JavaWeb小工程實戰演練（三）

用戶信息查詢功能

1. 網頁設計

本能地想找一個表格的模板，奈何模板之家裏並沒用，所以只好自己寫一個界面了。。ค(TㅅT)

界面極其簡陋，湊合着用。。

2. 後臺代碼實現

在實現查詢功能之前，先分析一下：在（二）中，管理員登錄完成後重定向到FindServletByPage這個servlet中，我們應該在這個servlet裏面實現分頁查詢的功能，相比較查詢所有信息，分頁查詢每次只查詢一定數量的信息並且顯示在界面中，使得界面條理清晰，更友好，而查詢所有信息並且顯示在一個界面上，顯然當數據龐大時，就顯得界面冗長了。因此，我們將一個Page封裝成一個JavaBean。

PageBean類

package cn.hehewocao.POJO;

import java.util.List;

public class PageBean<T> {
    private int page;   //當前頁數
    private int row;    //  分頁條數
    private List<T> list;   //查詢的每頁記錄
    private int count;  //總記錄數
    private int pages;   //展示數據的總頁數

    public PageBean() {
    }

    public int getPage() {
        return page;
    }

    public void setPage(int page) {
        this.page = page;
    }

    public int getRow() {
        return row;
    }

    public void setRow(int row) {
        this.row = row;
    }

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

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

    public int getCount() {
        return count;
    }

    public void setCount(int count) {
        this.count = count;
    }

    public int getPages() {
        return pages;
    }

    public void setPages(int pages) {
        this.pages = pages;
    }

    @Override
    public String toString() {
        return "PageBean{" +
                "page=" + page +
                ", row=" + row +
                ", list=" + list +
                ", count=" + count +
                ", pages=" + pages +
                '}';
    }
}

分頁查詢Servlet：FindServletByPage

package cn.hehewocao.Servlet;

import cn.hehewocao.POJO.User;
import cn.hehewocao.Service.UserService;
import cn.hehewocao.Service.UserServiceImp;
import org.apache.commons.beanutils.BeanUtils;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.util.List;
import java.util.Map;

import cn.hehewocao.POJO.PageBean;

@WebServlet("/findServletByPage")
public class FindServletByPage extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        req.setCharacterEncoding("utf-8");
        String page = req.getParameter("page");
        String rows = req.getParameter("rows");
        Map<String, String[]> parameterMap = req.getParameterMap();//查詢條件
        UserService us = new UserServiceImp();
        PageBean<User> pb = us.findByPage(page, rows, parameterMap);
        req.setAttribute("pageBean", pb);//保存查詢後的PageBean對象
        req.setAttribute("condition",parameterMap);//將查詢條件保存到request中，以便回顯
        req.getRequestDispatcher("list.jsp").forward(req, resp);//轉發到list.jsp顯示數據

    }
}

UserServiceImp類中添加方法：

public PageBean<User> findByPage(String _page, String _rows, Map<String,String[]> info) {//封裝PageBean對象

        PageBean<User> pb = new PageBean<User>();
        //設置默認值
        if ("".equals(_page) || _page == null) {
            _page = "1";
        }

        if ("".equals(_rows) || _rows == null) {
            _rows = "5";
        }

        int page = Integer.parseInt(_page);
        int rows = Integer.parseInt(_rows);

        if(page < 1){
            page = 1;
        }

        if(rows < 1){
            rows = 1;
        }

        //設置查詢的頁數和每頁的記錄條數
        pb.setPage(page);
        pb.setRow(rows);

        UserDao ud = new UserDaoImp();
        int count  = ud.findCount(info);
        //總記錄數
        pb.setCount(count);

        int startIndex = (page - 1) * rows;

        List<User> list  = ud.findByPage(startIndex,rows,info);

        if (list == null || list.size() == 0){
            return null;
        }

        //該頁記錄集合
        pb.setList(list);

        //頁數
        int pages = count % rows == 0 ? count/rows : count/rows + 1;
        pb.setPages(pages);

        return pb;
    }

UserDaoImp類中添加方法：

   public int findCount(Map<String, String[]> info) {//查詢總記錄數

        /*初始化sql語句*/
        String sql = "select count(*) from user where 1 = 1 ";
        JdbcTemplate jdbcTemplate = new JdbcTemplate(JDBCUtils.getDateSource());
        List<String> list = new ArrayList<String>();
        for (String key : info.keySet()) {

            if (!"".equals(info.get(key)[0]) && info.get(key)[0] != null) {

                if (!key.equals("page")) {

                    if (!key.equals("rows")) {
                        sql += " and " + key + " like ? ";
                        list.add("%" + info.get(key)[0] + "%");
                    }
                }
            }
        }
        return jdbcTemplate.queryForObject(sql, list.toArray(), int.class);

    }

3. JSP頁面設計
該界面主要就是從request中獲取PageBean對象中保存的數據

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <!-- 上述3個meta標籤*必須*放在最前面，任何其他內容都*必須*跟隨其後！ -->
    <title>用戶管理</title>

    <!-- Bootstrap -->
    <link href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap.min.css" rel="stylesheet">

    <!-- HTML5 shim 和 Respond.js 是爲了讓 IE8 支持 HTML5 元素和媒體查詢（media queries）功能 -->
    <!-- 警告：通過 file:// 協議（就是直接將 html 頁面拖拽到瀏覽器中）訪問頁面時 Respond.js 不起作用 -->
    <!--[if lt IE 9]>
    <script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/html5shiv.min.js"></script>
    <script src="https://cdn.jsdelivr.net/npm/[email protected]/dest/respond.min.js"></script>
    <![endif]-->

