java – 使用Byte Buddy进行方法委派

我在使用Byte Buddy时遇到一个简单的例子,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,但是我得到了这个异常:

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)

我究竟做错了什么?

最佳答案 你的假设是正确的. Byte Buddy无法将void non-type分配给Void类型.但是,当您使用@RuntimeType注释拦截器时,Byte Buddy可以从void方法为引用类型赋值null:

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);
  }
}
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