Tuesday, August 20, 2013

Chunked File loading with APEX Listener + HTML5

  I just found the HTML5 File API the other day so I had to see what I could do with the APEX Listener's RESTful services. There's a bunch of blogs on what can be done such as on HTML5rocks  .

  The end result is that the new File api let's javascript get details of the file and slice it up into parts. Then I made a pretty simple REST end point to receive the chunks and put them back together again.

The actual sending part of the javascript is here
function sendChunk(chunkNumber){
        var reader = new FileReader();
        var start = chunkSize * (chunkNumber-1);
        var end = start + chunkSize -1;
      // create the slice of the file
        var fileContent = selectedFile.slice(start, end);   
      // grab the length
        var length = fileContent.size;
      
      // read the slice of the file
        reader.readAsArrayBuffer(fileContent);      
      
      $.ajax({
        url: uri,
        type: "POST",
        data: fileContent,
        processData: false,
        beforeSend: function(xhr) {
          // pass in the chunk size,offset,name 
          // as headers
                        xhr.setRequestHeader('x-chunknumber', chunkNumber);
                        xhr.setRequestHeader('x-filename', selectedFile.name);
                        xhr.setRequestHeader('x-offset', start );
                        xhr.setRequestHeader('x-chunksize', length );
                        xhr.setRequestHeader('x-content-type', selectedFile.type );

                    },
        success: function (data, status) {
          console.log(data);
          console.log(status);
          bytesUploaded += length;
          // set the percent complete 
          var percentComplete = ((bytesUploaded / selectedFile.size) * 100).toFixed(2);          
          $("#fileUploadProgress").text(percentComplete + " %");
          
          // make a link to the REST that can deliver the file
          $("#downloadLink").html("New File");
          
          // if there's more chunks send them over
          if ( chunkNumber < chunks ) {
             sendChunk(chunkNumber+1);
          }
        },
        error: function(xhr, desc, err) {
          console.log(desc);
          console.log(err);
        }
      });
      
    }    
 

The next step is to make the HTTP Headers into bind variable so the plsql block will be able to use them.


declare
  p_b         blob;
  p_body      blob;
  p_offset    number;
  p_filename  varchar2(4000);
  p_raw       long raw;
  p_chunksize varchar2(200);
  p_status    varchar2(200);
begin
  -- pull the binds into locals
  p_offset    := :OFFSET + 1;
  p_body      := :body;
  p_filename  := :filename;
  p_chunksize := :chunksize;

  -- NOT FOR PRODUCTION OR REAL APPS
  -- If there is a file already with this name nuke it since this is chunk number one.
  if ( :chunkNumber = 1 ) then
    p_status := 'DELETING';
     delete from chunked_upload
      where filename = p_filename;
  end if;

  -- grab the blob storing the first chunks
  select blob_data
         into p_b
    from chunked_upload
   where filename = p_filename
    for update of blob_data;

  p_status :=' WRITING';

  -- append it
  dbms_lob.append(p_b, p_body);

commit;
exception 
  -- if no blob found above do the first insert
  when no_data_found then
     p_status :=' INSERTING'; 
     insert into CHUNKED_UPLOAD(filename,blob_data,offset,content_type)
      values ( p_filename,p_body,p_offset,:contenttype);  
commit;
  when others then
      -- when something blows out print the error message to the client
      htp.p(p_status);
      htp.p(SQLERRM);
end;



A very simple html page for testing it all out.


Here's a quick video of how it all works.




Here's the complete Javascript/html for this sample.


JS Bin

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