptName from emp as e left join dept as d on e.dept_id = d.id")
    public List<Emp> list();

    /**
     * 查询员工总数
     */
    @Select("select count(*) from emp e left join dept d on e.dept_id = d.id")
    Long count();
}
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package com.zidiu.service.impl;

import com.github.pagehelper.Page;
import com.github.pagehelper.PageHelper;
import com.zidiu.mapper.EmpMapper;
import com.zidiu.pojo.Emp;
import com.zidiu.pojo.PageResult;
import com.zidiu.service.EmpService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class EmpServiceImpl implements EmpService {
    @Autowired
    private EmpMapper empMapper;

    /**
     * 查询员工列表
     */
    @Override
    public PageResult<Emp> page(Integer page, Integer pageSize) {
        //1. 设置分页参数，页码和每页记录数
        PageHelper.startPage(page,pageSize);
        //2. 执行查询
        List<Emp> empList = empMapper.list();
        Page<Emp> p = (Page<Emp>) empList;

        //3. 封装结果
        return new PageResult<Emp>(p.getTotal(), p.getResult());
    }
}
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