Inside Web Dynpro for Java

Transcription

1 Chris Whealy 2008 AGI-Information Management Consultants May be used for personal purporses only or by libraries associated to dandelon.com network. Inside Web Dynpro for Java "m HOCHSCHULE M LIECHTENSTEIN Bibliothek Galileo Press Bonn Boston

2 Author's Apology Preface to the Second Edition 21 Part I: Background Introduction...,...,.« Why Did SAP Decide to Build Their Own Web Development Framework? What Is Web Dynpro? Causes of Poor Web Dynpro Implementations How Web Dynpro Differs from Other Web Development. Tools ' The Fundamental Difference Between Web Dynpro and. Other Web Development Tools A Quick History Lesson The Original Design Concept : The Web Dynpro Implementation The Design Philosophy Behind Web Dynpro Design Influences Why Do I Need an SAP-Supplied Server To Run a Web Dynpro Application? The.Influence of MVC on Web Dynpro The User's Mental Model A Top-Down Approach Interacting with Business Objects Simplifying the Editor The Essence of the MVC Design Concept The Data Consumer-Generator Concept in Web Dynpro The Influence of SAP's Requirements on Web Dynpro.' The Consequences of a Declarative Approach to Ul Design :' Decoupling Data Presentation from Data Processing The Influence of Focus Groups on Web Dynpro What Do I Need To Understand To Be Successful with Web Dynpro? Using Web Dynpro to Reproduce the User's Mental Model of the Data 48

3 Understanding the Data Generator-Consumer Concept Is Writing a Web Dynpro Program Just a Matter of Writing Models, Views, and Controllers?...' 48 Part II: The Fundamental Concepts 2 The Web Oynpro GouMJonent Concept.,...,...,....,...« A Typical MVC Architecture The Web Dynpro Component Concept How Does a Web Dynpro Component Alter Reenskaug's Original Design?.: ' Why Bother with Components? Inside the Web Dynpro Component What Do the Different Parts of the Component Do? The Programmatic Parts of a Component : 60 j The Visual Parts of a Component Inside a Web Dynpro Controller Architecture of Non-Visual Controllers Architecture of Visual Controllers Controller Interaction Communication Between Controllers...: Usage Declarations ; Context Mapping Data Bjnding Summary of the Roles Played by the Different. Controllers Web Dynpro Applications or "Where Does My Component Sit in the Big Scheme of Things?" Accessing Web Dynpro Functionality from a Browser ;... ' Simple Application Structure More Realistic Application Structure Application Properties, Application Parameters Start Up and Shut Down Managing Web Dynpro Components ~ 87 10

4 3 Desifrting a Web Dynpro Application...».*..^,**-« The SAP Component.Mpdel...,...,.-, Development Component Naming Conventions Child Development Components Software Components, Full Component Hierarchy Developing Without the NWDI..: Architectural Concepts of the NWD, The Design Time Repository (DTR) The Component Build Service (CBS) The Change Management Service (CMS) Building Web Dynpro Applications Using the NWDI : A Frequently Asked Question Sharing Web Dynpro Functionality Between Multiple DCs Preparation and Planning The Rule of the-seven P's You Get What You Pay For There Is No Substitute for Good Training and Experience Oh and by the Way, Can You Just Add this Functionality?.' : The Partner Over-Sells Themselves Functional Scope Realistic Deadlines and Trained Project Staff What's the Value of Not Making a Mistake? Access to Business Functionality Planning the User Interface: Creating a Story Board Analysis of the Business Process from Various Perspectives Design Avoid Monolithic Coding Structures Avoid Excessive Fragmentation...: Getting the Balance Right ; Component Hierarchy Using Model Components in the Component Hierarchy Component Interface Definitions Configuration Requirements Localization Requirements

5 3.5.9 Location of Business Processing Implementation Management of Child Component Instances Intercomponent Communication Internal Data Storage Within Web Dynpro Components Centralized Functionality.; Correct Use of Standard Hook Methods Phase Model Processing and Component Instantiation Web Dynpro Hook Methods The Relationship Between Phase Model Processing and Web Dynpro Windows Phase Model Processing Transport Data to Data Container doapplicationstatechange; The Floating Step Part 1.'...'., Validate and Transport Data..., Call System Event Handlers..., Call Service Event Handlers Application Event Handlers -. : dobeforenavigation Navigation and View Initialization Dynamic Ul Manipulation Client Specific Ul Validation dopostprocessing doapplicationstatechange:the Floating Step- Part 2...' Response Rendering, Summary 159 Part III: Basic Development 5 The Context at Design Time.,..,.,..., 5.1 Nodes Attributes Node and Attribute Data Types Context Attribute Data Types that Can Supply Data to Ul Elements

