SAP Web应用服务器
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Web应用服务器 (WAS或者Web AS)是NetWeaver解决方案的一个组件。在SAP看来，web应用服务器是他们大部分产品运行的基础。
概览
它的基本功能是用于基于SAP标准解决方案编程语言(通常是ABAP)的web开发，但新版本也允许使用Java语言进行开发。有了web应用服务器，在web环境下基于SAP解决方案基础设施发布查询，程序和ABAP应用就有了可能。新版的WAS也支持像Java这样的开放标准。6.20以上的版本里可以单独创建ABAP程序，Java程序或者两者的混合。
Architecture
The architecture of SAP Web Application Server can be separated into five areas:
- Presentation layer. In the presentation layer, the user interface can be developed with Java Server Pages (JSP), Business Server Pages (BSP), or with Web Dynpro technology. The underlying business layer provides the business content in Java or ABAP.
- Business layer. The business layer consists of a J2EE certified run-time environment that processes the requests passed from the ICM and dynamically generates the responses. The business logic can be written either in ABAP or in Java based on the J2EE standard. Developers can implement business logic and persistence with Enterprise JavaBeans (EJB) using the J2EE environment. Developers can also access the business objects of applications running in the ABAP environment to benefit from their business logic and persistence.
- Integration layer. The local integration engine is an integral part of SAP Web AS and allows instant connection to SAP XI. The local integration engine provides messaging services that exchange messages between the components that are connected in SAP XI.
- Connectivity layer. The Internet Communication Manager (ICM) dispatches user interface requests to the presentation layer and provides a single framework for connectivity using various communication protocols. Currently, modules are available for Hypertext Transfer Protocol (HTTP), HTTPS (extension of HTTP running under the Secure Socket Layer (SSL)), Simple Mail Transfer Protocol (SMTP), Simple Object Access Protocol (SOAP), and Fast Common Gateway Interface (FastCGI).
- Persistence layer. The persistence layer supports database independence and scalable transaction handling. Business logic can be developed completely independent of the underlying database and operating system. Database independence is also made possible by support for open standards. The database interface ensures optimized data access from within the ABAP environment through Open SQL. SAP propagates the outstanding capabilities of Open SQL for ABAP to Open SQL for Java and offers a variety of standard Application Programming Interfaces (APIs) to application programmers, such as SQLJ. Other technologies, such as Java Data Objects (JDO) and container managed persistence (CMP) for EJB, or the direct use of the Java Database Connectivity (JDBC) API, are also supported.