el表达式遇到的问题

org.apache.el.parser.ParseException: Encountered " <ILLEGAL_CHARACTER> "= "" at line 1, column 14.
Was expecting one of:
"}" ...
"." ...
"[" ...
">" ...
"gt" ...
"<" ...
"lt" ...
">=" ...
"ge" ...
"<=" ...
"le" ...
"==" ...
"eq" ...
"!=" ...
"ne" ...
"&&" ...
"and" ...
"||" ...
"or" ...
"*" ...
"+" ...
"-" ...
"/" ...
"div" ...
"%" ...
"mod" ...

错误原因：在JSP页面使用了非法表达式<a href="<c:url value='/OperationServlet20'/>?method=queryAll&currentPage=${pb.currentPage=1}">首页</a>