Difference between core and core_rt jstl tag

Question

When I use <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %> for my struts 1.3.10 project, it throws following exception:

org.apache.jasper.JasperException: The absolute uri: http://java.sun.com/jsp/jstl/core cannot be resolved in either web.xml or the jar files deployed with this application
    org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:56)
    org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:445)
    org.apache.jasper.compiler.ErrorDispatcher.jspError(ErrorDispatcher.java:117)
    org.apache.jasper.compiler.TagLibraryInfoImpl.generateTLDLocation(TagLibraryInfoImpl.java:311)
    org.apache.jasper.compiler.TagLibraryInfoImpl.<init>(TagLibraryInfoImpl.java:152)
    org.apache.jasper.compiler.Parser.parseTaglibDirective(Parser.java:410)
    org.apache.jasper.compiler.Parser.parseDirective(Parser.java:475)
    org.apache.jasper.compiler.Parser.parseElements(Parser.java:1427)
    org.apache.jasper.compiler.Parser.parse(Parser.java:138)
    org.apache.jasper.compiler.ParserController.doParse(ParserController.java:242)
    org.apache.jasper.compiler.ParserController.parse(ParserController.java:102)
    org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:198)
    org.apache.jasper.compiler.Compiler.compile(Compiler.java:373)
    org.apache.jasper.compiler.Compiler.compile(Compiler.java:353)
    org.apache.jasper.compiler.Compiler.compile(Compiler.java:340)
    org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:646)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:357)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    org.apache.struts.action.RequestProcessor.doForward(RequestProcessor.java:1083)
    org.apache.struts.tiles.TilesRequestProcessor.doForward(TilesRequestProcessor.java:295)
    org.apache.struts.action.RequestProcessor.processForwardConfig(RequestProcessor.java:396)
    org.apache.struts.tiles.TilesRequestProcessor.processForwardConfig(TilesRequestProcessor.java:347)
    org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:232)
    org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
    org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:462)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:728)

Then when I have changed it to

<%@ taglib uri="http://java.sun.com/jstl/core_rt" prefix="c" %>

it works fine. I like to know what is the difference between these two and why its throws exception when I try to use <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>. Btw I using server apache-tomcat-7.0.42. Please help me.

Glob

Answer 1

Unless you are using a very old version of JSP (JSP 1.2 or 1.1 to be exact) you shouldn't be using either of those. Those are JSTL 1.0 URIs and are not suited to modern versions of JSP.

The two libraries differed in that one would allow run-time expressions as tag attribute values, and one wouldn't. In modern JSP and JSTL, where the JSP engine does all expression evaluation, it's no longer relevant.

Fucus

@vhisal-kukreja, how to know the version of jsp in netbean? – Glob

@gjman2, Create simple JSP page and put following code : JSP Version : <%= JspFactory.getDefaultFactory().getEngineInfo().getSpecificationVersion()%> – Fucus

my jsp is 2.2, now doing wat? – Glob

Answer 2

In JSTL 1.0, there are two versions of every template library:

• one that doesn't allow expressions (e.g. http://java.sun.com/jstl/core)
• one that does allow expressions (e.g. http://java.sun.com/jstl/core_rt);

Didn't allow expressions	Did allow expressions
c.tld	c-rt.tld
fmt.tld	fmt-rt.tld
x.tld	x-rt.tld
sql.tld	sql-rt.tld

With JSTL 1.1, there is no longer this dichotomy.

JSTL version	Namespace	tld
1.0	http://java.sun.com/jstl/core	c.tld
1.0	http://java.sun.com/jstl/core_rt	c-rt.tld
1.0	http://java.sun.com/jstl/fmt	fmt.tld
1.0	http://java.sun.com/jstl/fmt_rt	c-rt.tld
1.1	http://java.sun.com/jsp/jstl/core	c.tld
1.1	http://java.sun.com/jsp/jstl/fmt	fmt.tld

Actinomycin

Answer 3

I think you get the exception because the URI is different for the _rt version (_rt appended), so your taglib import is wrong for the tags in the jar you are using.

The difference is that one kind allows expression language ${someExpr} and the term relies on scriptlets <%= some code %>. You should be able to find proper details with a Google.

Tufted