catching NoClassDefFoundError

[fang eve]

Is there any way to try catch this error: java.lang.NoClassDefFoundError?? thanks.

OR

Is there any method to check the package path?
[ June 29, 2006: Message edited by: Bear Bibeault ]

[Bear Bibeault]

Nothing to do with JSP, so moved to the Java in General (beginner) forum.

[Christophe Verré]

You should not try to catch this serious error, but solve it when it happens.

[Jim Yingst]

Well, usually you shouldn't. I can imagine some contexts where it's a perfectly reasonable thing to do, e.g. if you're using a ClassLoader as part of a larger framework, and the failure of something within the ClassLoader isn't necessarily grounds to bring down the entire framework. However, this is the sort of thing you should only do if you're pretty sure you know what you're doing. This is tre of many Errors - yes you can catch them, and sometimes it's actually a good idea. But if you're not sure why the error might occur in the first place, and can't tell whether or not this should seriously affect the application, you shouldn't do it.

But to answer the original question as asked:

[fang eve ]: Is there any way to try catch this error: java.lang.NoClassDefFoundError??

Yes, if you are sure you want to do this, you catch it exactly the same way you would catch any Exception or other Throwable: with a catch block giving the name of the Throwable class you're trying to catch, or a superclass

try {
    // something risky...
} catch (NoClassDefFoundError e) {
     // do something useful in response here
}

[Jesper de Jong]

Don't try to catch NoClassDefFoundError. Any exception that ends with "...Error" should not be caught - it means something really unexpected happened in the JVM. It's not something a user program should try to handle.

If you want to load classes dynamically, use reflection (see the Javadoc documentation of the package java.lang.reflect and of class java.lang.Class).

If you try to create an instance of a class via reflection (using Class.forName(...)) and the class can't be found, you will not get a NoClassDefFoundError, but a ClassNotFoundException instead.

[Jim Yingst]

To the extent this has been moved to the Beginner forum, I'll just say I disagree in general - but it's good enough advice for beginners. As long as they don't become trapped believing that's the case for the rest of their careers...

[fang eve]

i have the following import statement
<%@ page import= "com.a.core.io.Ano"%>
<%@ page import= "com.a.core.kernel.Ci"%>
<%@ page import= "com.a.serviceProviders.Spaa"%>
<%@ page import= "com.a.core.nlp.text.action.Xa"%>
<%@ page import= "com.a.apps.smart.Ssf"%>
<%@ page import= "com.a.sdk.An"%>
<%@ page import= "com.mysql.jdbc.Driver"%>


<jsp:useBean id="an" class="com.a.sdk.An" scope="application"/>
<jsp:useBean id="ano" class="com.a.core.io.Ano" scope="session"/>

i will get the Error.

However if i took away the line:
<jsp:useBean id="an" class="com.a.sdk.AgentNetwork" scope="application"/>
there wont be error.

Does this mean that the problem is cause by the bean? If yes, what is the problem?

thanks
[ June 30, 2006: Message edited by: fang eve ]

[fang eve]

Originally posted by Jesper Young:
Don't try to catch NoClassDefFoundError. Any exception that ends with "...Error" should not be caught - it means something really unexpected happened in the JVM. It's not something a user program should try to handle.

how to check the JVM? I placing my files on server. I can't check the JVM.
I can't check all the exception error (i using system.out.print) as i cant view the tomcat console. Is just purely from the web, i have no idea where went wrong. I check the log file, but the error is display as what the page shows. Any way to get what the tomcat console print out?
[ June 30, 2006: Message edited by: fang eve ]

[Christophe Verré]

Send us the exception you've got (the full trace)

[fang eve]

HTTP Status 500 -

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

javax.servlet.ServletException
at org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:498)
at org.apache.jsp.ndpreceiver_edit_jsp._jspService(Unknown Source)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:92)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:809)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:162)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:240)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:187)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:809)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:200)
at org.apache.catalina.core.ApplicationFilterChain.access$000(ApplicationFilterChain.java:51)
at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:129)
at java.security.AccessController.doPrivileged(Native Method)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:125)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:209)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:596)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:433)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:948)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:144)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:596)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:433)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:948)
at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2358)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:133)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:596)
at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:118)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:594)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:116)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:594)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:433)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:948)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:127)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:596)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:433)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:948)
at org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:152)
at org.apache.jk.server.JkCoyoteHandler.invoke(JkCoyoteHandler.java:300)
at org.apache.jk.common.HandlerRequest.invoke(HandlerRequest.java:374)
at org.apache.jk.common.ChannelSocket.invoke(ChannelSocket.java:743)
at org.apache.jk.common.ChannelSocket.processConnection(ChannelSocket.java:675)
at org.apache.jk.common.SocketConnection.runIt(ChannelSocket.java:866)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:683)
at java.lang.Thread.run(Thread.java:595)

root cause

java.lang.NoClassDefFoundError
at sun.reflect.GeneratedConstructorAccessor5.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:494)
at java.lang.Class.newInstance0(Class.java:350)
at java.lang.Class.newInstance(Class.java:303)
at java.beans.Beans.instantiate(Beans.java:204)
at java.beans.Beans.instantiate(Beans.java:48)
at org.apache.jsp.ndpreceiver_edit_jsp._jspService(Unknown Source)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:92)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:809)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:162)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:240)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:187)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:809)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:200)
at org.apache.catalina.core.ApplicationFilterChain.access$000(ApplicationFilterChain.java:51)
at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:129)
at java.security.AccessController.doPrivileged(Native Method)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:125)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:209)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:596)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:433)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:948)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:144)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:596)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:433)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:948)
at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2358)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:133)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:596)
at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:118)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:594)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:116)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:594)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:433)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:948)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:127)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:596)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:433)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:948)
at org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:152)
at org.apache.jk.server.JkCoyoteHandler.invoke(JkCoyoteHandler.java:300)
at org.apache.jk.common.HandlerRequest.invoke(HandlerRequest.java:374)
at org.apache.jk.common.ChannelSocket.invoke(ChannelSocket.java:743)
at org.apache.jk.common.ChannelSocket.processConnection(ChannelSocket.java:675)
at org.apache.jk.common.SocketConnection.runIt(ChannelSocket.java:866)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:683)
at java.lang.Thread.run(Thread.java:595)

Apache Tomcat/4.1.31
[ June 30, 2006: Message edited by: fang eve ]

[Jim Yingst]

[fang]: However if i took away the line:
<jsp:useBean id="an" class="com.a.sdk.AgentNetwork" scope="application"/>
there wont be error.

Ignoring the stack trace, it sounds like there's a missing (or out-of-date) jar file or war file somewhere. Specifically, whatever jar/war was supposed to define the class com.a.sdk.AgentNetwork - that's where the problem probably is.

[fang eve]

Ok, how do i check whether the jar file is out of date? i have check the jar file, they are in the correct path, i run the application using localhost, it can find the jar file.

Is only at the server, i gt this error. That make me wonder what is really wrong.
[ June 30, 2006: Message edited by: fang eve ]