如何在嵌套参数parameter中获取批注? [英] How to get annotations in nested parameter parameter?

问题描述

如果我有这样的功能，

public void park( List< @myNote("list") List< @myNote("integer") Integer>> l){ System.out.println("park"); }

如果我使用Parameter.getAnnotations()和Paramter.getDeclaredAnnotation，则只能获取@myNote("list").有什么方法可以获取批注@myNote("integer")?

If I use Parameter.getAnnotations() and Paramter.getDeclaredAnnotation, I can only get @myNote("list"). Are any ways to get the annotation @myNote("integer")?

这可能与推荐答案

以下是用于打印注释的代码，因此您可以看到在反射API中可以找到它们的位置.

Here is code to print the annotations, so you can see where in the reflection API they can be found.

基本上，您调用 param.getAnnotatedType() ，检查 AnnotatedParameterizedType ，然后调用 getAnnotatedActualTypeArguments() 来获取泛型类型参数，然后递归执行.

Basically, you call param.getAnnotatedType(), check if the AnnotatedType is an AnnotatedParameterizedType, and call getAnnotatedActualTypeArguments() to get the generic type arguments, and do that recursively.

对于每个AnnotatedType(顶级或嵌套)，您调用

For each AnnotatedType, top-level or nested, you call getDeclaredAnnotations() or getAnnotations() to get the annotations on that type.

我添加了其他内容，以便您可以了解其工作原理.

I added extra stuff, just so you can see how it works.

public class Test {
    public static void main(String[] args) {
        Method method = Test.class.getDeclaredMethod("park", List.class, Map.class);
        for (Parameter param : method.getParameters()) {
            System.out.println("Parameter: " + param);
            printAnnotatedType(1, param.getAnnotatedType());
        }
    }
    static void printAnnotatedType(int indent, AnnotatedType type) {
        System.out.println("  ".repeat(indent) + "AnnotatedType: " + type);
        System.out.println("  ".repeat(indent + 2) + "Type: " + type.getType());
        for (Annotation annotation : type.getDeclaredAnnotations()) {
            System.out.println("  ".repeat(indent + 2) + "Annotation: " + annotation);
        }
        if (type instanceof AnnotatedParameterizedType) {
            AnnotatedParameterizedType pt = (AnnotatedParameterizedType) type;
            for (AnnotatedType typeArg : pt.getAnnotatedActualTypeArguments()) {
                printAnnotatedType(indent + 1, typeArg);
            }
        }
    }
    public void park(@myNote("p0") List< @myNote("list") List< @myNote("integer") @myOther Integer>> l,
                     @myNote("p1") Map< @myNote("key") Long, @myNote("value") String> m) {
        System.out.println("park");
    }
}

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE_USE)
@interface myNote {
    String value();
}

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE_USE)
@interface myOther {
}

输出

Parameter: java.util.List<java.util.List<java.lang.Integer>> arg0
  AnnotatedType: @myNote(value="p0") java.util.List<@myNote(value="list") java.util.List<@myNote(value="integer") @myOther() java.lang.Integer>>
      Type: java.util.List<java.util.List<java.lang.Integer>>
      Annotation: @myNote(value="p0")
    AnnotatedType: @myNote(value="list") java.util.List<@myNote(value="integer") @myOther() java.lang.Integer>
        Type: java.util.List<java.lang.Integer>
        Annotation: @myNote(value="list")
      AnnotatedType: @myNote(value="integer") @myOther() java.lang.Integer
          Type: class java.lang.Integer
          Annotation: @myNote(value="integer")
          Annotation: @myOther()
Parameter: java.util.Map<java.lang.Long, java.lang.String> arg1
  AnnotatedType: @myNote(value="p1") java.util.Map<@myNote(value="key") java.lang.Long, @myNote(value="value") java.lang.String>
      Type: java.util.Map<java.lang.Long, java.lang.String>
      Annotation: @myNote(value="p1")
    AnnotatedType: @myNote(value="key") java.lang.Long
        Type: class java.lang.Long
        Annotation: @myNote(value="key")
    AnnotatedType: @myNote(value="value") java.lang.String
        Type: class java.lang.String
        Annotation: @myNote(value="value")

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