Web分页实现及实例演示(一）——subList()

时间：2021-05-12 21:03:32

源码 点击打开链接

其他web项目传送门http://blog.csdn.net/u011299745/article/details/53547279


有一个学生表，可以通过姓名进行模糊查找，或者性别查找。


使用subList()实现,步骤（MVC）：

  1. （M）根据查询条件生成有一定信息的Student对象，查询出所有符合条件的学生，所有信息存储在List<Map<k,v>>中。
  2. 遍历结果，用Map<k,v>来实例化Student，所有符合条件的学生，存入List<Student>。（这个List就是通过输入条件查找到的所有结果，结果可能太多所以需要分页显示）
  3. 用上一步的List，和每页大小（pageSize）、当前页（pageNum）实例化一个Pager对象。Pager对象包含总页数，总条数，当前页，每页大小，当前页显示的对象（使用List.subList()来截取）。用传入的参数可以计算出来。
  4. (C)在servlet中初始化参数，实现上面的步骤，将结果Pager对象存成一个属性，jsp中可以使用。同时存入查询条件，方便下页等标签使用。
  5. （V）Jsp界面中可以通过EL表达式，取得上一步存入的结果，显示。下一页等标签可以使用js或者url传值，主要是pageNum+1，还有上次查询的条件。点击跳转到servlet，根据同样的查询条件和pageNum，计算新的Pager对象，在jsp显示。
核心代码： 
//JdbcUtil.java jdbc工具包，有查询、更新、释放
package com.xf.page.util;import java.io.InputStream;import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.ResultSetMetaData;import java.sql.SQLException;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import java.util.Properties;/** * @author XF *JDBC工具类 */public class JdbcUtil {private static String USERNAME;private static String PASSWORD;private static String DRIVER;private static String URL;private Connection connection;private PreparedStatement pstmt;private ResultSet resultSet;static{loadConfig();}/** * 加载数据库配置信息,并给相关的属性赋值 */public static void loadConfig(){USERNAME = "root";PASSWORD = "root";DRIVER = "com.mysql.jdbc.Driver";URL = "jdbc:mysql://localhost:3306/page"; //根据项目选择dataBase}public JdbcUtil() {}public Connection getConnection() {try {Class.forName(DRIVER);connection = DriverManager.getConnection(URL, USERNAME, PASSWORD);} catch (Exception e) {throw new RuntimeException("get connection error!");}return connection;}/** * 执行更新操作 * @param sql sql语句 * @param params 执行参数 * @return 执行结果 * @throws SQLException */public boolean updateByPreparedStatement(String sql, List<?> params)throws SQLException {boolean flag = false;int result = -1;// 表示当用户执行添加删除和修改的时候所影响数据库的行数pstmt = connection.prepareStatement(sql);int index = 1;// 填充sql语句中的占位符if (params != null && !params.isEmpty()) {for (int i = 0; i < params.size(); i++) {pstmt.setObject(index++, params.get(i));}}result = pstmt.executeUpdate();flag = result > 0 ? true : false;return flag;}/** * 执行查询操作 * @param sql sql语句 * @param params 执行参数 * @return * @throws SQLException */public List<Map<String, Object>> findResult(String sql, List<?> params)throws SQLException {List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();int index = 1;pstmt = connection.prepareStatement(sql);if (params != null && !params.isEmpty()) {for (int i = 0; i < params.size(); i++) {pstmt.setObject(index++, params.get(i));}}resultSet = pstmt.executeQuery();ResultSetMetaData metaData = resultSet.getMetaData();int cols_len = metaData.getColumnCount();while (resultSet.next()) {Map<String, Object> map = new HashMap<String, Object>();for (int i = 0; i < cols_len; i++) {String cols_name = metaData.getColumnName(i + 1);Object cols_value = resultSet.getObject(cols_name);if (cols_value == null) {cols_value = "";}map.put(cols_name, cols_value);}list.add(map);}return list;}/** * 释放资源 */public void releaseConn() {if (resultSet != null) {try {resultSet.close();} catch (SQLException e) {e.printStackTrace();}}if (pstmt != null) {try {pstmt.close();} catch (SQLException e) {e.printStackTrace();}}if (connection != null) {try {connection.close();} catch (SQLException e) {e.printStackTrace();}}}}

