SpringBoot实现分页查询

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前言:

学习了SpringBoot分页查询的两种写法,一种是手动实现,另一种是使用框架实现。现在我将具体的实现流程分享一下。

首先是手动实现分页查询:

先复习一下,SQL中的limit关键字,下面一行sql语句的意思是从第二个数据开始查,查询出两条数据

SELECT * FROM sys_user limit 1,2;

使用limit前一个参数pageNum是从第几个数据开始查,后一个参数pageSize是查询多少条数据,

注意数据库查询pageNum=0代表第一个数据。

那么在Springboot中该如何写呢?

controller:

//    分页查询
//    接口路径:/user/page?pageNum=1&pageSize=10
//    @RequestParam接收
//    limit第一个参数= (pageNum-1)+pageSize
    @GetMapping("/page")
    public List<User> findPage(@RequestParam Integer pageNum,@RequestParam Integer pageSize){
        pageNum = (pageNum-1);
        return userMapper.selectPage(pageNum,pageSize);
    }
}

mapper:

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

这样就写好了,测试一下:

完善一下controller,添加查询 总条数的方法:

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

接下来是关联前端分页和后台数据:

修改分页页面homeView:使用fetch()请求分页数据

created() {
    //请求分页数据
    fetch("localhost:9090/user/page?pageNum=1&pageSize=2").then(res =>res.json()).then(res =>{
      console.log(res)
    })
  },

fetch得到的是一个字符串数据,需要将其转换成Json格式,使用console.log()打印数据

@JsonIgnore忽略某一个属性的注解 

修改前端页面表格数据:

表格数据对应数据库的属性

<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>

修改前端数据内容:

data() {
    return {
      tableData: [],  //表格的值默认为空数组
      total: 0,  //查询条数默认为0
      msg: "hello 阿晴",
      collapseBtnClass: 'el-icon-s-fold',
      isCollapse: false,
      sideWidth: 200,
      logoTextShow: true,
      headerBg: 'headerBg'
    }
  },

渲染页面:

created() {
    //请求分页数据
    fetch("http://localhost:9090/user/page?pageNum=1&pageSize=2").then(res =>res.json()).then(res =>{
      console.log(res)
      this.tableData = res.data
      this.total = res.total
    })
  },

分页函数:

<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>



load() {
      fetch("http://localhost:9090/user/page?pageNum="+this.pageNum+"&pageSize=" + this.pageSize)
          .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()
    }
  }

实现分页功能:

 

模糊查询:

controller:

@GetMapping("/page")
    public Map<String, Object> findPage(@RequestParam Integer pageNum, @RequestParam Integer pageSize,@RequestParam String username){
        pageNum = (pageNum-1)*pageSize;
        List<User> data = userMapper.selectPage(pageNum,pageSize,username);
        Integer total = userMapper.selectTotal();
        Map<String,Object> res = new HashMap<>();
        res.put("data",data);
        res.put("total",total);
        return res;
    }

mapper:

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

测试一下:

 在前端绑定:

<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>
 data() {
    return {
      tableData: [],
      total: 0,
      pageNum: 1,
      pageSize: 2,
      username: "",
      msg: "hello 阿晴",
      collapseBtnClass: 'el-icon-s-fold',
      isCollapse: false,
      sideWidth: 200,
      logoTextShow: true,
      headerBg: 'headerBg'
    }
  },
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
      })
    },

  结语:坚定目标,日日精进,必有所成。共勉! !