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Java Servlet 下载

转载 作者：行者123 更新时间：2023-12-02 08:20:39 27 4
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我编写了一个servlet，用于检查http header ，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>

加载的 URL 为 http://localhost:8080/HttpHeader/ 。我尝试调试但从未发现任何奇怪的地方。请帮我。

谢谢。

最佳答案

改变

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

小建议:请记住 servlet 的无状态性质 - servlet 是单例。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。这是因为您有许多字段应该针对每个客户端，实际上这些字段可能会被错误地修改，因为同时调用 Servlet:对于一个客户端，它会工作，对于多个客户端，您的 servlet 可能会被破坏 -如果您有多个客户，请更改您的实现方式。

关于Java Servlet 下载，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/5528699/

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