The function size must be used with a prefix when a default namespace is not

错误信息：
20:23:34.035 %PARSER_ERROR[l] [qtp180406984-43] ERROR o.a.struts2.dispatcher.Dispatcher - Exception occurred during processing request: /page/zlcx/data_detail_ywsc.jsp(99,10) PWC6296: The function size must be used with a prefix when a default namespace is not specified
org.apache.jasper.JasperException: /page/zlcx/data_detail_ywsc.jsp(99,10) PWC6296: The function size must be used with a prefix when a default namespace is not specified
at org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:78) ~[org.apache.jasper.glassfish_2.1.0.v201007080150.jar:na]
at org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:373) ~[org.apache.jasper.glassfish_2.1.0.v201007080150.jar:na]
at org.apache.jasper.compiler.ErrorDispatcher.jspError(ErrorDispatcher.java:201) ~[org.apache.jasper.glassfish_2.1.0.v201007080150.jar:na]
at org.apache.jasper.compiler.Validator$ValidateVisitor$1FVVisitor.visit(Validator.java:1590) ~[org.apache.jasper.glassfish_2.1.0.v201007080150.jar:na]
at org.apache.jasper.compiler.ELNode$Function.accept(ELNode.java:164) ~[org.apache.jasper.glassfish_2.1.0.v201007080150.jar:na]
at org.apache.jasper.compiler.ELNode$Nodes.visit(ELNode.java:235) ~[org.apache.jasper.glassfish_2.1.0.v201007080150.jar:na]
at org.apache.jasper.compiler.ELNode$Visitor.visit(ELNode.java:302) ~[org.apache.jasper.glassfish_2.1.0.v201007080150.jar:na]
at org.apache.jasper.compiler.ELNode$Root.accept(ELNode.java:95) ~[org.apache.jasper.glassfish_2.1.0.v201007080150.jar:na]
at org.apache.jasper.compiler.ELNode$Nodes.visit(ELNode.java:235) ~[org.apache.jasper.glassfish_2.1.0.v201007080150.jar:na]
at org.apache.jasper.compiler.Validator$ValidateVisitor.validateFunctions(Validator.java:1613) ~[org.apache.jasper.glassfish_2.1.0.v201007080150.jar:na]
at org.apache.jasper.compiler.Validator$ValidateVisitor.getJspAttribute(Validator.java:1356) ~[org.apache.jasper.glassfish_2.1.0.v201007080150.jar:na]
at org.apache.jasper.compiler.Validator$ValidateVisitor.checkXmlAttributes(Validator.java:1133) ~[org.apache.jasper.glassfish_2.1.0.v201007080150.jar:na]
at org.apache.jasper.compiler.Validator$ValidateVisitor.visit(Validator.java:850) ~[org.apache.jasper.glassfish_2.1.0.v201007080150.jar:na]
at org.apache.jasper.compiler.Node$CustomTag.accept(Node.java:1501) ~[org.apache.jasper.glassfish_2.1.0.v201007080150.jar:na]

修改前代码：(left是java.util.List)

<c:if test="${${(left.size()<16) || (empty left) } }">

解决方案：
一、引入标签

<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>

二、调正代码

<c:if test="${((fn:length(left))<16) || (empty left) }">