/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright 1997-2008 Sun Microsystems, Inc. All rights reserved.
 *
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License. You can obtain
 * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
 * or glassfish/bootstrap/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 *
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
 * Sun designates this particular file as subject to the "Classpath" exception
 * as provided by Sun in the GPL Version 2 section of the License file that
 * accompanied this code.  If applicable, add the following below the License
 * Header, with the fields enclosed by brackets [] replaced by your own
 * identifying information: "Portions Copyrighted [year]
 * [name of copyright owner]"
 *
 * Contributor(s):
 *
 * If you wish your version of this file to be governed by only the CDDL or
 * only the GPL Version 2, indicate your decision by adding "[Contributor]
 * elects to include this software in this distribution under the [CDDL or GPL
 * Version 2] license."  If you don't indicate a single choice of license, a
 * recipient has the option to distribute your version of this file under
 * either the CDDL, the GPL Version 2 or to extend the choice of license to
 * its licensees as provided above.  However, if you add GPL Version 2 code
 * and therefore, elected the GPL Version 2 license, then the option applies
 * only if the new code is made subject to such option by the copyright
 * holder.
 *
 *
 * This file incorporates work covered by the following copyright and
 * permission notice:
 *
 * Copyright 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.jasper.runtime;

import java.io.IOException;
import java.io.Writer;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Iterator;

import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspFactory;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.JspApplicationContext;
import javax.servlet.jsp.tagext.BodyContent;
import javax.servlet.jsp.el.ExpressionEvaluator;
import javax.servlet.jsp.el.VariableResolver;
import javax.servlet.jsp.el.ImplicitObjectELResolver;
import javax.servlet.jsp.el.ScopedAttributeELResolver;

import javax.el.ELException;
import javax.el.ELResolver;
import javax.el.ELContext;
import javax.el.BeanELResolver;
import javax.el.ArrayELResolver;
import javax.el.MapELResolver;
import javax.el.ResourceBundleELResolver;
import javax.el.ListELResolver;
import javax.el.CompositeELResolver;
import javax.el.ValueExpression;
import javax.el.FunctionMapper;
import javax.el.MethodExpression;
import javax.el.ExpressionFactory;

import com.sun.org.apache.commons.logging.Log;
import com.sun.org.apache.commons.logging.LogFactory;
import org.apache.jasper.Constants;
import org.apache.jasper.compiler.Localizer;
import org.apache.jasper.security.SecurityUtil;

/**
 * Implementation of the PageContext class from the JSP spec.
 *
 * @author Anil K. Vijendran
 * @author Larry Cable
 * @author Hans Bergsten
 * @author Pierre Delisle
 * @author Mark Roth
 * @author Jan Luehe
 * @author Kin-man Chung
 */
public class PageContextImpl extends PageContext {

    // Logger
    private static Log log = LogFactory.getLog(PageContextImpl.class);

    // per-servlet state
    private BodyContentImpl[] outs;
    private int depth;
    private Servlet servlet;
    private ServletConfig config;
    private ServletContext context;
    private JspFactory factory;
    private boolean needsSession;
    private String errorPageURL;
    private int	bufferSize;
    private JspApplicationContextImpl jspApplicationContext;
    private ELResolver elResolver;
    private ELContext elContext;

    // page-scope attributes
    private HashMap attributes;
    private boolean isNametableInitialized;

    // per-request state
    private ServletRequest request;
    private ServletResponse response;
    private HttpSession session;

    // initial output stream
    private JspWriter out;
    private JspWriterImpl baseOut;

    /*
     * Constructor.
     */
    PageContextImpl(JspFactory factory) {
        this.factory = factory;
	this.outs = new BodyContentImpl[0];
	this.attributes = new HashMap(16);
	this.depth = -1;
    }

    public void initialize(Servlet servlet,
			   ServletRequest request,
                           ServletResponse response,
			   String errorPageURL,
                           boolean needsSession,
			   int bufferSize,
                           boolean autoFlush) throws IOException {

	_initialize(servlet, request, response, errorPageURL, needsSession,
		    bufferSize, autoFlush);
    }

    private void _initialize(Servlet servlet,
			     ServletRequest request,
			     ServletResponse response,
			     String errorPageURL,
			     boolean needsSession,
			     int bufferSize,
			     boolean autoFlush) throws IOException {

	// initialize state
	this.servlet = servlet;
	this.config = servlet.getServletConfig();
	this.context = config.getServletContext();
	this.needsSession = needsSession;
	this.errorPageURL = errorPageURL;
	this.bufferSize = bufferSize;
	this.request = request;
 	this.response = response;

	// Setup session (if required)
	if (request instanceof HttpServletRequest && needsSession)
	    this.session = ((HttpServletRequest)request).getSession();
	if (needsSession && session == null)
	    throw new IllegalStateException
                ("Page needs a session and none is available");

