예제 #1
0
 public BeanBinding(Class<?> beanClass) {
   assert !beanClass.isArray() : "Bean is an array: " + beanClass;
   assert !beanClass.isPrimitive() : "Bean is primitive type: " + beanClass;
   myBeanClass = beanClass;
   myTagName = getTagName(beanClass);
   assert !StringUtil.isEmptyOrSpaces(myTagName) : "Bean name is empty: " + beanClass;
 }
  /**
   * Create a default object of the given type. Prefers constructors with as few arguments as
   * possible. Creates an empty proxy for interfaces.
   *
   * @param type type to instantiate
   * @return default instance
   * @throws Exception if the default instance could not be created
   */
  private static Object instantiateType(Class<?> type) throws Exception {
    if (type.isPrimitive()) return Defaults.defaultValue(type);
    else if (type == Void.class) return null;
    else if (type.isArray()) return Array.newInstance(type, 0);
    else if (type.isInterface())
      return Proxy.newProxyInstance(
          type.getClassLoader(),
          new Class[] {type},
          new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
              return null;
            }
          });

    // Take a constructor with as few params as possible
    Constructor constructor = type.getDeclaredConstructors()[0];
    for (Constructor<?> c : type.getDeclaredConstructors()) {
      if (c.getParameterTypes().length < constructor.getParameterTypes().length) constructor = c;
    }

    Object[] params = new Object[constructor.getParameterTypes().length];
    for (int i = 0; i < constructor.getParameterTypes().length; i++) {
      params[i] = instantiateType(constructor.getParameterTypes()[i]);
    }
    return constructor.newInstance(params);
  }