代码实现：
login.jsp：
<%@ 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 = "/checkCodeServlet1?time="+new Date().getTime();
}
}
</script>
<style>
div{
color: red;
}
</style>
</head>
<body>
<form action="/loginServlet1" method="post">
<table>
<tr>
<td>用户名</td>
<td><input type="text" name="username"></td>
</tr>
<tr>
<td>密码</td>
<td><input type="password" name="password"></td>
</tr>
<tr>
<td>验证码</td>
<td><input type="text" name="checkCode"></td>
</tr>
<tr>
<td colspan="2"><img id="img" src="/checkCodeServlet1"></td>
</tr>
<tr>
<td colspan="2"><input type="submit" value="登陆"></td>
</tr>
</table>
</form>
<div><%=request.getAttribute("cc_error")%></div>
<div><%=request.getAttribute("login_error")%></div>
</body>
</html>
CheckCodeServlet：
@WebServlet("/checkCodeServlet1")
public class CheckCodeServlet1 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
int width = 100;
int height = 50;
//1、创建一对象，在内存中画图（验证码图片对象）
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
//2、美化图片
//填充背景色
Graphics g = image.getGraphics();
g.setColor(Color.PINK);
g.fillRect(0,0,width,height);
//画边框
g.setColor(Color.BLUE);
g.drawRect(0,0,width-1,height-1);
//写验证码
String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789";
//生成随机角标
Random ra = new Random();
StringBuilder sb = new StringBuilder();
for (int i = 1; i <= 4; i++) {
int index = ra.nextInt(str.length());
//获取字符
char c = str.charAt(index);
sb.append(c);
//写验证码
g.drawString(c+"",width/5*i,height/2);
}
String checkCode_session = sb.toString();
//将验证码存入session
request.getSession().setAttribute("checkCode_session",checkCode_session);
//画干扰线
g.setColor(Color.GREEN);
//随机生成坐标点
for (int i = 0; i < 10; i++) {
int x1 = ra.nextInt(width);
int x2 = ra.nextInt(width);
int y1 = ra.nextInt(height);
int y2 = ra.nextInt(height);
g.drawLine(x1,y1,x2,y2);
}
//3、将图片输出到页面展示
ImageIO.write(image,"jpg",response.getOutputStream());
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
}
LoginServlet：
@WebServlet("/loginServlet1")
public class LoginServlet1 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1、设置request编码
request.setCharacterEncoding("utf-8");
//2、获取参数
String username = request.getParameter("username");
String password = request.getParameter("password");
String checkCode = request.getParameter("checkCode");
//3、先获取生成的验证码
HttpSession session = request.getSession();
String checkCode_session = (String) session.getAttribute("checkCode_session");
//判断验证码是否正确
if (checkCode_session.equalsIgnoreCase(checkCode)){
//忽略大小写比较
//验证码正确
//判断用户名和密码是否一致
if ("zs".equals(username) && "123".equals(password)){//需要调用UserDao查询数据库
//登录成功
//存储信息,用户信息
session.setAttribute("user",username);
//重定向到success.jsp
response.sendRedirect(request.getContextPath()+"/success.jsp");
}else {
//登录失败
//存储提示信息到request
request.setAttribute("login_error","用户名或密码错误");
//转发到登录页面
request.getRequestDispatcher("/login.jsp").forward(request,response);
}
}else {
//验证码不一致
//存储提示信息到request
request.setAttribute("cc_error","验证码错误");
//转发到登录页面
request.getRequestDispatcher("/login.jsp").forward(request,response);
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
}
success.jsp：
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<h1><%= request.getSession().getAttribute("user")%>,欢迎您</h1>
</body>
</html>
细节处理
login.jsp
<div><%=request.getAttribute("cc_error")==null ? "" : request.getAttribute("cc_error")%></div>
<div><%=request.getAttribute("login_error")==null ? "" : request.getAttribute("login_error")%></div>
loginServlet：
@WebServlet("/loginServlet1")
public class LoginServlet1 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1、设置request编码
request.setCharacterEncoding("utf-8");
//2、获取参数
String username = request.getParameter("username");
String password = request.getParameter("password");
String checkCode = request.getParameter("checkCode");
//3、先获取生成的验证码
HttpSession session = request.getSession();
String checkCode_session = (String) session.getAttribute("checkCode_session");
//删除session中存储的验证码
session.removeAttribute("checkCode_session");
//判断验证码是否正确
if (checkCode_session != null && checkCode_session.equalsIgnoreCase(checkCode)){
//忽略大小写比较
//验证码正确
//判断用户名和密码是否一致
if ("zs".equals(username) && "123".equals(password)){//需要调用UserDao查询数据库
//登录成功
//存储信息,用户信息
session.setAttribute("user",username);
//重定向到success.jsp
response.sendRedirect(request.getContextPath()+"/success.jsp");
}else {
//登录失败
//存储提示信息到request
request.setAttribute("login_error","用户名或密码错误");
//转发到登录页面
request.getRequestDispatcher("/login.jsp").forward(request,response);
}
}else {
//验证码不一致
//存储提示信息到request
request.setAttribute("cc_error","验证码错误");
//转发到登录页面
request.getRequestDispatcher("/login.jsp").forward(request,response);
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
}
标签：String,checkCode,request,验证码,案例,细节,session,response From： https://www.cnblogs.com/xjw12345/p/16587358.html