Uploading and Downloading Files in Web Dynpro Tables

Uploading and Downloading Files in Web Dynpro Tables 

Uploading and Downloading Files in Web Dynpro Tables Applies to: Web Dynpro for Java UI Development, SAP NetWeaver 2004s

Prerequisite This article is an addition to the tutorial Uploading and Downloading Files in Web Dynpro Java in SAP  NetWeaver 2004s comprising 2004s comprising more advanced technical details. Please read this tutorial first to understand the principles of file upload and download in SAP NetWeaver 2004s. Both articles are based on the same Web Dynpro sample application.

Summary In SAP NetWeaver 04 file download and upload inside Web Dynpro Table UI Table UI elements was subject to significant technical restrictions which are all solved in the NetWeaver 04s release. This article and its related Web Dynpro sample project demonstrate how to upload and download image resources with different mime types per table line, how to store these image resources in a multiple context node of the controller context and how to instantly display an uploaded image in a table cell by utilizing the new Java dictionary type Resource and Resource and its related new Web Dynpro Java APIs. Additionally the article comprises an in-depth description of the new on-demand streaming technique combined technique combined with 0-byte resource creation which creation which yields a heavily reduced context memory consumption on server side.

Author: Author: Bertram Ganz Company: Company: SAP AG Created on: on: 19 February 2007

Author Bio After his studies in mathematics, physics and computer science Bertram Ganz finished his teacher training at a German grammar school stressing technical sciences. He has been a member of the Web Dynpro Java Runtime development team (SAP NetWeaver ESI Foundation UI) since 2002. The main focus of his work is on knowledge transfer, rollout, and documentation. Bertram regularly publishes articles on Web Dynpro in the context of the S AP NetWeaver Application Server. Bertram is co-author of the books “Maximizing Web Dynpr o for Java” and “Java Programming with the Web Application Server”.

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Uploading and Downloading Files in Web Dynpro Tables 

Table of Contents Uploading Uploadi ng and Downloading Downloading Files in Web Dynpro Tables ........ ................. ................... ................... .................. .................. ................. ........ 1 Applies to: .......... ................... .................. .................. .................. ................... ................... .................. .................. ................... ................... .................. .................. ................ ................ ......... 1 Prerequisite................ Prerequisite ................................. .................................. .................................. ................................... ................................... .................................. ................................ ............... 1 Summary.......................... Summary......... .................................. .................................. .................................. .................................. .................................. ....................................... ........................... ..... 1 Author Bio .......... ................... .................. .................. .................. ................... ................... .................. .................. ................... ................... .................. .................. ................ ................ ......... 1 Table of Content Contents s .......... ................... .................. .................. ................... ................... .................. .................. ................... ................... .................. .................. ................... ............. ... 2 Introduction Introduct ion ......... .................. ................... ................... .................. .................. .................. ................... ................... .................. .................. ................... ................... ................ .............. ....... 3 What’s New in SAP NetWea NetWeaver ver 04s ......... ................... ................... .................. .................. ................... ................... .................. .................. .................. ......... 3 Context Definit Definition ion and Data Binding.............. Binding....................... ................... ................... .................. .................. ................... ................... .................. ............. .... 4 Event Paramete Parameterr Based Table Interacti Interaction on.......... ................... .................. .................. .................. ................... ................... .................. .................. ......... 5 Defining Definin g Action UploadI UploadImg mg ........ .................. ................... .................. .................. ................... ................... .................. .................. .................. ................... ............... ..... 5 Implementing the Parameter Mapping Relation............. Relation.............................. .................................. .................................. ............................ ........... 6 Implementing Implemen ting the Upload Action Event Handler Handler.......... ................... .................. .................. ................... ................... .................. .................. ......... 6 Downloading Downloa ding Files in a Table Using On-Dema On-Demand nd Streams Streams......... .................. .................. .................. ................... ................... ............... ...... 7 Example ......... .................. .................. .................. ................... ................... .................. .................. .................. ................... ................... .................. .................. ................. ................ ........ 7 Solution Solutio n in SAP NetWeav NetWeaver er 04s: Using On-Deman On-Demand d Streams......... Streams .................. .................. ................... ................... ............... ...... 8 Context Definit Definition ion and Data Binding.............. Binding....................... ................... ................... .................. .................. ................... ................... .................. ............. .... 9 Populating Populat ing the Context Node Resources and Creating 0-Byte Resources .......... ................... ................... ............ .. 10 Implementing Implemen ting the Calculate Calculated d Context Attribute Getter Method ......... ................... ................... ................... ................... ........... .. 12 Related Content Content............... ................................ .................................. .................................. .................................. ................................... ................................... ........................ ....... 13 Sample Applicati Application on ......... ................... ................... .................. ................... ................... .................. ................... ................... .................. ................... ................... ................. ........ 13 Copyright.......................... Copyright......... .................................. .................................. .................................. .................................. .................................. ...................................... ......................... .... 14