//SublistStudentDaoImpl.java 查询满足条件的对象，并传入参数，生成Pager对象，即结果
package com.xf.page.dao;import java.sql.SQLException;import java.util.ArrayList;import java.util.List;import java.util.Map;import com.xf.page.model.Pager;import com.xf.page.model.Student;import com.xf.page.util.JdbcUtil;public class SublistStudentDaoImpl implements StudentDao {//调用方法getAllStudent，然后根据传入的参数，生成Pager对象，即结果。@Overridepublic Pager<Student> findStudent(Student searchModel, int pageNum,int pageSize) {// TODO Auto-generated method stubList<Student> allStudents = getAllStudent(searchModel);Pager<Student > pager = new Pager<Student>(pageNum, pageSize, allStudents);System.out.println("DaoImpl: pageNum= "+pageNum);return pager;}//查找所有满足条件的对象private List<Student> getAllStudent(Student searchModel){List<Student> result = new ArrayList<Student>();List<Object> paramList = new ArrayList<Object>();String stuName = searchModel.getName();//System.out.println("impl : name: "+stuName);int gender = searchModel.getGender();StringBuilder sql = new StringBuilder("select * from t_student where 1=1");if(stuName != null && !stuName.equals("")){sql.append(" and stu_name like ?");paramList.add("%"+stuName+"%");}if(gender == Constant.GENDER_FEMALE || gender == Constant.GENDER_MALE){sql.append(" and gender = ?");paramList.add(gender);}JdbcUtil jdbcUtil = null;try {jdbcUtil = new JdbcUtil();jdbcUtil.getConnection();List<Map<String, Object>> mapList = jdbcUtil.findResult(sql.toString(), paramList);if(mapList != null){for(Map<String, Object> map:mapList){Student s = new Student(map);//System.out.println("name: "+s.getName());result.add(s);}}} catch (SQLException e) {// TODO Auto-generated catch blockthrow new RuntimeException("查询所有数据异常!",e);}finally{if(jdbcUtil != null){jdbcUtil.releaseConn();}}return result;}}
</pre><pre name="code" class="java">//Pager.java <span style="font-family: Arial, Helvetica, sans-serif;">根据传入参数实例化Pager对象，计算相应的信息</span>
package com.xf.page.model;import java.io.Serializable;import java.util.List;public class Pager<T> implements Serializable {/** *  */private static final long serialVersionUID = -1380898667849848066L;private int pageSize;private int currentPage;private int totalRecord;//一共多少条记录private int totalPage;private List<T> dataList;//根据传入参数实例化Pager对象，计算相应的信息以及结果dataListpublic Pager(int pageNum, int pageSize, List<T> sourceList){if(sourceList == null) return;this.totalRecord = sourceList.size();this.pageSize = pageSize;this.totalPage = this.totalRecord / this.pageSize;//非整除+1if(this.totalRecord % this.pageSize != 0) this.totalPage +=1;//当前第几页,大于总页数则赋值为总页数，小于1则赋值为1if(this.totalPage < pageNum){this.currentPage = this.totalPage;}else{this.currentPage = pageNum;}if(this.currentPage < 1) this.currentPage =1;int fromIndex = this.pageSize * (this.currentPage -1);int toIndex = this.pageSize * this.currentPage > this.totalRecord? this.totalRecord: this.pageSize * this.currentPage;this.dataList = sourceList.subList(fromIndex, toIndex);}public Pager() {super();}public Pager(int pageSize, int currentPage, int totalRecord, int totalPage,List<T> dataList) {super();this.pageSize = pageSize;this.currentPage = currentPage;this.totalRecord = totalRecord;this.totalPage = totalPage;this.dataList = dataList;}public int getPageSize() {return pageSize;}public void setPageSize(int pageSize) {this.pageSize = pageSize;}public int getCurrentPage() {return currentPage;}public void setCurrentPage(int currentPage) {this.currentPage = currentPage;}public int getTotalRecord() {return totalRecord;}public void setTotalRecord(int totalRecord) {this.totalRecord = totalRecord;}public int getTotalPage() {return totalPage;}public void setTotalPage(int totalPage) {this.totalPage = totalPage;}public List<T> getDataList() {return dataList;}public void setDataList(List<T> dataList) {this.dataList = dataList;}public static long getSerialversionuid() {return serialVersionUID;}}

