Could not invoke Java compiler, please make sure jikesw

we are running the application on Jrun for many years and suddenly we see the following error. Can anybody tell us what would be the problem? 07/22 12:02:06 error Could not invoke Java compiler, please make sure jikesw is in /usr/jrun4/bin or put a JDK bin directory in your path. jrunx.compiler.JavaCompiler$NoCompilerFoundException: Could not invoke Java compiler, please make sure jikesw is in /usr/jrun4/bin or put a JDK bin directory in your path.         at jrunx.compiler.JavaCompiler.outProcessCompile(JavaCompiler.java:434)         at jrunx.compiler.JavaCompiler.compile(JavaCompiler.java:126)         at jrunx.compiler.JavaCompiler.compile(JavaCompiler.java:94)         at jrun.jsp.Translator.compilePage(Translator.java:176)         at jrun.jsp.Translator.translate(Translator.java:254)         at jrun.jsp.Translator.translate(Translator.java:101)         at jrun.jsp.JSPEngine.translateJSP(JSPEngine.java:693)         at jrun.jsp.JSPServlet.translate(JSPServlet.java:125)         at jrun.jsp.JSPServlet.service(JSPServlet.java:113)         at jrun.servlet.ServletInvoker.invoke(ServletInvoker.java:91)         at jrun.servlet.JRunInvokerChain.invokeNext(JRunInvokerChain.java:42)         at jrun.servlet.JRunRequestDispatcher.invokeNext(JRunRequestDispatcher.java:449)         at jrun.servlet.JRunRequestDispatcher.forwardInvoke(JRunRequestDispatcher.java:418)         at jrun.servlet.JRunRequestDispatcher.forward(JRunRequestDispatcher.java:175)         at org.apache.struts.action.RequestProcessor.doForward(RequestProcessor.java:1069)         at org.apache.struts.action.RequestProcessor.processForwardConfig(RequestProcessor.java:455)