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File Property Discovery For Better Asset Management

 The FutureWare Web Library's FileUpload component is aserver-sideobjectthat accepts a file upload from a web browserfor selectedfile types,and then saving them to the server's filesystem. Foruploaded imagefiles (i.e., BMP, JPG, GIF and PNG) the objectcanabstract certainimage properties (e.g., height and width in pixels)forsubsequentprocessing. For JPG files, the object can additionallyabstracttheCOMMENT and the 16 application-specific descriptions (i.e.,theAPPnnmarkers) that can be imbedded within the binary image stream.Theobjectdoes not allow any modification to any uploaded file.

Server Operating Requirements

 The FileUpload object's operating environment is any WindowsNT/2Kserver.It is included in this FutureWare product distributionasa classobject for Microsoft's Active Server Pages that is addedasa classto the server's Registry as an installed DLL, and isbeingused successfullywith Microsoft's Internet Information Server,O'Reilly'sWebSiteProserver, and Omnicron Technologies' OHTTPD server,andcan be usedwith Chili!Soft's ASP products that operate underWindowsNT/2K Servers.

It is also available as a Delphi DCU (included in this FutureWareproductdistribution)that can be included in any project that usesthe TWebBrokerobject,by including the object's DCU in the invokingObject Pascalsourcefile interface usessection.

In addition to web browser uploads of image files, it can also handleMicrosoft'sWordand Excel documents, text and HTML files.

Fileupload Object's Typical Usage

File uploads are submitted within an HTML form, using the "FILE"inputtype.An example of such a form is contained in the"fwlfileuploaddemo.html"page,which would be filled out by auser at a browser that complieswiththe HTML 3.2 specification.
The server processes the form and abstracts the uploaded file,alongwithother form data, by using the following general steps:

1. Create the FileUpload object
2. Call the object's "AnalyzeContent" method
3. Access and manipulate the object properties as required
4. Call the object's "SaveFileUpload" method
5. Release the object

Examples of how to use the FileUpload object are included in thisFutureWareproductdistribution, and described in several followingsections.

Restricting File Type Submittals At The Client

File submittals from a browser client can be restricted to specificfiletypes by ajavascript function invoked on the form'sOnSubmitevent, which isdescribed in the includedreference document and includedin the demo HTML pages.

Accessing Form Data

Most servers have a read-forward-only mode of retrieving formdata,suchas name-value pairs. To avoid possible loss, formdata shouldnotbe accessed directly from the server's requestobject, but insteadaccessedthrough the FWLFileUpload object'sseveral form propertiesafter theobject has been created andthe "AnalyzeContent" methodhas been invoked.

Form Design Requirements

An example of a form that invokes the FWL FileUpload object iscontainedinthe "fwlfileuploaddemo.html" page, which has to havethe form'sACTIONvalue set to the appropriate web server target(ASP or DLLas noted).Additionally, the following declaration mustbe includedin the FORM'sattributes section: ENCTYPE="multipart/form-data".Ifthisdeclaration is missing then the error message "3: No Content"willoccuras noted in the "sErrorMessage" property described below.

ASP Script Example

The ASP script "fwlfu_asp_demo.asp" gives an example of how theFWLFileUploadobject can be used in an interpreted ASP environment.ThisASP scriptcan be invoked from the "fwlfu_asp_demo.html"page byreplacing the'asp_demo_path_here' placeholder with theserver pathto the foldercontaining the "fwlfu_asp_demo.asp" script.

ISAPI/NSAPI Example

The Delphi project "FWLFU_DelphiDemo.dpr" gives an example of howtheFWLFileUpload object can be used in an ISAPI/NSAPI environment.The"uFWLFU_DelphiDemo.pas"source file contains the Object Delphicode as asample of how touse the Delphi version of the FileUploadobject. Thisdll can be invokedfrom the "fwlfu_delphi_demo.html"page by replacingthe 'delphi_demo_path_here'placeholder with theserver path to thefolder containing the "FWLFU_DelphiDemo.dll"file.

