DownloadUtil

//只需要将文件写到servlet输出流中就可以了
package util;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletResponse;

public class DownloadUtil {

    private HttpServlet servlet;

    private HttpServletResponse response;

    public DownloadUtil(HttpServlet servlet, HttpServletResponse response) {
        this.servlet = servlet;
        this.response = response;
    }

    /**
     * this method will produce a query window to query
     * where this file should be stored
     */
    public void produceQuiryWindow() {
        String mainpath = servlet.getServletContext().getRealPath("/");

        String srcpath = mainpath + "\\WEB-INF\\src\\sourceFile\\s.pdf";

        System.out.println(srcpath);

        response.reset();
        //set MIME type, tell the browser how to process it
        response.setContentType("application/pdf");
        // excel file will use this content type
        // response.setContentType("application/ms-excel");
        // MIME type for MSWord doc
        // response.setContentType( "application/msword" );
        // MIME type for csv
        // response.setContentType("application/x-csv");
       
        // set file type information, and how to open it
        response.setHeader("Content-Disposition",
                "attachment;filename=news.pdf");
        InputStream is = null;
        OutputStream os = null;
        try {
            is = new FileInputStream(srcpath);

            os = response.getOutputStream();

            int len = 0;
            byte[] b = new byte[1024];

            while ((len = is.read(b)) > 0) {
                os.write(b, 0, len);
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }finally{
            try{
                os.close();
                is.close();
            }catch(IOException e){
                e.printStackTrace();
            }
           
        }

    }

    /**
     * no query window copy the file from the sourceFile folder to the
     * targetFile foler
     */
    public void copytonewfolder() {
        String mainpath = servlet.getServletContext().getRealPath("/");

        String srcpath = mainpath + "\\WEB-INF\\src\\sourceFile\\s.pdf";

        System.out.println(srcpath);
       
        InputStream is = null;
        OutputStream os2 = null;
        try {
            is = new FileInputStream(srcpath);

            String targetPath = mainpath
                    + "\\WEB-INF\\src\\targetFile\\newS.pdf";
            os2 = new FileOutputStream(targetPath);

            int len = 0;
            byte[] b = new byte[1024];

            while ((len = is.read(b)) > 0) {
                os2.write(b);
            }

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }finally{
            try{
                os2.close();
                is.close();
            }catch(IOException e){
                e.printStackTrace();
            }

        }

    }

}