在Google App Engine上使用ByteBuddy创建类时出现反射错误

Question

I am trying to define a sublclass dynamically from a concrete class using ByteBuddy as follows

Class<? extends MyConcreteClass> dynamicType = new ByteBuddy()
    .subclass(MyConcreteClass.class, ConstructorStrategy.Default.DEFAULT_CONSTRUCTOR)
    .name(dynamicClassName)
    .annotateType(MyConcreteClass.class.getDeclaredAnnotations())
    .make()
    .load(MyConcreteClass.class.getClassLoader())
    .getLoaded();

This code works from within a JUnit test, but when I run it under Google App Engine, I get the following exception.

java.lang.IllegalStateException: Cannot access java.lang.reflect.Parameter#getModifiers
at net.bytebuddy.description.method.ParameterList$ForLoadedExecutable$Dispatcher$ForJava8CapableVm.getParameterCount(ParameterList.java:261)
at net.bytebuddy.description.method.ParameterList$ForLoadedExecutable.size(ParameterList.java:157)
at net.bytebuddy.description.method.ParameterList$TypeSubstituting.size(ParameterList.java:582)
at net.bytebuddy.matcher.CollectionSizeMatcher.matches(CollectionSizeMatcher.java:34)
at net.bytebuddy.matcher.CollectionSizeMatcher.matches(CollectionSizeMatcher.java:13)
at net.bytebuddy.matcher.MethodParametersMatcher.matches(MethodParametersMatcher.java:32)
at net.bytebuddy.matcher.MethodParametersMatcher.matches(MethodParametersMatcher.java:13)
at net.bytebuddy.matcher.ElementMatcher$Junction$Conjunction.matches(ElementMatcher.java:101)
at net.bytebuddy.matcher.ElementMatcher$Junction$Conjunction.matches(ElementMatcher.java:101)
at net.bytebuddy.matcher.FilterableList$AbstractBase.filter(FilterableList.java:96)
at net.bytebuddy.dynamic.scaffold.subclass.ConstructorStrategy$Default$2.doExtractConstructors(ConstructorStrategy.java:82)
at net.bytebuddy.dynamic.scaffold.subclass.ConstructorStrategy$Default.extractConstructors(ConstructorStrategy.java:176)
at net.bytebuddy.dynamic.scaffold.subclass.SubclassDynamicTypeBuilder.applyConstructorStrategy(SubclassDynamicTypeBuilder.java:185)
at net.bytebuddy.dynamic.scaffold.subclass.SubclassDynamicTypeBuilder.make(SubclassDynamicTypeBuilder.java:162)
at net.bytebuddy.dynamic.scaffold.subclass.SubclassDynamicTypeBuilder.make(SubclassDynamicTypeBuilder.java:155)
at net.bytebuddy.dynamic.DynamicType$Builder$AbstractBase.make(DynamicType.java:2559)
...
Caused by: java.lang.IllegalAccessException: Reflection is not allowed on public int java.lang.reflect.Executable.getParameterCount()
at com.google.appengine.tools.development.agent.runtime.Runtime.verifyWhiteListed(Runtime.java:90)
at com.google.appengine.tools.development.agent.runtime.Runtime.invoke(Runtime.java:125)
at net.bytebuddy.description.method.ParameterList$ForLoadedExecutable$Dispatcher$ForJava8CapableVm.getParameterCount(ParameterList.java:259)

The exception is thrown while executing the method make() .

Is there a way to make this work under the GAE?

Answer 1

That's a very random restriction and most definitely a bug on the GAE. Please report it.

As a background: Byte Buddy detects a JVM's version and offers features accordingly. In this case, it detects that the parameter API that was added with Java 8 exists and uses it. However, GAE seems to disallow its use via reflection.