页面如下
<%@ page contentType="text/html; charset=gb2312" language="java" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/xml" prefix="x" %>

<c:import url="/jstlTest/book.xml" var ="url" />
<x:parse xml="${url}"  var="book"   scope="session"       />
<x:set select="$book/book/title" var="title" scope="session" />
<b><x:out select="$title"/></b><br>  

报错：type Exception report

message 

description The server encountered an internal error () that prevented it from fulfilling this request.

exception 

javax.servlet.ServletException: javax.servlet.jsp.JspException: Content is not allowed in prolog.
org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:844)
org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:781)
org.apache.jsp.isJSTLxml_jsp._jspService(org.apache.jsp.isJSTLxml_jsp:94)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:322)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:291)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)


root cause 

org.xml.sax.SAXParseException: Content is not allowed in prolog.
com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(Unknown Source)
com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(Unknown Source)
org.apache.taglibs.standard.tag.common.xml.ParseSupport.parseInputSource(ParseSupport.java:227)
org.apache.taglibs.standard.tag.common.xml.ParseSupport.parseInputSourceWithFilter(ParseSupport.java:193)
org.apache.taglibs.standard.tag.common.xml.ParseSupport.parseReaderWithFilter(ParseSupport.java:199)
org.apache.taglibs.standard.tag.common.xml.ParseSupport.parseStringWithFilter(ParseSupport.java:206)
org.apache.taglibs.standard.tag.common.xml.ParseSupport.doEndTag(ParseSupport.java:138)
org.apache.jsp.isJSTLxml_jsp._jspx_meth_x_parse_0(org.apache.jsp.isJSTLxml_jsp:139)
org.apache.jsp.isJSTLxml_jsp._jspService(org.apache.jsp.isJSTLxml_jsp:78)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:322)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:291)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

请教各们，我的环境  JDK1.5 + Tomcat 5