纯Sevlet登陆页面与数据分页显示
一、大致流程如下：
分别对应三个sevlet，Login.java LoginCL.java Wel.java
代码如下：
Login.java
package com.example;
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;
public class Login extends HttpServlet{
public void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
resp.setContentType("text/html;charset=utf-8");
PrintWriter pw = resp.getWriter();
pw.println("<html>");
pw.println("<body>");
pw.println("<h1>登陆界面</h1>");
pw.println("<form action=logincl method=post>");
pw.println("用户名:<input type=text name=username><br>");
pw.println("密码:<input type=password name=passwd><br>");
pw.println("<input type=submit value=login><br>");
pw.println("</form>");
pw.println("</body>");
pw.println("</html>");
}
public void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
this.doGet(req, resp);
}
}
LoginCL.java
//用户验证
package com.example;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class LoginCL extends HttpServlet{
public void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
//接受用户名和密码
String u = req.getParameter("username");
String p = req.getParameter("passwd");
//操作数据库
Connection ct = null;
Statement stat = null;
ResultSet rs = null;
try {
Class.forName("com.mysql.jdbc.Driver");
ct = DriverManager.getConnection("jdbc:mysql://localhost:3306/yuippe",
"root", "123456");
stat = ct.createStatement();
rs = stat.executeQuery("SELECT passwd FROM users WHERE username='" + u +
"'" );
if(rs.next()){
//说明用户存在
String dbpasswd = rs.getString(1);
if(p.equals(dbpasswd)){
//用户信息存入session
HttpSession hs = req.getSession(true);
hs.setMaxInactiveInterval(60);
hs.setAttribute("name", u);
//跳转
resp.sendRedirect("wel");
}else{
resp.sendRedirect("login");
}
}else{
//不合法
//跳转
resp.sendRedirect("login");
}
} catch (Exception e) {
e.printStackTrace();
}finally{
try
{
if(rs != null){
rs.close();
}
if(stat != null){
stat.close();
}
if(ct != null){
ct.close();
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
public void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
this.doGet(req, resp);
}
}
Wel.java
//欢迎界面
package com.example;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.Statement;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class Wel extends HttpServlet{
public void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
HttpSession hs = req.getSession(true);
String val = (String)hs.getAttribute("name");
//判断
if(val == null){
//非法
resp.sendRedirect("login");
}
//分页
int pageSize = 3;//一页显示几条记录
int pageNow = 1; //目前显示的页数
int rowCount = 0;//共有多少条记录（查表）
int pageCount = 0;//共有多少页(计算)
//动态的接受pageNow
String spageNow = req.getParameter("pageNow");
if(spageNow != null)
pageNow = Integer.parseInt(spageNow);
//操作数据库
Connection ct = null;
PreparedStatement ps = null;
ResultSet rs = null;
try {
Class.forName("com.mysql.jdbc.Driver");
ct = DriverManager.getConnection("jdbc:mysql://localhost:3306/yuippe",
"root", "123456");
ps = ct.prepareStatement("SELECT COUNT(*) FROM users");
rs = ps.executeQuery();
if(rs.next())
rowCount = rs.getInt(1);
//共分为多少页
if(rowCount % pageSize == 0){
pageCount = rowCount/pageSize;
}else{
pageCount = rowCount/pageSize + 1;
}
ps.close();
rs.close();
//每页上需要显示的结果
ps = ct.prepareStatement("SELECT * FROM users LIMIT " + (pageNow-1)*pageSize + ","
+ pageSize +";");
rs = ps.executeQuery();
resp.setContentType("text/html;charset=utf-8");
PrintWriter pw = resp.getWriter();
pw.println("<html>");
pw.println("<body>");
pw.println("<table border='1'>");
//显示结果表格
pw.println("<tr><th>userId</th><th>username</th><th>passwd</th><th>grade</th></tr>");
while(rs.next()){
pw.println("<tr>");
pw.println("<td>" + rs.getInt(1) + "</td>");
pw.println("<td>" + rs.getString(2) + "</td>");
pw.println("<td>" + rs.getString(3) + "</td>");
pw.println("<td>" + rs.getInt(4) + "</td>");
pw.println("</tr>");
}
pw.println("</table>");
//显示上一页
if(pageNow != 1)
pw.println("<a href=wel?pageNow=" + (pageNow-1) + ">"+"上一页"+"</a>");
//显示5个页面超链接
for(int i=pageNow; i < pageNow+5; i++){
pw.println("<a href=wel?pageNow="+i+">" +i+ "</a>");
}
//显示下一页
if(pageNow != pageCount)
pw.println("<a href=wel?pageNow=" + (pageNow+1) + ">"+"下一页"+"</a>");
pw.println("</body>");
pw.println("</html>");
} catch (Exception e) {
e.printStackTrace();
}finally{
try
{
if(rs != null){
rs.close();
}
if(ps != null){
ps.close();
}
if(ct != null){
ct.close();
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
public void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
this.doGet(req, resp);
}
}
web.xml配置文件如下：
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee/web_2_4.xsd"
wersion="2.4">
<servlet>
<servlet-name>login</servlet-name>
<servlet-class>com.example.Login</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>login</servlet-name>
<url-pattern>/login</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>logincl</servlet-name>
<servlet-class>com.example.LoginCL</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>logincl</servlet-name>
<url-pattern>/logincl</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>wel</servlet-name>
<servlet-class>com.example.Wel</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>wel</servlet-name>
<url-pattern>/wel</url-pattern>
</servlet-mapping>
</web-app>
二、分页显示
分别定义四个变量
int pageSize = 3;//一页显示几条记录
int pageNow = 1; //目前所在的页面
int rowCount = 0;//共有多少条记录（查表）
int pageCount = 0;//共有多少页(计算)
rowCount通过查表得到：
ps = ct.prepareStatement("SELECT COUNT(*) FROM users");
rs = ps.executeQuery();
if(rs.next())
rowCount = rs.getInt(1);
pageCount通过计算可得：
if(rowCount % pageSize == 0){
pageCount = rowCount/pageSize;
}else{
pageCount = rowCount/pageSize + 1;
}
三、结果如下：