下载文件Utils

package com.cplatform.util.io;

import org.apache.commons.logging.*;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import com.cplatform.util.business.ParamComm;

public class DownFile extends HttpServlet {
    private static org.apache.commons.logging.Log log = LogFactory.getLog(DownFile.class);
    private static final String CONTENT_TYPE = "text/html; charset=GBK";

    //Initialize global variables
    public void init() throws ServletException { }

    //Process the HTTP Get request
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws
            ServletException, IOException {

        String fileName = request.getParameter("fileName"); //取得文件名,包括后辍名,可用File类的getName()方法获得
        String filePath = request.getParameter("filePath"); //取得文件路径,服务器端点的绝对路径，如：E:\jsp\。可用File类的getAbsolutePath()方法获得
        String saveName = request.getParameter("saveName"); //文件保存在本地的名字


        if (log.isDebugEnabled()) {
            log.debug("Acquire parameters:");
            log.debug("File Name: " + fileName);
            log.debug("File Path: " + filePath);
            log.debug("Save Name: " + saveName);
        }

        if (filePath!=null) {
            String temp;
            if (System.getProperty("file.separator").equals("/")) {
                temp = "/";
            } else if( filePath.lastIndexOf("/")>0 ){
                temp = "/";
            } else {
                temp = "\\";
            }
            if (!filePath.endsWith(temp)) {
                int position = filePath.lastIndexOf(temp);
                fileName = filePath.substring(position+1);
                filePath = filePath.substring(0,position+1);

                if (log.isDebugEnabled()) {
                    log.debug("Split file path parameter into file path (" +
                            filePath + ") and file name (" + fileName + ").");
                }
            }

            //~ 转码的问题已由filter统一处理
            // fileName = Chinese.fromPage(fileName);

            if (saveName==null || saveName.equals("")) {
                saveName = fileName;
            }

            //~ 转码的问题已由filter统一处理
            // saveName = Chinese.toDatabase(saveName);

            File file = new File(filePath+fileName);

            if (file.exists()) {
                response.reset();

                response.setContentType("*/*;charset=gbk"); //这里设成 */* 是因为可以让浏览器根据文件的后辍来自动选择一种文件类型
              
                response.setHeader("Content-disposition",
                        "attachment; filename=" + new String(saveName.getBytes("GBK"),"iso8859-1")); //在下载文件名里显示服务器端的文件名

                int size = (int) file.length();

                java.io.OutputStream os = response.getOutputStream();
                java.io.FileInputStream fis = new java.io.FileInputStream(filePath +
                        fileName);

                int len = 1024;

                if (size > (1024 * 1024) && size < (1024 * 1024 * 10)) {
                    len = 10240;
                }
                else if (size > (1024 * 1024 * 10)) {
                    len = 102400;
                }

                byte[] b = new byte[len];
                int i;

                try {
                    while ( (i = fis.read(b)) > 0) {
                        os.write(b, 0, i);
                    }

                } catch (IOException e) {
                    if (log.isInfoEnabled()) {
                        log.info("下载文件出错：" + e.getMessage());
                    }
                } finally {

                    try { fis.close(); } catch (IOException e) { }
                    try {
                        os.flush();
                        os.close();
                    } catch (IOException e) { }
                }

            } else {
                response.setContentType(CONTENT_TYPE);
                PrintWriter out = response.getWriter();
                out.println("<html>");
                out.println("<head><title>FileDown</title></head>");
                out.println("<body bgcolor=\"#ffffff\">");
                out.println(
                        "<script>alert('文件不存在，下载失败！');window.close();</script>");
                out.println("</body></html>");
            }
//        file.delete();//下载后删除源文件
        } else {
            response.setContentType(CONTENT_TYPE);
            PrintWriter out = response.getWriter();
            out.println("<html>");
            out.println("<head><title>FileDown</title></head>");
            out.println("<body bgcolor=\"#ffffff\">");
            out.println(
                    "<script>alert('文件参数不全，下载失败！');window.close();</script>");
            out.println("</body></html>");
        }

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws
            ServletException, IOException {
        doGet(request, response);
    }

    //Clean up resources
    public void destroy() {}

}