6 5.5 Terminology Concerning Nodes and Attributes What's the Difference Between Value Nodes and. Model Nodes? ; Value Nodes Model Nodes, The Most Important Node Properties to Understand * Node Cardinality Node Selection Cardinality The Singleton Property, : Should Node Names Be Singular or Plural? General Naming Conventions..' Identifying a Specific Node Attribute Calculated Attributes Implementing a Getter Method Implementing a Setter Method Coding Principles for Getter and Setter Methods Internal Context Mapping ' External Context Mapping Supply Functions Dispose Functions, Coding Principles for Supply and Dispose Functions Recursive Context Nodes Creating Recursive Context Nodes Mapping Recursive Context Nodes Restrictions on the Use of Recursive Nodes Fundamental Principles of the Context 205 Context Stelctare at Runtime,..-..«.,...,..*...,...,,» t] Generated Classes : The Typed Context API ;., Background to the typedaccessrequired Flag.. ; The Byte Code Minimizer Generated Classes and Context Mapping Working with Value Nodes Accessing the Context Through the Typed API Accessing a Node Element, Accessing all Elements in a Node Creating a New Node Element Treating the Node Lineltems as a Singleton Node Treating the Node Lineltems as a Non-Singleton Node 221

7 6.2.7 Accessing the Context Through the Generic API Working with Model Nodes = Adding Elements to a Model Node Collection Binding Elements to a Model Node Collection Working with Recursive Nodes Using the WDCopyService How are UI Elements Stored Within a View Controller? Editing a View Layout, Adding Ul Elements to the View Layout Editing Existing Ul Elements on the View Layout Putting Data on the Screen ' Data*Bindjng Binding Ul Properties to the Context Controlling U Element Behavior from the Context Impact of Data Binding on the Coding Avoiding a Possible Source of Confusion ; Layout Managers Flow Layout Row Layout, Matrix Layout Grid Layout.*! Layout Manager Properties Principles for the Efficient Use of layout Managers Composite Ul Elements A Simple Composite Ul Element Composite, Composite Ul Elements Binding Table Ul Elements to the Context Runtime Behavior of a Table Ul Element Ul Element Events and View Controller Actions Declaration and Association with a Ul Element Event...: Implementation Action Types Event Types Coding Generated by an Action Declaration Parameter Mapping Multiple Ul Element Events Handled by One Action Event Handler

8 Further Decoupling of the Ul Advanced Parameter Mapping Example Generic Ul Services' Simple Value Selector Extended Value Selector Extending the List of Values Shown in a Simple or Extended Value Selector Object Value Selector Implementing an'object Value Selector Using Messages and the Message Manager Location of Messages on the Screen, Accessing the Message Manager Reporting a Simple Message Locale-Dependent Text at Runtime Reporting a Message Held in the Message Pool Relating Messages with UI Elements Locale-Dependent Text Defined in the Java Dictionary :...! Defining Placeholders Within a Message Text 285 7A0.9 Process Control Using the Message Manager Internationalization Externalization, Web Dynpro i18n Concept S2X: SAP's Use.of.the XLIFF Standard Storing Language-Specific Text in XLF Files Translating XLF Files.: Use of the S2X Editor Within NWDS Editing Message Pool XLF Files Runtime Locale Determination 294 Part IV: Advanced Development 9 Dynamic Context Manipulation 9.1 Dynamic Addition of an Unmapped Context Node Before the Coding Details Are Discussed, Though Now for the Coding Dynamic Creation of a Hierarchy of Context Nodes 302

9 9,2 Dynamic Addition ofa Mapped Context Node Technique Technique : Method replicatenodelnfoo ' Working with Tree Ul Elements Types of Tree UI Element Building a Tree Whose Depth Is Known at Design Time....,.,.,..., Building a Tree Whose Depth Is Unknown at Design Time...'...,.,,. " Building a Contexj; Node Suitable, for a Tree Ul Element,,,..., Making a Tree Node Interactive Properties of Tree Ul Elements' Efficient Use of Actions to Enable and Disable Ul Elements Programmatic Assignment of Actions to Ul Element Objects Accessing Existing Ul Elements in a View Layout Accessing Ul Elements by Name Accessing Ul Elements Generically Introduction to Dynamic View Generation The Principles of Dynamic View Construction..; Is There a Simpler Way of Doing It? The Fundamental Principles of Dynamic View Layout Construction Dynamic Constructioh of a Ul Element Hierarchy Implementation Example Implementation ofthe Method wddomodifyviewo Implementation of the Method shownodeo Implementation of the Method shownodeascolumnso Implementation of the Method shownodeastableo Implementation of the Method getuielemento Implementing an OVS Basic Concept Assigning the OVS Extension to a Context"Attribute OVS Processing OVS Implementation

