After completing the small tasks left for myself, I feel that my understanding of paging is not very deep. I followed the school sister to learn paging, but I just copied all the code of the school sister directly and used it directly, and there is basically no correct code. Understand; this time, I used my own paging technology in the user management list I wrote. Although I still refer to the code of the original senior, but in a different way, I did not store the paging object in the session object like the senior. , paste the code below
The first is the paging interface, which is inherited by the Dao layer
package com.test.util;
import com.test.entity.Users;
import java.util.List;
/**
* @Description interface for paging, inherited by Dao layer, override these two methods
* Created by sjz on 2016/9/19.
*/
public interface PageInterface {
/**
* Query all records, use some variables in the paging object to get
* @param sPage
* @return list
*/
public List<Users> findAll(SplitPage sPage);
/**
* Query the number of records
* @return int
*/
public int getTotalRows();
}
The Dao layer rewrites two methods in the interface
@Override
public List<Users> findAll(SplitPage sPage) {
List<Users> list = new ArrayList<Users>();
ResultSet rs = null;
try{
Class.forName(DRIVER);
Connection conn = DriverManager.getConnection(URL,USERNAME,PASSWORD);
String sql = "SELECT * FROM t_users LIMIT ?,?";
PreparedStatement ps = conn.prepareStatement(sql);
ps.setInt(1, sPage.getPageRow() * (sPage.getCurrentPage() - 1));
ps.setInt(2, sPage.getPageRow());
rs = ps.executeQuery();
while(rs.next()){
Users user = new Users();
user.setId(rs.getInt("id"));
user.setUsername(rs.getString("username"));
user.setPassword(rs.getString("password"));
user.setContent(rs.getString("content"));
user.setPhoto(rs.getString("photo"));
list.add(user);
}
} catch (ClassNotFoundException e) {
e.printStackTrace ();
} catch (SQLException e) {
e.printStackTrace ();
}
return list;
}
@Override
public int getTotalRows() {
int totalRows = 0;
try {
Class.forName(DRIVER);
Connection conn = DriverManager.getConnection(URL,USERNAME,PASSWORD);
String sql = "SELECT COUNT(*) FROM t_users";
PreparedStatement ps = conn.prepareStatement(sql);
ResultSet rs = ps.executeQuery();
while(rs.next()){
totalRows = rs.getInt(1);
}
} catch (ClassNotFoundException e) {
e.printStackTrace ();
} catch (SQLException e) {
e.printStackTrace ();
}
return totalRows;
}
Then there is the paging entity class, which is used to handle the jump between pages
package com.test.util;
/**
* Paging object
* Created by sjz on 2016/9/19.
*/
public class SplitPage {
public final static String FIRSTPAGE = "first";//首页
public final static String LASTPAGE = "last";//尾页
public final static String PREVIOUSPAGE = "previous";//上一页
public final static String NEXTPAGE = "next";//下一页
private int pageRow = 5;//Display 5 pieces of data per page
private int totalRows = 0;//Number of data, provided by Dao
private int currentPage = 1;//Current page
private int firstPage = 1;//Home
private int totalPage = 1;//Total number of pages
public int getPageRow() {
return pageRow;
}
public void setPageRow(int pageRow) {
this.pageRow = pageRow;
this.totalPage = this.totalRows / this.pageRow
+ ((this.totalRows % this.pageRow == 0) ? 0 : 1);
}
public int getTotalRows() {
return totalRows;
}
public void setTotalRows(int totalRows) {
this.totalRows = totalRows;
this.totalPage = this.totalRows/this.pageRow+((this.totalRows%this.pageRow==0)?0:1);
}
public int getCurrentPage() {
return currentPage;
}
public void setCurrentPage(int currentPage) {
this.currentPage = currentPage;
}
public int getFirstPage() {
return firstPage;
}
public void setFirstPage(int firstPage) {
this.firstPage = firstPage;
}
public int getTotalPage () {
return totalPage;
}
public int toNewPage(String flag) { //Get the number of pages for the next operation
int newPage = this.currentPage;//Define the number of new pages as the current page
if (flag != null && !"".equals(flag)) { //The request parameter is not empty
if (SplitPage.FIRSTPAGE.equals(flag)) { //If the incoming parameter is the first page
newPage = 1; //The number of new pages is the first page
} else if (SplitPage.LASTPAGE.equals(flag)) { //If the passed parameter is the last page
newPage = this.totalPage; //The number of new pages is the last page
} else if (SplitPage.NEXTPAGE.equals(flag)) { //If the incoming parameter is the next page
newPage = this.currentPage
+ ((this.currentPage == this.totalPage) ? 0 : 1);// If the current page is equal to the total number of pages, it will not go backward (+1)
System.out.println(newPage);
} else if (SplitPage.PREVIOUSPAGE.equals(flag)) { //If the incoming parameter is the previous page
newPage = this.currentPage
- ((this.currentPage == this.firstPage) ? 0 : 1);// If the current page is equal to the first page, it will not move forward (-1)
} else {
// passed in is a numeric string parameter
//System.out.println(flag+"llll");
newPage = Integer.parseInt(flag.trim());
}
} else {// The requested parameter is empty, the current page number remains unchanged
newPage = this.currentPage;
}
this.setCurrentPage(newPage);// Remember to reset the current page
return newPage;
}
}
Then there is the servlet, which just adds some passed parameters on the original basis, and changes the list method
package com.test.controller;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;
import com.jspsmart.upload.File;
import com.jspsmart.upload.SmartUpload;
import com.jspsmart.upload.SmartUploadException;
import com.test.dao.UsersDao;
import com.test.entity.Users;
import com.test.util.SplitPage;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.jsp.JspFactory;
import javax.servlet.jsp.PageContext;
import static java.lang.System.out;
/**
* Created by sjz on 2016/9/14.
