springboot-分页功能

1.分页功能的作用

分页功能作为各类网站和系统不可或缺的部分(例如百度搜索结果的分页等)
,当一个页面数据量大的时候分页作用就体现出来的,其作用有以下5个。
(1)减少系统资源的消耗
(2)提高数据库的查询性能
(3)提升页面的访问速度
(4)符合用户的浏览习惯
(5)适配页面的排版

2.建立测试数据库

由于需要实现分页功能,所需的数据较多

DROP TABLE IF EXISTS tb_user;

CREATE TABLE tb_user (
    id int(11) NOT NULL AUTO_INCREMENT COMMENT '主键id',
    name varchar(100) NOT NULL DEFAULT '' COMMENT '登录名',
    password varchar(100) NOT NULL DEFAULT '' COMMENT '密码',
    PRIMARY KEY (id) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8;

insert into tb_user (id,name,password)
value (1,'C','123456'),
(2,'C++','123456'),
(3,'Java','123456'),
(4,'Python','123456'),
(5,'R','123456'),
(6,'C#','123456');

insert into tb_user (id,name,password) value (7,'test1','123456');
insert into tb_user (id,name,password) value (8,'test2','123456');
insert into tb_user (id,name,password) value (9,'test3','123456');
insert into tb_user (id,name,password) value (10,'test4','123456');
insert into tb_user (id,name,password) value (11,'test5','123456');
insert into tb_user (id,name,password) value (12,'test6','123456');
insert into tb_user (id,name,password) value (13,'test7','123456');
insert into tb_user (id,name,password) value (14,'test8','123456');
insert into tb_user (id,name,password) value (15,'test9','123456');
insert into tb_user (id,name,password) value (16,'test10','123456');
insert into tb_user (id,name,password) value (17,'test11','123456');
insert into tb_user (id,name,password) value (18,'test12','123456');
insert into tb_user (id,name,password) value (19,'test13','123456');
insert into tb_user (id,name,password) value (20,'test14','123456');
insert into tb_user (id,name,password) value (21,'test15','123456');
insert into tb_user (id,name,password) value (22,'test16','123456');
insert into tb_user (id,name,password) value (23,'test17','123456');
insert into tb_user (id,name,password) value (24,'test18','123456');
insert into tb_user (id,name,password) value (25,'test19','123456');
insert into tb_user (id,name,password) value (26,'test20','123456');
insert into tb_user (id,name,password) value (27,'test21','123456');
insert into tb_user (id,name,password) value (28,'test22','123456');
insert into tb_user (id,name,password) value (29,'test23','123456');
insert into tb_user (id,name,password) value (30,'test24','123456');
insert into tb_user (id,name,password) value (31,'test25','123456');
insert into tb_user (id,name,password) value (32,'test26','123456');
insert into tb_user (id,name,password) value (33,'test27','123456');
insert into tb_user (id,name,password) value (34,'test28','123456');
insert into tb_user (id,name,password) value (35,'test29','123456');
insert into tb_user (id,name,password) value (36,'test30','123456');
insert into tb_user (id,name,password) value (37,'test31','123456');
insert into tb_user (id,name,password) value (38,'test32','123456');
insert into tb_user (id,name,password) value (39,'test33','123456');
insert into tb_user (id,name,password) value (40,'test34','123456');
insert into tb_user (id,name,password) value (41,'test35','123456');
insert into tb_user (id,name,password) value (42,'test36','123456');
insert into tb_user (id,name,password) value (43,'test37','123456');
insert into tb_user (id,name,password) value (44,'test38','123456');
insert into tb_user (id,name,password) value (45,'test39','123456');
insert into tb_user (id,name,password) value (46,'test40','123456');
insert into tb_user (id,name,password) value (47,'test41','123456');
insert into tb_user (id,name,password) value (48,'test42','123456');
insert into tb_user (id,name,password) value (49,'test43','123456');
insert into tb_user (id,name,password) value (50,'test44','123456');
insert into tb_user (id,name,password) value (51,'test45','123456');

3.分页功能返回的结果封装

新建一个util包并在包中新建Result通用结果类,代码如下:

package ltd.newbee.mall.entity;

public class User {
    private Integer id;
    private String name;
    private String password;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

