As a system, the SAP J2EE Engine consists of three logical layers:
- SAP Java Enterprise Runtime – comprises low-level modules that provide functions such as class loading, cluster communication, persistent configuration data management, and so on. For more information, see SAP Java Enterprise Runtime.
- Pluggable components – consists of interfaces, libraries and services components that provide various runtime functions and programming APIs. For more information, see Pluggable Components.
- Applications layer – refers to the applications that are deployed and run on the SAP J2EE Engine. For more information, see Applications.
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What is the session? Why we need it?
As the HTTP is a stateless protocol, the web server can response to the request from each client, but it cannot remember previous requests from the same client. It is difficult to build the web site such as shopping on-line that requires to distinguish from different clients to retain contextual information. The session concept is involved to solve there issues.
In session management whenever a request comes for any resource, a unique token is generated by the server and transmitted to the client. We can also say that the process of managing the state of a web based client is through the use of session IDs. Session IDs are used to uniquely identify a client browser, while the server side processes are used to associate the session ID with a level of access.
Generally speaking, there are three methods to implement the session concept:
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The database connection for SAP J2EE engine is created during the AS Java installation. The database user SAP<SID>DB, password and db server connection string is stored in the secure storage file, located at usrsap<SID>SYSglobalsecuritydataSecStore.properties in the installation folder.
These DB information as well as the default administrator user can be maintained using Config Tool (Execute <AS_Java_install_dir>configtoolconfigtool.bat). Start the Config Tool and select secure store. The configuration for the secure storage in the file system appears.
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I have been working in SAP Java world for several years. As per my experience, it is difficult for newcomers to start working on SAP Java field. There are many new terminologies and technologies that always freak out people at the beginning especially those aren’t familiar with Java language. I would like to share my limited experience with everyone on how to go through this tough period and become a senior developer.
1. Java Language
Before you begin to study any SAP specific Java technologies/tools, Java language is a fundamental thing that you must have a good command of. This not only means Java syntax and grammar, it also contains other aspects you need to know in order write a high quality codes. Below is a check list.
a. Java Syntax and Grammar
b. Java programming standards
c. J2SE API – I/O, Email, JDBC, etc.
d. J2EE programming – JSP/Servlet, EJB, Web Service, etc.
e. Write, compile, deploy and run Java application using an IDE like eclipse/netbeans.
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