FileServlet serving from FTP

Question

Hello!
I'm trying to create a bean that opens a PDF file from another FTP server. I have it open from a local path, but can't get it to open from a FTP host. Your help is appreciated.
Thanks in advance!
-Tony
package aiView;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.net.URLConnection;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import sun.net.ftp.FtpClient;
public class FileServlet extends HttpServlet {
    private FtpClient m_client;
    private String host = "";
    private String user = "";
    private String password = "";
    private String sDir = "";
    public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws IOException {
            m_client = new FtpClient(host);
            m_client.login(user, password);
            m_client.cd(sDir);
            m_client.binary();
        // Define base path somehow. You can define it as init-param of the servlet.
        String filePath = "/files";
        //Not working
        //String filePath = m_client.cd(sDir);
        // String filePath = getServletContext().getRealPath("/WEB-INF/files");
        // Get file name from request.
        String fileName = request.getParameter("name")+".pdf";
        // Check if file name is supplied to the request.
        if (fileName != null) {
            // Strip "../" and "..\" (avoid directory sniffing by hackers!).
            fileName = fileName.replaceAll("\\.+(\\\\|/)", "");
        } else {
            // Do your thing if the file name is not supplied to the request.
            // Throw an exception, or show default/warning page, or just ignore it.
            fileName = "filenotfound.pdf";
            response.sendRedirect("FileNotFoundError.jsp");
            return;
        // Prepare file object.
        File file = new File(filePath, fileName);
        // Check if file actually exists in filesystem.
        if (!file.exists()) {
            // Do your thing if the file appears to be non-existing.
            // Throw an exception, or show default/warning page, or just ignore it.
            //fileName = "filenotfound.pdf";
            response.sendRedirect("FileNotFoundError.jsp");
            return;
        // Get content type by filename.
        String contentType = URLConnection.guessContentTypeFromName(fileName);
        // If content type is unknown, then set the default value.
        // For all content types, see: http://www.w3schools.com/media/media_mimeref.asp
        if (contentType == null) {
            contentType = "application/pdf";
        // Prepare streams.
        BufferedInputStream input = null;
        BufferedOutputStream output = null;
        try {
            // Open file file.
            input = new BufferedInputStream(new FileInputStream(file));
            int contentLength = input.available();
            // Init servlet response.
            response.reset();
            response.setContentLength(contentLength);
            response.setContentType(contentType);
            response.setHeader(
                    "Content-disposition", "attachment; filename=\"" + fileName + "\"");
            output = new BufferedOutputStream(response.getOutputStream());
            // Write file contents to response.
            while (contentLength-- > 0) {
                output.write(input.read());
            // Finalize task.
            output.flush();
        } catch (IOException e) {
            // Something went wrong?
            e.printStackTrace();
        } finally {
            // Gently close streams.
            if (input != null) {
                try {
                    input.close();
                } catch (IOException e) {
                    e.printStackTrace();
                    // This is a serious error. Do more than just printing a trace.
            if (output != null) {
                try {
                    output.close();
                } catch (IOException e) {
                    e.printStackTrace();
                    // This is a serious error. Do more than just printing a trace.
}Edited by: ynotlim333 on Oct 19, 2007 1:17 AM
Edited by: ynotlim333 on Oct 19, 2007 1:19 AM

Answer 1

Well,Alright here is an example which i would try to implement.
Say,there is a table in dataBase which has below schema
TABLE fileTable{
    fileId --- PK -- Auto Generated;
    fileNameWithPath - varchar2(200);
    createdDate -- DATE;
}and their is a DTO Mapped to that table called FileDTOBean
public class FileDTOBean implements serializable{
   private String fileId = "";
   private String fileNameWithPath ="";
   private Date createdDate = null;
    /** Setters & getters for respective properties */
}Assuming that their is a DAO called FileServiceDAO which has method called getFileDTO(String fileId) which return an instance of FileDTOBean for a given fileId.
by executing a query like
"select fileId,fileNameWithPath,createdDate from fileTable where fileId = ?"and you would be using a dedicated Business Object for the same purpose.
