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 [e-mail]
 *
 */
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>