How to Upload and Download Files in an Web Dynpro for Java Application
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Some Theory
The Web Dynpro UI Element Library provides two special UI elements (FileDownload and FileUpload) with
which you can download files from the Web Dynpro runtime environment or upload them there. This is
performed using declarative data binding. Here, Web Dynpro runtime automatically transports different types
of MIME files between the client-side user interface or UI element and the server-side controller context.
In contrast to the semi-declarative approach in SAP NetWeaver 04, which was based on invoking the
IWDModifiableBinaryType-API in the controller code, the new dictionary simple type Resource within
SAP NetWeaver 04s yields a fully-declarative data transport of MIME resources between Web Dynpro client
and controller context on server side. The old IWDModifiableBinaryType-API should not be used
anymore since SAP NetWeaver 04s. The reasons for this are described in the chapter Implementation
Details.
In SAP NetWeaver 04s file download and upload was significantly enhanced and simplified with the following
new features:
Dictionary Type Resource: The new Java dictionary type Resource allows to bind FileUpload and
FileDownload UI elements to context attribtues storing MIME files named resources. In SAP
NetWeaver 04 the primitive type binary must be used.
Java Type IWDResource: The new Web Dynpro interface IWDResource is the Java type
counterpart of the dictionary type Resource. It allows to store the file content (binary resource data)
and the file metadata (MIME type, resource name) in one object. Consequently the resource
metadata (MIME type, file name) must no longer be stored in the context attribute info
(IWDAttributeInfo) using a modifiable binary type and may therefore differ among multiple
resources or node elements stored in the same context node.
Web Dynpro Factory WDResourceFactory: Resource objects of type IWDResource can easily
be created with the new Web Dynpro factory class WDResourceFactory. This factory class
significantly simplifies the implementation of file download scenarios where statically deployed or
dynamically created resources must be stored in the context.
Zero Coding File Upload: With the new Java dictionary type Resource it is no longer needed to
implement the type modification of a binary context attribute by invoking the
IWDModifiableBinaryType API in the controller code. Consequently file upload can be realized
in a purely declarative, zero coding approach. You just have to bind a FileUpload UI element to a
context attribute of type Resource. The Web Dynpro Runtime then automatically transports the
uploaded file to the context attribute as an object of type IWDResource.
File Download Behaviors: The behavior of the FileDownload UI Element can now be defined with
the new Java dictionary type FileDownloadBehavior. Its enumeration specifys three different file
download behaviors: open resource in-place without opening a dialog window, save resource in local
file system (open dialog) and open resource depending on the MIME type of the downloaded file
(open dialog).
Downloading Files in Tables On-Demand: The new on-demand streaming technique allows to
download the resource content on-demand when the user actually requests it on client side.
Especially when using the FileDownload UI element as table cell editor this new technique yields a
heavily reduced context memory consumption on server side.
Using the Virus Scan Interface
To enhance your system’s virus protection when working with files or documents processed by your Web
Dynpro applications, you can add external virus scanners to your SAP system using the Virus Scan
Interface.
To connect the FileUpload service contained in the Web Dynpro runtime environment to a virus scanner, you
need to activate the predefined virus scan profile webdynpro_FileUpload. This profile must be
activated/deactivated by the SAP J2EE Engine administrator. When delivered, profile
webdynpro_FileUpload is switched off. The Virus Scan Interface cannot be used for the Web Dynpro
FileDownload service.
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