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Uploading and Downloading Files in Web Dynpro Tables 

Introduction In this article we discuss an interesting and important use case for the Web Dynpro UI elements FileDownload and FileDownload and FileUpload : Uploading and downloading files in a Table UI element, or using the UI elements FileDownload and  FileUpload as table cell editors. In contrast to the form-based examples in the first tutorial we now find answers on the following technical questions: •

How to upload image resources with different mime types (png, gif, jpg etc.) per table line?

•

How to store these image resources in a multiple context node of the controller context?

•

How to instantly display an uploaded image in a table cell?

•

How to stream resource content (binary resource data) from server to client on-demand so that the controller so that it must not be initially streamed to the controller context befor the user actually downloads it?

What’s New in SAP NetWeaver 04s In SAP NetWeaver 04 file download and upload inside tables was subject to significant technical restrictions which are all solved in the NetWeaver 04s release. The solution is based on the following new features: •

•

•

•

New Dictionary Type Resource : The new Java dictionary type Resource allows Resource allows to bind FileUpload and FileDownload UI elements to context attributes storing MIME files named resources. In SAP NetWeaver 04 the primitive type binary must be used. New Java Type IWDResource : The new Web Dynpro interface IWDResource is the Java type counterpart of the dictionary type Resource . Resource objects of this type can be created with the new Web Dynpro factory class WDResourceFactory . Independant MIME Types: Types : In addition the new Java type IWDResource allows to store the file content (binary resource data) and the file metadata (MIME type, resource name) in one object. Consequently the MIME type can differ among the context node elements stored in the table’s data node. In SAP NetWeaver 04 the storage of file content and file metadata was separated between context attribute info ( IWDAttributeInfo ) on context node level and context attribute (byte array) on context nodel element level. Consequently it was not possible to upload or download files with different MIME types in a Table UI Table UI element. Downloading Files in Tables On-Demand: On-Demand : The new on-demand streaming technique allows technique allows to download the resource content on-demand when on-demand when the user actually requests it on client side. Especially when using the FileDownload UI FileDownload UI element as table cell editor this new technique yields a heavily reduced context memory consumption on server side. Initially, the controller context stores so-called 0-byte resources which resources which do not comprise any binary content yet but only the resource metadata like MIME type and file name. Every requested binary resource content gets streamed to the client on-demand by on-demand by invoking a calculated context attribute getter method of a Web Dynpro controller on server side.

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Uploading and Downloading Files in Web Dynpro Tables 

Uploading Files in a Table

Within this section we demonstrate how to realize a simple use case of a FileUpload table FileUpload table cell editor (see screenshot above): 1. The user selects an image file in the client’s file system. 2. The image resource is uploaded to the server by clicking a LinkToAction UI LinkToAction UI element in the next table column. 3. The uploaded image is instantly displayed in another table column ( Image ). ). 4. The mime type of the uploaded images can be different in all table rows. Context Definition and Data Binding

V i e w L a yo yo u t Table

V i e w C on o n t e x t D e f i n i t i on on Root Node Java Dictionary Simple Types

Resources Column

FileUpload - resource Column

Image - source

0..n

Attribute Name

Attribute Type

1

UploadImgResource

Resource

2

UploadImgURL

string

De s i g n T i m e

Figure 1: Defining Data Binding and Context for File Upload in a Table at Design time  The context and data binding definition for our file-upload-in-table file-upload-in-table scenario is scenario is quite simple. The property resource of resource of the FileUpload table FileUpload table cell editor is bound to the context attribute UploadImgResource of UploadImgResource of dictionary type com.sap.ide.webdynpro.uielement-definitions.Resource (see (see figure 1, point 1). After uploading the image file to the server the context attribute in the related node element stores it as an object of type Resource .

