Reading headers is very straightforward; just call the
getHeader method of the HttpServletRequest, which returns a String if the header was supplied on this request, null otherwise. However, there are a couple of headers that are so commonly used that they have special access methods. The getCookies method returns the contents of the Cookie header, parsed and stored in an array of Cookie objects. See the separate section of this tutorial on cookies. The getAuthType and getRemoteUser methods break the Authorization header into its component pieces. The getDateHeader and getIntHeader methods read the specified header and then convert them to Date and int values, respectively. Rather than looking up one particular header, you can use the
getHeaderNames to get an Enumeration of all header names received on this particular request. Finally, in addition to looking up the request headers, you can get information on the main request line itself. The
getMethod method returns the main request method (normally GET or POST, but things like HEAD, PUT, and DELETE are possible). The getRequestURI method returns the URI (the part of the URL that came after the host and port, but before the form data). The getRequestProtocol returns the third part of the request line, which is generally "HTTP/1.0" or "HTTP/1.1". ShowRequestHeaders.java
package hall;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.*;
public class ShowRequestHeaders extends HttpServlet {
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
String title = "Servlet Example: Showing Request Headers";
out.println(ServletUtilities.headWithTitle(title) +
"<BODY BGCOLOR=\"#FDF5E6\">\n" +
"<H1 ALIGN=CENTER>" + title + "</H1>\n" +
"<B>Request Method: </B>" +
request.getMethod() + "<BR>\n" +
"<B>Request URI: </B>" +
request.getRequestURI() + "<BR>\n" +
"<B>Request Protocol: </B>" +
request.getProtocol() + "<BR><BR>\n" +
"<TABLE BORDER=1 ALIGN=CENTER>\n" +
"<TR BGCOLOR=\"#FFAD00\">\n" +
"<TH>Header Name<TH>Header Value");
Enumeration headerNames = request.getHeaderNames();
while(headerNames.hasMoreElements()) {
String headerName = (String)headerNames.nextElement();
out.println("<TR><TD>" + headerName);
out.println(" <TD>" + request.getHeader(headerName));
}
out.println("</TABLE>\n</BODY></HTML>");
}
public void doPost(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}Output
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