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
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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：
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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：
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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：
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/** * 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：
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<!--分页--> <!--查询用户列表--> < 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 > <!--查询用户总数--> < 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：
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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：
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@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
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：
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< link href = "plugins/jqgrid-5.8.2/ui.jqgrid-bootstrap4.css" rel = "external nofollow" rel = "stylesheet" /> <!--jqGrid依赖jQuery,因此需要先引入jquery.min.js文件，下方地址为字节跳动提供的cdn地址--> < script src = "http://s3.pstatp测试数据/cdn/expire-1-M/jquery/3.3.1/jquery.min.js" ></ script > <!--grid.locale-cn.js为国际化所需的文件，-cn表示中文--> < 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：
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<!--jqGrid必要DOM，用于创建表格展示列表数据--> < table id = "jqGrid" class = "table table-bordered" ></ table >
<!--jqGrid必要DOM，分页信息区域--> < 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：
jqGrid()方法中的参数及含义如图所示。
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：
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<!DOCTYPE html> < html lang = "en" > < head > < meta charset = "UTF-8" > < title >jqGrid分页测试</ title > <!--引入bootstrap样式文件--> < link rel = "stylesheet" href = "/static/bootstrap-5.3.0-alpha3-dist/css/bootstrap.css" rel = "external nofollow" /> < link href = "jqGrid-5.8.2/css/ui.jqgrid-bootstrap4.css" rel = "external nofollow" rel = "stylesheet" /> </ head > < body > < div style = "margin: 24px;" > <!--数据展示列表，id为jqGrid--> < table id = "jqGrid" class = "table table-bordered" ></ table > <!--分页按钮展示区--> < div id = "jqGridPager" ></ div > </ div > </ body > <!--jqGrid依赖jQuery,因此需要先引入jquery.min.js文件，下方地址为字节跳动提供的cdn地址--> < script src = "http://s3.pstatp测试数据/cdn/expire-1-M/jquery/3.3.1/jquery.min.js" ></ script > <!--grid.locale-cn.js为国际化所需的文件，-cn表示中文--> < 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：
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$( 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()); }); }); |
总结
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原文链接：https://blog.csdn.net/LingDIHong/article/details/130020677
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