引起原因：java.lang.NoSuchFieldError：ruleMemo

Question

I am getting this exception - sadly, i'm trying to enhance a project to use ivy instead of ant, and while normally I do a process of

"add new library file"

"run program"

"check what library file it claims to need when it crashes"

this time the program crashes with

Caused by: java.lang.NoSuchFieldError: ruleMemo

This isn't very useful, naturally, and I don't have a clue where to look. Opening up the stacktrace items yields no whiff of a ruleMemo member... has anybody seen this before and know what class is calling/uses this?

What lib file to use would also be useful, but not quite as useful as the class!

Whoop - let me put a stacktrace in so somebody doesn't just roll their own class with ruleMemo as a member and tell me i need it!

Caused by: java.lang.NoSuchFieldError: ruleMemo
at org.drools.lang.DRLLexer.<init>(DRLLexer.java:96)
at org.drools.compiler.DrlParser.getParser(DrlParser.java:207)
at org.drools.compiler.DrlParser.parse(DrlParser.java:60)
at org.drools.compiler.PackageBuilder.addPackageFromDrl(PackageBuilder.java:165)
at sun.reflect.GeneratedMethodAccessor79.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.springframework.util.MethodInvoker.invoke(MethodInvoker.java:276)
at org.springframework.beans.factory.config.MethodInvokingFactoryBean.doInvoke(MethodInvokingFactoryBean.java:160)
at org.springframework.beans.factory.config.MethodInvokingFactoryBean.afterPropertiesSet(MethodInvokingFactoryBean.java:150)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1369)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1335)
... 70 more

Answer 1

Root cause analysis

I suspect you're using version 4.0.1 of the drools compiler jar?

• http://grepcode.com/file/repository.jboss.org/nexus/content/repositories/releases/org.drools/drools-compiler/4.0.1/org/drools/lang/DRLLexer.java#93

That jar is only compatible with version 3.0.1 of the antlr-runtime jar:

• http://grepcode.com/file/repo1.maven.org/maven2/org.antlr/antlr-runtime/3.0.1/org/antlr/runtime/Lexer.java#Lexer

Recommendation

I recommend two things:

• Use a more modern version of drools (Version 4.0.1 is not available in Maven Central )
• Use a ibiblio resolver to pull your dependencies from Maven Central or a local maven repository proxy.

Combining ivy with a Maven repository manager will ensure the correct interdependencies are retrieved.