        // initialize the initial out ...
        depth = -1;
        if (this.baseOut == null) {
            this.baseOut = new JspWriterImpl(response, bufferSize, autoFlush);
        } else {
            this.baseOut.init(response, bufferSize, autoFlush);
        }
        this.out = baseOut;

        this.isNametableInitialized = false;
        setAttribute(Constants.FIRST_REQUEST_SEEN, "true", APPLICATION_SCOPE);

    }

    private void initializePageScopeNameTable() {
        isNametableInitialized = true;
        // register names/values as per spec
        setAttribute(OUT, this.out);
        setAttribute(REQUEST, request);
        setAttribute(RESPONSE, response);

        if (session != null)
            setAttribute(SESSION, session);

        setAttribute(PAGE, servlet);
        setAttribute(CONFIG, config);
        setAttribute(PAGECONTEXT, this);
        setAttribute(APPLICATION, context);
    }

    public void release() {
        out = baseOut;
	try {
            // Do not flush the buffer even if we're not included (i.e.
            // we are the main page. The servlet will flush it and close
            // the stream.
            ((JspWriterImpl)out).flushBuffer();
	} catch (IOException ex) {
	    log.warn("Internal error flushing the buffer in release()");
	}

	servlet = null;
	config = null;
	context = null;
        elContext = null;
        elResolver = null;
        jspApplicationContext = null;
	needsSession = false;
	errorPageURL = null;
	bufferSize = JspWriter.DEFAULT_BUFFER;
	request = null;
	response = null;
        depth = -1;
	baseOut.recycle();
	session = null;

	attributes.clear();
    }

    public Object getAttribute(final String name) {

        if (name == null) {
            throw new NullPointerException(
                    Localizer.getMessage("jsp.error.attribute.null_name"));
        }

        if (SecurityUtil.isPackageProtectionEnabled()){
            return AccessController.doPrivileged(new PrivilegedAction(){
                public Object run(){
                    return doGetAttribute(name);
                }
            });
        } else {
            return doGetAttribute(name);
        }

    }

    private Object doGetAttribute(String name){
        if (!isNametableInitialized) {
            initializePageScopeNameTable();
        }
        return attributes.get(name);
    }

    public Object getAttribute(final String name, final int scope) {

        if (name == null) {
            throw new NullPointerException(
                    Localizer.getMessage("jsp.error.attribute.null_name"));
        }

        if (SecurityUtil.isPackageProtectionEnabled()){
            return AccessController.doPrivileged(new PrivilegedAction(){
                public Object run(){
                    return doGetAttribute(name, scope);
                }
            });
        } else {
            return doGetAttribute(name, scope);
        }

    }

    private Object doGetAttribute(String name, int scope){
        switch (scope) {
            case PAGE_SCOPE:
                if (!isNametableInitialized) {
                    initializePageScopeNameTable();
                }
                return attributes.get(name);

            case REQUEST_SCOPE:
                return request.getAttribute(name);

            case SESSION_SCOPE:
                if (session == null) {
                    throw new IllegalStateException(
                        Localizer.getMessage("jsp.error.page.noSession"));
                }
                return session.getAttribute(name);

            case APPLICATION_SCOPE:
                return context.getAttribute(name);

            default:
                throw new IllegalArgumentException("Invalid scope");
        }
    }

    public void setAttribute(final String name, final Object attribute) {

        if (name == null) {
            throw new NullPointerException(
                    Localizer.getMessage("jsp.error.attribute.null_name"));
        }

        if (SecurityUtil.isPackageProtectionEnabled()){
            AccessController.doPrivileged(new PrivilegedAction(){
                public Object run(){
                    doSetAttribute(name, attribute);
                    return null;
                }
            });
        } else {
            doSetAttribute(name, attribute);
        }
    }

    private void doSetAttribute(String name, Object attribute){
        if (attribute != null) {
            if (!isNametableInitialized) {
                initializePageScopeNameTable();
            }
            attributes.put(name, attribute);
        } else {
            removeAttribute(name, PAGE_SCOPE);
        }
    }

    public void setAttribute(final String name, final Object o, final int scope) {

        if (name == null) {
            throw new NullPointerException(
                    Localizer.getMessage("jsp.error.attribute.null_name"));
        }

        if (SecurityUtil.isPackageProtectionEnabled()){
            AccessController.doPrivileged(new PrivilegedAction(){
                public Object run(){
                    doSetAttribute(name, o, scope);
                    return null;
                }
            });
        } else {
            doSetAttribute(name, o, scope);
        }

