Presentation Services

As we have seen, technologies such as BC4J and Oracle Forms are good for writing, testing, and maintaining your business logic. There are other technologies, however, that are better suited for displaying your applications. Presentation Services deliver dynamic content to client browsers, supporting servlets, business intelligence, PL/SQL Server Pages, JavaServer Pages, Perl/CGI scripts, and PHP. You can use Presentation Services to build your presentation layer for your web applications. While Oracle puts these services into a separate group , you can think of them grouped with the Business Logic Services in that your application logic can reside within these components. We recommend, however, that you break your business logic into executable components , which can then be called or invoked by these services.

Apache JServ (mod_jserv) is a module for the Apache web server that implements Sun Microsystems s Java Servlet API for running server-side Java code. Java servlets must be executed from within a Java Virtual Machine (JVM), and hence any servlet execution environment must include a JVM. The complexity of adding a JVM to the Apache server would degrade the Apache architecture, so the solution adopted for Apache JServ was to separate the JVM from the Apache server. This separation provides several benefits:

  • It allows the use of any compatible JVM from any vendor. No modifications need be made to the web server when a change is made to the JVM (such as by an upgrade).

  • It improves stability by separating the processes, allowing process-level protections by the operating system. If the JVM should crash or be mis-configured, the web server will still operate normally.

  • It allows for advanced functionality, including automatic startup, separate JVMs for different configurations, and the capability to support load balancing on high traffic sites.

While the Apache module for handling servlet requests (mod_jserv) is still available in Oracle Application Server 10 g , it is provided for backwards compatibility only. Oracle recommends converting your legacy applications to use OC4J.

OC4J is the core J2EE run-time component of Application Server 10 g implemented as a module (mod_oc4j) in the Apache web server. OC4J is J2EE 1.3 compatible and runs on Java 2 Platform, Standard Edition (J2SE) distributions, making it easy to use and highly productive for developers, while at the same time offering outstanding performance and scalability for production environments. OC4J provides complete support for the technologies listed in Table 1-3.

Table 1-3: Java Technologies Supported by OC4J

Java Technology

Version of Specification Supported in Oracle Application Server 10 g

JSPs

1.2

Servlets

2.3

EJBs

2.0

JMS

1.0.2b

Java Database Connectivity (JDBC)

2.0

Simple Object Access Protocol (SOAP)

1.1

Web Services Description Language (WSDL)

1.1

Universal Description, Discovery, and Integration (UDDI)

2.0

OC4Js are discussed in 15.

JSPs is a server-side technology that is an extension to the Java Servlet technology. JSPs have a dynamic scripting capability that works in tandem with HTML code, separating the user interface from content generation, enabling designers to change the overall page layout without altering the underlying dynamic content. Developers can benefit by using JSP technology without having to learn the Java language; they extend the JSP language through the use of simple tag handlers and easily maintain pages through the use of the JSP Standard Tag Library (JSTL). JSPs are discussed in 15.

PSPs is a technology provided by Oracle. It works on the same principles as JSPs, except that it uses PL/SQL as its scripting language. This can be beneficial for shops with minimal Java expertise. PSPs are compiled components executed as Oracle Stored Procedures. The Oracle PSP service includes the PSP Compiler and the PL/SQL Web Toolkit. Existing web pages can be made dynamic by embedding PL/SQL tags to perform database operations and display the results. Because PSPs are executed as stored procedures, it is important to note that the processing of PSPs occurs on the Oracle Database server. All of the other technologies discussed in this book execute on the Oracle Application Server. Chapter 7 discusses PSPs.



Oracle Application Server 10g Web Development
Oracle Application Server 10g Web Development (Oracle Press)
ISBN: 0072255110
EAN: 2147483647
Year: 2004
Pages: 192

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