Why the request.getInputStream() return nothing?

Question

I use this code to display the request content :
<%
   java.util.Enumeration headerNames = request.getHeaderNames();
   while(headerNames.hasMoreElements()) {
     out.println(request.getHeader((String)headerNames.nextElement()) + "<br/>");
   int contentLength = request.getContentLength();
   byte[] buffer = new byte[contentLength];
   java.io.InputStream inputStream = request.getInputStream();
   inputStream.read(buffer);
   String content = new String(buffer);
   out.println(content.length());
   out.println(content);
%>It displayed:
image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, application/vnd.ms-powerpoint, application/vnd.ms-excel, application/msword, */*
http://127.0.0.1:8080/test/
zh-cn
application/x-www-form-urlencoded
gzip, deflate
Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0)
127.0.0.1:8080
20
Keep-Alive
no-cache
JSESSIONID=51895EB733CE767A5176BD62111221EA
20
I use the "out.println(content.length());" to check the length of the content,it displayed 20.
But when i try displaying the content,it display nothing. Why?
I think that javax.servlet.http.HttpServletRequest is an object that warp the HTTP1.1 request message (including the header and the message entity).
So i want to display it on the JSP page.
In some book, it told me this will display message like:
-----------------------------7d137a26e18
Content-Disposition: form-data; name="name"
123
-----------------------------7d137a26e18
Content-Disposition: form-data; name="introduce"
I am...
I am..
-----------------------------7d137a26e18
Content-Disposition: form-data; name="file3"; filename="C:\Autoexec.bat"
Content-Type: application/octet-stream
But why it dosn't display anything?

Answer 1

Why the "content" length is 20 but it didn't display anythingMost probably the JSPServlet has already read the parameters from the input stream for itself.
Try it from a servlet:
package servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class InputStreamTest extends HttpServlet {
    protected void doGet(HttpServletRequest arg0, HttpServletResponse arg1) throws ServletException, IOException {
        doPost(arg0, arg1);
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        PrintWriter out = response.getWriter();
        java.util.Enumeration headerNames = request.getHeaderNames();
        while (headerNames.hasMoreElements()) {
            out.println(request.getHeader((String) headerNames.nextElement()) + "<br/>");
        int contentLength = request.getContentLength();
        out.println("<hr>");
        out.println("Content length = " +contentLength);
        if (contentLength > 0) {
            byte[] buffer = new byte[contentLength];
            java.io.InputStream inputStream = request.getInputStream();
            inputStream.read(buffer);
            String content = new String(buffer);
            out.println(content.length());
            out.println(content);
}Cheers,
evnafets