目的

在接口中实现如下方法，获取T的实例化对象

public interface Base<T> {


    default T getInstanceOfT() {
        T bean;
	/*...代码*/
        return bean;
    }

}

准备工具类

public class ReflectUtils {

    private ReflectUtils(){
    }

    public static <T> T newBean(Class<T> clazz){
        T t = null;
        try {
            t = clazz.newInstance();
        } catch (InstantiationException | IllegalAccessException e) {
            log.error(e.getMessage(),e);
        }
        return t;
    }

    public static ParameterizedType getParameterizedType( Class<?> interfaceType, Class<?> implementationClass) {
        if (implementationClass == null) {
            // If the super class is Object parent then return null
            return null;
        }

        // Get parameterized type
        ParameterizedType currentType = getParameterizedType(interfaceType, implementationClass.getGenericInterfaces());

        if (currentType != null) {
            // return the current type
            return currentType;
        }

        Class<?> superclass = implementationClass.getSuperclass();

        return getParameterizedType(interfaceType, superclass);
    }

    public static ParameterizedType getParameterizedType(Class<?> superType, Type... genericTypes) {
        ParameterizedType currentType = null;

        for (Type genericType : genericTypes) {
            if (genericType instanceof ParameterizedType) {
                ParameterizedType parameterizedType = (ParameterizedType) genericType;
                if (parameterizedType.getRawType().getTypeName().equals(superType.getTypeName())) {
                    currentType = parameterizedType;
                    break;
                }
            }
        }

        return currentType;
    }
}

最终实现

interface Base<T> {

    default T getinstanceOfT(){
        T bean;
        ParameterizedType parameterizedType = getParameterizedType(BaseDTO.class, getClass());
        if(parameterizedType==null)
            return null;
        Class<T> clazz = (Class<T>) parameterizedType.getActualTypeArguments()[0];
        bean = newBean(clazz);
        return bean;
    }

}