无法读取servlet中的表单字段 [英] Unable to read form field in servlet

问题描述

嘿，我对servlet环境很陌生。在这里，我试图将表单发布到我的servlet，如下所示：

Hey I am quite new to servlet environment. Here I am trying to post a form to my servlet with something like this:

<form action="OnlineExam?q=saveQuestion" method="post" enctype="multipart/form-data">
        <fieldset>
        <legend>Question</legend>
        <textarea class="questionArea" id="question" name="question">Enter Question.</textarea>
        <br class="clearFormatting"/>
        Attach File<input type="file" name="file" />

        <input class="optionsInput" value="Option A" name="A" onfocus = "clearValues('A')" onblur = "setValues('A')"/>
        <br class="clearFormatting"/>

        <input class="optionsInput" value="Option B" name="B" onfocus = "clearValues('B')" onblur = "setValues('B')"/>
        <br class="clearFormatting"/>

        <input class="optionsInput" value="Option C" name="C" onfocus = "clearValues('C')" onblur = "setValues('C')"/>
        <br class="clearFormatting"/>

        <input class="optionsInput" value="Option D" name="D" onfocus = "clearValues('D')" onblur = "setValues('D')"/>
        <br/>

        <input type="submit" value="Save" />
        <input type="reset" value="Cancel" />
        <button style="display: none" onclick="return deleteQuestion()" >Delete</button>
        </fieldset>
        </form>

servlet是这样的：

And the servlet is something like this:

protected void doGet(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
if(request.getParameter("q").equals("saveQuestion")){           
                saveQuestion(request);
            }
}

protected void doPost(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

public void saveQuestion(HttpServletRequest request){
                 Enumeration enum = request.getParameterNames();
                 while (enum.hasMoreElements()) {
                   String pName = (String) enum.nextElement();
                   String[] pValues = request.getParameterValues(pName);
                   System.out.print("<b>"+pName + "</b>: ");
                   for (int i=0;i<pValues.length;i++) {
                      System.out.print(pValues[i]);
                   }
                   out.print("<br>");
                 }
}

但它只打印q参数而不打印其他参数表单字段。

But it is printing only the q parameter not the other form fields.

我还试图用 request.getParameter（question）来获取它们但这是也不行。所以我哪里出错了。实际上我来自PHP背景，最近开始用java编写，所以请帮忙。

I also tried to get them with the request.getParameter("question") but this was also not working. So where i am going wrong. actually i am from PHP background and recently started coding in java so please help.

提前致谢

推荐答案

当您使用 enctype =multipart / form-data时，您无法像通常那样访问请求参数[即的request.getParameter（ 问题）]。您必须使用 MultipartRequest 对象。

When you use enctype="multipart/form-data" you can not access request parameter as you normally do[that is request.getParameter("question")]. You have to use MultipartRequest object.

您还可以在POST中提交表单，然后在servlet中将其重定向到doGet。为什么这样？为什么不直接在表单提交中使用GET作为方法。

And also you submit form in POST and then in servlet you redirect it to doGet. Why so? Why don't directly use GET as a method in form submit.

演示使用MultipartRequest：

Demo to use MultipartRequest:

String ph="images\\";
MultipartRequest req=new MultipartRequest(request, ph);
String question=req.getParameter("question");
System.out.println("Question: "+question);

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