2 Overview of the Oracle JSP Implementation

OC4J General Features

OC4J is a high-performance, J2EE-compliant set of containers and services providing a scalable and reliable server infrastructure. In Oracle Application Server 10g Release 2 (10.1.2), OC4J complies with the J2EE 1.3 specification.

For developer convenience, OC4J has been integrated with Oracle JDeveloper and other development tools, and can run in a standalone mode separate from Oracle Application Server during the development process.

Java applications built with any development tool can be deployed to OC4J, which supports standard EAR or WAR file deployment. You can debug applications deployed to OC4J through standard Java profiling and debugging facilities.

For security, OC4J supports Secure Socket Layer (SSL) and HTTPS functionality.

OC4J Services

OC4J supports the following Java and J2EE services:

• J2EE Connector Architecture (JCA): JCA defines a standard architecture for connecting J2EE platforms to heterogeneous enterprise information systems such as ERP systems, mainframe transaction processing, database systems, and legacy applications.

• Java Transaction API (JTA) and two-phase commits: JTA allows simultaneous updates to multiple resources in a single, coordinated transaction.

• Java Message Service (JMS) integration: This integration allows compatibility between the Oracle JMS implementation and those of other JMS providers.

• Java Naming and Directory Interface (JNDI): JNDI associates names with resources for lookup purposes.

• Java Authentication and Authorization Service (JAAS): The Oracle implementation of JAAS and the Java2 security model provides complete support for development and deployment of secure applications and for fine-grained authorization and access control.

• JDBC data sources: This is the standard mechanism for connecting to a database.

See the Oracle Application Server Containers for J2EE Services Guide for information.

OC4J Containers

The OC4J 10.1.2 implementation supplies the following J2EE containers:

• A JSP container complying with the Sun JSP 1.2 specification

  The JSP bundle also supplies tag libraries to implement Web services, caching capabilities, SQL access, file access, and other features. For further overview of the JSP container provided with OC4J, see "Overview of the JSP Implementation in OC4J".

• A servlet container complying with the servlet 2.3 specification (with key features described immediately below)

• An EJB container complying with the EJB 2.0 specification (with key features described below)

OC4J containers have been instrumented to support the Dynamic Monitoring Service (DMS) to provide runtime performance data. You can view this data through Enterprise Manager.

OC4J Standalone

In a production environment, it is typical to use OC4J inside a complete Oracle Application Server environment, including the Oracle HTTP Server (as described in "Oracle HTTP Server and mod_oc4j"), OracleAS Web Cache, and Enterprise Manager.

For a development environment, OC4J is also available as a standalone component by downloading OC4J_extended.zip from the Oracle Technology Network at the following location:

http://www.oracle.com/technology/tech/java/oc4j

When using OC4J standalone, you can use its own HTTP Web listener through port 8888. For information about OC4J standalone, see the Oracle Application Server Containers for J2EE Stand Alone User's Guide (downloadable with OC4J_extended.zip) and the Oracle Application Server Containers for J2EE Servlet Developer's Guide.

History and Integration of JSP Containers

In Oracle9iAS Release 1.0.2.2, the first release to include OC4J, there were two JSP containers: 1) a container developed by Oracle and known as "OracleJSP"; 2) a container licensed from Ironflare AB and known as the "Orion JSP container".

The OracleJSP container offered several advantages, including useful value-added features and enhancements such as for globalization. The Orion container also offered advantages, including superior speed, but had disadvantages as well. It did not always exhibit standard behavior when compared to the JSP reference implementation (Tomcat), and its support for internationalization and globalization was not as complete.

Oracle9iAS Release 2 (9.0.2) first integrated the OracleJSP and Orion containers into a single JSP container referred to in this manual as the "OC4J JSP container". This container offers the best features of both previous versions, runs efficiently as a servlet in the OC4J servlet container, and is integrated with other OC4J containers as well. The integrated container primarily consists of the OracleJSP translator and the Orion container runtime, running with a simplified dispatcher and the OC4J core runtime classes.

JSP Front-End Servlet and Configuration

The JSP container in OC4J uses the front-end servlet oracle.jsp.runtimev2.JspServlet. See "JSP Configuration in OC4J".

For non-OC4J environments, use the old front-end servlet, oracle.jsp.JspServlet.

OC4J JSP Features for JSP 1.2

In the OC4J 10.1.2 implementation, the OC4J JSP container is fully compliant with the JSP 1.2 specification. Most functionality introduced in this specification is in the area of custom tag libraries.

• Tag library features:

  • There is a tag handler interface that allows iteration through a tag body without having to maintain and access a body content object.

  • You can create a tag-library-validator class and associate it with a tag library. A validator instance will check any JSP page that uses the library, to verify that it meets whatever constraints you desire.

  • For convenience, you can declare servlet event listeners in a tag library descriptor file instead of in the web.xml file. This enables you to more conveniently manage application and session resources associated with usage of the tag library.

  • You can package multiple tag libraries and their TLD files inside a single JAR file.

  See Chapter 8, "JSP Tag Libraries" for details about these features, and "Overview of Tag Library Changes Between the JSP 1.1 and 1.2 Specifications" for a more detailed summary.

• XML features:

  • The OC4J JSP container previously supported a standard XML-alternative syntax, but this is replaced with newer technology according to the current JSP specification.

  • The OC4J JSP container generates an XML view of every translated page, which is a mapping to an XML document that describes the page. This view is available for use by tag-library-validator classes.

  See Chapter 5, "JSP XML Support" for information about these features.