*/
public class UsersServlet extends javax.servlet.http.HttpServlet {
protected void doPost(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException {
doGet(request,response);
}
protected void doGet(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException {
request.setCharacterEncoding("UTF-8");
response.setCharacterEncoding("UTF-8");
String method = request.getParameter("method");
out.println(method);
switch (method){
case "insert" :
insert(request,response);
break;
case "delete" :
delete(request,response);
break;
case "toUpdate":
int id3 = Integer.parseInt(request.getParameter("id"));
Users user3 = UsersDao.selectById(id3);
request.setAttribute("user",user3);
request.getRequestDispatcher("../show.jsp").forward(request,response);
case "update" :
System.out.println(request.getPart("id")+"aaaa");
int id = Integer.parseInt(request.getParameter("id"));
update(request,response,id);
break;
case "select" :
//select(request,response);
int id2 = Integer.parseInt(request.getParameter("id"));
Users user2 = UsersDao.selectById(id2);
request.setAttribute("user",user2);
request.getRequestDispatcher("../show.jsp").forward(request,response);
break;
case "list" :
//list(request,response);\
UsersDao uDao = new UsersDao ();
SplitPage sPage = new SplitPage();
int totalRows = uDao.getTotalRows();
sPage.setTotalRows (totalRows);
String flag = request.getParameter("flag");
String current = request.getParameter("current");
if(current!=null){
int currentPage = Integer.parseInt(current);
sPage.setCurrentPage(currentPage);
}
int newPage = sPage.toNewPage(flag);
List<Users> list = uDao.findAll(sPage);
request.setAttribute("list",list);
request.setAttribute("sPage",sPage);
request.getRequestDispatcher("../list.jsp").forward(request,response);
break;
}
}
private void insert(HttpServletRequest request, HttpServletResponse response) {
SmartUpload su = new SmartUpload();
JspFactory _jspxFactory = null;
PageContext pageContext = null;
_jspxFactory = JspFactory.getDefaultFactory();
pageContext = _jspxFactory.getPageContext(this,request,response,"",true,8192,true);
try {
su.initialize(pageContext);
su.upload ();
PrintWriter out = response.getWriter();
out.println("Upload" + su.save("picture") + "Successful files!!!"+"<br>");
String username = su.getRequest().getParameter("username");
String password = su.getRequest().getParameter("password");
String content = su.getRequest().getParameter("content");
File file = su.getFiles (). GetFile (0);
if (file.isMissing())
System.out.println("No file selected");
String photo = file.getFileName();
String path = "/picture";
path = path + "/" + photo;
file.saveAs(path, SmartUpload.SAVE_VIRTUAL);
System.out.println(photo);
Users user = new Users();
user.setUsername(username);
user.setPassword(password);
user.setContent(content);
user.setPhoto(photo);
if(UsersDao.insert(user)){
out.println("success");
response.setHeader("refresh", "3;UsersServlet?method=list&flag=first");
} else{
out.println("Failed");
response.setHeader("refresh", "3;UsersServlet?method=insert");
}
} catch (ServletException e) {
e.printStackTrace ();
} catch (SmartUploadException e) {
e.printStackTrace ();
} catch (IOException e) {
e.printStackTrace ();
}
}
private void delete(HttpServletRequest request, HttpServletResponse response) {
int id = Integer.parseInt(request.getParameter("id"));
try{
if(UsersDao.delete(id)){
out.println("success");
request.getRequestDispatcher("UsersServlet?method=list&flag=first").forward(request,response);
} else{
out.println("Failed");
request.getRequestDispatcher("../list.jsp").forward(request,response);
}
} catch (ServletException e) {
