Using JSTL causes deferredExpression error on change

Question

I recently removed all scriptlets on my project as advised by this post. But now, if I try and make a change to one of my views, I get a deferredExpression error. To get rid of the error, I simply have to terminate, then restart the project.

What is going on here? Is eclipse not able to compile jstl on the fly? Is there something I can change so I don't have to redeploy every time I make a change?

Stack Trace

java.lang.NoSuchFieldError: deferredExpression
    at org.apache.taglibs.standard.tag.common.core.ForEachSupport.release(ForEachSupport.java:212)
    at org.apache.jasper.runtime.TagHandlerPool.release(TagHandlerPool.java:166)
    at org.apache.jsp.l.profile_jsp._jspDestroy(profile_jsp.java:114)
    at org.apache.jasper.runtime.HttpJspBase.destroy(HttpJspBase.java:88)
    at org.apache.jasper.servlet.JspServletWrapper.destroy(JspServletWrapper.java:428)
    at org.apache.jasper.servlet.JspServletWrapper.getServlet(JspServletWrapper.java:139)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:329)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
    at com.google.appengine.tools.development.PrivilegedJspServlet.access$101(PrivilegedJspServlet.java:23)
    at com.google.appengine.tools.development.PrivilegedJspServlet$2.run(PrivilegedJspServlet.java:59)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.google.appengine.tools.development.PrivilegedJspServlet.service(PrivilegedJspServlet.java:57)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
    at com.google.appengine.tools.appstats.AppstatsFilter.doFilter(AppstatsFilter.java:141)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.appspot.MySite.Controller.FacebookLogin.doFilter(FacebookLogin.java:140)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.HeaderVerificationFilter.doFilter(HeaderVerificationFilter.java:35)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:58)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.StaticFileFilter.doFilter(StaticFileFilter.java:122)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.BackendServersFilter.doFilter(BackendServersFilter.java:97)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
    at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
    at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
    at com.google.apphosting.utils.jetty.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:70)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at com.google.appengine.tools.development.JettyContainerService$ApiProxyHandler.handle(JettyContainerService.java:351)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.Server.handle(Server.java:326)
    at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
    at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923)
    at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:547)
    at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)
    at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
    at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
    at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)

Answer 1

java.lang.NoSuchFieldError: deferredExpression
at apache.taglibs.standard.tag.common.core.ForEachSupport.release(ForEachSupport.java:212)

Your classpath is polluted with different JSTL implementation versions. This particular exception means that you've both the jstl-1.2.jar file of JSTL 1.2 and the standard.jar file of JSTL 1.1 or 1.0 in the classpath. This field is introduced in JSTL 1.2 and the ForEachSupport class is present in the both JAR files. Apparently at some point the one of standard.jar is been loaded and used while still having the JSTL 1.2 API in JVM memory.

The solution is to remove the standard.jar. You don't need it for JSTL 1.2 at all.

See also:

• Our JSTL wiki page (to learn about what JARs you need)

---

Update: as per the comments, you actually need to remove the jstl-1.2.jar as well, because the Servlet 2.5 compatible version of GAE/Jetty apparently already ships with JSTL 1.1 out the box. This was conflicting with JSTL 1.2. in your webapp.

Answer 2

You most likely have two versions of JSTL (javax.servlet:jstl:). Remove the older version and make sure you update the version everywhere you were using the older one, and you should be good.