토비의 봄 TV 2.5회 - 수퍼 타입 토큰(2), 스프링 ResolvableType

(시청일 : 20171001)

- https://www.youtube.com/watch?v=y_uGSqpE4So : 2회에서 설명했던 수퍼 타입 토큰의 예제를 좀 더 효율적으로 개선하는 방법과 스프링이 제공하는 ResolvableType 사용법을 간단히 설명합니다.

■ Super Type Token (2회로 부터 개선된 버전)

 

public class SuperTypeToken {

    static Class TypeSafeMap {

        Map<Type, Object> map = new HashMap<>();

    <T> void put(TypeReference<T> tr, T value) {

        map.put(tr.type, value);

    }

    <T> T get(TypeReference<T> tr) {

        if (tr.type instanceof Class<?>)

            return ((Class<T>)tr.type).cast(map.get(tr.type));

        else

            return ((Class<T>)((ParameterizedType)tr.type).getRawType()).cast(map.get(tr.type)); // TR<List<String>>

    }

}

    static class TypeReference<T> {

        Type type;

        public TypeReference() {

            Type stype = getClass().getGenericSuperclass();

            if (stype instanceof ParameterizedType) {

                this.type = ((ParameterizedType) stype).getActualTypeArguments()[0];

            } else throw new RuntimeException();

        }

    }

    public static void main(String[] args) throws Exception {

        TypeReference m = new TypeSafeMap();

        m.put(new TypeReference<Integer>() {}, 1);

        m.put(new TypeReference<String>() {}, "String");

        m.put(new TypeReference<List<Integer>>() {}, Arrays.asList(1,2,3)); // List<Integer>

        m.put(new TypeReference<List<String>>() {}, Arrays.asList("a","b","c")); // List<String>

        m.put(new TypeReference<List<List<String>>>() {}, Arrays.asList(Arrays.asList("a","b"),Arrays.asList("c","d"),Arrays.asList("e"))); // List<String>

        System.out.println(m.get(new TypeReference<Integer>() {})); // 1

        System.out.println(m.get(new TypeReference<String>() {})); // String

        System.out.println(m.get(new TypeReference<List<Integer>>() {})); // [1, 2, 3]

        System.out.println(m.get(new TypeReference<List<String>>() {})); // [a, b, c]

        System.out.println(m.get(new TypeReference<List<List<String>>>() {})); // [[a, b], [c, d], [e]]

        Map<String, String> map = new HashMap<>();

        map.put("key1", "value1");

        map.put("key2", "value2");

        m.put(new TypeReference<Map<String, Stirng>>(), map);  // {key1=value1, key2=value2}

    }

}

■ 스프링 4.0버전 이상에서 지원하는 ResolvableType 예제 코드

public class SuperTypeToken {

    static class TypeReference<T> {

        Type type;

        public TypeReference() {

            Type stype = getClass().getGenericSuperclass();

            if (stype instanceof ParameterizedType) {

                this.type = ((ParameterizedType) stype).getActualTypeArguments()[0];

            } else throw new RuntimeException();

        }

    }

    public static void main(String[] args) throws Exception {

        //ResolvableType rt = ResolvableType.forClass(TypeReference.class);

        ResolvableType rt = ResolvableType.forInstance(new TypeReference<List<String>>() {});

        

        System.out.println(rt.getSuperType().getGenerics(0).getType()); // java.Util.List<java.lang.String>

        System.out.println(rt.getSuperType().getGenerics(0).getNested(2).getType()); // class.java.lang.String

        System.out.println(rt.getSuperType().hasUnresolvableGenerics()); // false

        System.out.println(ResolvableType.forInstance(new ArrayList<String>()).hasUnresolvableGenerics()); // true

    }

}