SAP NetWeaver Web Dynpro ABAP 开发指南

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"Web Dynpro ABAP编程指南是SAP NetWeaver开发者指南的一部分，主要针对SAP NetWeaver 2004s版本的Web Dynpro ABAP开发。这份文档由SAP AG出版，提供了关于如何使用ABAP进行Web Dynpro应用开发的详细指导。" 在Web Dynpro ABAP编程中，以下几个关键知识点是非常重要的： 1. **Web Dynpro概念**：Web Dynpro是一种用于构建企业级Web应用程序的技术，它提供了丰富的用户界面（UI）设计和强大的业务逻辑处理能力。它包含组件（Components）、视图（Views）、控制器（Controllers）和上下文（Context）等核心概念。 2. **组件（Components）**：组件是Web Dynpro应用程序的基本单元，包含了所有必要的UI元素、业务逻辑和数据模型。开发者可以创建多个视图和控制器在一个组件内，以实现不同功能和展示方式。 3. **视图（Views）**：视图是用户界面的可视化部分，用于显示数据并允许用户交互。视图可以是静态的，也可以是动态的，可以通过控制器改变其内容和布局。 4. **控制器（Controllers）**：控制器负责处理用户输入、执行业务逻辑和更新视图。一个组件可以有多个控制器，每个控制器专注于特定的用户交互或业务流程。 5. **上下文（Context）**：上下文是组件中存储数据的地方，类似于Java Bean的概念。它提供了模型（Model）与视图和控制器之间的数据交换机制。 6. **模型（Model）**：模型负责管理数据，可以来源于数据库、其他服务或外部系统。模型将数据抽象化，使视图和控制器能够独立于数据源进行操作。 7. **事件处理**：Web Dynpro ABAP支持事件驱动的编程模型，事件可以由用户交互、系统状态变化或定时器触发。控制器通过处理这些事件来响应用户操作或系统变化。 8. **接口和依赖注入**：Web Dynpro ABAP支持定义和使用接口，以及依赖注入技术，这有助于提高代码的可重用性和可测试性。 9. **屏幕元素（Elements）**：Web Dynpro提供了多种屏幕元素，如文本字段、按钮、选择框等，用于构建用户界面。开发者可以自定义这些元素的行为和外观。 10. **表达式语言（Expression Language）**：Web Dynpro ABAP有自己的表达式语言，用于在视图和控制器中进行简单的数据操作和条件判断。 11. **调试和测试**：SAP提供了专门的工具进行Web Dynpro ABAP应用的调试和测试，包括模拟用户交互、检查运行时状态和性能分析。 12. **版本管理和部署**：Web Dynpro ABAP支持版本控制，允许开发者在不中断生产系统的情况下进行开发和测试。完成的组件可以发布到不同的系统，如开发、质量保证和生产环境。请注意，以上内容仅涵盖了Web Dynpro ABAP编程的一些基本概念和关键知识点。实际的开发过程中，开发者还需要深入学习和掌握更多细节，如数据绑定、异常处理、性能优化等方面的知识。此外，SAP提供的文档和工具是学习Web Dynpro ABAP的重要资源，建议结合实际操作来提升理解和应用能力。

Basics May 2006

Web Dynpro ABAP: Development in Detail 10

Data Binding Using the Wizard

A wizard is available for some UI elements to make it easier to specify the design of the UI

element by including the structure of the corresponding context node in the layout design.

Example:

When a table is bound to a context node using a wizard, it is not necessary

to create each table column individually. Instead the wizard provides the

corresponding context and once you selected the context node, it also provides

the available attributes. You can now select the node attributes to be actually

displayed in the table. In addition, you can change several properties of the

column elements. When the wizard operation is completed, the required table

columns in the view layout are created and the required data binding is

performed.

You start the wizard by selecting the option Create Binding in the context menu of a UI

element in the tree structure below the root container.

