メソッドチェインなし

NotMethodChain.java

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Optional;
import java.util.function.Function;
import java.util.function.Supplier;

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@interface Annotation {
  String value() default "test";
}


enum Hoge {
  @Annotation TES, Hoge;
  String value;

  Hoge(){
    Class<? extends Hoge> clazz=this.getClass();
    Field field=null;
    try {
      field = clazz.getDeclaredField(this.toString());
    } catch (NoSuchFieldException|SecurityException e) {
    }
    if(field!=null){
      Annotation annotation=field.getAnnotation(Annotation.class);
      if(annotation!=null){
        for(Method method:annotation.annotationType().getDeclaredMethods()){
          Field f;
          try {
            f = clazz.getDeclaredField(method.getName());
            if(f.getType().isAssignableFrom(method.getReturnType())){
              f.set(this,method.invoke(annotation));
            }
          } catch (NoSuchFieldException | IllegalArgumentException | IllegalAccessException | InvocationTargetException e) {
          }
        }
      }
    }
    
    /* メソッドチェイン版はコメントアウト
    Function<String, Optional<Field>> fieldGetter=createFieldGetter(this.getClass());
    fieldGetter.apply(this.toString())
    .flatMap(enun->Optional.ofNullable(enun.getAnnotation(Annotation.class)))
    .ifPresent(annotation->{
      Arrays.stream(annotation.annotationType().getDeclaredMethods())
      .forEach(method->{
        fieldGetter.apply(method.getName())
        .filter(field->field.getType().isAssignableFrom(method.getReturnType()))
        .ifPresent(field->{
          try {
            field.set(this, method.invoke(annotation));
          } catch (IllegalAccessException|InvocationTargetException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
          }
        });
      });
    });*/
    System.out.println(this.value);
  }

  // ラムダ内で発生した例外を握りつぶせなかったのでボツ
  <T> Optional<T> getValue(Supplier<T> f, Class<? extends Exception>... exceptions) {
    try {
      return Optional.ofNullable(f.get());
    } catch (Exception e) {
      return Optional.empty();
    }
  }

  Function<String, Optional<Field>> createFieldGetter(Class<?> clazz) {
    return (name) -> Hoge.getField(clazz, name);
  }

  Optional<Field> getField(Class<?> clazz, String name) {
    try {
      return Optional.ofNullable(clazz.getDeclaredField(name));
    } catch (NoSuchFieldException | SecurityException e) {
      // 全てを握りつぶすマン！！
    }
    return Optional.empty();
  }

}