By Chris Morales,2014-10-09 10:20
12 views 0

当指定的值为null, 空字符串, 或者是空的java.util.Collection,或者




     Person person = new Person();



     request.setAttribute("toms", person);


    <logic:empty name="toms">

     bean is empty



    <logic:empty name="toms" property="name">

     property name is empty


    This tag evaluates its nested body content only if the specified value is either absent (i.e. null), an empty string (i.e. a java.lang.String with a length of zero), or an empty java.util.Collection or java.util.Map (tested by the .isEmpty() method on the respective interface).

    JSTL: The equivalent JSTL tag is <c:if> using the empty operator. For example,

    <c:if test="${empty sessionScope.myBean.myProperty}"> do something </c:if>

    Since: Struts 1.1

    Attribute Description Name

    The variable to be compared is the JSP bean specified by

    this attribute, if property is not specified, or the value

    of the specified property of this bean, if property is name specified.

    [RT Expr]

    The variable to be compared is the property (of the bean property specified by the name attribute) specified by this

    Attribute Description Name

    attribute. The property reference can be simple, nested,

    and/or indexed.

    [RT Expr]

    The bean scope within which to search for the bean named

    by the name property, or "any scope" if not specified. scope

    [RT Expr]

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