后端接口返回的数据会根据以上格式进行数据封装,包括业务码、返回信息、实际的数据结果。这个格式是开发人员自行设置的,如果有其他更好的方案也可以进行适当的调整。

在util包中新建PageResult通用结果类,代码如下:

package ltd.newbee.mall.util;

import java.util.List;

/**
 * 分页工具类
 */
public class PageResult {
    //总记录数
    private int totalCount;
    //每页记录数
    private int pageSize;
    //总页数
    private int totalPage;
    //当前页数
    private int currPage;
    //列表数据
    private List<?> list;

    /**
     *
     * @param totalCount 总记录数
     * @param pageSize 每页记录数
     * @param currPage 当前页数
     * @param list 列表数据
     */
    public PageResult(int totalCount, int pageSize, int currPage, List<?> list) {
        this.totalCount = totalCount;
        this.pageSize = pageSize;
        this.currPage = currPage;
        this.list = list;
        this.totalPage = (int) Math.ceil((double) totalCount / pageSize);
    }

    public int getTotalCount() {
        return totalCount;
    }

    public void setTotalCount(int totalCount) {
        this.totalCount = totalCount;
    }

    public int getPageSize() {
        return pageSize;
    }

    public void setPageSize(int pageSize) {
        this.pageSize = pageSize;
    }

    public int getTotalPage() {
        return totalPage;
    }

    public void setTotalPage(int totalPage) {
        this.totalPage = totalPage;
    }

    public int getCurrPage() {
        return currPage;
    }

    public void setCurrPage(int currPage) {
        this.currPage = currPage;
    }

    public List<?> getList() {
        return list;
    }

    public void setList(List<?> list) {
        this.list = list;
    }
}

4.分页功能代码具体实现

4.1数据层

在UserDao接口中新增两个方法findUsers()和getTotalUser(),代码如下所示:

/**
     * 返回分页数据列表
     * 
     * @param pageUtil
     * @return
     */
    List<User> findUsers(PageQueryUtil pageUtil);

    /**
     * 返回数据总数
     * 
     * @param pageUtil
     * @return
     */
    int getTotalUser(PageQueryUtil pageUtil);

在UserMapper.xml文件中新增这两个方法的映射语句,代码如下所示:


    
    <select id="findUsers" parameterType="Map" resultMap="UserResult">
        select id,name,password from tb_user
        order by id desc
        <if test="start!=null and limit!=null">
            limit #{start}.#{limit}
        if>
    select>
    
    <select id="getTotalUser" parameterType="Map" resultType="int">
        select count(*) from tb_user
    select>

4.2业务层

新建service包,并新增业务类UserService,代码如下所示:

import ltd.newbee.mall.dao.UserDao;
import ltd.newbee.mall.entity.User;
import ltd.newbee.mall.util.PageResult;
import ltd.newbee.mall.util.PageQueryUtil;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class UserService {

    @Autowired
    private UserDao userDao;

    public PageResult getUserPage(PageQueryUtil pageUtil){
        //当前页面中的数据列表
        List<User> users = userDao.findUsers(pageUtil);
        //数据总条数,用于计算分页数据
        int total = userDao.getTotalUser(pageUtil);
        //分页信息封装
        PageResult pageResult = new PageResult(users,total,pageUtil.getLimit(),pageUtil.getPage());
        return pageResult;
    }
}

首先根据当前页面和每页条数查询当前页的数据集合,然后调用select count(*)语句查询数据的总条数用于计算分页数据,最后将获取的数据封装到PageResult对象中并返回给控制层。

4.3控制层

在controller包中新建PageTestController类,用于实现分页请求的处理并返回查询结果,代码如下所示:

@RestController
@RequestMapping("users")
public class PageTestController {

    @Autowired
    private UserService userService;

    //分页功能测试
    @RequestMapping(value = "/list",method = RequestMethod.GET)
    public Result list(@RequestParam Map<String,Object> params){
        Result result = new Result();
        if (StringUtils.isEmpty(params.get("page"))||StringUtils.isEmpty(params.get("limit"))){
            //返回错误码
            result.setResultCode(500);
            //错误信息
            result.setMessage("参数异常!");
            return result;
        }
        //封装查询参数
        PageQueryUtil queryParamList = new PageQueryUtil(params);
        //查询并封装分页结果集
        PageResult userPage = userService.getUserPage(queryParamList);
        //返回成功码
        result.setResultCode(200);
        result.setMessage("查询成功");
        //返回分页数据
        result.setData(userPage);
        return result;
    }
}

