下载处理Servlet工具类

原文：http://javatar.iteye.com/blog/72265




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>