hi all, The performance of the JSTL XML 1.1 tags is really poor. Version 1.0 was much faster maybe because it used Jaxen and it cached parsed XPath statements, while the current Xalan based implementation does not. Since some of my pages were too slow, I tried to restore the 1.0 code in XPathUtil.java and managed to recompile. I discovered that the tags are now 100 TIMES FASTER! A modified XPathUtil and a test JSP are attached. (I also put a compiled webapp at: http://purl.org/net/flavio/jstl-test.tar.gz )
Basically it's the same XPathUtil from version 1.0.6 but some methods throw JspTagException instead of SAXPathException. What the developers are planning to do about this performance problem? What are the reasons behind the switch from Jaxen to Xalan? And finally... Will you accept my patch and go back to Jaxen? regards, Flavio Tordini P.S. the patch also fixes bug 30068 http://issues.apache.org/bugzilla/show_bug.cgi?id=30068
<%@ taglib prefix="x" uri="http://java.sun.com/jsp/jstl/xml"; %> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"; %> <c:import url="test.xml" varReader="reader"> <x:parse doc="${reader}" var="myDoc" scope="request"/> </c:import> <% long start = System.currentTimeMillis(); %> <x:forEach select="$myDoc/test/item"> <x:out select="@name"/> <x:out select="."/> </x:forEach> <%= System.currentTimeMillis() - start %>
/* * Copyright 1999,2004 The Apache Software Foundation. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.taglibs.standard.tag.common.xml; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServletRequest; import javax.servlet.jsp.JspTagException; import javax.servlet.jsp.PageContext; import javax.servlet.jsp.tagext.Tag; import javax.servlet.jsp.tagext.TagSupport; import org.jaxen.Context; import org.jaxen.ContextSupport; import org.jaxen.FunctionContext; import org.jaxen.SimpleNamespaceContext; import org.jaxen.UnresolvableException; import org.jaxen.VariableContext; import org.jaxen.XPath; import org.jaxen.XPathFunctionContext; import org.jaxen.dom.DOMXPath; import org.jaxen.dom.DocumentNavigator; import org.saxpath.SAXPathException; import org.w3c.dom.Node; /** * <p>Support for tag handlers that evaluate XPath expressions.</p> * * @author Shawn Bayern */ // would ideally be a base class, but some of our user handlers already // have their own parents public class XPathUtil { //********************************************************************* // Constructor /** * Constructs a new XPathUtil object associated with the given * PageContext. */ public XPathUtil(PageContext pc) { pageContext = pc; } //********************************************************************* // Support for JSTL variable resolution private static final String PAGE_NS_URL = "http://java.sun.com/jstl/xpath/page";; private static final String REQUEST_NS_URL = "http://java.sun.com/jstl/xpath/request";; private static final String SESSION_NS_URL = "http://java.sun.com/jstl/xpath/session";; private static final String APP_NS_URL = "http://java.sun.com/jstl/xpath/app";; private static final String PARAM_NS_URL = "http://java.sun.com/jstl/xpath/param";; private static final String INITPARAM_NS_URL = "http://java.sun.com/jstl/xpath/initParam";; private static final String COOKIE_NS_URL = "http://java.sun.com/jstl/xpath/cookie";; private static final String HEADER_NS_URL = "http://java.sun.com/jstl/xpath/header";; private static final String PAGE_P = "pageScope"; private static final String REQUEST_P = "requestScope"; private static final String SESSION_P = "sessionScope"; private static final String APP_P = "applicationScope"; private static final String PARAM_P = "param"; private static final String INITPARAM_P = "initParam"; private static final String COOKIE_P = "cookie"; private static final String HEADER_P = "header"; protected class JstlVariableContext implements VariableContext { // retrieves object using JSTL's custom variable-mapping rules public Object getVariableValue(String namespace, String prefix, String localName) throws UnresolvableException { // I'd prefer to match on namespace, but this doesn't appear // to work in Jaxen if (prefix == null || prefix.equals("")) { return notNull( pageContext.findAttribute(localName), prefix, localName); } else if (prefix.equals(PAGE_P)) { return notNull( pageContext.getAttribute(localName,PageContext.PAGE_SCOPE), prefix, localName); } else if (prefix.equals(REQUEST_P)) { return notNull( pageContext.getAttribute(localName, PageContext.REQUEST_SCOPE), prefix, localName); } else if (prefix.equals(SESSION_P)) { return notNull( pageContext.getAttribute(localName, PageContext.SESSION_SCOPE), prefix, localName); } else