JavaServer Pages, Second Edition

Appendix D. JSP API Reference

Besides the JSP elements described in Appendix A, the JSP specification also defines a number of Java classes and interfaces. Instances of some of these classes are assigned to the implicit variables available to scripting elements and JSTL Expression Language (EL) expressions in a JSP page. Others are used to develop custom actions and to allow JSP container vendors to encapsulate internal implementations. This appendix describes the classes and interfaces in all these categories in the JSP 1.2 specification, as well as the classes and interfaces exposed through the JSP types defined by the Servlet 2.3 specification.

Implicit Variables

The JSP specification defines a number of implicit variables. Most of the implicit variables have types defined by classes and interfaces in the Servlet specification’s javax.servlet.http package, but two are part of the JSP javax.servlet.jsp package, and one is part of the Java core API. Scripting elements in a JSP page can use these objects to access request and response information as well as objects saved in one of the JSP scopes: page, request, session, and application.

Most of these objects are also available to JSTL EL expressions through the EL implicit variables. The detailed sections include the EL expression in the Synopsis sections where applicable