Servlet 在 doPost 方法中获取 GET 和 POST 的参数

Question

My problem is when I'm trying to access a POST Variable with request.getParameter("name") , it works perfectly. But in some conditions, when a POST request arrives at my application, I also need to get GET Parameter from the Query String.

As far as I can see, with getParameter , you can only access current request's parameters, but, as in my condition, as I said, I also need to fetch GET Parameters inside doPost method.

Is there a way to fetch GET Parameters without parsing the Query String?

Answer 1

If you have parameters with the same name in the query string and in the posted form data, use getParameterValues() .

Example:-

String fromQuery = request.getParameterValues("name")[0];
String fromForm = request.getParameterValues("name")[1];

Answer 2

The getParameter() method can return (if possible) both GET and POST parameters as it works transparently between GET and POST . You don't need to do any explicit work to get the GET parameters. you can use getParameter for both query parameters and POST parameters.

But should you do it? - It's considered a poor design practice especially if there is sensitive information to be sent.

Take a look at this answer:

• HTTP POST with URL query parameters -- good idea or not?

Answer 3

I think you have a confusion here. You can retrieve all the request parameters (in both GET or POST or others) using the same getParameter(..) depending upon the type of request. If it's a GET request, you can retrieve all the GET parameters.

If it's a POST request, you can retrieve all the POST parameters. You get parameters using getParameter(...) . And you make one request at a time. If you make a POST request in html or JSP file, you use doPost method receive all the parameters. At this point, there is nothing in GET request. Then after that, you make a GET request, you retrieve all the parameters in doGet method. At this moment, there is nothing in POST. Remember, HTTP requests are stateless.

Answer 4

To complete @Rei answer check out this code :

your form

<form action="?nom=nom1">
<input type="hidden" name="nom" value="nm2"/>

your doPost

System.out.println(request.getParameter("nom"));
        
String s = "";
for(String ss : request.getParameterValues("nom")) {
    s += "|" + ss;
}
System.out.println(s);
System.out.println(request.getParameterMap().get("nom"));

what will be printed

nom1
|nom1|nm2
[Ljava.lang.String;@c7068db

ps : thanks to Julien for the code and testing