Java Servlet下载

Question

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. 我写了一个用于检查http标头的servlet，但我不知道为什么当页面加载时，它会自动开始下载。

    /*
 * 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/ . 加载的URL是http：// localhost：8080 / HttpHeader / 。 I try to debug but never found anything weird. 我尝试调试但从未发现任何奇怪的东西。 Please help me. 请帮我。

Thanks. 谢谢。

Answer 1

change 更改

response.setContentType("text/html;charset=UTF-8");
//instead of: 
//response.setContentType("/text/html;charset=UTF-8");

Small adivce: Remember about stateless nature of servlet - servlets are singletons. 小adivce：记住servlet的无状态特性 - servlet是单例。 It's mean that, in your case, if 2 clients call your servlet, result'll be unpredictable. 这意味着，在您的情况下，如果2个客户端调用您的servlet，结果将是不可预测的。 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. 这是因为你有许多字段应该是每个客户端特定的，实际上这些字段可能被错误地修改，因为同时调用Servlet：对于一个客户端它将工作，对于多个servlet可以被打破 - 如果您有多个客户，请更改您的实施。

Answer 2

oRemove these lines from your code (or comment them) o从代码中删除这些行（或注释它们）

response.setContentType("/text/html;charset=UTF-8");
response.setBufferSize(8192);

response.setHeader("Content-Encoding", "gzip");

this will stop the page getting downloaded 这将阻止页面下载

and you will get an out put containing the details of the request.. 并且您将获得包含请求详细信息的输出。

Hope this helps... 希望这可以帮助...

Java Servlet下载

问题描述

2 个解决方案

解决方案1
2 已采纳 2011-04-03 10:25:24

解决方案2
0 2011-04-03 09:36:22

Java Servlet下载

问题描述

2 个解决方案

解决方案1 2 已采纳 2011-04-03 10:25:24

解决方案2 0 2011-04-03 09:36:22

解决方案1
2 已采纳 2011-04-03 10:25:24

解决方案2
0 2011-04-03 09:36:22