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Uploading and Downloading Files in Web Dynpro Tables 

To instantly display this image resource in an Image table Image table cell editor, we bind its source property source property to the context attribute UploadImgURL of type String (2). String  (2). This means we must programmatically get the URL of the uploaded resource object which is stored in context attribute Resource. We will see later, that this URL can easily be retrieved by invoking the IWDResource -API.

View Layout

V i ew e w C o n t e x t St a t e

Table

Resources

Node Elements

Uploaded Image

3 Runtime

4

Attribute Name

Attribute Type

UploadImgResource

Resource

UploadImgURL

string

Figure 2: Data binding of Uploaded Images to the Context at Runtime  At runtime all Image UI Image UI elements in table column Image (see Image (see figure 2, point 3) are bound to the context attribute UploadImgURL of the corresponding context node element (4). As the MIME type information is associated with the resource objects on node element level but not with the context attribute information (of type IWDAttributeInfo ) on node level all uploaded images can have different MIME types. Event Parameter Based Table Interaction When the user clicks the LinkToAction UI LinkToAction UI element the selected image resource is uploaded to the server. Within the related action event handler we must know the table line in which the user selected a local image file so that we can get the required image URL. Technically speaking we must get a reference to either the table’s lead selection or to the node element directly. As we want to avoid an implicit lead selection change when the user selects a table line we apply another table interaction technique: parameter mapping in combination with the table compatibiltyMode  nw04plus (which nw04plus (which is identical with the property value auto for auto for all components newly created in NW04s). With this approach a reference to the action-triggering node element is automatically passed to the corresponding action event handler by the Web Dynpro Java Runtime. Defining Action Uploading Within the TableView controller TableView controller we define a new Action: • • •

Name: Name: UploadImage  Text : Upload . This text will be displayed in every line of table column Upload . Parameter: Parameter: resourceElement of resourceElement of type IPrivateTableView.IResourcesElement . This is the generated context interface for the node element objects in the data node Resources to Resources to which the Table UI Table UI element is bound.

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Uploading and Downloading Files in Web Dynpro Tables 

Implementing the Parameter Mapping Relation The parameter mapping relation between the LinkToAction UI LinkToAction UI element event parameter nodeElement and the action parameter resourceElement is implemented within the wdDoModifyView() hook method: Parameter Mapping – TableView.java TableView.java  public static void wdDoModifyView(IPrivateT wdDoModifyView(IPrivateTableView ableView wdThis, IPrivateTableView.IContextNode IPrivateTableView.IContextN ode wdContext, com.sap.tc.webdynpro.progmodel.api.IWDView com.sap.tc.webdynpro.progmo del.api.IWDView view, boolean view, boolean firstTime) { //@@begin wdDoModifyView if (firstTime) { IWDLinkToAction linkToAction = (IWDLinkToAction) view.getElement("UploadImgLinkToAction" view.getElement( "UploadImgLinkToAction"); ); linkToAction.mappingOfOnAction() .addSourceMapping("nodeElement" .addSourceMapping( "nodeElement", , "resourceElement" "resourceElement"); ); } //@@end }

Implementing the Upload Action Event Handler Within the action event handler onActionUPloadImg() we finally get the URL of the uploaded image resource of type IWDResource and copy it to the context attribute UploadImgURL so that the image is instantly displayed on the UI. The URL of an object of type IWDResource can easily be retrieved by invoking the interface method IWDResource.getURL(int fileDownloadBehavior) . The integer value for the parameter fileDownloadBehavior can be calculated with the method WDFileDownloadBehavior.ordinal() . To display the uploaded image file in-place or in-place or in-table we in-table we pass the ordinal integer value for the constant WDFileDownloadBehaviour.OPEN_INPLACE.

