java - 是否可以扩展@Delegate Activity 注释的DelegateProcessor？

Question

我目前正在开发一个 Activity 注释，它是 Xtend Activity 注释 @Delegate 的调整版本。我已经有了一个丑陋的版本，它只是类 DelegateProcessor 及其内部类 Util 的改编副本。但这意味着我复制了整个类，只是在两种方法中调整了几行代码。

我尝试扩展 DelegateProcessor 和 Util 来覆盖我需要更改的几个方法。即使在最小的设置中(参见代码)，这也不起作用。我认识到 Javadoc 标签建议我不要这样做，但我无法相信除了复制整个 300 行代码之外没有其他方法。

这是我的最小设置:

import com.google.common.annotations.Beta
import com.google.common.annotations.GwtCompatible
import java.lang.annotation.Documented
import java.lang.annotation.ElementType
import java.lang.annotation.Target
import java.util.List
import org.eclipse.xtend.lib.annotations.Delegate
import org.eclipse.xtend.lib.annotations.DelegateProcessor
import org.eclipse.xtend.lib.macro.Active
import org.eclipse.xtend.lib.macro.TransformationContext
import org.eclipse.xtend.lib.macro.TransformationParticipant
import org.eclipse.xtend.lib.macro.declaration.MutableMemberDeclaration

/**
 * Copy of the Xtend {@link Delegate} annotation.
 */
@Beta
@GwtCompatible
@Target(ElementType.FIELD, ElementType.METHOD)
@Active(DelegateDeclaredProcessor)
@Documented
annotation DelegateDeclared {
    /**
     * Optional list of interfaces that this delegate is restricted to.
     * Defaults to the common interfaces of the context type and the annotated
     * element.
     */
    Class<?>[] value = #[]
}

@Beta
class DelegateDeclaredProcessor extends DelegateProcessor implements TransformationParticipant<MutableMemberDeclaration> {

    override doTransform(List<? extends MutableMemberDeclaration> elements, extension TransformationContext context) {
        val extension util = new Util(context) // Overridden to use my own Util class, which i want to adapt later on.
        elements.forEach [
            if (validDelegate) {
                methodsToImplement.forEach[method|implementMethod(method)]
            }
        ]
    }

    @Beta
    static class Util extends DelegateProcessor.Util { // this is where I want to later override some methods.
        new(TransformationContext context) {
            super(context)
        }
    }
}

此代码在使用注释时会产生以下错误:

    Error during annotation processing:
java.lang.NullPointerException
    at org.eclipse.xtend.lib.annotations.DelegateProcessor$Util.listedInterfaces(DelegateProcessor.java:258)
    at org.eclipse.xtend.lib.annotations.DelegateProcessor$Util.areListedInterfacesValid(DelegateProcessor.java:184)
    at org.eclipse.xtend.lib.annotations.DelegateProcessor$Util._isValidDelegate(DelegateProcessor.java:67)
    at org.eclipse.xtend.lib.annotations.DelegateProcessor$Util.isValidDelegate(DelegateProcessor.java:592)
    at jce.util.DelegateDeclaredProcessor.lambda$0(DelegateDeclaredProcessor.java:28)
    at jce.util.DelegateDeclaredProcessor$$Lambda$15311/667735929.accept(Unknown Source)
    at java.lang.Iterable.forEach(Iterable.java:75)
    at jce.util.DelegateDeclaredProcessor.doTransform(DelegateDeclaredProcessor.java:36)

这里有什么问题吗？我做错了什么还是不可能这样做？是否有另一种方法可以创建现有 Activity 注释的改编版本，例如 @Delegate？

Answer 1

看起来你错过了一些覆盖

@Beta
static class Util extends DelegateProcessor.Util { // this is where I want to later override some methods.

    extension TransformationContext context

    new(TransformationContext context) {
        super(context)
        this.context = context
    }

    override getDelegates(TypeDeclaration it) {
        declaredMembers.filter[findAnnotation(findTypeGlobally(DelegateDeclared)) !== null]
    }

    override listedInterfaces(MemberDeclaration it) {
        findAnnotation(findTypeGlobally(DelegateDeclared)).getClassArrayValue("value").toSet
    }

}