Byte Buddy的方法委派

时间:2016-01-07 16:10:55

标签: java bytecode byte-buddy

我遇到一个使用Byte Buddy的简单示例的问题,这是我的代码:

import static java.util.Arrays.asList;
import java.util.stream.Stream;
import net.bytebuddy.ByteBuddy;
import net.bytebuddy.dynamic.loading.ClassLoadingStrategy;
import net.bytebuddy.implementation.MethodDelegation;

public class Foo {
  public static class Bar {
    public void bar (String s, Integer i) {
      System.out.println ("s:" + s + " i:" + i);
    }
  }
  public static class Baz {
    public void baz (Integer i, String s) {
      System.out.println ("i:" + i + " s:" + s);
    }
  }

  public static void main (String[] args) {
    try {
      Class<?> c = new ByteBuddy ()
        .subclass (Object.class)
        .defineMethod ("bar", Void.class, asList (String.class, Integer.class), 1)
        .intercept (MethodDelegation.to (new Bar ()))
        .defineMethod ("baz", Void.class, asList (Integer.class, String.class), 1)
        .intercept (MethodDelegation.to (new Baz ()))
        .make ()
        .load (Foo.class.getClassLoader (), ClassLoadingStrategy.Default.WRAPPER)
        .getLoaded ();
      Stream.of (c.getDeclaredMethods ()).forEach (System.out::println);
    } catch (Exception e) {
      e.printStackTrace ();
    }
  }
}

我期望工作并转发对受尊重的拦截器实例的调用,但是我得到了这个例外:

java.lang.IllegalArgumentException: None of [protected void java.lang.Object.finalize() throws java.lang.Throwable, public final void java.lang.Object.wait(long,int) throws java.lang.InterruptedException, public final native void java.lang.Object.wait(long) throws java.lang.InterruptedException, public final void java.lang.Object.wait() throws java.lang.InterruptedException, public boolean java.lang.Object.equals(java.lang.Object), public java.lang.String java.lang.Object.toString(), public native int java.lang.Object.hashCode(), public final native java.lang.Class java.lang.Object.getClass(), protected native java.lang.Object java.lang.Object.clone() throws java.lang.CloneNotSupportedException, public final native void java.lang.Object.notify(), public final native void java.lang.Object.notifyAll(), public void Foo$Bar.bar(java.lang.String,java.lang.Integer)] allows for delegation from public java.lang.Void net.bytebuddy.renamed.java.lang.Object$ByteBuddy$P87HQ3lQ.bar(java.lang.String,java.lang.Integer)
at net.bytebuddy.implementation.bind.MethodDelegationBinder$Processor.process(MethodDelegationBinder.java:881)
at net.bytebuddy.implementation.MethodDelegation$Appender.apply(MethodDelegation.java:1218)
at net.bytebuddy.dynamic.scaffold.TypeWriter$MethodPool$Record$ForDefinedMethod$WithBody.applyBody(TypeWriter.java:510)
at net.bytebuddy.dynamic.scaffold.TypeWriter$MethodPool$Record$ForDefinedMethod.apply(TypeWriter.java:444)
at net.bytebuddy.dynamic.scaffold.TypeWriter$Default$ForCreation.create(TypeWriter.java:3193)
at net.bytebuddy.dynamic.scaffold.TypeWriter$Default.make(TypeWriter.java:1481)
at net.bytebuddy.dynamic.scaffold.subclass.SubclassDynamicTypeBuilder.make(SubclassDynamicTypeBuilder.java:234)
at net.bytebuddy.dynamic.DynamicType$Builder$AbstractBase$AbstractDelegatingBuilder.make(DynamicType.java:2177)
at Foo.main(Foo.java:55)

最奇怪的部分位于该异常消息的最后:

[...] public void Foo$Bar.bar(java.lang.String,java.lang.Integer)] allows for delegation from public java.lang.Void net.bytebuddy.renamed.java.lang.Object$ByteBuddy$P87HQ3lQ.bar(java.lang.String,java.lang.Integer)

我做错了什么?

2 个答案:

答案 0 :(得分:2)

你的假设是正确的。 Byte Buddy无法将void非类型分配给Void类型。但是,当您使用null注释拦截器时,Byte Buddy可以将@RuntimeType分配给void方法中的引用类型:

public class Bar {
  @RuntimeType
  public void bar (String s, Integer i) {
    System.out.println ("s:" + s + " i:" + i);
  }
}
public class Baz {
  @RuntimeType
  public void baz (Integer i, String s) {
    System.out.println ("i:" + i + " s:" + s);
  }
}

答案 1 :(得分:0)

当我提交并回顾我的问题时,我认为问题可能出在void返回,而不是Void,当然,更改拦截器的返回类型有效