Upload Action Action Event Handler Handler – TableView.java //@@begin javadoc:onActionUploadImg(Se javadoc:onActionUploadImg(ServerEvent) rverEvent) /** Declared validating event handler. */ //@@end //@@en d  public void onActionUploadImg( com.sap.tc.webdynpro.progmodel.api.IWDCustomEvent com.sap.tc.webdynpro.progmo del.api.IWDCustomEvent wdEvent, com.sap.tc.wd.tut.fileupdownload.comp.wdp .IPrivateTableView.IResourcesElement resourceElement ) { //@@begin onActionUploadImg(ServerEv onActionUploadImg(ServerEvent) ent)

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Uploading and Downloading Files in Web Dynpro Tables 

// if a file in the FileUpload field exists (resourceElement.getUploadImgResource() gResource() != null ) { if (resourceElement.getUploadIm null) // copy URL string from IWDResource object to // context attribute 'UploadImgURL'. Image gets // visible on the UI based on data binding definition. resourceElement.setUploadImgURL( resourceElement.getUploadImgResource().getUrl( ;  WDFileDownloadBehaviour.OPEN_INPLACE.ordinal()))  WDFileDownloadBehaviour.O PEN_INPLACE.ordinal())); } //@@end }

Within SAP NetWeaver 04 we must use the Web Dynpro Binary Cache service Cache service to create an object of type IWDCachedWebResource from the image byte array stored in the context.

Downloading Files in a Table Using On-Demand Streams

When using a FileDownload UI FileDownload UI element as table cell editor in NW 04 we must be aware of the potentially high memory consumption within the controller context on server side. To understand this problem let’s look at the following file download example. Example Please note, that the technical description of this example is based on SAP NetWeaver 04. Afterwards we will present a solution which can only be implemented in SAP NetWeaver 04s using on-demand streams .

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Uploading and Downloading Files in Web Dynpro Tables 

100 Tab le Li nes / PDF PDF Files …

PDF load load

Context

load

Context Context

Table UI Se r v e r Si d e

 …

100 Users Initial Memory Consumption

Cl i e n t Si d e

A FileDownload UI FileDownload UI element is used as cell editor inside a Table UI Table UI element in order to download a contract PDF document for every displayed customer. We assume that every PDF document has 1MB file size and that the table displays 100 customers. To download one single PDF file on client side we must initially store the content of all 100 PDF files as byte arrays within the controller context, in total 100 MB. MB. Although Web Dynpro supports table paging on client side (only the data of the visible rows is sent to the client) it does not support context paging on server side. This means that a supply function initially populates the data node with all 100 node elements which can be potentially displayed in the table. Every node element stores the byte array of 1 PDF resource in a context attribute of type binary . Now we assume that our customer table view is simultaneously displayed by 100 concurrent users. As every user is running in its own Web Dynpro session the total memory consumption for all PDF files in the controller contexts on server side sums up to 10 GB. GB. The high memory consumption is based on the fact, that all downloadable resources must be fully stored in the controller context’s node elements in advance before the user actually requests or downloads them on the client. This is based on the following circumstances: •

•

Data Binding: Binding: The FielDownload UI FielDownload UI element property data must data must be bound to the context attribute storing the binary data (content) of the downloadable resource. In NW 04 the Web Dynpro Runtime stores this resource in its binary cache and sends the related download URL to the client. UI Element Event Model: Model: The FielDownload UI FielDownload UI element does not provide an action event like onDownload which onDownload which triggers a roundtrip and which could be handled in an action event handler on server side. Consequently the application developer has no possibility to initialize a binary context attribute lazily before lazily before the user actually downloads it and to store the corresponding byte array in it ondemand.

Solution in SAP NetWeaver 04s: Using On-Demand Streams In SAP NetWeaver 04s we can apply a new function in Web Dynpro which solves the above memory consumption problem: •

•

Context Attribute of type Resource : The FileDownload UI FileDownload UI element must be bound to a context attribute of type com.sap.ide.webdynpro.uielementdefinitons.Resource  c om.sap.ide.webdynpro.uielementdefinitons.Resource  . 0-Byte Resource Creation: Creation: At runtime we initially create so-called 0-byte resource objects and objects and store them in the controller context. A 0-byte resource is resource is an object instance of type IWDResource comprising resource metadata  but no binary resource content (0-byte). content (0-byte). This means we just set the variables resourceName (file resourceName (file name) and resourceType (MIME resourceType (MIME type) and then store these resource objects in the context initially. The resource content (byte arrays, java.io.InputStream or IWDInputStream objects) is streamed to these resource objects later on-demand in case the client requests it ( on-demand streaming ). ). How to create a 0-byte resource object of type IWDResource with the WDResourceFactory class will be described in section Populating the Context Node Resources and Creating 0-Byte Resources .

