CODEWITHSUNDEEP
javajetty
Noah
Noah

Reputation: 1046

java.lang.NoClassDefFoundError for nested class at run-time? (Dependency problems?)

Ok, here's the situation:

I have three files: 1. TScan.java 2. Test.java 3. ScanServlet.java

I write my mail class, TScan in the TScan.java file, and inside that class, there is a nested class (not a sub-class), called TEntry. TScan has a main() used for testing and other methods that use the nested TEntry class with no problems.

Also, Test.java is a fancier testing program that uses items from TScan.java, including the TScan and TEntry classes with no problems. TScan.java and Test.java were developed and tested in Eclipse (and it compiles/runs fine from the command line as well).

So TScan is working to a useful point, and I wanted to include it in a webapp. Installed Jetty and wrote ScanServlet.java, which runs in Jetty, no problems.

I started referencing TScan and it started giving the error above for TScan. Changing the ClassPath to include the TScan.class file didn't work, so I made a JAR file and stuck it in the WEB-INF/lib/ folder of the WebApp, and now ScanServlet compiles filen, and seems to find TScan at run-time, however it gives the NoClassDefFounfError TScan$TEntry at run-time. This doesn't make sense to me, since: 1. Obviously it's finding the TScan class now (Since it's not complaining about that at compile or run-time) 2. The error occurs in the TScan.java file (TEntry isn't reference directly except by TScan), which runs fine in stand-alone mode! 3. I made TEntry public, and it still doesn't work.

I have found a lot of questions about NoClassDefFoundError, but none dealing with nested classes, especially with Jetty.

Bear in mind I am more used to Delphi, where if it compiles, it runs. (And ABAP which is more or less the same).

If someone has a solution I will be thrilled, otherwise, I am considering:

Upvotes: 2

Views: 1806

Answers (2)

jesse mcconnell
jesse mcconnell

Reputation: 7182

Looks like you are limping along because your not using any formal build tools that apply rigor and convention to your development. Before messing around what is where and how to manage your handful of classes...start using a real build system that produces a jar file that contains what you need. Maven, Ant, Buildr, whatever...something that applies some convention or configuration. Don't leverage anything any IDE gives you in terms of compiling or exporting something that is supposed to be runnable...you can't trust any of that bunk.

With a proper build mechanism and ideally declarative dependencies and the like you can address your issue in a iterative fashion to resolve the NCDFE. my 2 cents at least

[edit] On your specific issue, I suspect your running into the webapp classloader configuration. By default classes in /lib are not exposed to webapp contexts. You will need to setParentLoaderPriority on the webapp context to true or bundle your classes as a war file. Also use --dry-run on the cli to help sort out what jar files are being loaded up by jetty.

Upvotes: 0

davidfrancis
davidfrancis

Reputation: 3849

How have you created your jar file and does it contain TScan$TEntry.class in the correct folder?
An inner or nested class still produces a .class file which you need to ship

Upvotes: 3

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