e.printStackTrace ();
} catch (IOException e) {
e.printStackTrace ();
}
}
private void update(HttpServletRequest request, HttpServletResponse response, int id) {
SmartUpload su = new SmartUpload();
JspFactory _jspxFactory = null;
PageContext pageContext = null;
_jspxFactory = JspFactory.getDefaultFactory();
pageContext = _jspxFactory.getPageContext(this,request,response,"",true,8192,true);
try {
su.initialize(pageContext);
su.upload ();
PrintWriter out = response.getWriter();
out.println("Upload" + su.save("picture") + "Successful files!!!"+"<br>");
String username = su.getRequest().getParameter("username");
String password = su.getRequest().getParameter("password");
String content = su.getRequest().getParameter("content");
File file = su.getFiles (). GetFile (0);
if (file.isMissing())
System.out.println("No file selected");
String photo = file.getFileName();
String path = "/picture";
path = path + "/" + photo;
file.saveAs(path, SmartUpload.SAVE_VIRTUAL);
System.out.println(photo);
Users user = new Users();
user.setUsername(username);
user.setPassword(password);
user.setContent(content);
user.setPhoto(photo);
if(UsersDao.update(user,id)){
out.println("success");
response.setHeader("refresh", "3;UsersServlet?method=list&flag=first");
} else{
out.println("Failed");
response.setHeader("refresh", "3;UsersServlet?method=insert&flag=first");
}
} catch (ServletException e) {
e.printStackTrace ();
} catch (SmartUploadException e) {
e.printStackTrace ();
} catch (IOException e) {
e.printStackTrace ();
}
}
private void select(HttpServletRequest request, HttpServletResponse response) {
}
private void list(HttpServletRequest request, HttpServletResponse response) {
}
}
The last is list.jsp, which adds some code to better implement the function
<%@ page import="com.test.entity.Users" %>
<%@ page import="java.util.List" %>
<%@ page import="com.test.util.SplitPage" %><%--
Created by IntelliJ IDEA.
User: lenovo
Date: 2016/9/18
Time: 9:36
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>User List</title>
</head>
<body>
<tr>
<td>User ID</td>
<td>Username</td>
<td>User Profile</td>
<td>Photo</td>
</tr><br>
<%
SplitPage sPage = (SplitPage)request.getAttribute("sPage");
List<Users> list = (List<Users>) request.getAttribute("list");
for (int i=0;list!=null&&i<list.size();i++){
%>
<tr>
<td><%=list.get(i).getId()%></td>
<td><%=list.get(i).getUsername()%></td>
<td><%=list.get(i).getContent()%></td>
<td><img src="../picture/<%=list.get(i).getPhoto()%>" style="width:100px;height:100px;"></td>
<a href="UsersServlet?method=select&id=<%=list.get(i).getId()%>">修改</a>
<a href="UsersServlet?method=delete&id=<%=list.get(i).getId()%>">删除</a>
</tr>
<br>
<%
}
%>
<div id="foot">
<a href="UsersServlet?method=list&flag=<%=SplitPage.FIRSTPAGE%>¤t=<%=sPage.getCurrentPage()%>">首页</a>
<a href="UsersServlet?method=list&flag=<%=SplitPage.PREVIOUSPAGE%>¤t=<%=sPage.getCurrentPage()%>">上一页</a>
<a href="UsersServlet?method=list&flag=<%=SplitPage.NEXTPAGE%>¤t=<%=sPage.getCurrentPage()%>">下一页</a>
<a href="UsersServlet?method=list&flag=<%=SplitPage.LASTPAGE%>¤t=<%=sPage.getCurrentPage()%>">末页</a>
<%
for (int i = 1; i <= sPage.getTotalPage(); ++i) { //Control the total number of pages
%>
<a href="UsersServlet?method=list&flag=<%=i%>¤t=1"><%=i%></a>
<%
}
%>
</select>
<label><%=sPage.getCurrentPage()%>/<%=sPage.getTotalPage()%>page<!-- current page/total page-->
</label>
</div>
</body>
</html>
In addition to these, all the other page jump addresses are followed by some parameters to modify the sPage object that is re-instantiated every time you visit, in order to achieve page jumps