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Uploading and Downloading Files in Web Dynpro Tables 

•

Calculated Context Attribute and On-Demand Streaming: Streaming: Instead of streaming the downloadable binary data to the context initially it is streamed to the client on-demand. This is achieved by invoking the getter method of an additional calculated context attribute which attribute which is referenced by the 0-byte resource object and which returns an object of type IWDInputStream . The required server roundtrip is automatically triggered when the user clicks the file download link in the Web Dynpro view layout.

Summary The process of 0-byte resource creation doesn't creation doesn't initially allocate memory for the file content of the resource object but only for the file metadata. It enables the streaming of this content to be put off until it is actually requested by the client. Instead of being streamed to the context when the table view first gets visible on the UI, the streaming of the file content is deferred until the client actually downloads it and until the calculated context attribute getter method is invoked in the controller on server side. Initially the client only receives the metadata (URL, metadata (URL, file name, MIME type) which is needed to prepare the later download of the file content (in content (in case it is triggered by the user). Context Definition and Data Binding The following diagrams illustrate the context definition and data binding relation of the on-demand stream file download technique:

View Layout

V i e w C o n t e x t D ef ef i n i t i o n Root Node Resources

Table

Attribute Name

Attribute Type

DwldImgOnDemResourceText

string

1

DwldImgOnDemResource

Resource

2

DwldImgOnDemStreamCalc

IWDInputStream 

Column

FileDownload - re reso sour urce ce

Java Dictionary Simple Types

Calculated  Context Attribute

Design Tim e Figure 3: Data binding and Context Definition for On-Demand File Download at Design time  5. The FileDownload UI FileDownload UI element property resource is resource is bound to the context attribute DwldImgOnDemResource of DwldImgOnDemResource  of dictionary type Resource (see Resource (see figure 3, point 1). 6. Additionally a read-only calculated context calculated context attribute DwldImgOnDemStreamCalc  DwldImgOnDemStreamCalc of of type IWDInputStream must be defined (2). There is no data binding relation between the FileDownload  UI element and this calculated context attribute. The relation between the context attribute DwldImgOnDemResource of DwldImgOnDemResource  of type IWDResource to the calculated context attribute DwldImgOnDemStreamCalc of DwldImgOnDemStreamCalc  of type IWDInputStream is implemented in the controller code.

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Uploading and Downloading Files in Web Dynpro Tables 

V i e w L a y ou ou t

V i e w C o nt nt e x t S t a t e

Table

Resources Node Elements

On-Demand Image Image 1 Image 2 Image 3

3 4

retrieve IWDInputStream  object in calculated context attribute getter

Runtime Figure 4: On-Demand File Download in a Table at Runtime  When the user triggers a file download on client side (figure 4, 3) the Web Dynpro Runtime invokes the getter method of the calculated context attribute DwldImgOnDemStreamCalc  DwldImgOnDemStreamCalc returning returning the file content or the binary resource data to be streamed to the client (figure 4, 4). Populating the Context Node Resources and Creating 0-Byte Resources Now let’s have a look at the controller code for our on-demand stream solution. To stream files from the file or backend system on server side to the client on-demand we must instantiate empty instances empty instances of type IWDResource when populating the context data node. A data node is node is a the context node to which the Table UI Table UI element is bound. In this sample application we just populate the data node with three node elements so that the table comprises only three table lines (implemented in supply function supplyResources() . 0-Byte Resource Creation Every node element stores an image resource of another MIME type to be downloaded by the client. The creation of a 0-byte resource object resource object is implemented by invoking a special method of the WDResourceFactory class:  WDResourceFactory.createRe source( IWDAttributePointer attributePointer, java.lang.String resourceName,  WDWebResourceType type)

We do not pass any resource content as content as a byte array to the resource factory but we only pass a pointer to the calculated context attribute instance in the same node element instead. To avoid code redundancy we encapsulate the creation of a 0-byte resource in the private controller method create0ByteResource() .

