How to implement paging query in javaweb? Javaweb code to implement paging query-javaTutorial-php.cn

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Javaweb paging technology implementation

Paging technology is to obtain data through SQL statements (below). For specific implementation, see the following code

//分页查询语句
select * from 表名 where limit page , count;
和
//获取表中的总数据，确定页数
select count(*) from 表名;

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Don’t talk nonsense and go straight to the code

Front-end code:

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="js/jquery-3.3.1.js"></script>
    <link rel="stylesheet" href="css/bootstrap.min.css">
</head>
<body>

<div>
    <div class="row clearfix">
        <div class="col-md-12 column">
            <table class="table table-bordered table-hover">
                <thead>
                <tr>
                    <th>City_ID</th>
                    <th>City_EN</th>
                    <th>City_CN</th>
                    <th>Country_code</th>
                    <th>Country_EN</th>
                    <th>Country_CN</th>
                    <th>Province_EN</th>
                    <th>Province_CN</th>
                </tr>
                </thead>
                <tbody id="tbody">

                </tbody>
            </table>
            <!--分页-->
            第<span id="paging">1</span>页/
            共<span id="countPage">1</span>页/
            <a id="homePage">Home</a>/
            <a id="prevPage">Prev</a>/
            <a id="nextPage">Next</a>/
            转到第：
            <input type="text" style="width: 2em" id="pageNum">
            页
            <a id="goPage">Go</a>


        </div>
    </div>
</div>
</body>
<script>
    $(function () {
        //页面初始化 （显示第一页）
        selectPage(1);
        home();
        prev();
        next();
        goPage();
    })
    function selectPage(pageCode) {
        //分页查询 pageCode：页数
        $.ajax("getCity",{
            type:"get",
            data:{"currenPage":pageCode},
            success:function (data) {
                $("#tbody").html("");
                //总页数
                $("#countPage").text(data.totalPage);

                $.each(data.pageData,function (index,obj) {
                    var clazz="";
                    if(index%2==0){
                        clazz="success";
                    }
                    $("#tbody").append(
                        "<tr class=&#39;"+clazz+"&#39;>\n" +
                        "<td>"+obj.cityId+"</td>\n" +
                        "<td>"+obj.cityEn+"</td>\n" +
                        "<td>"+obj.cityCn+"</td>\n" +
                        "<td>"+obj.countryCode+"</td>\n" +
                        "<td>"+obj.countryEn+"</td>\n" +
                        "<td>"+obj.countryCn+"</td>\n" +
                        "<td>"+obj.provinceEn+"</td>\n" +
                        "<td>"+obj.provinceCn+"</td>\n" +
                        "</tr>"
                    );
                })

            }
        });
    }
    //第一页
    function home() {
        $("#homePage").on("click",function () {
            $("#paging").text(1);
            selectPage(1);
        })
    }

    //上一页
    function prev() {
        $("#prevPage").on("click",function () {
            var prevText=$("#paging").text();
            var prevNum=parseInt(prevText);
            prevNum=prevNum-1;
            if(prevNum<=1){
                selectPage(1);
                $("#paging").text(1);
                return;
            }
            $("#paging").text(prevNum);
            selectPage(prevNum);
        })
    }
    //下一页
    function next() {
        $("#nextPage").on("click",function () {
            //获取文本的值 页数
            var prevText=$("#paging").text();
            //类型转换
            var prevNum=parseInt(prevText);
            //总页数
            var countText=$("#countPage").text();
            //类型转换
            var countNum = parseInt(countText);
            //页数加1
            prevNum=prevNum+1;
            //判断超出了总页码
            if(prevNum>=countNum){
                selectPage(countNum);
                $("#paging").text(countNum);
                return;
            }
            //设置网页增加的值
            $("#paging").text(prevNum);
            //调用分页查询
            selectPage(prevNum);
        })
    }
    //去到几页
    function goPage() {
        $("#goPage").on("click",function () {
            var pageNum=parseInt($("#pageNum").val());
            var countPage=parseInt($("#countPage").text())
            //判断超出了总页码
            if(pageNum>=countPage){
                selectPage(countPage);
                $("#paging").text(countPage);
                $("#pageNum").val(countPage);
                return;
            }
            //判断低于了总页码
            if(pageNum<=1){
                selectPage(1);
                $("#paging").text(1);
                $("#pageNum").val(1);
                return;
            }
            selectPage(pageNum);
            $("#paging").text(pageNum);
        })
    }

</script>
</html>

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Backend servlet code:

