JavaServer Pages, 3rd Edition

Name

Declaration

Synopsis

Declarations are used to declare scripting language variables or methods. The content must be a complete valid declaration in the language defined by the page directive. The JSP implicit scripting variables aren’t visible in a declaration element.

When the language is Java, a variable declared by a declaration element ends up as an instance variable in the JSP page implementation class. It’s therefore visible to parallel threads (requests) processing the page and needs to be handled in a thread-safe manner. A thread-safe alternative is to declare variables within a scriptlet element instead. It then becomes a local variable of the method in the page implementation class used to process each request, and isn’t shared by parallel threads.

Syntax 1: In a regular JSP page

<%! declaration %>

Syntax 2: In a JSP Document (a JSP page written in XML syntax)

<jsp:declaration>declaration</jsp:declaration>

Attributes

None.

Example

<%! int globalCounter = 0; %>