Attributes Flagged as "Nullable"

For some UI elements (for example, those of a numeric type or of the type T) that are bound

to a context attribute, any fields without a value are automatically output with the value null. In

the case of the type NUM4C, this is the value “0000“, while for the type T it is “00:00:00“, and

so on.

This behavior may be undesirable in some cases and can therefore be stopped by carrying

out the following steps:

● First, you must use the method IF_WD_CONTEXT_NODE_INFO=>SET_NULLABLE( )

to flag the value in the node info as nullable. You can either set individual attributes or

all attributes of a node as nullable.

● In your second step, you must set the actual value to “null”. For this purpose, the

interface IF_WD_CONTEXT_NODE provides the method set_attribute_null(

'”Node_Name”' ). Another possibility is to enter an empty string in the input field (that is,

delete any contents).

1.2.4 UI Element Actions

Several UI elements contain actions [externaly]. Actions are special events triggered by

activities of the user on the user interface of an application. Corresponding event handlers

specify the subsequent processes of the application. The following example illustrates the

procedure:

You create an action for UI element Button. In the event handler method

of this action, you specify the response of the application when the user selects

the UI element Button.

An action is always linked to exactly one event handler method. In some cases, however, you

might want to simultaneously use the same action for multiple UI elements in a view. For

more information on the required parameterization for multiple-use actions, refer to Parameter

Mapping [page 11].

Basics May 2006

Web Dynpro ABAP: Development in Detail 11

Creating Actions

As is the case with data binding, actions of UI elements are created and maintained in the

properties table of the View Editor.

Event Handler Methods

When you create a new action, the corresponding event handler method is created

automatically. It is empty at first and the application developer can insert source code using

the ABAP Editor. The event handler methods are – like all other methods of the view - part of

the view controller. Therefore, they are listed in the table of the Methods tab in the View

Editor.

Controller Methods

Event handler methods are special methods of a controller – in this case, of the view

controller. From a technical point of view, they do not differ from other controller methods like

the initial method WDDOINIT or the method WDDOEXIT. Due to a convention, however, their

names have the prefix ONACTION followed by the action name specified by the application

developer. Example:

If an action of a UI element has the name GO, the corresponding event

handler method is automatically called ONACTIONGO.

For information on programming event handler methods and example programs, refer to

Programming Controller Methods [page 12].

1.2.4.1 Parameter Mapping

Parameter mapping is used for multiple use of actions. If you use one action for several

events - for example, multiple buttons - you require unique information to specify the desired

assignment. You can get this information using parameter mapping.

We do not recommend that you pass the action ID – that is, use the

standard parameter IDs - since this method is not platform-independent.

Parameter mapping is performed by a program:

DATA PARAMETERS TYPE WDR_NAME_VALUE_LIST.

DATA PARAMETER TYPE WDR_NAME_VALUE.

DATA data_ref TYPE REF TO data.

FIELD-SYMBOLS <data> TYPE any.

" Parameters can be simple values

PARAMETER-NAME = 'LINES_TO_INSERT'.

PARAMETER-VALUE = '3'.

PARAMETER-TYPE = CL_ABAP_TYPEDESCR=>TYPEKIND_STRING.

INSERT PARAMETER INTO TABLE PARAMETERS.

" Parameters can be object references

PARAMETER-NAME = 'CUSTOMER'.

PARAMETER-OBJECT = customer_object.

PARAMETER-TYPE = CL_ABAP_TYPEDESCR=>TYPEKIND_OREF.

INSERT PARAMETER INTO TABLE PARAMETERS.

Basics May 2006

Web Dynpro ABAP: Development in Detail 12

" Parameters can be deep data objects (structure/table)

CREATE OBJECT data_ref LIKE table.

ASSIGN data_ref->* TO <data>.

<data> = table.

PARAMETER-NAME = 'TABLE'.

PARAMETER-DREF = data_ref.

