为什么我的servlet request.getParameter返回null
[英]Why does my servlet request.getParameter return null
问题描述
I am trying to run following code 
我正在尝试运行以下代码
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
response.setContentType("text/html");
PrintWriter out = response.getWriter();
int i = 1, j = 1;
String title = "Web Movie";
out.println("<html>");
out.println("<head>");
out.println("<title>" + title + "</title>");
out.println("</head>");
out.println("<body");
out.println("<h1>Seat Information</h1>");
out.println("<center>");
out.println("<form method='get' action='Theatre'> ");
out.println("<table border=1 cellpadding=0 cellspacing=0 width=70%>");
out.println("<tr>");
out.println("<th>Row</th>");
out.println("<th colspan = 8>Seat</th>");
out.println("</tr>");
//Table hien thi thong tin ghe
for(i = 0; i < 8; i++) {
out.println("<tr>");
out.println("<td style='text-align:center;'>" + (char)(i + 'A') + "</td>");
for(j = 1; j < 9; j++) {
out.println("<td id = " + (char)(i + 'A') + j + " onclick='showResult(this.id);' style='text-align:center;'>" + j + "</td>");
}
out.println("</tr>");
}
out.println("</table>");
out.println("</form>");
out.println("<p>Vi tri ngoi:</p>");
out.println("<input id = 'text2' name='Seat'><br>");
out.println("<script>");
out.println("function showResult(clicked_id){");
out.println("document.getElementById('text2').value = clicked_id");
out.println("}");
out.println("</script>");
out.println("</body>");
out.println("</html>");
out.println(request.getParameter("Seat"));
}`
but getParameter always null. 但是getParameter始终为null。
2 个解决方案
解决方案1
0 2018-05-16 10:16:03
The only reason request.getParameter("Seat") will return you null is: The parameter "Seat" is not a part of request. request.getParameter("Seat")返回null的唯一原因是：参数"Seat"不是请求的一部分。 Since it a GET request it should be a part of query string. 由于它是GET请求，因此应成为查询字符串的一部分。 Also the parmeter "Seat" is case sensitive. 参数“ Seat”也区分大小写。
解决方案2
0 2018-05-16 10:21:46
If your servlet URL is http://server.com/context/myservlet , then you will need to add the " Seat " parameter to it. 如果您的servlet URL是http://server.com/context/myservlet ，那么您将需要在其中添加“ Seat ”参数。 Here is how the toy URL should look like after adding the parameter: 添加参数后，玩具URL如下所示：
http://server.com/context/myservlet?Seat=foo http://server.com/context/myservlet?Seat=foo
So you have to add the expression Seat=foo , were Seat is the parameter name and foo it's value. 因此，您必须添加表达式Seat=foo ，其中Seat是参数名称，而foo是值。
If you want to know more abot URL's check this page here: 如果您想了解更多的bott URL，请在这里检查此页面：
https://developer.mozilla.org/en-US/docs/Learn/Common_questions/What_is_a_URL https://developer.mozilla.org/zh-CN/docs/Learn/Common_questions/What_is_a_URL
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