I have wrote a servlet which is used to check http header but I don’t know why when the page is loaded, it starts downloading automatically.
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
// ===================================================
package HttpHeader;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;
import java.util.zip.GZIPOutputStream;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpSession;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
// ===================================================
public class HeaderServlet extends HttpServlet {
private static final long serialVersionUID = 1234L;
private ServletConfig m_ServletConfig;
private ServletContext m_ServletContext;
private boolean m_HasCompress;
private int m_ContentLength;
private Cookie[] m_Cookies;
private String m_AuthenticationType;
private String m_RemoteUser;
private String m_ContentType;
private String m_Method;
private String m_RequestURI;
private String m_Date;
private String m_QueryStr;
private String m_Protocol;
private Enumeration<String> m_HeaderNames;
private HttpSession m_Session;
//======================================================
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
try {
/* TODO output your page here
out.println("<html>");
out.println("<head>");
out.println("<title>Servlet HeaderServlet</title>");
out.println("</head>");
out.println("<body>");
out.println("<h1>Servlet HeaderServlet at " + request.getContextPath () + "</h1>");
out.println("</body>");
out.println("</html>");
*/
} finally {
out.close();
}
}
@Override
protected void doHead(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String encoding = request.getHeader("Accept-Header");
if(encoding != null && encoding.indexOf("gzip") != -1)
{
m_HasCompress = true;
}
else
{
m_HasCompress = false;
}
m_ContentLength = request.getContentLength();
m_Cookies = request.getCookies();
// Basic, Form, Client certification authentication,
// digest authentication
// Same with CGI AUTH_TYPE
m_AuthenticationType = request.getAuthType();
m_RemoteUser = request.getRemoteUser();
m_ContentType = request.getContentType();
// Return get, post, delete, put
// Same with CGI REQUEST_METHOD
m_Method = request.getMethod();
m_RequestURI = request.getRequestURI();
// Same with CGI QUERY_STRING
m_QueryStr = request.getQueryString();
// Same with CGI SERVER_PROTOCOL
m_Protocol = request.getProtocol();
m_HeaderNames = request.getHeaderNames();
m_Session = request.getSession(true);
/* Accept
* = MIME type
*
* Accept-Charset
* = UTF-8
*
* Accpet-Encoding
* = Compression - gzip
*
* Accept-Language
* = us
*
* Authorization
* = Login
*
* Content-Length
* = Post request
*
* Cookie
* Host
*
* If-Modified-since
* = Implements getLastModified
* = Get request
*
* If-Unmodified-since
* = Post request
*
* Referer
* = Request origin
*
* User Agent
* = Mozilla
*/
}
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
PrintWriter out = null;
try {
doHead(request, response);
response.setContentType("/text/html;charset=UTF-8");
response.setBufferSize(8192);
if(m_HasCompress)
{
out = new PrintWriter(new GZIPOutputStream(response.getOutputStream()));
response.setHeader("Content-Encoding", "gzip");
}
else
{
out = response.getWriter();
}
if (out != null) {
String docType = "<!DOCTYPE HTML PUBLIC "
+ "\"-//W3C//DTD HTML 4.01 "
+ "Transitional//EN\">\n\n";
out.println(docType
+ "<html> <head> "
+ " <title> Http Request Header<title>"
+ "Requst Method : " + m_Method + "<p></p>"
+ "Request URI : " + m_RequestURI + "<p></p>"
+ "Request Protocol : " + m_Protocol + "<p></p><p></p>"
+ "<table BORDER=1 ALIGN =\"CENTER\">"
+ "<TH>Header Name <TH>Header Value");
String headerName = new String();
String headerValue = new String();
while(m_HeaderNames.hasMoreElements())
{
headerName = m_HeaderNames.nextElement();
if(headerName != null)
{
headerValue = request.getHeader(headerName);
out.println("<TR><TD>" + headerName);
out.println(" <TD>" + headerValue);
}
}
out.println("</table>" + "<p></p>"
+ "</head></html>");
out.close();
}
}
finally {
out.close();
}
/*
* HTTP 1.1 request headers
* Request Header set by browser
* Get Reqeust - Query Data same line
* POst Request - Query Data next line
*
*/
//processRequest(request, response);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// processRequest(request, response);
}
@Override
public String getServletInfo() {
return "Short description";
}// </editor-fold>
}
// ===================================================
<%@page contentType="text/html" pageEncoding="UTF-8"%>
<%@taglib prefix="f" uri="http://java.sun.com/jsf/core"%>
<%@taglib prefix="h" uri="http://java.sun.com/jsf/html"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<%--
This file is an entry point for JavaServer Faces application.
--%>
<f:view>
<html>
<head>
<meta http-equiv="REFRESH" content="0; url=HeaderServlet; charset=UTF-8"/>
<title>JSP Page</title>
</head>
<body>
<h1><h:outputText value="JavaServer Faces"/></h1>
</body>
</html>
</f:view>
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
<context-param>
<param-name>javax.faces.PROJECT_STAGE</param-name>
<param-value>Development</param-value>
</context-param>
<servlet>
<servlet-name>Faces Servlet</servlet-name>
<servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet>
<servlet-name>HeaderServlet</servlet-name>
<servlet-class>HttpHeader.HeaderServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Faces Servlet</servlet-name>
<url-pattern>/faces/*</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>HeaderServlet</servlet-name>
<url-pattern>/HeaderServlet</url-pattern>
</servlet-mapping>
<session-config>
<session-timeout>
30
</session-timeout>
</session-config>
<welcome-file-list>
<welcome-file>faces/welcomeJSF.jsp</welcome-file>
</welcome-file-list>
</web-app>
The URL loaded is http://localhost:8080/HttpHeader/.
I try to debug but never found anything weird.
Please help me.
Thanks.
change
Small adivce:
Remember about stateless nature of servlet – servlets are singletons. It’s mean that, in your case, if 2 clients call your servlet, result’ll be unpredictable. This is because you’ve many fields which should be specific per client, actually those fields could be modify incorrectly, because of concurrently call to the Servlet: For one client it’ll be work, For more than one your servlet can be broken – change your implementatio if you have more than one client.