//SublistServlet.java 
package com.xf.page.servlet;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import com.xf.page.dao.Constant;import com.xf.page.model.Pager;import com.xf.page.model.Student;import com.xf.page.service.StudentService;import com.xf.page.service.SublistStudentServiceImpl;public class SublistServlet extends HttpServlet {/** *  */private static final long serialVersionUID = -5459092412782251847L;private StudentService studentService = new SublistStudentServiceImpl();/** * The doGet method of the servlet. <br> * * This method is called when a form has its tag value method equals to get. *  * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doPost(request,response);}/** * The doPost method of the servlet. <br> * * This method is called when a form has its tag value method equals to post. *  * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */public void doPost(HttpServletRequest req, HttpServletResponse res)throws ServletException, IOException {//请求中含有中文，讲req编码设置为utf-8req.setCharacterEncoding("utf-8");//接受request参数,先赋值为默认值，避免为null，发生errorString name = req.getParameter("name");System.out.println("servlet : name: "+name);//int gender = Constant.DEFAULT_GENDER;String genderStr = req.getParameter("gender");if(genderStr != null && !("".equals(genderStr.trim()))){gender = Integer.parseInt(genderStr);}//int pageNum = Constant.DEFAULT_PAGE_NUM;String pageNumStr = req.getParameter("pageNum");if(pageNumStr != null && !("".equals(pageNumStr.trim()))){pageNum = Integer.parseInt(pageNumStr);}//int pageSize = Constant.DEFAULT_PAGE_SIZE;String pageSizeStr = req.getParameter("pageSize");if(pageSizeStr != null && !("".equals(pageSizeStr.trim()))){pageSize = Integer.parseInt(pageSizeStr);}//组装查询条件Student searchModel = new Student();searchModel.setName(name);searchModel.setGender(gender);//查询结果Pager<Student> result = studentService.findStudent(searchModel, pageNum, pageSize);//存储返回的结果req.setAttribute("result", result);//存储查询信息，为下页，上页等标签保留查询信息req.setAttribute("name", name);req.setAttribute("gender", gender);req.getRequestDispatcher("/sublistStudent.jsp").forward(req, res);}}


//sublistStudent.jsp
<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%><%@taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>    <base href="<%=basePath%>">        <title>学生信息</title>    <meta http-equiv="pragma" content="no-cache"><meta http-equiv="cache-control" content="no-cache"><meta http-equiv="expires" content="0">    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"><meta http-equiv="description" content="This is my page"><!--<link rel="stylesheet" type="text/css" href="styles.css">--><style type="text/css"></style>  <%  String context = request.getContextPath();   %>  </head>     <body>  <h2>学生信息</h2>    <div>    <form action="<%=context%>/servlet/sublistServlet" id= "stuForm" method="post">    姓名    <input type='text' name="name" id="name" >     性别    <select name="gender" id="gender">    <option value="-1">全部</option>    <option value="1">男</option>    <option value="2">女</option>    </select>      <input type="submit" value="查询">    </form>    </div>    <div>    学生信息列表:<br><br>    <!-- 后台返回结果为空 -->    <c:if test="${fn:length(result.dataList) eq 0 }">    <span>查询结果不存在</span>    </c:if>        <!-- 后台返回结果不为空 -->    <c:if test="${fn:length(result.dataList) gt 0}">       <table  border= 1px;>    <tr height="30" >    <th width="130">姓名</th>    <th width="130">性别</th>    <th width="130">年龄</th>    <th width="230">家庭住址</th>    </tr>    <c:forEach items="${result.dataList }" var="student">    <tr>    <td><c:out value="${student.name }"></c:out></td>    <td><c:if test="${student.gender eq 1 }">男</c:if><c:if test="${student.gender eq 2 }">女</c:if></td>    <td><c:out value="${student.age }"></c:out></td>    <td><c:out value="${student.address }"></c:out></td>    </tr>    </c:forEach>    </table><br>    共${result.totalRecord }条记录，共${result.totalPage }页，当前第${result.currentPage}页       <a href="servlet/sublistServlet?pageNum=1&name=${name}&gender=${gender}" >首页</a>    <!-- 这类标签必须带有查询信息 -->    <a href="servlet/sublistServlet?pageNum=${result.currentPage+1 }&name=${name}&gender=${gender}" >下一页</a>    <a href="servlet/sublistServlet?pageNum=${result.currentPage-1 }&name=${name}&gender=${gender}" >上一页</a>    <a href="servlet/sublistServlet?pageNum=${result.totalPage }&name=${name}&gender=${gender}" >尾页</a>    </c:if>    </div>  </body></html>

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