分页功能的交互流程:前端将所需页码和条数参数传输给后端,后端在接收分页请求后对分页参数进行计算,并利用MySQL的limit关键字查询对应的记录,在查询结果被封装后返回给前端。在TestUserControler类上使用的是@RestController注解,该注解相当于@ResponseBody+@Controller的组合注解。

5.jqGrid分页插件

jqGrid是一个用来显示网格数据的jQuery插件。开发人员通过使用jqGrid可以轻松实现前端页面与后台数据的Ajax异步通信并实现分页功能。同时,jqGrid是一款代码开源的分页插件,源码也一直处于迭代更新的状态中。
下载地址:jqGrid
下载jqGrid后解压文件,将解压的文件直接拖进项目的static目录下
springboot-分页功能_第1张图片
以下是jqGrid实现分页的步骤:
首先,在前端页面代码中引入jqGrid分页插件所需的源文件,代码如下所示:

<link href="plugins/jqgrid-5.8.2/ui.jqgrid-bootstrap4.css" rel="stylesheet"/>

<script src="http://s3.pstatp.com/cdn/expire-1-M/jquery/3.3.1/jquery.min.js">script>

<script src="plugins/jqgrid-5.8.2/grid.locale-cn.js">script>
<script src="plugins/jqgrid-5.8.2/jquery.jqGrid.min.js">script>

其次,在页面中需要展示分页数据的区域添加用于jqGrid初始化的代码:


<table id="jqGrid" class="table table-bordered">table>


<div id="jqGridPager">div>

最后,调用jqGrid分页插件的jqGrid()方法渲染分页展示区域,代码如下所示:
springboot-分页功能_第2张图片

springboot-分页功能_第3张图片

jqGrid()方法中的参数及含义如图所示。
springboot-分页功能_第4张图片
jqGrid前端页面测试:
在resources/static目中新建jqgrid-page-test.html文件,代码如下所示:

DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>jqGrid分页测试title>
    
    <link rel="stylesheet" href="/static/bootstrap-5.3.0-alpha3-dist/css/bootstrap.css"/>
    <link href="jqGrid-5.8.2/css/ui.jqgrid-bootstrap4.css" rel="stylesheet"/>
head>
<body>
<div style="margin: 24px;">
    
    <table id="jqGrid" class="table table-bordered">table>
    
    <div id="jqGridPager">div>
div>
body>

<script src="http://s3.pstatp.com/cdn/expire-1-M/jquery/3.3.1/jquery.min.js">script>

<script src="plugins/jqgrid-5.8.2/grid.locale-cn.js">script>
<script src="plugins/jqgrid-5.8.2/jquery.jqGrid.min.js">script>
<script src="jqgrid-page-test.js">script>
html>

jqGrid初始化
在resources/static目录下新建jqgrid-page-test.js文件,代码如下所示:

$(function () {
    $("#jqGrid").jqGrid({
        url: 'users/list',
        datatype: "json",
        colModel: [
            {label: 'id',name: 'id', index: 'id', width: 50, hidden: true,key:true},
            {label: '登录名',name: 'name',index: 'name', sortable: false, width: 80},
            {label: '密码字段',name: 'password',index: 'password', sortable: false, width: 80}
        ],
        height: 485,
        rowNum: 10,
        rowList: [10,30,50],
        styleUI: 'Bootstrap',
        loadtext: '信息读取中...',
        rownumbers: true,
        rownumWidth: 35,
        autowidth: true,
        multiselect: true,
        pager: "#jqGridPager",
        jsonReader:{
            root: "data.list",
            page: "data.currPage",
            total: "data.totalCount"
        },
        prmNames:{
            page: "page",
            rows: "limit",
            order: "order"
        },
        gridComplete: function () {
            //隐藏grid底部滚动条
            $("#jqGrid").closest(".ui-jqgrid-bdiv").css({"overflow-x": "hidden"});
        }
    });
    $(window).resize(function () {
        $("jqGrid").setGridWidth($(".card-body").width());
    });
});

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