java - 如何使用MethodDelegation或Forwarding创建Byte Buddy代理？

当我尝试执行以下操作时，在加载调用中出现异常：

  Field datasourceExtensionField = Grid.class.getDeclaredField("datasourceExtension");
  datasourceExtensionField.setAccessible(true);
  RpcDataProviderExtension rpcDataProviderExtension = (RpcDataProviderExtension) datasourceExtensionField.get(grid);

  Field activeItemHandlerField = RpcDataProviderExtension.class.getDeclaredField("activeItemHandler");
  activeItemHandlerField.setAccessible(true);
  Object activeItemHandler = activeItemHandlerField.get(rpcDataProviderExtension);

  Field keyMapperField = activeItemHandler.getClass().getDeclaredField("keyMapper");
  keyMapperField.setAccessible(true);
  KeyMapper original = (KeyMapper) keyMapperField.get(activeItemHandler);

  KeyMapper wrapper = new ByteBuddy() //
      .subclass(KeyMapper.class) //
      .defineField("original", KeyMapper.class, Visibility.PUBLIC) //
      .method(ElementMatchers.any()) //
      .intercept(Forwarding.toField("original")) //
      .method(ElementMatchers.named("get")) //
      .intercept(MethodDelegation.to(new KeyMapperWrapper(grid, original))) //
      .make() //
      .load(KeyMapperWrapper.class.getClassLoader()) //
      .getLoaded() //
      .newInstance();

  // give wrapper the reference to the original
  wrapper.getClass().getDeclaredField("original").set(wrapper, original);

  // replace original with wrapper
  keyMapperField.set(activeItemHandler, wrapper);

例外：

java.lang.VerifyError: Bad access to protected data in invokevirtual
Exception Details:
  Location:
    com/vaadin/server/KeyMapper$ByteBuddy$WlWljaQa.clone()Ljava/lang/Object; @4: invokevirtual
  Reason:
    Type 'com/vaadin/server/KeyMapper' (current frame, stack[0]) is not assignable to 'com/vaadin/server/KeyMapper$ByteBuddy$WlWljaQa'
  Current Frame:
    bci: @4
    flags: { }
    locals: { 'com/vaadin/server/KeyMapper$ByteBuddy$WlWljaQa' }
    stack: { 'com/vaadin/server/KeyMapper' }
  Bytecode:
    0x0000000: 2ab4 000c b600 1cb0

    at java.lang.Class.getDeclaredFields0(Native Method)
    at java.lang.Class.privateGetDeclaredFields(Class.java:2583)
    at java.lang.Class.getDeclaredField(Class.java:2068)
    at net.bytebuddy.implementation.LoadedTypeInitializer$ForStaticField.onLoad(LoadedTypeInitializer.java:101)
    at net.bytebuddy.implementation.LoadedTypeInitializer$Compound.onLoad(LoadedTypeInitializer.java:180)
    at net.bytebuddy.dynamic.TypeResolutionStrategy$Passive.initialize(TypeResolutionStrategy.java:75)
    at net.bytebuddy.dynamic.DynamicType$Default$Unloaded.load(DynamicType.java:4525)
    at net.bytebuddy.dynamic.DynamicType$Default$Unloaded.load(DynamicType.java:4514)
    at test.KeyMapperWrapper.patch(KeyMapperWrapper.java:62)

我显然不了解Forwarding应该如何工作，我在做什么错？

我的意图是用一个代理替换现有的KeyMapper，在该代理中我重写一个方法，并将其余方法委托给原始方法。

编辑：我现在也尝试使用MethodDelegation，它引发相同的异常：

 .method(ElementMatchers.any()) //
 .intercept(MethodDelegation.to(original)) //
 .method(ElementMatchers.named("get")) //
 .intercept(MethodDelegation.to(new KeyMapperWrapper(grid, original))) //

最佳答案

这是Byte Buddy中的错误。但是，您尝试创建的类型不合法，Byte Buddy无法为您提供正确的错误消息。子类化时，覆盖protected方法是合法的。但是，由于可见性的限制，在另一种类型上调用这些方法并不总是合法的。因此，在转接呼叫时，只能覆盖public方法。您想要做的是匹配：

.method(ElementMatchers.isPublic())

该错误不再发生的地方。我已经添加了一个修复程序，可以在Byte Buddy的下一个发行版本（1.5.8）中为您提供此错误消息。