JSP: Duplicate local variable session

Topic:  JSP 2.0

Application Server: JBoss 4.0.2 / Tomcat 5.5.9

Exception:

An error occurred at line: 10 in the jsp file: /Test.jsp
Generated servlet error:
Duplicate local variable session


	org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandler.java:84)
	org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:328)
	org.apache.jasper.compiler.JDTCompiler.generateClass(JDTCompiler.java:397)
	org.apache.jasper.compiler.Compiler.compile(Compiler.java:288)
	org.apache.jasper.compiler.Compiler.compile(Compiler.java:267)
	org.apache.jasper.compiler.Compiler.compile(Compiler.java:255)
	org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:556)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:293)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:810)
	org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:81)

Resolution:

There are 9 implicit objects available for use in JSP pages – these objects are out, request, response, session, application, config, exception, pageContext and page. Any attempt to declare variables within a JSP scriptlet with any of the 9 implicit object names results in a Duplicate local variable error. Changing the declared variable name will remove the error.