PARAMETER-OREF = CL_ABAP_TYPEDESCR=>TYPEKIND_DREF.

INSERT PARAMETER INTO TABLE PARAMETERS.

" Specify parameter mapping

CL_WD_BUTTON->MAP_ON_ACTION( parameters ).

" Read parameter mapping

CL_WD_BUTTON->MAPPED_ON_ACTION( importing parameters = parameters ).

When the event is triggered, the linked action is called using the following parameters:

● Web Dynpro ABAP standard parameters [externaly] (ID and CONTEXT_ELEMENT)

● Special parameters of the UI element

● Event parameters specified in the parameter mapping

The parameters can be defined as method parameters of the action. The type of method

parameters must be MOVE-compatible with the parameter values.

All method parameters are mandatory. If not all method parameters are

filled with event parameters when calling the action, an exception is raised.

Parameter values can also be read using the WDEVENT object:

= WDEVENT->GET_INT( 'LINES_TO_INSERT' ).

= WDEVENT->GET_OBJECT( 'CUSTOMER' ).

= WDEVENT->GET_CONTEXT_ELEMENT( 'CONTEXT_ELEMENT' ).

= WD_EVENT->GET_DATA( EXPORTING name = 'TABLE' importing value = table ).

1.2.5 Action Event Handlers

If an action [externaly] of a UI element is triggered on the user interface of a Web Dynpro

application, the event handler of the view controller linked to this action is automatically

called. In the event handler, the application developer adds the source code for the steps that

will trigger the action. Examples for these steps:

● Reading, editing, and resetting context elements

● Calling function modules

● Triggering navigation

Programming

From a technical point of view, an event handler differs from other controller methods only in

that it also responds to the event assigned to the event handler. For programming all

controller methods, you can choose from several special classes with attributes and methods

used to execute the processing steps specific to Web Dynpro. The following simple example

describes in detail a possible structure of a controller method for the handling of an action.

Basics May 2006

Web Dynpro ABAP: Development in Detail 14

First, all of the required internal variables are declared:

● INPUT_NODE is declared as an internal variable for the context node of the user input

● TABLE_NODE is declared as an internal variable for the context node of the result table

● CAR is declared as an internal variable of the user input

● FLIGHTS is declared as an internal table for the result representation

In this example, the table

FLIGHTS refers to the Dictionary table SPFLI and therefore does not

need be declared in more detail.

Importing the User Input

The internal variable INPUT_NODE is bound to the context node INPUT_NODE:

INPUT_NODE = WD_CONTEXT->GET_CHILD_NODE( 'INPUT_NODE' ).

To do this, you use the attribute WD_CONTEXT and the method GET_CHILD_NODE of the

interface IF_WD_CONTEXT_NODE [externaly] which is available in the Web Dynpro

framework.

The attribute

WD_CONTEXT is always a reference to the local controller context: The method

ONACTIONGO is a method of the current view controller. This means that WD_CONTEXT is the

reference to the context of the current view in this case (see chapter Reference Variable

WD_CONTEXT) [page 19]

The method

GET_CHILD_NODE returns the reference to the context node INPUT_NODE.

The method

GET_ATTRIBUTE of the same interface subsequently reads the context attribute:

INPUT_NODE->GET_ATTRIBUTE( exporting Name = 'IN1'

importing Value = CAR ).

This method retrieves the value of the attribute IN1 from the context node INPUT_NODE and

passes it to the internal variable CAR.

This means that the value of the UI element Inputfield is passed to the method

ONACTIONGO using the view context and can now be edited.

Filling the Result Table

The internal table FLIGHTS is filled using a formatted class which, in this example, is called

CL_WD_FLIGHT_MODEL and contains the method GET_FLIGHTS_BY_CARRID. Variable CAR is

passed to this method.

FLIGHTS = CL_WD_FLIGHT_MODEL=>GET_FLIGHTS_BY_CARRID( CAR ).

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