DynaActionForm中可以添加实体类型吗

[yl_521]

    <form-bean name="bookForm" type="org.apache.struts.action.DynaActionForm">
      <form-property name="books" type="com.accp.entity.Books" />
      <form-property name="name" type="java.lang.String" />
    </form-bean>

	public ActionForward execute(ActionMapping mapping, ActionForm form,
			HttpServletRequest request, HttpServletResponse response) {
		DynaActionForm bookForm = (DynaActionForm) form;
		System.out.println(bookForm.get("name"));
		//(Books)(bookForm.get("books"));
		return null;
	}

以上两段为部分代码，动态的formbean可以添加string类型的成员，而且在action中也可以成功获取到，但为什么添加一个BookS实体类型后，在action中无法获取呢？