FileServiceDelegateImpl.java:
=====================
package com.webapp.commons.delegate.impl;
import java.lang.management.ManagementFactory;
import java.lang.management.MemoryUsage;
import javax.servlet.http.HttpServletResponse;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;
import org.apache.commons.net.ftp.FTPClient;
  * @Author : RaHuL ShArMa
  * @Version : v1.0
/**The Delegate class could be used as a Bsuiness Object which provides services to give access to different stored in Database/local system/remote mapped network drive/FTP registered by specfic fileId from database*/
public class FileServiceDelegateImpl implements FileServiceDelegate{
          private static FileServiceDelegate fsd = null;
          private static FileServiceDAO fd = null;
          protected FileServiceDelegateImpl(){ 
               this.fd = FileServiceDAO.getCurrentInstance();
          public static synchronize FileServiceDelegate getCurrentInstance(){
                if(fsd == null)
                  fsd = new FileServiceDelegateImpl();
                return fsd;
          public void exportFTPFile(HttpServletResponse reponse,String ftpUri,String userName,String password,String fileId,boolean content)throws Exception{
                  InputStream fis = null;                 
                  BufferedInputStream input = null;
                  BufferedOutputStream output = null;       
                  int contentLength = 0;
                  FileDTOBean fdto = this.fd.getFileDto(fileId);
                  FTPClient ftpClient = null;
                  try{
                      String fileName = fdto.getFileName();
                      ftpClient = new FTPClient();
                      ftpClient.connect(ftpUri);
                      ftpClient.login(ftpUri);
                      fis =  ftpClient.retrieveFileStream(fileName);
                        // Getting the Mime-Type
                       String contentType = URLConnection.guessContentTypeFromStream(fis);          
                       if(contentType == null)
                            contentType = "application/octet-stream";
                        fis = new FileInputStream(fdto.getFileNameWidPath());
                        contentLength = fis.available(); 
                        // Trying to get the Generic Buffer Size w.r.t other factors
                        int readSize = this.getGenericSize(contentLength.available());                           
                        input = new BufferedInputStream(fis,readSize);
                        response.setContentType(contentType);
                        response.setContentLength(contentLength);
                        if(content) 
                           response.setHeader("Content-Disposition","attachment;filename=\"+fdto.getFileNameWidPath()+"\");
                        output = new BufferedOutputStream(response.getOutputStream(),readSize);
                        // output the streaming request
                        this.streamData(input,output,readSize);  
                   }catch(Exception e) {          
                        throw new Exception(e.getCause());
         /**The actual method which sends back the respective response to the supposed client by picking up the content from       
         the specified*/
         public void exportFile(HttpServletResponse reponse,String fileId,boolean content) throws Exception{
                  InputStream fis = null;                 
                  BufferedInputStream input = null;
                  BufferedOutputStream output = null;       
                  int contentLength = 0;
                  FileDTOBean fdto = this.fd.getFileDto(fileId);
                  URL url = null;
                  URLConnection urlConn = null;
                  try{
                        String filePath = fdto.getFileNameWidPath().trim();
                         if(!filename.startsWith("ftp://"))
                           fis = new FileInputStream(filname);
                         else{
                            url = new URL(filePath);
                            urlConn = url.openConnection(); 
                            fis = urlConn.getInputStream();
                        // Getting the Mime-Type
                       String contentType = URLConnection.guessContentTypeFromStream(fis);           
                       if(contentType == null)
                            contentType = "application/octet-stream";
                        contentLength = fis.available(); 
                        // Trying to get the Generic Buffer Size w.r.t other factors
                        int readSize = this.getGenericSize(contentLength.available());                           
                        input = new BufferedInputStream(fis,readSize);
                        response.setContentType(contentType);
                        response.setContentLength(contentLength);
                        if(content) 
                           response.setHeader("Content-Disposition","attachment;filename=\"+fdto.getFileNameWidPath()+"\");
