Order of request.getParameterNames()

问题

How do I get all the parameterNames in an HTML form in the same sequence as they are in the form.

i.e if the form contains .... FirstName, LastName, MiddleName and Age . the output should appear in the same sequence

I have tried using the following but this shifts the order of the output:

Enumeration paramNames = request.getParameterNames();
while(paramNames.hasMoreElements())
{
      String paramName =
(String)paramNames.nextElement();
      out.print(paramName);
}

回答1:

I don't think there's nothing in the HTTP spec that forces browsers to send parameters in the order they appear in the form. You can work it around by prefixing a number to the name of the parameter like:

FirstName --> 0_FirstName
LastName --> 1_LastName
....

After that you could basically order the elements by the prefix. It is an ugly solution but it is the only way to do it. Something like ...

//Assuming you fill listOfParameters with all the parameters.
    Collections.sort(listOfParameters, new Comparator<String>() {
       int compare(String a,String b) {
            return Integer.getInt(a.substring(0,a.indexOf("_"))) - Integer.getInt(a.substring(0,b.indexOf("_")))
       }
    }
    );
    for (String param : listOfParameters) {
        //traverse in order of the prefix
    }

By the way - does it really matters the order in which you receive the parameters ?

回答2:

None of the answers here really did answer my question. A HttpServletRequest saves all it's parameters in a HashMap, and a HashMap has NO ORDER. So, I saved the order of the parameters in an ordered ArrayList and saved it in a HttpSession, so I could retrieve the order of the parameters by querying the ArrayList (that was saved in the session) and achieve what I wanted!

回答3:

request.getParameterNames () uses HashMap internally to store the name value pairs of form fields. There is no order maintained in this. if you need this in order then , some sort of naming convention for form parameters to control the order of retrieval.

SortedSet temp = new SortedSet();
Enumeration enumeration = request.getParameterNames();
while (enumeration.hasMoreElements()) 
{
        temp.add((String)enumeration.nextElement());
}

回答4:

Updated: U can user sorted set for that. note that u must have all the parameter with different name. (in this case it is most likely) Write any pref.ix as your parameter name for ex.

    <input type="text" name="1step">
    <input type="text" name="2step">

and so on...

then in java code you can write

    SortedSet ss = new TreeSet();
     Enumeration<String> enm=request.getParameterNames();
    while(enm.hasMoreElements())
    {
        String pname = enm.nextElement();
    }
            Iterator i=ss.iterator();
            while(i.hasNext())
    {
        String param=(String)i.next();
        String value=request.getParameter(param);
    }

回答5:

HTML or Jsp Page

<input type="text" name="1UserName">
<input type="text" name="2Password">
<input type="text" name="3MobileNo">
<input type="text" name="4country">

and so on...

then in java code

SortedSet ss = new TreeSet();
Enumeration<String> enm=request.getParameterNames();
while(enm.hasMoreElements()){
    String pname = enm.nextElement();
    ss.add(pname);
}
Iterator i=ss.iterator();
while(i.hasNext()) {
    String param=(String)i.next();
    String value=request.getParameter(param);
}

来源：https://stackoverflow.com/questions/4733373/order-of-request-getparameternames

标签

java

servlets

request