所以我正在尝试创建一个登录servlet和一个注册servlet。但我似乎无法让它发挥作用。
我正在尝试建立一个在线商店，您必须先登录才能开始购物。我是网络应用程序开发的新手，所以请耐心等待。
这是我的代码：
登录：
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
try (PrintWriter out = response.getWriter())
{
String username = request.getParameter("userName");
String password = request.getParameter("password");
if(!username.equals("") && !password.equals(""))
{
for(Customer c : Data.getCustomers())
{
if(c.getUserName().equals(username) && c.getPasword().equals(password))
{
response.sendRedirect("Catalogue.html");
}
else
{
out.println("<!DOCTYPE html>");
out.println("<html>");
out.println("<head>");
out.println("<title>Invalid username or password</title>");
out.println("</head>");
out.println("<body>");
out.println("<h1>Ooops, something went wrong</h1>");
out.println("<h2><b>Wrong username or password.</b></h2>");
out.println("<h2>Please </h2>");
out.println("<form>"
+ "<input type=\"button\" value=\"Try again\""
+ "onClick=\"history.go(-1);"
+ "return true; \"></form>\"");
out.println("</body>");
out.println("</html>");
}
}
}
}
}
注册：
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
response.setContentType("text/html;charset=UTF-8");
String contextPath = request.getContextPath();
try (PrintWriter out = response.getWriter())
{
String firstname = request.getParameter("firstName");
String lastname = request.getParameter("lastName");
String username = request.getParameter("userName");
String password = request.getParameter("password");
String email = request.getParameter("email");
Customer c = new Customer(firstname, lastname, username, password, email);
if (request.getParameter("register") != null)
{
equals("") || username.equals("") || password.equals("") || email.equals(""))
{
out.println("<!DOCTYPE html>");
out.println("<html>");
out.println("<head>");
out.println("<title>Missing info</title>");
out.println("</head>");
out.println("<body>");
out.println("<h1>Ooops, something went wrong</h1>");
out.println("<h2><b>Please fill out all the fields to register.</b></h2>");
out.println("<form>"
+ "<input type=\"button\" value=\"Try again\""
+ "onClick=\"history.go(-1);return true; \"></form>");
out.println("</body>");
out.println("</html>");
} else
{
for (Customer customer : Data.getCustomers())
{
if (!username.equals(customer.getUserName()) && !password.equals(customer.getPasword()))
{
Data.addNewCustomer(firstname, lastname, username, password, email);
response.sendRedirect("Catalogue.html");
} else
{
out.println("<!DOCTYPE html>");
out.println("<html>");
out.println("<head>");
out.println("<title>Invalid username</title>");
out.println("</head>");
out.println("<body>");
out.println("<h1>Ooops, try again!</h1>");
out.println("<h2><b>Username already in use</b></h2>");
out.println("<h2>Please choose another one and</h2>");
out.println("<form>"
+ "<input type=\"button\" value=\"Try again\""
+ "onClick=\"history.go(-1);"
+ "return true; \"></form>");
out.println("</body>");
out.println("</html>");
}
}
}
}
}
}
HTML登录：
<html>
<head>
<title>Login</title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
</head>
<body>
<center><h1>Login</h1></center>
<form action="LoginServlet"
method="post">
<center><dl>
<dt><b>Please fill in your username and password to login: </b></dt>
<dd>Username:
<input type="text" name="userName"></dd>
<dd>Password:
<input type="password" name="password"></dd>
</dl></center>
<center>
<input type="submit" name="Login" value="Login">
<input type="submit" name="cancel" value="Cancel">
<br><br><br><br><br><br>
<b>If you don't have an account, please </b>
<a href='Registration.html'>register</a><b>.</b>
<br><br><br><img src="online-shop.jpg">
</form>
</center>
</body>
</html>
HTML注册：
<html>
<head>
<title>Register</title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
</head>
<body>
<center><h1>Register</h1></center>
<form method="post" action="RegistrationServlet">
<center><dl>
<dt><b>Please fill in the information below to register: </b></dt>
<dd>Firstname:
<input type="text" name="firstName"></dd>
<dd>Lastname:
<input type="text" name="lastName"></dd>
<dd>Username:
<input type="text" name="userName"></dd>
<dd>Password:
<input type="password" name="password"></dd>
<dd>E-mail:
<input type="text" name="email"></dd>
</dl></center>
<center>
<input type="submit" name="register" value="Submit" >
<input type="submit" name="register" value="Cancel" >
<br><br><br><img src="online-shop.jpg">
</form>
</center>
</body>
</html>
答案 0 :(得分：0)
您可以输入一些日志来至少检查
我认为您会发现，当Data.getCustomers()返回零客户时，您的每个servlet都会落在其processRequest()方法的底部，而无需发送重定向或在响应中打印任何内容＆＃ 39;输出流。 （如果任何表单字段留空，则注册servlet将发送其错误响应。）
此外，我认为当您有客户时，您会发现您的servlet以有趣的方式失败。他们都扫描提供的客户并为每个执行操作。你真正想要的是不同的：查找匹配给定用户名的现有客户（不考虑密码）;然后根据整体查找是否成功采取行动（包括检查密码）。也许不是检索和循环所有客户，而是添加方法Data.getCustomerByUsername(String)会更方便。如果你不能这样做，那么你可以在servlet类中添加一个类似的方法。
答案 1 :(得分：0)
once try like this
out.println("<form><a href=\"catalogue.html\">link</a></form></body></html>");