<% String str1=null; String str2=""; String str3="aa"; ArrayList al1=null; ArrayList al2=new ArrayList(); ArrayList al3=new ArrayList(); al3.add("aa"); request.setAttribute("str1", str1); request.setAttribute("str2", str2); request.setAttribute("str3", str3); request.setAttribute("al1", al1); request.setAttribute("al2", al2); request.setAttribute("al3", al3); %> <c:if test="${empty str1 }"> str1 </c:if> <c:if test="${empty str2 }"> str2 </c:if> <c:if test="${empty str3 }"> str3 </c:if> <c:if test="${empty al1 }"> al1 </c:if> <c:if test="${empty al2 }"> al2 </c:if> <c:if test="${empty al3 }"> al3 </c:if>
测试结果是:str1 str2 al1 al2
说明: