[GROOVY-9075] The exception message should be more clear when a GroovyObject's metaClass is wrong

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 2.4.16, 3.0.0-alpha-4, 2.5.6
• Component/s: groovy-runtime
• Assignee: Unassigned
• Reporter: Xiaoguang Wang
• Created: 11/Apr/19 08:05
• Updated: 25/Nov/19 23:51

Description

If a GroovyObject's metaClass is overwritten by mistake, the accesses to the instance may cause an exception with unclear message.

 

We have met the problem too many times and have spent a lot of time on debugging (and teaching everyone never to use `BeanUtils.copyProperties`, etc)

 

If there is a try-catch (or some other check) in the runtime code and report this problem more clearly, it will save everyone's time to debug. Or, is there any better solution to this problem, eg: check the class type in `MetaClassImpl.setProperty`, `DefaultGroovyMethods.setMetaClass` ?

 

import groovy.transform.CompileStatic

//@CompileStatic
class C1 {
    int x
}
//@CompileStatic
class C2 {
    int x
}

//@CompileStatic
class TestGroovy {
    static void main(String[] args) {
        def c1 = new C1()
        def c2 = new C2()
        c1.metaClass = c2.metaClass  //eg: org.springframework.beans.BeanUtils.copyProperties
        // or c1.setMetaClass(c2.getMetaClass())

        c1.x += 1  // crash here with unclear exception, but c1.setX() works
    }
}

 

/*
without @CompileStatic
Exception in thread "main" java.lang.IllegalArgumentException: object is not an instance of declaring class
   at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
   at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   at java.lang.reflect.Method.invoke(Method.java:498)
   at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:98)
   at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
   at org.codehaus.groovy.runtime.metaclass.MethodMetaProperty$GetBeanMethodMetaProperty.getProperty(MethodMetaProperty.java:76)
   at org.codehaus.groovy.runtime.callsite.GetEffectivePogoPropertySite.getProperty(GetEffectivePogoPropertySite.java:85)
   at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callGetProperty(AbstractCallSite.java:299)

with @CompileStatic
Exception in thread "main" java.lang.IllegalArgumentException: object is not an instance of declaring class
   at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
   at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   at java.lang.reflect.Method.invoke(Method.java:498)
   at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:98)
   at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
   at groovy.lang.MetaClassImpl.setProperty(MetaClassImpl.java:2726)
   at groovy.lang.MetaClassImpl.setProperty(MetaClassImpl.java:3785)
   at C1.setProperty(TestGroovy.groovy)
   at org.codehaus.groovy.runtime.InvokerHelper.setProperty(InvokerHelper.java:213)
   at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.setProperty(ScriptBytecodeAdapter.java:497)
 */

Issue Links

• links to: GitHub Pull Request #994