How to upload files on a web page

How to upload files on a web page

Public class uploadservlet extends httpservlet { // Default maximum allowable file size is 100 K Static final int max_size = 102400; // Instance variables to store root and success message String rootpath, successmessage; /** * Init method is called when servlet is initialized. */ Public void Init (servletconfig config) throws servletexception { Super. INIT (config ); // Get path in which to save file Rootpath = config. getinitparameter (rootpath ); If (rootpath = NULL) { Rootpath = /; } /* Get message to show when upload is complete. used only if A success redirect page is not supplied .*/ Successmessage = config. getinitparameter (successmessage ); If (successmessage = NULL) { Successmessage = File Upload complete !; } } /** * Dopost reads the uploaded data from the request and writes * It to a file. */ Public void dopost (httpservletrequest request, Httpservletresponse response) { Servletoutputstream out = NULL; Datainputstream in = NULL; Fileoutputstream fileout = NULL; Try { /* Set content type of response and get handle to output Stream in case we are unable to redirect client */ Response. setcontenttype (text/plain ); Out = response. getoutputstream (); } Catch (ioexception E) { // Print error message to standard out System. Out. println (error getting output stream .); System. Out. println (error Description: + E ); Return; } Try { // Get content type of client request String contenttype = request. getcontenttype (); // Make sure content type is multipart/form-Data If (contenttype! = NULL & contenttype. indexof ( Multipart/form-data )! =-1) { // Open input stream from client to capture Upload File In = new datainputstream (request. getinputstream ()); // Get length of content data Int formdatalength = request. getcontentlength (); // Allocate a byte array to store content data Byte databytes [] = new byte [formdatalength]; // Read file into byte array Int bytesread = 0; Int totalbytesread = 0; Int sizecheck = 0; While (totalbytesread <formdatalength) { // Check for maximum file size Violation Sizecheck = totalbytesread + in. Available (); If (sizecheck> max_size) { Out. println (Sorry, file is too large to upload .); Return; } Bytesread = in. Read (databytes, totalbytesread, Formdatalength ); Totalbytesread + = bytesread; } // Create string from byte array for easy manipulation String file = new string (databytes ); // Since byte array is stored in string, release memory Databytes = NULL; /* Get boundary value (boundary is a unique string that Separates content data )*/ Int lastindex = contenttype. lastindexof (= ); String boundary = contenttype. substring (lastindex + 1, Contenttype. Length ()); // Get directory web variable from request String directory =; If (file. indexof (name =/directory/)> 0) { Directory = file. substring ( File. indexof (name =/directory /)); // Remove carriage return Directory = directory. substring ( Directory. indexof (/n) + 1 ); // Remove carriage return Directory = directory. substring ( Directory. indexof (/n) + 1 ); // Get directory Directory = directory. substring (0, Directory. indexof (/N)-1 ); /* Make sure user didnt select a directory higher in The directory tree */ If (directory. indexof (...)> 0) { Out. println (security error: You cant upload + To a directory higher in the directory tree .); Return; } } // Get successpage web variable from request String successpage =; If (file. indexof (name =/successpage/)> 0) { Successpage = file. substring ( File. indexof (name =/successpage /)); // Remove carriage return Successpage = successpage. substring ( Successpage. indexof (/n) + 1 ); // Remove carriage return Successpage = successpage. substring ( Successpage. indexof (/n) + 1 ); // Get success page Successpage = successpage. substring (0, Successpage. indexof (/N)-1 ); } // Get overwrite flag web variable from request String overwrite; If (file. indexof (name =/overwrite/)> 0) { Overwrite = file. substring ( File. indexof (name =/overwrite /)); // Remove carriage return Overwrite = overwrite. substring ( Overwrite. indexof (/n) + 1 ); // Remove carriage return Overwrite = overwrite. substring ( Overwrite. indexof (/n) + 1 ); // Get overwrite flag Overwrite = overwrite. substring (0, Overwrite. indexof (/N)-1 ); } Else { Overwrite = false; } // Get overwritepage web variable from request String overwritepage =; If (file. indexof (name =/overwritepage/)> 0) { Overwritepage = file. substring ( File. indexof (name =/overwritepage /)); // Remove carriage return Overwritepage = overwritepage. substring ( Overwritepage. indexof (/n) + 1 ); // Remove carriage return Overwritepage = overwritepage. substring ( Overwritepage. indexof (/n) + 1 ); // Get overwrite page Overwritepage = overwritepage. substring (0, Overwritepage. indexof (/N)-1 ); } // Get filename of Upload File String SaveFile = file. substring ( File. indexof (filename =/) + 10 ); SaveFile = SaveFile. substring (0, SaveFile. indexof (/n )); SaveFile = SaveFile. substring ( SaveFile. lastindexof (//) + 1, SaveFile. indexof (/)); /* Remove boundary markers and other multipart/form-Data Tags from beginning of Upload File Section */ Int Pos; // position in Upload File // Find position of Upload File section of request Pos = file. indexof (filename = /); // Find position of content-Disposition line Pos = file. indexof (/N, POS) + 1; // Find position of Content-Type line Pos = file. indexof (/N, POS) + 1; // Find position of blank line Pos = file. indexof (/N, POS) + 1; /* Find the location of the next boundary marker (Marking the end of the upload file data )*/ Int boundarylocation = file. indexof (boundary, POS)-4; // Upload File lies between POs and boundarylocation File = file. substring (Pos, boundarylocation ); // Build the full path of the Upload File String filename = new string (rootpath + directory + SaveFile ); // Create File object to check for existence of File File checkfile = new file (filename ); If (checkfile. exists ()) { /* File exists, if overwrite flag is off, give Message and abort */ If (! Overwrite. tolowercase (). Equals (true )) { If (overwritepage. Equals ()) { /* Overwrite HTML page url not supported ed, respond With generic message */ Out. println (Sorry, file already exists .); } Else { // Redirect client to overwrite HTML page Response. sendredirect (overwritepage ); } Return; } } /* Create File object to check for existence Directory */ File filedir = new file (rootpath + directory ); If (! Filedir. exists ()) { // Directory doesnt exist, create it Filedir. mkdirs (); } // Instantiate file output stream Fileout = new fileoutputstream (filename ); // Write the string to the file as a byte array Fileout. Write (file. getbytes (), 0, file. Length ()); If (successpage. Equals ()) { /* Success HTML page url not supported ed, respond Generic success message */ Out. println (successmessage ); Out. println (file written to: + filename ); } Else { // Redirect client to Success HTML page Response. sendredirect (successpage ); } } Else // request is not multipart/form-Data { // Send error message to client Out. println (request not multipart/form-Data .); } } Catch (exception E) { Try { // Print error message to standard out System. Out. println (error in dopost: + E ); // Send error message to client Out. println (an unexpected error has occurred .); Out. println (error Description: + E ); } Catch (exception f ){} } Finally { Try { Fileout. Close (); // close file output stream } Catch (exception f ){} Try { In. Close (); // close input stream from client } Catch (exception f ){} Try { Out. Close (); // close output stream to client } Catch (exception f ){} } } }