bytebuddy能否拦截一个方法调用，让它调用第二个对象的私有方法？

Question

给定一个 class A 使用 public 方法 overrideMe(B that, C arg) 和第二个 class B 使用私有方法 callMe(C arg)。是否可以使用 bytebuddy 生成一个子类，该子类将从已实现的 overrideMe(B that, C arg) 中调用私有方法 callMe(C arg)？这基本上会模仿 JVM 反射 GeneratedMethodAccessor，它正是这样做的。

目前，我正在尝试使用这样的 MethodCall：

Method callMeHandler = B.class.getDeclaredMethod("callMe");
callMeHandler.setAccessible(true);
MethodCall methodCall = MethodCall.invoke(callMeHandler).onArgument(0);
if(callMeHandler.getParameterCount() == 1)
    methodCall = methodCall.withArgument(1);

Composable coercedMethodCall = methodCall
           .withAssigner(ReferenceTypeAwareAssigner.INSTANCE, Typing.DYNAMIC);

String className = callMeHandler.getDeclaringClass().getName()
       + "$_generatedAccessor$" + callMeHandler.getName()
       + "$" + accessorCounter.getAndIncrement();

new ByteBuddy().subclass(GeneratableHandlerInvocation.class)
               .name(className)
               .method(ElementMatchers.named("invoke"))
               .intercept(Advice.to(GeneratableHandlerInvocation.class)
                                .wrap(coercedMethodCall))
               .make()
               .load(callMeHandler.getDeclaringClass().getClassLoader())
               .getLoaded()
               .newInstance();

，但它抱怨

java.lang.IllegalStateException: Cannot invoke private void com.mycompany.secret.B.callMe() virtually
    at net.bytebuddy.implementation.MethodCall$MethodInvoker$ForVirtualInvocation$WithImplicitType.invoke(MethodCall.java:2124)
    at net.bytebuddy.implementation.MethodCall$Appender.apply(MethodCall.java:2400)
    at net.bytebuddy.asm.Advice$Appender$EmulatingMethodVisitor.resolve(Advice.java:7156)
    at net.bytebuddy.asm.Advice$Appender.apply(Advice.java:7109)
    at net.bytebuddy.dynamic.scaffold.TypeWriter$MethodPool$Record$ForDefinedMethod$WithBody.applyCode(TypeWriter.java:614)
    at net.bytebuddy.dynamic.scaffold.TypeWriter$MethodPool$Record$ForDefinedMethod$WithBody.applyBody(TypeWriter.java:603)
    at net.bytebuddy.dynamic.scaffold.TypeWriter$MethodPool$Record$ForDefinedMethod.apply(TypeWriter.java:521)
    at net.bytebuddy.dynamic.scaffold.TypeWriter$Default$ForCreation.create(TypeWriter.java:4102)
    at net.bytebuddy.dynamic.scaffold.TypeWriter$Default.make(TypeWriter.java:1612)
    at net.bytebuddy.dynamic.scaffold.subclass.SubclassDynamicTypeBuilder.make(SubclassDynamicTypeBuilder.java:174)
    at net.bytebuddy.dynamic.scaffold.subclass.SubclassDynamicTypeBuilder.make(SubclassDynamicTypeBuilder.java:155)
    at net.bytebuddy.dynamic.DynamicType$Builder$AbstractBase.make(DynamicType.java:2560)
    at net.bytebuddy.dynamic.DynamicType$Builder$AbstractBase$Delegator.make(DynamicType.java:2662)
    at com.mycompany.secret.Main.defineTheSpecialClass(Main.java:190)

Answer 1

不，这不可能。 JVM 的字节码验证器禁止它。所以，字节好友一开始就不允许你创建这样的方法调用。

如果您想更改 class 并允许这样的调用，请查看 Byte Buddy 的代理 API 和 Advice class，它允许您更改现有的代码。

bytebuddy能否拦截一个方法调用，让它调用第二个对象的私有方法？

Can bytebuddy intercept a method call and make it call a private method of a second object?

java

byte-buddy