[jetty-users] JSP: tmpFile.renameTo(classFile) failed, or javax/el/ELRes

[John English <john.foreign@xxxxxxxxx>]

I have a JSP app running on Jetty 7.2.0 which suddenly for no apparent
reason refuses to run. When I try to access a page I get a blank screen
(no 5xx error, which would be nicer) and an IOException:

  java.io.IOException: tmpFile.renameTo(classFile) failed
  at 
org.apache.jasper.compiler.SmapUtil$SDEInstaller.install(SmapUtil.java:235)
  at org.apache.jasper.compiler.SmapUtil.installSmap(SmapUtil.java:158)
  at org.apache.jasper.compiler.Compiler.generateClass(Compiler.java:390)
  ... and so on ...

If I delete the temporary directory where the compilation is happening,
it recreates it but now the error is different:

  Exception initializing page context
  java.lang.NoClassDefFoundError: javax/el/ELResolver
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(Unknown Source)
	at java.security.SecureClassLoader.defineClass(Unknown Source)
	at java.net.URLClassLoader.defineClass(Unknown Source)
	at java.net.URLClassLoader.access$100(Unknown Source)
	at java.net.URLClassLoader$1.run(Unknown Source)
	at java.net.URLClassLoader$1.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at 
org.apache.jasper.runtime.JspFactoryImpl.internalGetPageContext(JspFactoryImpl.java:157)
  ... and so on ...

The lib/jsp directory in my application has these jars (which used to
work with no problems):
  com.sun.el_1.0.0.v201004190952.jar
  ecj-3.6.jar
  javax.el_2.1.0.v201004190952.jar
  javax.servlet.jsp.jstl_1.2.0.v201004190952.jar
  javax.servlet.jsp_2.1.0.v201004190952.jar
  jetty-jsp-2.1-7.2.0.v20101020.jar
  org.apache.jasper.glassfish_2.1.0.v201007080150.jar
  org.apache.taglibs.standard.glassfish_1.2.0.v201004190952.jar
so javax.el.ELResolver should be found easily enough...

Can anyone explain what's happened here, and more importantly what I
need to do to fix it?
--
John English