用户向代理服务器发送请求，代理服务器从后端服务器上获取文件，并返回给用户
web.xml:

<servlet> <servlet-name>BigFile</servlet-name> <servlet-class>cn.ac.dsp.servlet.BigFile</servlet-class> </servlet> <servlet-mapping> <servlet-name>BigFile</servlet-name> <url-pattern>*.ts</url-pattern> </servlet-mapping>

servlet:

package cn.ac.dsp.servlet; import java.io.IOException; import java.io.InputStream; import java.io.PrintWriter; import java.io.StringWriter; import javax.servlet.ServletException; import javax.servlet.ServletOutputStream; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.apache.http.HttpEntity; import org.apache.http.HttpResponse; import org.apache.http.client.ClientProtocolException; import org.apache.http.client.HttpClient; import org.apache.http.client.methods.HttpGet; import org.apache.http.impl.client.DefaultHttpClient; import org.apache.http.params.CoreConnectionPNames; import org.apache.http.params.CoreProtocolPNames; import org.apache.log4j.Logger; import cn.ac.dsp.common.Constant; import cn.ac.dsp.common.SystemParameters; /** * 给静态大文件提供服务的servlet */ public class BigFile extends HttpServlet { private static final long serialVersionUID = 1L; private static final Logger log = Logger.getLogger(BigFile.class); /** * @see HttpServlet#HttpServlet() */ public BigFile() { super(); // TODO Auto-generated constructor stub } /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { log.info("request for bigfile"); long startTime = System.nanoTime(); String requestUrl = request.getRequestURI(); //请求的文件名 String filename = requestUrl.substring(requestUrl.lastIndexOf("/")); HttpClient httpClient = new DefaultHttpClient(); httpClient.getParams().setParameter(CoreConnectionPNames.CONNECTION_TIMEOUT, Constant.HttpConnTimeOut); httpClient.getParams().setParameter(CoreConnectionPNames.SO_TIMEOUT, Constant.SoConnTimeOut); httpClient.getParams().setParameter(CoreProtocolPNames.HTTP_CONTENT_CHARSET, "UTF-8"); //后端服务器的IP String serverIP = "192.168.101.190"; //后端服务器的文件地址 StringBuilder backUrl = new StringBuilder(); backUrl.append("http://"); backUrl.append(serverIP); backUrl.append("/LBA/bigfile/"); backUrl.append(filename); HttpGet httpGet = new HttpGet(backUrl.toString()); httpGet.getParams().setParameter(CoreProtocolPNames.HTTP_CONTENT_CHARSET, "UTF-8"); log.info("distribute bigfile to " + backUrl.toString()); HttpResponse backResponse; try { backResponse = httpClient.execute(httpGet); // log.info(backResponse.getParams().getParameter(CoreProtocolPNames.HTTP_CONTENT_CHARSET)); HttpEntity httpEntity = backResponse.getEntity(); InputStream in = httpEntity.getContent(); // BufferedReader br = new BufferedReader(new InputStreamReader(httpEntity.getContent(), "UTF-8")); byte[] buf = new byte[4096]; int readLength; response.setCharacterEncoding("UTF-8"); ServletOutputStream out = response.getOutputStream(); while((readLength = in.read(buf)) != -1){ out.write(buf, 0, readLength); } in.close(); out.flush(); out.close(); } catch (ClientProtocolException e) { StringWriter sw = new StringWriter(); e.printStackTrace(new PrintWriter(sw)); log.error("ClientProtocolException when redirect bigfile. " + sw.toString()); } catch (IOException e) { StringWriter sw = new StringWriter(); e.printStackTrace(new PrintWriter(sw)); log.error("IOException when redirect bigfile. " + sw.toString()); } long endTime = System.nanoTime(); System.out.println("Response time: " + (endTime-startTime) + " ns"); } /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub } }

参考：一个文件下载的Servlet

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