servlet实现文件下载的实用类分享

时间：2021-05-26

复制代码 代码如下:
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;
}
}

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