下载处理Servlet工具类

原文：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
        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>