Tiven Wang
Tiven Wang
Tiven Wang
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ABAP CDS - Abap Annotations

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Wang Tiven December 11, 2019
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Annotations

这里所讲的 ABAP Annotations 是指会被 ABAP 代码用到的 Annotations , 例如 @Semantics 类的 Annotations 有些是用在 OData 和 UI 的, 有些则是被 ABAP 代码用到的.

官方文档 ABAP CDS - ABAP Annotations

AbapCatalog Annotations

  • @AbapCatalog.buffering: 参考SAP Buffering of CDS Views
  • @AbapCatalog.compiler.compareFilter: 参考path expression specify whether the filter conditions are compared for the path expressions of a view. If the filter condition matches, the associated join expression is created only once, which generally improves performance. Otherwise a separate join expression is created for each filter condition. However, the results sets of both configurations can differ.
  • AbapCatalog.dbHints
  • AbapCatalog.preserveKey: 说明 CDS database view 的主键是否与关键字 KEY 定义的一致;
  • AbapCatalog.sqlViewAppendName
  • AbapCatalog.sqlViewName
  • AbapCatalog.viewEnhancementCategory[ ]

AccessControl Annotations

  • AccessControl.authorizationCheck: specifies implicit access control, 参考Access Control
    • #CHECK: 做检查
    • #NOT_ALLOWED: 不做使用权限检查来过滤数据, 如果有相应的 role 存在则会报警告
    • #NOT_REQUIRED: 不要求, 有就检查和过滤没有就不检查, 在运行时的行为和 #CHECK 是一样的, 但它可以在书面上告知没有 role 存在
    • #PRIVILEGED_ONLY: 只允许有 the addition WITH PRIVILEGED ACCESS in the FROM clause of an Open SQL query 的访问

EndUserText Annotations

  • EndUserText.heading:
  • EndUserText.label:
  • EndUserText.quickInfo:

Environment Annotations

  • Environment.sql.passValue
  • Environment.systemField: assigns an ABAP system field to parameter
    • #CLIENT
    • #SYSTEM_DATE
    • #SYSTEM_LANGUAGE
    • #SYSTEM_TIME
    • #USER

Metadata Annotations

  • Metadata.allowExtensions: 允许使用 metadata extensions 扩展 View 的 metadata
  • Metadata.ignorePropagatedAnnotations: specifies how propagated annotations are evaluated using the class CL_DD_DDL_ANNOTATION_SERVICE
  • Metadata.layer: specfies layer in CDS metadata extension
    • #CORE
    • #CUSTOMER
    • #INDUSTRY
    • #LOCALIZATION
    • #PARTNER
  • MetadataExtension.usageAllowed: specifies the distribution of the annotation in CDS metadata extensions

Semantics Annotations

  • Semantics.amount.currencyCode: Currency field
  • Semantics.currencyCode: Currency key
  • Semantics.quantity.unitOfMeasure: Quantity field
  • Semantics.unitOfMeasure: Unit key

CDS Views

首先我们要理清楚 CDS View 相关的 ABAP 对象. 当一个 CDS view 的 CDS data definition 被激活后, 有两种 ABAP Dictionary objects 会生成:

  • CDS entity:
    • 代表了实际的 CDS view, 它是基于 CDS database view 的并且多了一些属性如权限控制.
    • 它不能在 SE11 查看, 但可以在 abap 里用作为一个 data type 和被 Open SQL 读取.
    • 它可以作为其他 CDS Entity 的 data source, 但不能用作为 ABAP Dictionary 中的 classic dictionary objects 的数据类型;
  • CDS database view:
    • 是 CDS view 在 ABAP Dictionary 中的技术基础, 它实际上是一个只读的传统的 database view, 它的名字是来自于 @AbapCatalog.sqlViewName 注解.
    • 它被激活时相应的 SQL View 同时会被创建.
    • 如果其 CDS view 是 client-specific 的, 那么此 CDS database view 总是有一个 client 列, 而 CDS entity 却没有.
    • 可以被当作 any classic structure 来用, such as the type of a substructure, as an include structure, or as the row type of a table type.
    • 但不要用在 ABAP 代码里, 只能用在数据表或者传统数据视图能用在的地方 such as after the TYPE addition, 或者 in Open SQL read statements and also in Native SQL. 但是用在 Open SQL 里也已经不再支持了, 最好直接使用 CDS View entity 在 Open SQL 里.

A CDS view has two types of keys:

For CDS entities, KEY can be used to define key elements. This key is the semantic key of the CDS view. The key of the CDS database view is determined implicitly, as in a classic view. This key is the technical key of the CDS view.

Notes

  • CDS views are defined as platform-independent views. They can, however, contain components that are not currently supported by all database systems. Before an ABAP read, the class CL_ABAP_DBFEATURES can be used to determine whether the feature is supported in the current system, which stops an exception from being raised.

Client Handling in CDS Views

众所周知 ABAP Table 是分为 Client 相关和 Client 无关(cross-client)的, 所以当使用 CDS View 查询数据表时也会涉及 Client 字段问题.

