效果展示
JSP&Servlet 驗證碼登入 
JSP&Servlet 驗證碼登入 JSP&Servlet 驗證碼登入 登入頁面 login.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Login</title>
</head>
<script type="text/javascript">
function fun1() {
//1 獲得img對象
var img = document.getElementById("one");
//2 改變img對象 src屬性
img.src = "/Web1.1/SessionEServlet";
}
</script>
<body>
<form action="<%=request.getContextPath()%>/SessionDServlet">
使用者名: <input type="text" name="name" /><br/>
密碼: <input type="password" name="password" /><br/>
驗證碼: <input type="text" name="code" />
<img src="/Web1.1/SessionEServlet" width="150" id="one" onclick="fun1();"/>
<a href="javascript:void(0)" onclick="fun1();">看不清換一張</a><br/>
<input type="submit" value="登入" /><br/>
</form>
<font color="red">
<%=request.getAttribute("error")==null?"":request.getAttribute("error") %>
</font>
</body>
</html>
生成驗證碼 SessionEServlet
package Session;
import java.io.IOException;
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 cn.dsna.util.images.ValidateCode;
/**
* Servlet implementation class SessionEServlet
*/
@WebServlet("/SessionEServlet")
public class SessionEServlet extends HttpServlet {
private static final long serialVersionUID = L;
/**
* @see HttpServlet#HttpServlet()
*/
public SessionEServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 1 生成驗證碼
ValidateCode code = new ValidateCode(, , , );
// 2 将驗證碼儲存到session中
request.getSession().setAttribute("code", code.getCode());
// 3 将驗證碼圖檔輸出到浏覽器
response.setContentType("image/jpeg");
code.write(response.getOutputStream());
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
比對驗證碼 SessionDServlet.java
package Session;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class SessionDServlet
*/
@WebServlet("/SessionDServlet")
public class SessionDServlet extends HttpServlet {
private static final long serialVersionUID = L;
/**
* @see HttpServlet#HttpServlet()
*/
public SessionDServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1 獲得表單送出的驗證碼
String code1 = request.getParameter("code");
//2 獲得session中的正确驗證碼
String code2 = (String) request.getSession().getAttribute("code");
//3 比對是否一緻
if (code1 != null && code2 != null && code1.equals(code2)) {
//正确==> 成功頁面
response.sendRedirect("/Web1.1/index.jsp");
} else {
//不正确==> 回到表單 頁面 ,提示錯誤
request.setAttribute("error", "驗證碼錯誤!請重新輸入");
request.getRequestDispatcher("/checkcode/login.jsp").forward(request, response);
}
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