    }

    private void doSetAttribute(String name, Object o, int scope ){
        if (o != null) {
            switch (scope) {
            case PAGE_SCOPE:
                if (!isNametableInitialized) {
                    initializePageScopeNameTable();
                }
                attributes.put(name, o);
                break;

            case REQUEST_SCOPE:
                request.setAttribute(name, o);
                break;

            case SESSION_SCOPE:
                if (session == null) {
                    throw new IllegalStateException(
                        Localizer.getMessage("jsp.error.page.noSession"));
                }
                session.setAttribute(name, o);
                break;

            case APPLICATION_SCOPE:
                context.setAttribute(name, o);
                break;

            default:
                throw new IllegalArgumentException("Invalid scope");
            }
        } else {
            removeAttribute(name, scope);
        }
    }

    public void removeAttribute(final String name, final int scope) {

        if (name == null) {
            throw new NullPointerException(
                    Localizer.getMessage("jsp.error.attribute.null_name"));
        }
        if (SecurityUtil.isPackageProtectionEnabled()){
            AccessController.doPrivileged(new PrivilegedAction(){
                public Object run(){
                    doRemoveAttribute(name, scope);
                    return null;
                }
            });
        } else {
            doRemoveAttribute(name, scope);
        }
    }

    private void doRemoveAttribute(String name, int scope){
        switch (scope) {
        case PAGE_SCOPE:
            if (!isNametableInitialized) {
                initializePageScopeNameTable();
            }
            attributes.remove(name);
            break;

        case REQUEST_SCOPE:
            request.removeAttribute(name);
            break;

        case SESSION_SCOPE:
            if (session == null) {
            throw new IllegalStateException(
                        Localizer.getMessage("jsp.error.page.noSession"));
            }
            session.removeAttribute(name);
            break;

        case APPLICATION_SCOPE:
            context.removeAttribute(name);
            break;
            
        default:
            throw new IllegalArgumentException("Invalid scope");
        }
    }

    public int getAttributesScope(final String name) {

        if (name == null) {
            throw new NullPointerException(
                    Localizer.getMessage("jsp.error.attribute.null_name"));
        }

        if (SecurityUtil.isPackageProtectionEnabled()){
            return ((Integer)AccessController.doPrivileged(new PrivilegedAction(){
                public Object run(){
                    return Integer.valueOf(doGetAttributeScope(name));
                }
            })).intValue();
        } else {
            return doGetAttributeScope(name);
        }
    }

    private int doGetAttributeScope(String name){

        if (!isNametableInitialized) {
            initializePageScopeNameTable();
        }

        if (attributes.get(name) != null)
            return PAGE_SCOPE;

        if (request.getAttribute(name) != null)
            return REQUEST_SCOPE;

        if (session != null) {
            try {
                if (session.getAttribute(name) != null)
                    return SESSION_SCOPE;
            } catch (IllegalStateException ex) {
 	        // Session has been invalidated.
                // Ignore and fall through to application scope.
            }
        }

        if (context.getAttribute(name) != null)
            return APPLICATION_SCOPE;

        return 0;
    }

    public Object findAttribute(final String name) {
        if (SecurityUtil.isPackageProtectionEnabled()){
            return AccessController.doPrivileged(new PrivilegedAction(){
                public Object run(){
                    if (name == null) {
                        throw new NullPointerException(
                                Localizer.getMessage("jsp.error.attribute.null_name"));
                    }

                    return doFindAttribute(name);
                }
            });
        } else {
            if (name == null) {
                throw new NullPointerException(
                        Localizer.getMessage("jsp.error.attribute.null_name"));
            }

            return doFindAttribute(name);
        }
    }

    private Object doFindAttribute(String name){

        if (!isNametableInitialized) {
            initializePageScopeNameTable();
        }

        Object o = attributes.get(name);
        if (o != null)
            return o;

        o = request.getAttribute(name);
        if (o != null)
            return o;

 	if (session != null) {
	    try {
	        o = session.getAttribute(name);
 	    } catch (IllegalStateException ex) {
 	        // Session has been invalidated.
                // Ignore and fall through to application scope.
 	    }

 	    if (o != null) return o;
 	}

        return context.getAttribute(name);
    }


    public Enumeration<String> getAttributeNamesInScope(final int scope) {
        if (SecurityUtil.isPackageProtectionEnabled()){
            return (Enumeration<String>)
                    AccessController.doPrivileged(new PrivilegedAction(){
                public Object run(){
                    return doGetAttributeNamesInScope(scope);
                }
            });
        } else {
            return doGetAttributeNamesInScope(scope);
        }
    }

    private Enumeration<String> doGetAttributeNamesInScope(int scope){
        switch (scope) {
        case PAGE_SCOPE:
            if (!isNametableInitialized) {
                initializePageScopeNameTable();
            }
            return Collections.enumeration(attributes.keySet());
            