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Uploading and Downloading Files in Web Dynpro Tables 

Supply Function – TableView.java  public void supplyResources(IPrivateTa supplyResources(IPrivateTableView.IResourcesNode bleView.IResourcesNode node, IPrivateTableView.IContextElement IPrivateTableView.IContextE lement parentElement) { //@@begin supplyResources(IWDNode,IW supplyResources(IWDNode,IWDNodeElement) DNodeElement) String calcAttrName = IPrivateTableView.IResourcesElement.DWLD_IMG_ON_DEM_STREAM_CALC; IPrivateTableView.IResourcesElement IPrivateTableView.IResource sElement resourceElement; // ----------- 1. Resource Node Element -----------------------------resourceElement = wdContext.nodeResources() wdContext.nodeResources().createResourcesElement(); .createResourcesElement(); node.addElement(resourceElement); resourceElement.setDwldImgOnDemResourceText("SAP resourceElement.setDwldImgOnDemResourceText( "SAP Logo - JPG Image"); Image" ); resourceElement.setDwldImgOnDemResource( this.create0ByteResource this .create0ByteResource ( resourceElement, calcAttrName, "SAPLogo.jpg", "SAPLogo.jpg" , );  WDWebResourceType.JPG_IMAGE)  WDWebResourceType.JPG_IMA GE)); // ----------- 2. Resource Node Element -----------------------------resourceElement = wdContext.nodeResources() wdContext.nodeResources().createResourcesElement(); .createResourcesElement(); node.addElement(resourceElement); resourceElement. setDwldImgOnDemResourceText("SAP setDwldImgOnDemResourceText( "SAP NetWeaver - GIF Image"); Image" ); resourceElement.setDwldImgOnDemResource( .create0ByteResource ( this. this resourceElement, calcAttrName, "SAPNetWeaver.gif", "SAPNetWeaver.gif" , WDWebResourceType.PNG)); // ----------- 3. Resource Node Element -----------------------------resourceElement = wdContext.nodeResources() wdContext.nodeResources().createResourcesElement(); .createResourcesElement(); node.addElement(resourceElement); resourceElement.setDwldImgOnDemResourceText("SAP resourceElement.setDwldImgOnDemResourceText( "SAP TechEd - PNG Image"); Image" ); resourceElement.setDwldImgOnDemResource( .create0ByteResource ( this. this resourceElement, calcAttrName, "SAPTechEd.png", "SAPTechEd.png" , WDWebResourceType.GIF_IMAGE)); //@@end } ... //@@begin others /** * Returns a 0-byte resource object of type IWDResource which points to a * calclated attribute instance. * The getter method of this calculated attribute is invoked by the Web * Dynpro Java Runtime after the user triggered the file download on client * side and streams the file content back to the client on on-demand. */ (  private IWDResource create0ByteResource create0ByteResource( IWDNodeElement dataNodeElement, String calcAttrName, String resourceName, WDWebResourceType resourceType) { return WDResourceFactory.createResource( dataNodeElement.getAttributePointer(calcAttrName), resourceName, resourceType); } //@@end

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Uploading and Downloading Files in Web Dynpro Tables 

