反射获取声明泛型工具类

public static Type[] getGenericTypes(Type paramType) {
    Type type;
    for (type = paramType; type instanceof Class;
         type = ((Class<?>) type).getGenericSuperclass()) {
        if (Object.class.equals(type)) {
            Type[] genericInterfaces = ((Class<?>) type).getGenericInterfaces();
            if (genericInterfaces.length > 0 && Objects.nonNull(genericInterfaces[0])) {
                type = genericInterfaces[0];
            }
        }
    }
    if (type instanceof ParameterizedType) {
        ParameterizedType ty = (ParameterizedType) type;
        return ty.getActualTypeArguments();
    }
    return new Type[0];
}

@Test
void testGetGenericTypes() {
    class StringArrayList extends ArrayList<String> {
        private static final long serialVersionUID = 5735314375293577082L;
    }
    Type[] stringType = ReflectHelper.getGenericTypes(new TypeReference<String>() {}.getClass());
    Assertions.assertEquals(String.class, stringType[0]);
    Type[] stringArrayListType = ReflectHelper.getGenericTypes(StringArrayList.class);
    Assertions.assertEquals(String.class, stringArrayListType[0]);
    Type[] hashMapType = ReflectHelper.getGenericTypes(new HashMap<String, Object>() {}.getClass());
    Assertions.assertEquals(String.class, hashMapType[0]);
    Assertions.assertEquals(Object.class, hashMapType[1]);
}

package io.github.vampireachao.stream.core.reflect;

import java.lang.reflect.Type;

/**
 * 单个泛型类型
 *
 * @author VampireAchao
 * @since 2022/6/2 18:53
 */
public abstract class TypeReference<T> implements Type {

    /**
     * Returns a string describing this type, including information
     * about any type parameters.
     *
     * @return a string describing this type
     * @implSpec The default implementation calls {@code toString}.
     * @since 1.8
     */
    @Override
    public String getTypeName() {
        return ReflectHelper.getGenericTypes(this.getClass())[0].getTypeName();
    }

    public Type getType() {
        return ReflectHelper.getGenericTypes(this.getClass())[0];
    }
}