Database Reference
In-Depth Information
CHAPTER 3
SAP NetWeaver Application Server Java Overview
SAP NetWeaver Application Server Java (NW AS Java) provides a robust infrastructure for
building standards-based Java business applications for the enterprise. SAP recognized the
growing significance of the Java programming language and started incorporating the Java
infrastructure capability with SAP Web Application Server 6.10. SAP has further improved
the capability to develop and execute industry-compliant Java business applications in its
subsequent versions of the application server. NW 7.0 and NW 7.1 releases will be covered in
this chapter. The most current NW release available for general use is NW 7.1. SAP Solu-
tions Process Integration (PI) 7.1 and Mobile Infrastructure (MI) 7.1 run on NW 7.1.
Before we do a deep dive into the NW AS Java architecture, let us understand some im-
portant Java programming language concepts.
Java Programming Language Concepts
Java is an object-oriented programming language developed by Sun Microsystems in 1995.
The main advantage of the Java programming language is its write once, run anywhere ap-
proach. Java applications are compiled to bytecode that can be executed on any Java Virtual
Machine (JVM), regardless of the computer processor architecture. JVM is a software pro-
gram that will emulate a computer processor and execute the bytecode. This allows Java ap-
plications to be platform-independent.
Unlike traditional compilers that generate machine code for a specific platform, Java com-
pilers generate code (bytecode) for the JVM. The JVM acts as an interface between the Java
and the physical hardware. Since execution of the bytecode requires an interpretation step as
well, Java is considered both a compiled and an interpreted programming language. Because
of this Java programs could run slow, and this is its main disadvantage. Just In Time (JIT)
compilers and new performance optimization techniques are helping to mitigate some of the
Java performance problems.
The Java compiler generates class files from the source code that are executed by the
JVM. Multiple class files can be combined as an archive file and are referred to as jar files.
JVM and the Java compiler can read the class files directly from the jar archive.
Sun Microsystems (acquired by Oracle) markets the Java Software Development Kits
(SDKs) in three versions:
• J2EE (Java 2 Enterprise Edition)
• J2SE (Java 2 Standard Edition)
• J2ME (Java 2 Mobile Edition)
