手动实现分页功能

先理解分页查询原理

采用limit语句来实现分页

-- 页码PageNum  每页数据条目PageSize=5
-- 第一页 PageNum=0, limit 0,5
SELECT * FROM sys_user limit 0,5; 
-- 第二页 PageNum=1, limit 5,5
SELECT * FROM sys_user limit 5,5;
-- 公式： limit (PageNum-1)*PageSize, PageSize

代码实现

Controller

Mapper

相对应前端页面部分
HomeView.Vue

接口测试

前后端联动

Springboot跨域设置

有前端跨域问题

我们在后端统一设置，新建config-CorsConfig.java

跨域具体代码

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.cors.CorsConfiguration;
import org.springframework.web.cors.UrlBasedCorsConfigurationSource;
import org.springframework.web.filter.CorsFilter;

@Configuration
public class CorsConfig {

    // 当前跨域请求最大有效时长。这里默认1天
    private static final long MAX_AGE = 24 * 60 * 60;

    @Bean
    public CorsFilter corsFilter() {
        UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
        CorsConfiguration corsConfiguration = new CorsConfiguration();
        corsConfiguration.addAllowedOrigin("http://localhost:8080"); // 1 设置访问源地址
        corsConfiguration.addAllowedHeader("*"); // 2 设置访问源请求头
        corsConfiguration.addAllowedMethod("*"); // 3 设置访问源请求方法
        corsConfiguration.setMaxAge(MAX_AGE);
        source.registerCorsConfiguration("/**", corsConfiguration); // 4 对接口配置跨域设置
        return new CorsFilter(source);
    }
}

前端具体代码：

HomeView.Vue

<template>
  <el-container style="min-height: 100vh">

    <el-aside :width="sideWidth + 'px'" style="box-shadow: 2px 0 6px rgb(0 21 41 / 35%);">
      <el-menu :default-openeds="['1', '3']" style="min-height: 100%; overflow-x: hidden"
               background-color="rgb(48, 65, 86)"
               text-color="#fff"
               active-text-color="#ffd04b"
               :collapse-transition="false"
               :collapse="isCollapse"
      >
        <div style="height: 60px; line-height: 60px; text-align: center">
          <img src="../assets/logo.png" alt="" style="width: 20px; position: relative; top: 5px; right: 5px">
          <b style="color: white" v-show="logoTextShow">后台管理系统</b>
        </div>
        <el-submenu index="1">
          <template slot="title">
            <i class="el-icon-message"></i>
            <span slot="title">导航一</span>
          </template>
          <el-menu-item-group title="分组2">
            <el-menu-item index="1-3">选项3</el-menu-item>
          </el-menu-item-group>
          <el-submenu index="1-4">
            <template slot="title">选项4</template>
            <el-menu-item index="1-4-1">选项4-1</el-menu-item>
          </el-submenu>
        </el-submenu>
        <el-submenu index="2">
          <template slot="title">
            <i class="el-icon-menu"></i>
            <span slot="title">导航二</span>
          </template>
          <el-submenu index="2-4">
            <template slot="title">选项4</template>
            <el-menu-item index="2-4-1">选项4-1</el-menu-item>
          </el-submenu>
        </el-submenu>
        <el-submenu index="3">
          <template slot="title">
            <i class="el-icon-setting"></i>
            <span slot="title">导航三</span>
          </template>
          <el-submenu index="3-4">
            <template slot="title">选项4</template>
            <el-menu-item index="3-4-1">选项4-1</el-menu-item>
          </el-submenu>
        </el-submenu>
      </el-menu>
    </el-aside>

    <el-container>
      <el-header style="font-size: 12px; border-bottom: 1px solid #ccc; line-height: 60px; display: flex">
        <div style="flex: 1; font-size: 20px">
          <span :class="collapseBtnClass" style="cursor: pointer" @click="collapse"></span>
        </div>
        <el-dropdown style="width: 70px; cursor: pointer">
          <span>王小虎</span><i class="el-icon-arrow-down" style="margin-left: 5px"></i>
          <el-dropdown-menu slot="dropdown" >
            <el-dropdown-item style="font-size: 14px; padding: 5px 0">个人信息</el-dropdown-item>
            <el-dropdown-item style="font-size: 14px; padding: 5px 0">退出</el-dropdown-item>
          </el-dropdown-menu>
        </el-dropdown>

      </el-header>

      <el-main>
        <div style="margin-bottom: 30px">
          <el-breadcrumb separator="/">
            <el-breadcrumb-item :to="{ path: '/' }">首页</el-breadcrumb-item>
            <el-breadcrumb-item>用户管理</el-breadcrumb-item>
          </el-breadcrumb>
        </div>

        <div style="margin: 10px 0">
          <el-input style="width: 200px" placeholder="请输入名称" suffix-icon="el-icon-search" v-model="username"></el-input>
          <el-input style="width: 200px" placeholder="请输入邮箱" suffix-icon="el-icon-message" class="ml-5"></el-input>
          <el-input style="width: 200px" placeholder="请输入地址" suffix-icon="el-icon-position" class="ml-5"></el-input>
          <el-button class="ml-5" type="primary" @click="load">搜索</el-button>
        </div>

        <div style="margin: 10px 0">
          <el-button type="primary">新增 <i class="el-icon-circle-plus-outline"></i></el-button>
          <el-button type="danger">批量删除 <i class="el-icon-remove-outline"></i></el-button>
          <el-button type="primary">导入 <i class="el-icon-bottom"></i></el-button>
          <el-button type="primary">导出 <i class="el-icon-top"></i></el-button>
        </div>