10 11 Navigation and Irror Handling,, (,. m -«,... < H, rth» M, WWMft!,,« Navigation Processing The View Assembly Outbound Navigation Plugs Inbound Navigation Plugs Navigation Processing Re-Entrant Navigation Links 365 Suspend and Resume Plugs : Declaring Suspend and Resume Plugs Suspend and Resume Plug Processing : Requirements for an External. Website, : Configuring Time-Out Values 374 Error Handling The Input and Output Halves of the Phase Model Processing Centralized Error Handling Error Handling Across a Component Hierarchy 382 " Principles for Handling Errors Trapped Before Navigation Principles for Handling Errors Trapped After Navigation BflfflfllSaTt^nfolBlllllilllllllllillllllllllW Web Dynpro Components and Polymorphism 387 Pop-Up Windows Single Round-Trip Pop-Up Window Multiple Round-Trip Pop-Up Windows Opening an External Window Application and URL Properties Application Properties URL Properties A Brief History Lesson..' The Origins of RFC Java Connector and the Adaptive RFC La^er The Enterprise Connector The Common Model Interface 412

11 13.2 General Introduction to BAPIs What Is a BAPI? ABAP Function Module Interface Custom-Written RFC Modules Introduction to the Adaptive RFC Layer Creating Adaptive RFC Models Structuring a Model Explanation of Generated Model Classes Model Naming Convention Executable and Non-Executable Model Objects Model Structures The Model Dictionary Model Object Hierarchies and Relation Roles Web Dynpro Models and Development Components Using Model Objects in a Web Dynpro Controller Model Objects and the Context The Relationship Between the Contents of a Model Object and Its Corresponding Context Model Node Altering a Model Object's Logical System After It Has Been Created A Simple Example Using Context Model Nodes at Runtime Preparing the Context at Design Time Component Controller Coding View Controller Coding : Look at What Has Not Been Done Adapting to Changes in an RFC Interface Connecting to an SAP System Logon Parameters Language Client Identifying the Correct Backend System Logical JCo Destinations Prerequisites for Creating a Technical System Creating a Technical System Creating a JCo Destination TheJCo Pool Concept Pool Allocation Pool Naming Conventions Pool Definition

12 14.4 Pool Usage at Runtime : ; Correct Design of Web Dynpro Applications Incorrect Design of Web Dynpro Applications Correcting a Poor Model Architecture ; Model Scope Type ; Calculating JCO Pool Size : ' Metadata Connections Pool Optimization Metadata Connection Usage Impact of JCo Connections on the SAP Gateway Process Relationship Between JCO Destinations and ABAP Sessions Logging on to an SAP System ABAP Sessions Performing ABAP Database Updates Without ^ ' Causing an Unwanted'Session Change Statements to Avoid in an RFC Module Avoiding the Read-Write-Read.Problem 492 Web Dynpro Naming Placeholders 499 A.1 Web Dynpro Component Architecture 499 A.2 Web Dynpro Controllers 499 A.3 Model Objects :.,,..., 500 A.4 NetWeaver Development Infrastructure Entities 500 A.5 Context Entities 500 A.6 Generic and Composite Abbreviations 501 A.7 Subscripts for Composite Placeholders Using the SAP Recommended Suffixes 502 A.8 AS Java Placeholders..: 503 Naming Conventions 505 B.1 General Rules for Naming ;, 505 B.2 Naming Conventions for Coding Entities 505 B.2.1 Applications: ${n a } = ${a}app 505 B.2.2 Components: ${n c } = ${c}comp 506 B.2.3 Component Interface Views: ${n civ } = ${w}lnterfaceview 506 B.2.4 Component Usage: ${n u } = ${n c }${p}lnst or ${cid}${p}lnst 506 B.2.5 Custom Controllers: ${n cc } = ${cc}cust 506 B.2.6 Inbound Plugs: ${n pi } = ${p jn }ln 506 B.2.7 Models: ${n m } = ${m}model

13 B.2.8 Outbound Plugs: ${n po } = ${p out }Out, 507 B.2.9 Component Interface Definition: ${n cid } = ${cid}compl 507 B.2.10 Component Interface View Definition: ${n civ } = ${n cid }<any_name> 507 B.2.11 Views: ${n v } = ${v}view 507 B.2.12 Viewsets: S{n vs } = ${vs}viewset 508 B.2.13 Windows: ${w} = ${n c } or ${n c }Window or <any_name>window 508 C Exercise tp^display a File System Using a Recursive Context Node Structure 509 C..1 Create a New Web Dynpro DC 509 C.2 Create a Web Dynpro Component 510 C.3 Create a Java Bean to Represent a Directory Entry 510 C.4 ' Import the Java Bean as a Model, C.5 Component Controller Configuration 513 C.5.1 Declare Model Usage 513 C.5,2 Context Configuration, 513 C.5.3 Method Declarations and Coding 514 C.6 View Controller Configuration 517 C.6.1 Context Configuration 517 C.6.2 Create an Action 517 C.6.3 Editing the View Layout 518 C.6.4 View Controller Implementation 518 C.7 Create an Application 519 C.8 Comment on the Use of Standard SAP Icons, 520 D ABAP Coding 521 E Dictionary Structures 525 F The Author 527 Index :...: