本次案例爲Servlet+JDBC實現登陸功能的小例子的進階版本，關於與數據庫交互部分，這裏不再贅述
案例需求：
- 訪問帶有驗證碼的登錄頁面login.jsp
- 用戶輸入用戶名，密碼以及驗證碼。
- 如果用戶名和密碼輸入有誤，跳轉登錄頁面，提示:用戶名或密碼錯誤
- 如果驗證碼輸入有誤，跳轉登錄頁面，提示：驗證碼錯誤
- 如果全部輸入正確，則跳轉到主頁success.jsp，顯示：用戶名,歡迎您
分析
步驟
文件樹展示
1.配置文件和jar包在上個案例均有配置過，需要改的有：User類新增驗證碼成員變量，數據庫增加了一個驗證碼字段（無用，只是爲了UserDao包把查找到的數據值導入到User類不出錯）。
2.登陸界面
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>login</title>
<script>
window.onload = function(){
document.getElementById("img").onclick = function(){
this.src="/CaS/checkCodepic?time="+new Date().getTime();
}
}
</script>
<style>
div{
color: red;
}
</style>
</head>
<body>
<form action="/CaS/loginServlet" method="post">
<table>
<tr>
<td>用戶名</td>
<td><input type="text" name="username"></td>
</tr>
<tr>
<td>密碼</td>
<td><input type="password" name="password"></td>
</tr>
<tr>
<td>驗證碼</td>
<td><input type="text" name="checkCode"></td>
</tr>
<tr>
<td colspan="2"><img id="img" src="/CaS/checkCodepic"></td>
</tr>
<tr>
<td colspan="2"><input type="submit" value="登錄"></td>
</tr>
</table>
</form>
<div><%=request.getAttribute("cc_error") == null ? "" : request.getAttribute("cc_error")%></div>
<div><%=request.getAttribute("login_error") == null ? "" : request.getAttribute("login_error") %></div>
</body>
</html>
3.驗證碼，畫了個驗證碼，每次都把隨機數加入session中以便進行對比
package Test;
import javax.imageio.ImageIO;
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.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
@WebServlet("/checkCodepic")
public class CheckCodepic extends HttpServlet {
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
int width=100;
int height=50;
//創建圖片對象
BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
//美化圖片
//創建畫筆
Graphics g = image.getGraphics();
//畫筆顏色
g.setColor(Color.pink);
//畫個矩形，填充爲粉紅色
g.fillRect(0,0,width,height);
//給矩形加邊框
g.setColor(Color.blue);
g.drawRect(0,0,width-1,height-1);
//寫字母或數字
g.setColor(Color.green);
String str="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
Random rd=new Random();
StringBuilder sb=new StringBuilder();
for(int i=1;i<=4;i++){
int index = rd.nextInt(str.length());
char c = str.charAt(index);
sb.append(c);
g.drawString(c+"",width/5*i,height/2);
}
String checkCode_session = sb.toString();
//將驗證碼存入session
req.getSession().setAttribute("checkCode_session",checkCode_session);
//加干擾線
g.setColor(Color.blue);
for(int i=1;i<=10;i++){
int x1 = rd.nextInt(width);
int x2 = rd.nextInt(width);
int y1 = rd.nextInt(height);
int y2 = rd.nextInt(height);
g.drawLine(x1,y1,x2,y2);
}
//輸出展示
ImageIO.write(image,"jpg",resp.getOutputStream());
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doPost(req,resp);
}
}
4.loginServlet類，用來判斷驗證碼和用戶名密碼是否正確，注意先判斷驗證碼；注意重定向和請求轉發的不同，還有session的應用。
package Test;
import Test.dao.UserDao;
import Test.userclass.User;
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.Map;
@WebServlet("/loginServlet")
public class loginServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//設置request編碼
request.setCharacterEncoding("utf-8");
//獲取參數
// String username = request.getParameter("username");
// String password = request.getParameter("password");
// String checkCode = request.getParameter("checkCode");
// User user=new User();
// user.setUsername(username);
// user.setPassword(password);
// user.setCheckCode(checkCode);
Map<String, String[]> parameterMap = request.getParameterMap();
User user=new User();
try {
BeanUtils.populate(user,parameterMap);
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
UserDao userDao=new UserDao();
//先判斷驗證碼是否正確
String checkCode_session = (String)request.getSession().getAttribute("checkCode_session");
request.getSession().removeAttribute("checkCode_session");
if(checkCode_session!=null && checkCode_session.equalsIgnoreCase(user.getCheckCode())){//忽略大小寫
//如果正確，判斷用戶名密碼是否正確
User login = userDao.login(user);
if(login!=null){
//登陸成功，存儲用戶信息
request.getSession().setAttribute("username",login.getUsername());
//重定向到success.jsp
response.sendRedirect(request.getContextPath()+"/success.jsp");
}else{//登陸失敗，轉發到登陸界面
request.setAttribute("login_error","用戶名或密碼不正確");
request.getRequestDispatcher("/login.jsp").forward(request,response);
}
}else{ //如果不正確，轉發到登陸界面
request.setAttribute("cc_error","驗證碼不正確");
request.getRequestDispatcher("/login.jsp").forward(request,response);
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
}
5.成功登陸界面
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<h1><%=request.getSession().getAttribute("username")%>,歡迎您</h1>
</body>
</html>
結果
登陸界面
驗證碼錯誤情況
用戶名或密碼不正確情況
成功登陸