@ClientHandling.type 注解是决定 CDS View 使用哪种 Client 策略:

  • #INHERITED: Default value. Client 策略依赖于它所查询的数据源们, 如果它依赖的数据源里有一个是 client-specific, 那么它就是 client-specific, 否则就不是(或者称为 cross-client view).
  • #CLIENT_DEPENDENT: 此视图是 client-specific, 但前提是至少有一个数据源是 client-specific 的, 否则会有语法错误.
  • #CLIENT_INDEPENDENT: 此视图是 cross-client view, 但前提是没有任何一个数据源是 client-specific 的, 否则会有语法错误.

@ClientHandling.algorithm 注解决定了隐式 client handling 怎么执行.

  • #AUTOMATED: 是当 @ClientHandling.type 为 #INHERITED and #CLIENT_DEPENDENT 时的默认值. 不能和 #CLIENT_INDEPENDENT 一起用.
  • #SESSION_VARIABLE: 不能和 #CLIENT_INDEPENDENT 一起用. 它会在 WHERE 条件中加上 Client 列等于 $session.client 的值.
  • #NONE: #CLIENT_INDEPENDENT 时的默认值. 此不考虑客户端情况.

#AUTOMATED 和 #SESSION_VARIABLE 产生的结果是一样的, 但当你只考虑但客户端情况时 #SESSION_VARIABLE 有更好的效率.

SAP Buffering of CDS Views

https://help.sap.com/doc/abapdocu_751_index_htm/7.51/en-us/abencds_sap_puffer.htm

当对 CDS views 使用 SAP buffering 时, 它要满足以下条件:

  • 它不能包含任何其他视图(database views 或者 CDS Views)作为数据源;
  • 一个 client-specific view 只能使用 session variable 中唯一的一个 $session.client, cross-client view 不能使用任何 session variables;
  • The required key fields must be listed directly in the SELECT list. Key fields that only occur as arguments of expressions cannot be evaluated;

但是有一个问题值得思考, 当 ABAP 应用服务器是基于 HANA DB 时此 SAP Buffering 对于基于 CDS Views 访问的情况还是否有意义,因为 HANA DB 本身数据就是在内存中的?

SAP Buffering 涉及到的 CDS Annotations:

  • AbapCatalog.buffering.numberOfKeyFields: number of key fields when buffering generic areas
  • AbapCatalog.buffering.status: enables and disables buffering
  • AbapCatalog.buffering.type: defines the buffering type

path expression

一种关联和过滤 associations 的路径条件表达式, 可以对其指定 parameters 或者 attributes 来过滤:

... [viewEntity.]_assoc1[parameters][attributes]
               [._assoc2[parameters][attributes] ... ][.element] ...

例如:

define view invoice as
  select from
         /* Association "sales_order" with filter as data source */
         business_partner.sales_order[lifecycle_status <> 'C' and lifecycle_status <> 'X']
           as bpa_so //alias for data source
         /* Association only used in this view definition */
         association [0..1] to snwd_so_inv_head as _invoice_header
           on bpa_so.node_key = _invoice_header.so_guid
        { key bpa_so.node_key, //Field from ON-condition in _invoice_header
              bpa_so.so_id,
              bpa_so.note_guid, //Field from ON-condition in note_header
              bpa_so.lifecycle_status,
              /* Association is not published, but its element */
              _invoice_header.dunning_level,
              /* Association from data source is published here */
              bpa_so.note_header }
          /* Path expression in WHERE clause */
          where _invoice_header.dunning_level > '0';

Path expression 还可以用在 ABAP CDS DCL 的条件中.

path expression parameters

如果 data source 是一个带输入参数的 CDS View,则需要提供参数 parameters 给它.

path expression attributes

路径表达式的属性是指以下三种:

  • Declaration of monovalency: 声明是对一还是对多.
  • Category of the join expression: join 类型 inner join 或者 left outer join
  • Specified filter conditions: 指定过滤条件

[ [1|*:] [INNER|{LEFT OUTER} [WHERE]] [ cond_expr] ] ...

@ObjectModel.text.element:  [ 'SoldToPartyCountryName' ]
SoldToPartyCountry,

@Consumption: {
  groupWithElement: 'SoldToPartyCountry',
  filter.hidden: true
}
@EndUserText: {
    label:     'Customer Country Name',
    quickInfo: 'Customer Country Name'
}
_SoldToPartyCountry._Text[1: Language = $session.system_language].CountryName      as SoldToPartyCountryName,

cond_expr

ABAP CDS - cond_expr

Access Control

ABAP CDS - Access Control

  • CDS access control does not work for cross-client access.

The value #NOT_REQUIRED is recommended for entities for which no authorization checks are planned yet, but might be needed by the developer or customer laster. To prohibit roles for the entity, use the value #NOT_ALLOWED.

  • AccessControl.privilegedAssociations
  • AccessControl.personalData.blocking

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