• Character encoding features:

  The OC4J JSP implementation supports the pageEncoding attribute of the page directive. This enables you to specify a character encoding for the page source that is different than the character encoding for the response (specified in the contentType attribute).

  See "Content Type Settings".

Configurable JSP Extensions in OC4J

In addition to JSP 1.2 compliance, the OC4J JSP container in Oracle Application Server 10g Release 2 (10.1.2) includes the following notable features.

Also see "Overview of Oracle Value-Added Features".

The following have been supported since the OC4J 9.0.3 implementation:

• Mode switch to avoid JSP translation errors if you have duplicate settings for the same directive attribute within a single JSP translation unit

  The JSP specification mandates translation errors if you have duplicate settings for the same directive attribute within a single JSP translation unit, except for the page directive import attribute. These errors may be unwanted or inappropriate, for example, if a page and an included file both set an attribute to the same value (such as language="java").

  In "JSP Configuration Parameter Descriptions", see the description of the forgive_dup_dir_attr parameter.

• Separate mode switches for XML validation of web.xml file and TLD files

  Validation of web.xml is disabled by default but can be enabled. Validation of TLD files is enabled by default but can be disabled.

  In "JSP Configuration Parameter Descriptions", see the descriptions of the xml_validate and no_tld_xml_validate parameters.

• Mode flag for extra imports

  Use this to automatically import certain Java packages beyond the JSP defaults.

  In "JSP Configuration Parameter Descriptions", see the description of the extra_imports parameter.

• "Well-known" location for sharing tag libraries

  You can specify a directory where tag library JAR files can be placed for sharing across multiple Web applications.

  In "JSP Configuration Parameter Descriptions", see the description of the well_known_taglib_loc parameter.

• Configurable JSP timeout

  You can specify a timeout value for JSP pages, after which a page is removed from memory if it has not been requested again. In "JSP-Related OC4J Configuration Parameter Descriptions", see the description of the jsp-timeout parameter.

The following features have been supported since the OC4J 9.0.2 implementation:

• Mode switch for automatic page retranslation and reloading

  You have a choice of: 1) running JSP pages without any automatic reloading or retranslation of JSP pages; 2) automatically reloading any page implementation classes (but not JavaBeans or other dependency classes); or 3) automatically retranslating any JSP pages that have changed.

  In "JSP Configuration Parameter Descriptions", see the description of the main_mode parameter.

• Tag handler instance pooling

  To save time in tag handler creation and garbage collection, you can optionally enable pooling of tag handler instances. They are pooled in application scope. You can use different settings in different pages, or even in different sections of the same page. See "Disabling or Enabling Runtime or Compile-Time Tag Handler Reuse".

• Output mode for null output

  You can print an empty string instead of the default "null" string for null output from a JSP page.

  In "JSP-Related OC4J Configuration Parameter Descriptions", see the description of the jsp-print-null parameter.

• Single-threaded-model JSP instance pooling

  For single-threaded (non-thread-safe) JSP pages, page instances are pooled. There is no switch for this feature—it is always enabled.

Portability Across Servlet Environments

The JSP container is provided as a component of OC4J but is portable to other environments. Because the OC4J JSP container itself emulates certain required servlet features, this portability extends to older servlet environments. (Generally, a servlet 2.3 environment is required in order to support JSP 1.2 compliance.)

The servlet 2.0 specification was limited in that it provided only a single servlet context for each Java virtual machine, instead of a servlet context for each application. The OC4J JSP servlet emulation allows a full application framework in a servlet 2.0 environment, including providing applications with distinct servlet context and HTTP session objects.

Because of this extended functionality, the OC4J JSP container is not limited by the underlying servlet environment.

Global Includes

The OC4J JSP container provides a feature called global includes. You can use this feature to specify one or more files to statically include into JSP pages in or under a specified directory, through virtual JSP include directives. During translation, the JSP container looks for a configuration file, /WEB-INF/ojsp-global-include.xml, that specifies the included files and the directories for the pages.

This enhancement is particularly useful in migrating applications that had used globals.jsa or translate_params functionality in previous Oracle JSP releases. For more information, see "Oracle JSP Global Includes".

Support for Dynamic Monitoring Service

DMS adds performance-monitoring features to a number of Oracle Application Server components, including OC4J. The goal of DMS is to provide information about runtime behavior through built-in performance measurements so that users can diagnose, analyze, and debug any performance problems. DMS provides this information in a package that can be used at any time, including during live deployment. Data are published through HTTP and can be viewed with a browser.

The OC4J JSP container supports DMS features, calculating relevant statistics and providing information to DMS servlets such as the spy servlet and monitoring agent. Statistics include the following (using averages, maximums, and minimums, as applicable). Times are in milliseconds.

• Processing time of HTTP request

• Processing time of JSP service method

• Number of JSP instances created or available

• Number of active JSP instances

(Counts of JSP instances are applicable only for single-threaded situations, where isThreadSafe is set to false in a page directive.)

Standard configuration for these servlets is in the OC4J application.xml and default-web-site.xml configuration file. Use the Enterprise Manager to access DMS, display DMS information, and, if appropriate, alter DMS configuration.

Also see the Oracle Application Server Performance Guide, which contains precise definitions of the JSP metrics and detailed instructions for viewing and analyzing them.

Enhanced Servlet 2.0 Support

OC4J supports special features for a servlet 2.0 environment. It is highly advisable to migrate to the OC4J servlet 2.3 environment as soon as practical, but in the meantime, be aware of the following:

• An enhanced application framework for servlet 2.0 environments

• Extended globalization support for servlet 2.0 environments