/**
 * @author hh
 * @Date 2018/9/12
 */
@WebServlet("/getCity")
public class PageServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //获取当前页参数，第一次访问为空
        String currPage = req.getParameter("currenPage");
        // 判断，如果为空，则设置为1
        if (currPage == null || "".equals(currPage.trim())) {
            currPage = "1";
        }
        //调用service返回分页类实例
        PageBean<City> pageBean=new PageService().getPage(currPage);
        //设置相应文本类型
        resp.setContentType("application/json;charset=utf-8");
        //响应前端
        resp.getWriter().print(new Gson().toJson(pageBean));
    }
}

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City entity class:

package edu.nf.demo.entity;

/**
 * @author hh
 * @Date 2018/9/12
 */
public class City {
    private String cityId;
    private String cityEn;
    private String cityCn;
    private String countryCode;
    private String countryEn;
    private String countryCn;
    private String provinceEn;
    private String provinceCn;
    public String getCityId() {
        return cityId;
    }
    public void setCityId(String cityId) {
        this.cityId = cityId;
    }
    public String getCityEn() {
        return cityEn;
    }
    public void setCityEn(String cityEn) {
        this.cityEn = cityEn;
    }

    public String getCityCn() {
        return cityCn;
    }
    public void setCityCn(String cityCn) {
        this.cityCn = cityCn;
    }
    public String getCountryCode() {
        return countryCode;
    }
    public void setCountryCode(String countryCode) {
        this.countryCode = countryCode;
    }
    public String getCountryEn() {
        return countryEn;
    }
    public void setCountryEn(String countryEn) {
        this.countryEn = countryEn;
    }
    public String getCountryCn() {
        return countryCn;
    }

    public void setCountryCn(String countryCn) {
        this.countryCn = countryCn;
    }

    public String getProvinceEn() {
        return provinceEn;
    }

    public void setProvinceEn(String provinceEn) {
        this.provinceEn = provinceEn;
    }

    public String getProvinceCn() {
        return provinceCn;
    }

    public void setProvinceCn(String provinceCn) {
        this.provinceCn = provinceCn;
    }
}

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A class written by myself, specially used for paging query:

package edu.nf.demo.entity;

import java.util.List;

/**
 * @author hh
 * @Date 2018/9/12
 */
public class PageBean<T> {
    /**
     * 当前页， 默认显示第一页
     */
    private Integer currntPage = 1;
    /**
     * 查询返回的行数（每页显示的行数），默认每页显示10行
     */
    private int pageCount = 10;
    /**
     * 总记录数
     */
    private int totalCount;
    /**
     * 总页数 = 总记录数/每页显示的行数（+1）
     */
    private int totalPage;
    /**
     * 分页查询的数据,运用泛型，可以重复利用
     */
    private List<T> pageData;

    public int getTotalPage() {
        if (totalCount % pageCount == 0) {
            totalPage = totalCount / pageCount;
        } else {
            totalPage = totalCount / pageCount + 1;
        }
        return totalPage;
    }

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

    public int getCurrntPage() {
        return currntPage;
    }

    public void setCurrntPage(int currntPage) {
        this.currntPage = currntPage;
    }

    public int getPageCount() {
        return pageCount;
    }

    public void setPageCount(int pageCount) {
        this.pageCount = pageCount;
    }

    public int getTotalCount() {
        return totalCount;
    }

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


    public List<T> getPageData() {
        return pageData;
    }

    public void setPageData(List<T> pageData) {
        this.pageData = pageData;
    }
}

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Backend service, logical business layer:

/**
 * @author hh
 * @Date 2018/9/12
 */
public class PageService {

    public PageBean getPage(String currPage){
        //类型转换 当前页数
        Integer currenPage = Integer.valueOf(currPage);
        //实例化分页类
        PageBean<City> pageBean = new PageBean();
        //实例化CityDaoImpl类
        CityDaoImpl cityDao=new CityDaoImpl();

        //数据库第几行开始查询
        int startPage=(currenPage-1)*pageBean.getPageCount();
        //查询多少行数据 分页类里默认30行
        int selectCount=pageBean.getPageCount();
        //查询数据库获取分页返回的数据 : select * from regional_info limit startPage,selectCount
        List<City> list=cityDao.listCity(startPage,selectCount);
        //获取总数
        int cityCount=cityDao.getCityCount();
        //设置查询的数据
        pageBean.setPageData(list);
        //共多少行
        pageBean.setTotalCount(cityCount);
        //设置总页数
        pageBean.setTotalPage(cityCount/pageBean.getPageCount()+1);
        return pageBean;
    }
}

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