                        output = new BufferedOutputStream(response.getOutputStream(),readSize);
                        // output the streaming request
                        this.streamData(input,output,readSize);  
                   }catch(Exception e) {          
                        throw new Exception(e.getCause());
          /**The actual method which sends back the respective response to the supposed client by picking up data from the database*/
          public void exportDBData(HttpServletResponse reponse,String fileId,boolean content) throws Exception{
                  FileInputStream fis = null;                 
                  BufferedInputStream input = null;
                  BufferedOutputStream output = null;       
                  int contentLength = 0;
                  FileDTOBean fdto = this.fd.getFileDto(fileId);
                  if(fdto == null)
                    return;
                  try{
                        // Getting the Mime-Type
                        String contentType = fdto.getContentType();
                        bis = new ByteArrayInputStream(fdto.getData());
                        contentLength = bis.available(); 
                        // Trying to get the Generic Buffer Size w.r.t other factors
                        int readSize = this.getGenericSize(contentLength);                           
                        input = new BufferedInputStream(bis,readSize);
                        response.setContentType(contentType);
                        response.setContentLength(contentLength);
                        if(content) 
                           response.setHeader("Content-Disposition","attachment;filename=\"+fileName+"\");
                        output = new BufferedOutputStream(response.getOutputStream(),readSize);
                        // output the streaming request
                        this.streamData(input,output,readSize);  
                   }catch(Exception e) {          
                        throw new Exception(e.getCause());
        /**Outputs given results as per decided constraits*/ 
        public void streamData(BufferedInputStream input,BufferedOutputStream output,int readSize)throws Exception{
             try{
                byte buffer[] = new byte[readSize]; 
                int nByteRead = 0;
                while((nByteRead = input.read(buffer)) != -1)
                    output.write(buffer);                         
                output.flush();
             }catch(Exception exp){
               exp.printStackTrace(); 
               throw new Exception(exp.getCause());
             }finally{
                  if(input != null){
                        try {
                            input.close();
                        } catch (Exception ie) {
                         ie.printStackTrace(); 
                            throws new Exception(ie.getCause());
                  if (output != null) {
                          try {
                             output.close();
                          } catch (Exception ie) {                     
                             throws new Exception(ie.getCause());         
                  input = null;
                  output = null;
     /**Deciding Just by applying Best memory usage constraint and one can change the logic accordingly
      * with respective other factors like network load and etc
     public synchronize int getGenericSize(int length){
             int bufferSize = 512;
             MemoryUsage heapUsage = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage(); 
             double usageFactor =    (heapUsage.getInit() - heapUsage.getUsed()) / heapUsage.getMax();            
             bufferSize = (int)(length * usageFactor);
             if(bufferSize <= 512)
                  bufferSize = 512;
             else if(buffer >= 4096) 
                  bufferSize = 4096;                 
             return bufferSize;                            
}and the code in your Servlet/JSP/Struts Action/Backing bean would be like.
public void processAction(HttpServletRequest request,HttpServletResponse.......)throws Exception{
    String fileId = request.getParameter("fid");
        lets assume file associated to fileId is "ftp://username:[email protected]/movie1Poster.jpg;type=i"
    if(fileId == null)
         throw new Exception("invalid fileid passed");
    //Assuming ServiceLocator returns instance FileServiceDelegateImpl
    FileServiceDelegate fsd = ServiceLocator.get(FileServiceDelegate.class);
     fsd.exportFile(response,fileId,false);
    /* or try using for secure FTP Access
         fsd.exportFTPFile(response,"ftp.foobar.com","username","password",fileId,false);
}all you wud do in you jsp is to access respective file with
http://HOST:appPort/webContextName/urlPatternAssociated?fid=<FileId>
eg:
<img src="FileServlet?fid=F13245" width="300" height="300" />
<img src="FileAction.do?fid=F13245" width="300" height="300" />Hope this might help :)
REGARDS,
RaHuL