我正在学习 ByteBuddy 并尝试使用以下代码。
我定义了一个带有重载方法的 Animal 接口,并尝试创建一个覆盖这两种方法的类。 效果很好。 然后我尝试在生成的类中有一个字段并尝试调用该字段。 那时我遇到了例外情况。
以下是我的代码:
public interface Animal {
String sound();
String sound(boolean loud);
}
以下是 Main::main 方法的代码片段。
DynamicType.Unloaded<Animal> dogClassUnloaded = new ByteBuddy()
.subclass(Animal.class)
.name("Dog")
// we can use bytebuddy modifiers
.defineField("colour", String.class, Visibility.PUBLIC, FieldManifestation.FINAL)
.defineConstructor(Visibility.PUBLIC)
// or java modifiers -> Modifier.FINAL + Modifier.PRIVATE like that
.withParameter(String.class, "colour", Modifier.FINAL)
.intercept(
MethodCall.invokeSuper()
.andThen(
// field arguments are denoted by their index
FieldAccessor.ofField("colour").setsArgumentAt(0)
)
)
// There are different ways to match the methods, fields etc.
// https://www.tabnine.com/code/java/classes/net.bytebuddy.matcher.ElementMatchers
// intercepting no argument method
.method(ElementMatchers.named("sound")
.and(ElementMatchers.takesNoArguments())
)
.intercept(FixedValue.value("woof quiet"))
// intercepting overloaded method with arguments
.method(
ElementMatchers.named("sound")
.and(ElementMatchers.takesArgument(0, boolean.class))
)
.intercept(FixedValue.value("woof woof loud"))
.make();
Class<? extends Animal> dogClassLoaded = dogClassUnloaded
.load(Main.class.getClassLoader(), ClassLoadingStrategy.Default.WRAPPER)
.getLoaded();
Animal dog = dogClassLoaded.getDeclaredConstructor(String.class).newInstance("black");
// Animal dog = dogClassLoaded.getDeclaredConstructor().newInstance();
var x = dog.sound();
var y = dog.sound(true);
System.out.println(x);
System.out.println(y);
// What if Dog.class has other methods / fields not in Animal.class
Field m = dogClassLoaded.getDeclaredField("colour");
String colour = (String) m.get(dog);
System.out.println(colour);
当我尝试执行时出现以下异常:
Exception in thread "main" java.lang.IllegalStateException: public Dog(java.lang.String) does not accept 0 arguments
at net.bytebuddy.implementation.MethodCall$Appender.toStackManipulation(MethodCall.java:3553)
at net.bytebuddy.implementation.MethodCall$Appender.apply(MethodCall.java:3522)
at net.bytebuddy.implementation.bytecode.ByteCodeAppender$Compound.apply(ByteCodeAppender.java:156)
at net.bytebuddy.dynamic.scaffold.TypeWriter$MethodPool$Record$ForDefinedMethod$WithBody.applyCode(TypeWriter.java:730)
at net.bytebuddy.dynamic.scaffold.TypeWriter$MethodPool$Record$ForDefinedMethod$WithBody.applyBody(TypeWriter.java:715)
at net.bytebuddy.dynamic.scaffold.TypeWriter$MethodPool$Record$ForDefinedMethod.apply(TypeWriter.java:622)
at net.bytebuddy.dynamic.scaffold.TypeWriter$Default$ForCreation.create(TypeWriter.java:6043)
at net.bytebuddy.dynamic.scaffold.TypeWriter$Default.make(TypeWriter.java:2224)
at net.bytebuddy.dynamic.DynamicType$Builder$AbstractBase$UsingTypeWriter.make(DynamicType.java:4050)
at net.bytebuddy.dynamic.DynamicType$Builder$AbstractBase.make(DynamicType.java:3734)
at net.bytebuddy.dynamic.DynamicType$Builder$AbstractBase$Delegator.make(DynamicType.java:3986)
at tutorial.example_1.Main.main(Main.java:55)
它指出 make() 方法没有正确编译。这意味着课程没有按预期构建。
我认为 MethodCall.invokeSuper()
是问题所在,因为超类是一个接口。
解决方案是什么? 我正在使用 Java-17 和最新版本的 bytebuddy (1.13)