下载处理Servlet工具类
转自 http://javatar.iteye.com/blog/72265
项目中用到下载功能，一般都使用超链接做下载,
但txt, html, csv等会被浏览器直接打开，
写了一个工具类处理这个问题。
很简单，放上来备忘。

package com.xxx.servlet;import java.io.File;import java.io.FileInputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import javax.servlet.ServletConfig;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** * 下载处理Servlet * @author liangfei0201@163.com * */public class DownloadServlet extends HttpServlet {private static final long serialVersionUID = 1L;private static final String DEFAULT_ENCODING = "UTF-8";private static final int DEFAULT_BUFFER_SIZE = 4096;private String encoding = DEFAULT_ENCODING;private int bufferSize = DEFAULT_BUFFER_SIZE;public void init(ServletConfig sc) throws ServletException {super.init(sc);String paramEncoding = sc.getInitParameter("encoding");if (paramEncoding != null && paramEncoding.trim().length() > 0) {encoding = paramEncoding.trim();}String paramSize = sc.getInitParameter("bufferSize");if (paramSize != null && paramSize.matches("^[0-9]+$")) {bufferSize = Integer.parseInt(paramSize);}}public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doPost(request, response);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {// 查找文件File file = new File(getServletContext().getRealPath("/") + request.getServletPath());if (! file.exists()) {response.sendError(HttpServletResponse.SC_NOT_FOUND);return ;}// 设置response, 这几行是关键response.setContentType("application/x-msdownload; charset=" + encoding);response.addHeader("content-type", "application/x-msdownload;");response.addHeader("content-disposition", "attachment; filename="+ response.encodeURL(file.getName()));response.setContentLength((int)file.length());// 输出InputStream in = new FileInputStream(file);OutputStream out = response.getOutputStream();try {int length = 0;byte[] buffer = new byte[bufferSize];while ((length = in.read(buffer)) != -1) {out.write(buffer, 0, length);}out.flush();} finally {if (in != null) {in.close();}}}}

<servlet><servlet-name>download</servlet-name><servlet-class>com.xxx.servlet.DownloadServlet</servlet-class><init-param><param-name>encoding</param-name><param-value>GBK</param-value></init-param><init-param><param-name>bufferSize</param-name><param-value>8192</param-value></init-param><load-on-startup>4</load-on-startup></servlet><servlet-mapping><servlet-name>download</servlet-name><url-pattern>/download/*</url-pattern></servlet-mapping><servlet-mapping><servlet-name>download</servlet-name><url-pattern>*.csv</url-pattern></servlet-mapping><servlet-mapping><servlet-name>download</servlet-name><url-pattern>*.txt</url-pattern></servlet-mapping>