        <el-table :data="tableData" border stripe :header-cell-class-name="headerBg">
          <el-table-column prop="id" label="ID" width="80"></el-table-column>
          <el-table-column prop="username" label="用户名" width="140"></el-table-column>
          <el-table-column prop="nickname" label="昵称" width="120"></el-table-column>
          <el-table-column prop="email" label="邮箱"></el-table-column>
          <el-table-column prop="phone" label="电话"></el-table-column>
          <el-table-column prop="address" label="地址"></el-table-column>
          <el-table-column label="操作"  width="200" align="center">
            <template slot-scope="scope">
              <el-button type="success">编辑 <i class="el-icon-edit"></i></el-button>
              <el-button type="danger">删除 <i class="el-icon-remove-outline"></i></el-button>
            </template>
          </el-table-column>
        </el-table>
        <div style="padding: 10px 0">
          <el-pagination
              @size-change="handleSizeChange"
              @current-change="handleCurrentChange"
              :current-page="pageNum"
              :page-sizes="[2, 5, 10, 20]"
              :page-size="pageSize"
              layout="total, sizes, prev, pager, next, jumper"
              :total="total">
          </el-pagination>
        </div>
      </el-main>

    </el-container>
  </el-container>
</template>

<script>

export default {
  name: 'Home',
  data() {
    return {
      tableData: [],
      total: 0,
      pageNum: 1,
      pageSize: 2,
      username: "",
      msg: "hello Joyce",
      collapseBtnClass: 'el-icon-s-fold',
      isCollapse: false,
      sideWidth: 200,
      logoTextShow: true,
      headerBg: 'headerBg'
    }
  },
  created() {
    // 请求分页查询数据
    this.load()
  },
  methods: {
    collapse() {  // 点击收缩按钮触发
      this.isCollapse = !this.isCollapse
      if (this.isCollapse) {  // 收缩
        this.sideWidth = 64
        this.collapseBtnClass = 'el-icon-s-unfold'
        this.logoTextShow = false
      } else {   // 展开
        this.sideWidth = 200
        this.collapseBtnClass = 'el-icon-s-fold'
        this.logoTextShow = true
      }
    },
    load() {
      fetch("http://localhost:9090/user/page?pageNum="+this.pageNum+"&pageSize=" + this.pageSize + "&username=" + this.username)
          .then(res => res.json()).then(res => {
        console.log(res)
        this.tableData = res.data
        this.total = res.total
      })
    },
    handleSizeChange(pageSize) {
      console.log(pageSize)
      this.pageSize = pageSize
      this.load()
    },
    handleCurrentChange(pageNum) {
      console.log(pageNum)
      this.pageNum = pageNum
      this.load()
    }
  }
}
</script>

<style>
.headerBg {
  background: #eee!important;
}
</style>

后端完整代码：

UserController.java

package com.zj.demo.controller;

import com.zj.demo.entity.User;
import com.zj.demo.mapper.UserMapper;
import com.zj.demo.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

@RestController
@RequestMapping("/user")
public class UserController {


    @Autowired
    private UserMapper userMapper;

    @Autowired
    private UserService userService;

    // 新增和修改
    @PostMapping
    public Integer save(@RequestBody User user) {
        // 新增或者更新
        return userService.save(user);
    }

    // 查询所有数据
    @GetMapping
    public List<User> index() {
        List<User> all = userMapper.findAll();
        return all;
    }

    @DeleteMapping("/{id}")
    public Integer delete(@PathVariable Integer id) {
        return userMapper.deleteById(id);
    }

    // 分页查询
    //  接口路径：/user/page?pageNum=1&pageSize=10
    // @RequestParam接受
    // limit第一个参数 = (pageNum - 1) * pageSize
    // pageSize
    @GetMapping("/page")
    public Map<String, Object> findPage(@RequestParam Integer pageNum,
                                        @RequestParam Integer pageSize,
                                        @RequestParam String username) {
        pageNum = (pageNum - 1) * pageSize;
        username = "%" + username + "%";
        List<User> data = userMapper.selectPage(pageNum, pageSize, username);
        Integer total = userMapper.selectTotal(username);
        Map<String, Object> res = new HashMap<>();
        res.put("data", data);
        res.put("total", total);
        return res;
    }
}

UserMapper.java

package com.zj.demo.mapper;

import com.zj.demo.entity.User;
import org.apache.ibatis.annotations.*;

import java.util.List;

@Mapper
public interface UserMapper {

    @Select("SELECT * from sys_user")
    List<User> findAll();

    @Insert("INSERT into sys_user(username, password,nickname,email,phone,address) VALUES (#{username}, #{password}," +
            " #{nickname}, #{email},#{phone}, #{address})")
    int insert(User user);

    int update(User user);

    @Delete("delete from sys_user where id = #{id}")
    Integer deleteById(@Param("id") Integer id);

    @Select("select * from sys_user where username like #{username} limit #{pageNum}, #{pageSize}")
    List<User> selectPage(Integer pageNum, Integer pageSize, String username);

    @Select("select count(*) from sys_user where username like concat('%', #{username}, '%') ")
    Integer selectTotal(String username);

}

测试：

补充事项：

忽略某个字段【如Password字段】，不展示给前端，采用@JsonIgnore注解