Implementing the Calculated Context Attribute Getter Method After having implemented the supply function for the table’s data node Resources and Resources and after having created 0-byte resource objects of type IWDResource , we now implement the getter method of the calculated context attribute of type IWDInputStream . In this method we finally stream the binary content of the requested file or resource from the server to the Web Dynpro client on-demand . Calculated Attribute Getter Method – TableView.java TableView.java //@@begin javadoc:getResourcesDwldImgOnDemStreamCalc(IPrivateTableV javadoc:getResourcesDwldImgOn DemStreamCalc(IPrivateTableView.IResourcesElement) iew.IResourcesElement) /** * Getter method for calculated ttribute OnDemandStreamCalc of node Resources. * Return IWDInputStream object for given on on-demand resource, which is deployed * in the same deployable object part (Web Dynpro Component 'FileUpDownloadComp'). @param element * @param  element the element requested for the value * @return the calculated value for attribute DwldImgOnDemStreamCalc */ //@@end  public com.sap.tc.webdynpro.progmodel.api.IWDInputStream getResourcesDwldImgOnDemStreamCalc( IPrivateTableView.IResourcesElement IPrivateTableView.IResour cesElement element) { //@@begin getResourcesDwldImgOnDem getResourcesDwldImgOnDemStreamCalc(IPrivateTableView StreamCalc(IPrivateTableView.IResourcesElement) .IResourcesElement) IWDInputStream onDemandStream = null ; null; try { // ===== SIMPLE CODE only running in SAP NW 04s Stack 12 ======== // Based on a bug this simple coding cannot be implemented. The bug // will be fixed within NW04s SP Stack 12. /*IWDResource resource = WDWebResource.getWebResource( wdComponentAPI.getDeployableObjectPart(), element.getDwldImgOnDemResource().getResourceType(), element.getDwldImgOnDemResource().getResourceName()); InputStream inputStream = resource.read(false); return WDResourceFactory.createInp WDResourceFactory.createInputStream(inputStream);*/ utStream(inputStream);*/ // ===== WORKAROUND CODE ===================================== // Get path of the deployed web resource using the WDURLGenerator service. // NOTE: In a real life application the input stream is retrieved by executing a // corresponding model object (Adaptive RFC, Web Service). String resourcePath = WDURLGenerator.getResourcePath( wdComponentAPI.getDeployableObjectPart(), element.getDwldImgOnDemResource().getResourceName()); // Create file input stream for resource path. // NOTE: The file input stream cannot be closed here. As it is created on-demand // this is a minor restriction. FileInputStream fileInputStream = new FileInputStream( FileInputStream(new new File(resourcePath)); // Create an object of type IWDInputStream by passing the file input stream to the // WDResourceFactory service. onDemandStream = WDResourceFactory.createIn WDResourceFactory.createInputStream(fileInputStream) putStream(fileInputStream); } catch (IOException e) { wdComponentAPI.getMessageManager().reportMessage( IMessageFileUpDownloadComp.FNF, element.getDwldImgOnDemResource().getResourceName()}, urce().getResourceName()}, new Object[] { element.getDwldImgOnDemReso ); true); true } catch (WDAliasResolvingException e) { wdComponentAPI.getMessageManager() .reportException(e.getLocalizedMessage(), true ); true); } return onDemandStream;

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Uploading and Downloading Files in Web Dynpro Tables 

//@@end }

Within the calculated attribute getter method getResourcesDwldImgOnDemStreamCalc() we create an object of type IWDInputStream by passing a file input stream to the WDResourceFactory service class. In this way the 0-byte resource creation implemented creation implemented in the supply function gets finally completed on-  demand by demand by adding the missing content of the resource object which is already stored in the context attribute DwldImgOnDemResource. Keep in mind, that the streamed resource will not be re-calculated again after the first invocation of the calculated context attribute getter method, in our case getResourcesDwldImgOnDemStreamCalc() . After the first invocation of the getter method, the resource is streamed to the client and keeps cached in the Web Dynpro Binary Cache. The Web Dynpro Runtime does not re-invoke the calculated context attribute getter method for a completely initialized, cached resource which is already streamed to the client. Only in case the context attribute stores a 0-byte resource comprising resource comprising no content the calculated context attribute getter method gets invoked. Note In this example all image resources are deployed with the tutorial component, stored under the folder src/mimes/Components/com.sap.tc.wd.tut.fileupdownload.comp. FileUpDownloadComp , so that they can be easily retrieved using the Web Dynpro services WDURLGenerator and WDResourceFactory . In a real Web Dynpro application scenario the file content

must be retrieved by executing a corresponding model object (Adpative RFC, Adaptive Web Service) in the calculated context attribute getter method.

Related Content SDN Tutorial: Uploading and Downloading Files in Web Dynpro Java – SAP NetWeaver 04s SAP Online Help: File Upload and File Download

Sample Application This article is based on a Web Dynpro sample application, which is available for download on the SAP Developer Network (SDN) http://sdn.sap.com under 1. SDN Home → Developer Areas → Web Application Server → Web Dynpro Dynpro Sample Applications and Tutorials 2. Uploading and Downloading Files in SAP NetWeaver 04s (39) 3. Code Sample: Web Dynpro project TutWD_FileUpDownload_NW04s 

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Prerequisites The sample application is based on a SAP NetWeaver 04s – SP Stack 8 installation.

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Uploading and Downloading Files in Web Dynpro Tables 

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