当我尝试执行以下操作时,加载调用出现异常:
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);
异常:
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)
我显然不明白 Forwarding
应该如何工作,我做错了什么?
我的意图是用一个代理替换现有的 KeyMapper
,在代理中我覆盖一个方法,并将其余方法委托(delegate)给原始方法。
编辑:我现在也尝试使用 MethodDelegation
,它会引发相同的异常:
.method(ElementMatchers.any()) //
.intercept(MethodDelegation.to(original)) //
.method(ElementMatchers.named("get")) //
.intercept(MethodDelegation.to(new KeyMapperWrapper(grid, original))) //
最佳答案
这是字节好友中的一个错误。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。然而,由于可见性限制,在另一种类型上调用这些方法并不总是合法的。因此,当您转接调用时,您只能覆盖 public
方法。你要做的是匹配:
.method(ElementMatchers.isPublic())
错误不再发生的地方。我已经在 Byte Buddy 的下一个发行版本 (1.5.8) 中添加了一个修复程序来为您提供此错误消息。
关于java - 如何使用 MethodDelegation 或 Forwarding 创建 Byte Buddy 代理?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/40962305/