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File Upload and Download Procedures

Oracle provide a mechanism to upload and download files directly from the database using a Database Access Descriptor (DAD). In this article I'll demonstrate how it works with a simple example.

First a Database Access Descriptor (DAD) must be created.

For the upload to be successful the documents table must be created with the following structure.

CREATE TABLE documents (
  name           VARCHAR2(256) UNIQUE NOT NULL,
  mime_type      VARCHAR2(128),
  doc_size       NUMBER,
  dad_charset    VARCHAR2(128),
  last_updated   DATE,
  content_type   VARCHAR2(128),
  blob_content   BLOB
)
/

Next we create a package specification which will contain all the necessary code.

CREATE OR REPLACE PACKAGE document_api AS

PROCEDURE upload;
PROCEDURE upload (file  IN  VARCHAR2);
PROCEDURE download;
PROCEDURE download (file  IN  VARCHAR2);

END;
/
SHOW ERRORS

Then the package body.

CREATE OR REPLACE PACKAGE BODY document_api AS

-- ----------------------------------------------------------------------------
PROCEDURE upload AS
-- ----------------------------------------------------------------------------
  l_real_name  VARCHAR2(1000);
BEGIN

  HTP.htmlopen;
  HTP.headopen;
  HTP.title('Test Upload');
  HTP.headclose;
  HTP.bodyopen;

  HTP.header(1, 'Test Upload');

  HTP.print('<form enctype="multipart/form-data" action="document_api.upload" method="post">');
  HTP.print('  File to upload: <input type="file" name="file"><br />');
  HTP.print('  <input type="submit" value="Upload">');
  HTP.print('</form>');

  HTP.bodyclose;
  HTP.htmlclose;
END upload;
-- ----------------------------------------------------------------------------


-- ----------------------------------------------------------------------------
PROCEDURE upload (file  IN  VARCHAR2) AS
-- ----------------------------------------------------------------------------
  l_real_name  VARCHAR2(1000);
BEGIN

  HTP.htmlopen;
  HTP.headopen;
  HTP.title('File Uploaded');
  HTP.headclose;
  HTP.bodyopen;
  HTP.header(1, 'Upload Status');

  l_real_name := SUBSTR(file, INSTR(file, '/') + 1);

  BEGIN
    -- Delete any existing document to allow update.
    DELETE FROM documents
    WHERE  name = l_real_name;

    -- Update the prefixed name with the real file name.
    UPDATE documents
    SET    name = l_real_name
    WHERE  name = file;

    HTP.print('Uploaded ' || l_real_name || ' successfully.');
  EXCEPTION
    WHEN OTHERS THEN
      HTP.print('Upload of ' || l_real_name || ' failed.');
      HTP.print(SQLERRM);
  END;
  HTP.br;

  -- Create some links to demonstrate URL downloads.
  HTP.br;
  HTP.print('URL Downloads:');
  HTP.br;
  FOR cur_rec IN (SELECT name FROM documents) LOOP
    HTP.anchor('docs/' || cur_rec.name, 'docs/' || cur_rec.name);
    HTP.br;
  END LOOP;

  -- Create some links to demonstrate direct downloads.
  HTP.br;
  HTP.print('Direct Downloads:');
  HTP.br;
  FOR cur_rec IN (SELECT name FROM documents) LOOP
    HTP.anchor('document_api.download?file=' || cur_rec.name, 'document_api.download?file=' || cur_rec.name);
    HTP.br;
  END LOOP;

  HTP.bodyclose;
  HTP.htmlclose;
END upload;
-- ----------------------------------------------------------------------------


-- ----------------------------------------------------------------------------
PROCEDURE download IS
-- ----------------------------------------------------------------------------
  l_filename  VARCHAR2(255);
BEGIN
  l_filename := SUBSTR(OWA_UTIL.get_cgi_env('PATH_INFO'), 2);
  WPG_DOCLOAD.download_file(l_filename);
EXCEPTION
  WHEN OTHERS THEN
    HTP.htmlopen;
    HTP.headopen;
    HTP.title('File Downloaded');
    HTP.headclose;
    HTP.bodyopen;
    HTP.header(1, 'Download Status');
    HTP.print('Download of ' || l_filename || ' failed.');
    HTP.print(SQLERRM);
    HTP.bodyclose;
    HTP.htmlclose;
END download;
-- ----------------------------------------------------------------------------


-- ----------------------------------------------------------------------------
PROCEDURE download (file  IN  VARCHAR2) AS
-- ----------------------------------------------------------------------------
  l_blob_content  documents.blob_content%TYPE;
  l_mime_type     documents.mime_type%TYPE;
BEGIN
  SELECT blob_content,
         mime_type
  INTO   l_blob_content,
         l_mime_type
  FROM   documents
  WHERE  name = file;

  OWA_UTIL.mime_header(l_mime_type, FALSE);
  HTP.p('Content-Length: ' || DBMS_LOB.getlength(l_blob_content));
  OWA_UTIL.http_header_close;

  WPG_DOCLOAD.download_file(l_blob_content);
EXCEPTION
  WHEN OTHERS THEN
    HTP.htmlopen;
    HTP.headopen;
    HTP.title('File Downloaded');
    HTP.headclose;
    HTP.bodyopen;
    HTP.header(1, 'Download Status');
    HTP.print(SQLERRM);
    HTP.bodyclose;
    HTP.htmlclose;
END download;
-- ----------------------------------------------------------------------------

END;
/
SHOW ERRORS

Once this code is compiled a file can be uploaded by using the following URL format.

# Format
http://<server-name>:<port>/pls/<DAD>/document_api.upload

# Example
http://myserver:7777/pls/UTILS/document_api.upload

Alternatively, the upload can be performed by adjusting the form action in the upload.html file.

The second overload of the upload procedure does not really upload the file as this is done automatically by the DAD. It simply allows you to perform additional processing if necessary. Oracle prefixes a the file name with a generated folder name to reduce the posibility of name conflicts. In this example the files are renamed to their original names.

In addition the upload code produces two types of links to test the download code. The first set of links use the "document access path" and the "document access procedure" defined in the DAD. These allow access to the files using a regular URL, masking the procedure call which actually returns the file. Using the document access path in the URL causes the DAD to call the document access procedure. The requested file name must be retrieved from the URL and used in the WPG_DOCLOAD.download_file procedure call.

The second set of links call an alternative download procedure directly. In this case file name must be specified as a parameter.

For more information see the DAD documentation loaded on your server. This is typically accessed using a URL like the following.

http://yourserver:7777/pls/simpledad/admin_/help/feature.htm#1004906

Hope this helps. Regards Tim...

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