    <style>

        tr, th, td {
            text-align: center;
        }

    </style>

</head>
<body>


<div style="width: 70%;margin-left: 15%;margin-top: 50px;" align="center">
    <form class="form-inline" action="${pageContext.request.contextPath}/findServletByPage" method="post">
        <div class="form-group">
            <label>編號</label>
            <input id="id" type="text" name="id" value="${condition.id[0]}" placeholder="輸入編號" align="center"/>
        </div>
        <div class="form-group">
            <label>用戶名</label>
            <input id="username" type="text" value="${condition.username[0]}" name="username" placeholder="輸入用戶名" align="center"/>
        </div>
        <div class="form-group">
            <label>暱稱</label>
            <input type="text" id="nickname" value="${condition.nickname[0]}" name="nickname" placeholder="暱稱" align="center"/>
        </div>

        <div class="form-group">
            <label>地址</label>
            <input type="text" id="address" value="${condition.address[0]}" name="address" placeholder="地址" align="center"/>
        </div>

        <button type="submit" class="btn btn-default" id="find">查詢</button>&nbsp;&nbsp;&nbsp;
        <a  href="register.jsp"><button type="button" class="btn btn-primary">添加用戶</button></a>
    </form>
</div>


<div style="width: 80%;margin-left: 10%;margin-top: 50px;">
    <table class="table table-hover">
        <tr>
            <th>編號</th>
            <th>用戶名</th>
            <th>密碼</th>
            <th>暱稱</th>
            <th>性別</th>
            <th>生日</th>
            <th>手機號</th>
            <th>郵箱</th>
            <th>地址</th>
            <th>職業</th>
            <th>描述</th>
            <th colspan="2">操作</th>
        </tr>

        <c:if test="${not empty pageBean}">

            <c:forEach items="${pageBean.list}" var="user" begin="0" end="${pageBean.list.size() - 1}" step="1"
                       varStatus="s">
                <tr>
                    <td>${user.id}</td>
                    <td>${user.username}</td>
                    <td>${user.password}</td>
                    <td>${user.nickname}</td>
                    <td>${user.sex}</td>
                    <td>${user.birthday}</td>
                    <td>${user.phone}</td>
                    <td>${user.email}</td>
                    <td>${user.address}</td>
                    <td>${user.occupation}</td>
                    <td>${user.describes}</td>
                    <td><a href="${pageContext.request.contextPath}/updateUserForwordServlet?beforeUserId=${user.id}" name="del" id="update${s}">修改</a></td>
                    <td><a href="${pageContext.request.contextPath}/delServletById?delId=${user.id}" name="del" id="${s}"
                           onclick="delLine(this)">刪除</a></td>
                </tr>
            </c:forEach>
        </c:if>
    </table>
</div>


<%--分頁欄--%>
<div align="center" style="margin-top: 50px;">
    <nav aria-label="Page navigation">
        <ul class="pagination">


            <c:if test="${pageBean.page == 1}">
                <li class="disabled">
                    <a href="#"
                       aria-label="Previous">
                        <span aria-hidden="true">&laquo;</span>
                    </a>
                </li>
            </c:if>
            <c:if test="${pageBean.page != 1}">
                <li>
                    <a href="${pageContext.request.contextPath}/findServletByPage?page=${pageBean.page - 1}&rows=5&id=${condition.id[0]}&username=${condition.username[0]}&nickname=${condition.nickname[0]}&address=${condition.address[0]}"
                       aria-label="Previous">
                        <span aria-hidden="true">&laquo;</span>
                    </a>
                </li>
            </c:if>


            <c:forEach begin="1" end='${pageContext.request.getAttribute("pageBean").pages}' var="i">
                <c:if test="${pageBean.page == i}">
                    <li class="active"><a
                            href='${pageContext.request.contextPath}/findServletByPage?page=${i}&rows=5&id=${condition.id[0]}&username=${condition.username[0]}&nickname=${condition.nickname[0]}&address=${condition.address[0]}'>${i}</a></li>
                </c:if>
                <c:if test="${pageBean.page != i}">
                    <li><a href='${pageContext.request.contextPath}/findServletByPage?page=${i}&rows=5&id=${condition.id[0]}&username=${condition.username[0]}&nickname=${condition.nickname[0]}&address=${condition.address[0]}'>${i}</a></li>
                </c:if>
            </c:forEach>


            <c:if test="${pageBean.pages == pageBean.page}">
                <li class="disabled">
                    <a href="#"
                       aria-label="Next">
                        <span aria-hidden="true">&raquo;</span>
                    </a>
                </li>
            </c:if>

            <c:if test="${pageBean.pages != pageBean.page}">
                <li>
                    <a href="${pageContext.request.contextPath}/findServletByPage?page=${pageBean.page + 1}&rows=5&id=${condition.id[0]}&username=${condition.username[0]}&nickname=${condition.nickname[0]}&$address=${condition.address[0]}"
                       aria-label="Next">
                        <span aria-hidden="true">&raquo;</span>
                    </a>
                </li>
            </c:if>

        </ul>
    </nav>
    <p style="font-weight: bold">
        共${pageBean.count == null ? 0 : pageBean.count}條記錄,共${pageBean.pages == null ? 0 : pageBean.pages}頁</p>
</div>


<script>
    function delLine(obj) {
        if (confirm("確認刪除?")) {
            return true;
        }
    }


</script>


<!-- jQuery (Bootstrap 的所有 JavaScript 插件都依賴 jQuery，所以必須放在前邊) -->
<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/jquery.min.js"></script>
<!-- 加載 Bootstrap 的所有 JavaScript 插件。你也可以根據需要只加載單個插件。 -->
<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/js/bootstrap.min.js"></script>
</body>
</html>

至此就實現了用戶信息的分頁查詢功能。