Template handler displaying image

This document covers sample implementation for template GET handler displaying uploaded image using a custom upload REST template handlers. Both examples displays uploaded images into the plug-in sample application table UC_FROALA_SAMPLE_BLOBS.

Simple

handler features

The handler can be combined with handlers uploading an image Simple, Default Parameters and Custom parameters

Image checksum

handler features

• must be combined with handler uploading an image Image checksum
• uses access token static function decode to decode an image checksum
• if checksum is missing or malformed returns HTTP status 403 Forbidden

Requirements

Handler displaying uploaded image must meet the following requirements:

1. must use GET method
2. must be compilable at the run time
3. must return 200 HTTP status
4. must stream uploaded image content into browser buffer

Handler definition

Simple

Attribute	Value
RESTful Service Module	A custom RESTservice
Module Base Path	/customrest/
URI Template	display-simple/:fileid
Full URL	https://example-domain.com/ords/workspacename/customrest/display-simple/:fileid
Handler Method	GET
Source Type	PL/SQL
Mime Types Allowed	Not defined

Handler parameters

The upload handler doesn't require registering any resource parameters as long as REST specific bind variable :status_code is used to set request HTTP status.

Handler Source

The handler displaying uploaded image can be defined as PL/SQL code or media resource.

Simple

declare
  v_param_fileid  varchar2(4000) := :fileid;
  v_file_row      UC_FROALA_SAMPLE_BLOBS%ROWTYPE;
begin

  select 
    *
  into
    v_file_row
  from   
    UC_FROALA_SAMPLE_BLOBS   
  where   
    id = to_numbeR(v_param_fileid)
  ;

  sys.HTP.init;  
  sys.OWA_UTIL.mime_header(v_file_row.FILE_MIMETYPE, FALSE);  
  sys.HTP.p('Content-Length: ' || DBMS_LOB.getlength(v_file_row.FILE_CONTENT));  
  sys.HTP.p('Access-Control-Allow-Origin: *');  
  sys.HTP.p('Content-Disposition: filename="' || v_file_row.FILE_NAME || '"');
  sys.OWA_UTIL.http_header_close;  

  sys.WPG_DOCLOAD.download_file(v_file_row.FILE_CONTENT);

  :status_code := 200;
exception
  when no_data_found then
    :status_code := 404;
  when others then
    :status_code := 400;
end;

Handler Output

The handler output must be an image content streamed into the browser buffer. It can be done using handler source type media resource or PL/SQL code.

Snippet straming file content into the browser buffer

declare
  v_image_mimetype varchar2(4000);
  v_image_filename varchar2(4000);
  v_image_content  blob;
begin
  /* provide image data for declared variables */
  
  sys.HTP.init;  
  sys.OWA_UTIL.mime_header(v_image_mimetype, FALSE);  
  sys.HTP.p('Content-Length: ' || DBMS_LOB.getlength(v_image_content));  
  sys.HTP.p('Access-Control-Allow-Origin: *');  
  sys.HTP.p('Content-Disposition: filename="' || v_image_filename || '"');
  sys.OWA_UTIL.http_header_close;  

  sys.WPG_DOCLOAD.download_file(v_file_row.FILE_CONTENT);
  
  :status_code := 200;
end;