if (prefix.equals(APP_P)) { return notNull( pageContext.getAttribute(localName, PageContext.APPLICATION_SCOPE), prefix, localName); } else if (prefix.equals(PARAM_P)) { return notNull( pageContext.getRequest().getParameter(localName), prefix, localName); } else if (prefix.equals(INITPARAM_P)) { return notNull( pageContext.getServletContext(). getInitParameter(localName), prefix, localName); } else if (prefix.equals(HEADER_P)) { HttpServletRequest hsr = (HttpServletRequest) pageContext.getRequest(); return notNull( hsr.getHeader(localName), prefix, localName); } else if (prefix.equals(COOKIE_P)) { HttpServletRequest hsr = (HttpServletRequest) pageContext.getRequest(); Cookie[] c = hsr.getCookies(); for (int i = 0; i < c.length; i++) if (c[i].getName().equals(localName)) return c[i].getValue(); throw new UnresolvableException("$" + prefix + ":" + localName); } else throw new UnresolvableException("$" + prefix + ":" + localName); } private Object notNull(Object o, String prefix, String localName) throws UnresolvableException { if (o == null) { throw new UnresolvableException("$" + (prefix==null?"":prefix+":") + localName); } return o; } } //********************************************************************* // Support for XPath evaluation private PageContext pageContext; private static SimpleNamespaceContext nc; private static FunctionContext fc; private static DocumentNavigator dn; private static HashMap exprCache; /** Initialize globally useful data. */ private synchronized static void staticInit() { if (nc == null) { // register supported namespaces nc = new SimpleNamespaceContext(); SimpleNamespaceContext nc = new SimpleNamespaceContext(); nc.addNamespace("page", PAGE_NS_URL); nc.addNamespace("request", REQUEST_NS_URL); nc.addNamespace("session", SESSION_NS_URL); nc.addNamespace("application", APP_NS_URL); nc.addNamespace("param", PARAM_NS_URL); nc.addNamespace("initParam", INITPARAM_NS_URL); nc.addNamespace("header", HEADER_NS_URL); nc.addNamespace("cookie", COOKIE_NS_URL); // set up the global FunctionContext fc = XPathFunctionContext.getInstance(); // set up the global DocumentNavigator dn = DocumentNavigator.getInstance(); // create a HashMap to cache the expressions exprCache = new HashMap(); } } /** * Returns a String given an XPath expression and a single context * Node. */ public String valueOf(Node n, String xpath) throws JspTagException { staticInit(); try { XPath xp = new DOMXPath(xpath); // return xp.valueOf(getLocalContext(n)); return xp.stringValueOf(getLocalContext(n)); } catch (SAXPathException e) { throw new JspTagException("Error evaluating XPath.", e); } } /** Evaluates an XPath expression to a boolean value. */ public boolean booleanValueOf(Node n, String xpath) throws JspTagException { staticInit(); try { XPath xp = parse(xpath); return xp.booleanValueOf(getLocalContext(n)); } catch (SAXPathException e) { throw new JspTagException("Error evaluating XPath.", e); } } /** Evalutes an XPath expression to a List of nodes. */ public List selectNodes(Node n, String xpath) throws JspTagException { staticInit(); try { XPath xp = parse(xpath); return xp.selectNodes(getLocalContext(n)); } catch (SAXPathException e) { throw new JspTagException("Error evaluating XPath.", e); } } /** Evaluates an XPath expression to a single node. */ public Node selectSingleNode(Node n, String xpath) throws SAXPathException { staticInit(); XPath xp = parse(xpath); return (Node) xp.selectSingleNode(getLocalContext(n)); } /** Returns a locally appropriate Jaxen context given a node. */ private Context getLocalContext(Node n) { // set up instance-specific contexts VariableContext vc = new JstlVariableContext(); ContextSupport cs = new ContextSupport(nc, fc, vc, dn); Context c = new Context(cs); List l = new ArrayList(1); l.add(n); c.setNodeSet(l); return c; } /** * Retrieves a parsed version of the textual XPath expression. * The parsed version is retrieved from our static cache if we've * seen it previously. */ private XPath parse(String xpath) throws SAXPathException { XPath cached = (XPath) exprCache.get(xpath); if (cached == null) { cached = new DOMXPath(xpath); exprCache.put(xpath, cached); } return cached; } //********************************************************************* // Static support for context retrieval from parent <forEach> tag public static Node getContext(Tag t) throws JspTagException { ForEachTag xt = (ForEachTag) TagSupport.findAncestorWithClass( t, ForEachTag.class); if (xt == null) return null; else return (xt.getContext()); } }
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