Properties

The FWL FileUpload object has eight read-only properties that havevalidvaluesonly after the "AnalyzeContent" method (described below)hasbeeninvoked.

sErrorMessage: string
If an error is detected during either the "AnalyzeContent" or "SaveFileUpload"methodsthen this property will describe the error. If no erroris detectedthen this property will be empty. The number precedinga colon willbe the error number; the error description will followthe colon.The possible error numbers and messages are:

• 0: FWL Object Not Registered
• 1: Exceeds FileSize Limit
• 2: ClientRead Error
• 3: No Content
• 4: Incomplete Content
• 5: Missing Content
• 6: No File To Save
• 7: Uknown FileType
• 8: Boundry Missing
• 9: [SystemErrorMessage]

sFileName: string
Valid after the "AnalyzeContent" method call, the name of the fileuploadedwith its file extension. The case of the file name isnot alteredin any way. Set to UNK if the file is not a recognizedMIME type.

iFileSize: integer
Valid after the "AnalyzeContent" method call, the size of the uploadedfile.Set to 0 if the file is not a recognized type (i.e., BMP,JPG, GIF,PNG, DOC, TXT, XLS or HTML).

sFileType: string
Valid after the "AnalyzeContent" method call, describes the uploadedfileextension:

• JPG: JPG (or JPEG as JPG) image file
• GIF: GIF (87a or 89a) image file
• PNG: Portable Network Graphics image file
• DOC: MS Word file
• TXT: ASCII Text file
• XLS: MS Excel spreadsheet file
• HTML: HTML file
• ZIP: ZIPed file
• UNK: Unknown

iFormElementCount: integer
Valid after the "AnalyzeContent" method call, the number of formelementnames which have non-empty associated values.

iImageHeight: integer
Valid after the "AnalyzeContent" method call and only for BMP,JPG,GIF and PNG image files, indicates the first image's heightin pixels.For GIF image files, this is the height of the logicalscreen.

iImageWidth: integer
Valid after the "AnalyzeContent" method call and only for BMP,JPG,GIF and PNG image files, indicates the first image's widthin pixels.For GIF image files, this is the width of the logicalscreen.

sJPGComment: string
Valid after the "AnalyzeContent" method call and only for JPG imagefiles,the JPG's imbedded comment string (i.e., the COM marker),if any.

Methods

The FWL FileUpload object has five methods that return a value.TheDelphiTWebModule version of the object has a sixth method, beingtheCreate(),which does not return a value.

function AnalyzeContent: boolean
Called after the FWL FileUpload object is created, analyzes thewebrequest object's payload for analysis and parsing. Returns TRUEifno problems were encountered, FALSE otherwise. If returns FALSEthenthe "sErrorMessage" property will describe the error as notedabove.

procedure Create
For the Delphi TWebModule version only, creates the object andpreparesthe web request object's payload for analysis and parsing.Must bedone before the "AnalyzeContent" method call is used. Theobjectmust be explicitly released before exiting from the TWebModuleprocessingsection.

function sJPGAppData(ziAppIndex: integer): string
Validafter the "AnalyzeContent" method call and only for JPG imagefiles,returns the "Application" description (i.e., the APP0 throughAPP15markers) for the "ziAppIndex" value, which can range from'0' to'15'. By convention, '0' usually returns the string "JFIF".

function sFormElementName(ziIndex: integer): string
Validafter the "AnalyzeContent" method call, returns the formelementname, indexed by the "ziIndex" integer argument, that hasa non-emptyassociated value. The first element's index is '1',and the lastindex is the value in the "iFormElementCount" property.Returns anempty string if the "ziIndex" integer argument is eitherzero orexceeds the "iFormElementCount" property value.

function sFormElementValue(zsName: string): string
Valid after the "AnalyzeContent" method call, returns the valueassociatedwith the form element name, as a string. as specifiedin the "zsName"string argument.

function SaveFileUpload(zsFilePath: string): boolean
Valid after the "AnalyzeContent" method call, saves the uploadedfileas completely specified in the "zsFilePath" argument. ReturnsTRUEif the uploaded file was saved, FALSE otherwise. If returnsFALSEthen the "sErrorMessage" property will describe the erroras notedabove. **NOTE: XLS AND DOC FILES SHOULD BE CHECKED FORPOSSIBLE HARMFULMACROS AND SCRIPT EXECUTIONS BEFORE THEY ARE MADEAVAILABLE TO THEAPPLICATION ENVIRONMENT **

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