jsp实现Servlet文件下载的方法

前端技术 2023/09/03 JSP

本文实例讲述了jsp实现Servlet文件下载的方法。分享给大家供大家参考。具体如下：

package com;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.URLEncoder;
import java.util.Date;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import com.sun.xml.internal.messaging.saaj.packaging.mime.internet.MimeUtility;
/**
 * 文件下载类。为了防止客户端浏览器直接打开目标文件（例如在装了MS Office套件的Windows中的IE浏览器可能就会直接在IE浏览器中打开你想下载的doc或者xls文件），在响应头里加入强制下载的MIME类型。
 */
public class DownloadFile extends HttpServlet {
  private static final Log log = LogFactory.getLog(DownloadFile.class);
  public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException {
    long timeStart = 0;
    if(log.isDebugEnabled()){
      timeStart=System.currentTimeMillis();
    }
    response.setContentType(\"application/x-download charset=UTF-8\");
    java.io.FileInputStream fis = null;
    String filepath = request.getRealPath(\"\");
    javax.servlet.ServletOutputStream sos = null;
    // System.out.println(\"DownloadFile filename:\" + filename);
    try {
      if(request.getParameter(\"filename\")==null
          ||request.getParameter(\"showName\")==null){
        return;
      }
      String filename = request.getParameter(\"filename\");
      String showName = request.getParameter(\"showName\");
      request.setCharacterEncoding(\"UTF-8\");
      response.setCharacterEncoding(\"UTF-8\");
      java.io.File file = new java.io.File(filepath + filename);
      if (!file.exists()) {
        log.error(file.getAbsolutePath() + \" 文件不存在!\");
        return;
      }
      // 读取文件流
      fis = new java.io.FileInputStream(file);
      // 设置下载保存的文件名
      sos = response.getOutputStream();
      showName += filename.substring(filename.lastIndexOf(\".\"));
      String contentDisposition = \"\", browser = getBrowser(request);
      if (\"IE\".equals(browser)) {
        contentDisposition = \"attachment; filename=\" + URLEncoder.encode(showName, \"UTF-8\").replace(\"+\", \"%20\");
      } else if (\"CH\".equals(browser)) {
        contentDisposition = \"attachment; filename=\" + MimeUtility.encodeText(showName, \"UTF8\", \"B\");
      } else if (\"SF\".equals(browser)) {
        contentDisposition = \"attachment; filename=\" + new String(showName.getBytes(\"UTF-8\"), \"ISO8859-1\");
      } else {
        contentDisposition = \"attachment; filename*=UTF-8\'\'\" + URLEncoder.encode(showName, \"UTF-8\").replace(\"+\", \"%20\");
      }
      response.setHeader(\"Content-Disposition\", contentDisposition);
      int byteCount = 0; 
      if (fis != null) {
        byte[] buff = new byte[1024];
        int bytesRead;
        while(-1 != (bytesRead = fis.read(buff, 0, buff.length))) {
          sos.write(buff, 0, bytesRead);
          sos.flush();
          byteCount += bytesRead;
        } 
      }
      sos.flush();
      if(log.isDebugEnabled()){
        log.debug(\"文件下载完成，文件大小：\"+ byteCount +\"，总共用时:\"+ (new Date().getTime() - timeStart) +\"毫秒。\");
      }
    } catch(IOException ioe) {
      ioe.printStackTrace();
    } finally {
      try {
        if(fis!=null){
          fis.close();
        }
      } catch (IOException e) {
      } finally {
        try {
          if(sos!=null){
            sos.close();
          }
        } catch (IOException e) {
        }
      }
    }
  }
  public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    response.setContentType(\"text/html\");
    PrintWriter out = response.getWriter();
    out.println(\"<!DOCTYPE html PUBLIC \\\"-//W3C//DTD XHTML 1.0 Transitional//EN\\\" \\\"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd\\\">\");
    out.println(\"<html>\");
    out.println(\" <head>\");
    out.println(\"  <title>文件下载</title>\");
    out.println(\"  <meta http-equiv=\\\"Content-Type\\\" content=\\\"text/html; charset=UTF-8\\\" />\");
    out.println(\" </head>\");
    out.println(\" <body>\");
    out.print(\" This is \");
    out.print(this.getClass().getName());
    out.println(\", using the POST method\");
    out.println(\" </body>\");
    out.println(\"</html>\");
    out.flush();
    out.close();
  }
  private String getBrowser(HttpServletRequest request) {
    String userAgent = request.getHeader(\"USER-AGENT\").toLowerCase();
    if (userAgent != null) {
      if (userAgent.indexOf(\"msie\") >= 0) {
        return \"IE\";
      } else if (userAgent.indexOf(\"mozilla\") >= 0) {
        return \"FF\";
      } else if (userAgent.indexOf(\"applewebkit\") >= 0) {
        return \"CH\";
      } else if (userAgent.indexOf(\"safari\") >= 0) {
        return \"SF\";
      } else if (userAgent.indexOf(\"opera\") >= 0) {
        return \"OP\";
      }
    }
    return null;
  }
}

希望本文所述对大家的JSP程序设计有所帮助。

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