        case REQUEST_SCOPE:
            return request.getAttributeNames();

        case SESSION_SCOPE:
            if (session == null) {
            throw new IllegalStateException(
                        Localizer.getMessage("jsp.error.page.noSession"));
            }
            return session.getAttributeNames();

        case APPLICATION_SCOPE:
            return context.getAttributeNames();

        default:
            throw new IllegalArgumentException("Invalid scope");
        }
    }

    public void removeAttribute(final String name) {

        if (name == null) {
            throw new NullPointerException(
                    Localizer.getMessage("jsp.error.attribute.null_name"));
        }

        if (SecurityUtil.isPackageProtectionEnabled()){
            AccessController.doPrivileged(new PrivilegedAction(){
                public Object run(){
                    doRemoveAttribute(name);
                    return null;
                }
            });
        } else {
            doRemoveAttribute(name);
        }
    }

    private void doRemoveAttribute(String name){
        removeAttribute(name, PAGE_SCOPE);
        removeAttribute(name, REQUEST_SCOPE);
        if( session != null ) {
            try {
                removeAttribute(name, SESSION_SCOPE);
            } catch (IllegalStateException ex) {
                // Session has been invalidated.
                // Ignore and fall through to application scope.
            }
        }
        removeAttribute(name, APPLICATION_SCOPE);
    }
        
    public JspWriter getOut() {
	return out;
    }

    public HttpSession getSession() { return session; }
    public Servlet getServlet() { return servlet; }
    public ServletConfig getServletConfig() { return config; }
    public ServletContext getServletContext() {
	return config.getServletContext();
    }
    public ServletRequest getRequest() { return request; }
    public ServletResponse getResponse() { return response; }


    /**
     * Returns the exception associated with this page context, if any.
     * 
     * Added wrapping for Throwables to avoid ClassCastException
     * (see Bugzilla 31171 for details).
     *
     * @return The Exception associated with this page context, if any.
     */
    public Exception getException() {

        Throwable t = JspRuntimeLibrary.getThrowable(request);

        // Only wrap if needed
        if((t != null) && (! (t instanceof Exception))) {
            t = new JspException(t);
        }

        return (Exception) t;
    }


    public Object getPage() { return servlet; }


    private final String getAbsolutePathRelativeToContext(String relativeUrlPath) {
        String path = relativeUrlPath;

        if (!path.startsWith("/")) {
	    String uri = (String)
		request.getAttribute("javax.servlet.include.servlet_path");
	    if (uri == null)
		uri = ((HttpServletRequest) request).getServletPath();
            String baseURI = uri.substring(0, uri.lastIndexOf('/'));
            path = baseURI+'/'+path;
        }

        return path;
    }

    public void include(String relativeUrlPath)
	        throws ServletException, IOException {
        JspRuntimeLibrary.include(request, response, relativeUrlPath, out,
				  true);
    }

    /*
     * No need to execute include inside a privileged block, since it calls
     * ApplicationDispatcher include, which in turn is executed inside a
     * privileged block
     */
    public void include(String relativeUrlPath, boolean flush)
	        throws ServletException, IOException {
        JspRuntimeLibrary.include(request, response, relativeUrlPath, out,
				  flush);
    }

    public VariableResolver getVariableResolver() {
        return new VariableResolverImpl(this);
    }

    private ELResolver getELResolver() {
                                                                                
        if (elResolver == null) {
            // Create a CompositeELResolver
            CompositeELResolver celResolver = new CompositeELResolver();
                                                                                
            celResolver.add(new ImplicitObjectELResolver());
            // Add ELResolvers registered in JspApplicationContext
            JspApplicationContextImpl jaContext = getJspApplicationContext();
            Iterator<ELResolver> it = jaContext.getELResolvers();
            while (it.hasNext()) {
                celResolver.add(it.next());
            }
            celResolver.add(new MapELResolver());
            celResolver.add(new ResourceBundleELResolver());
            celResolver.add(new ListELResolver());
            celResolver.add(new ArrayELResolver());
            celResolver.add(new BeanELResolver());
            celResolver.add(new ScopedAttributeELResolver());
            elResolver = celResolver;
        }
        return elResolver;
    }
                                                                                
    public ELContext getELContext() {
        if (elContext == null) {
            elContext = getJspApplicationContext().createELContext(
                            getELResolver());
            elContext.putContext(javax.servlet.jsp.JspContext.class, this);
            ((ELContextImpl)elContext).setVariableMapper(
                new VariableMapperImpl());
        }
        return elContext;
    }

    JspApplicationContextImpl getJspApplicationContext() {
        if (jspApplicationContext == null) {
            jspApplicationContext =
                JspApplicationContextImpl.findJspApplicationContext(context);
        }
        return jspApplicationContext;
    }
                         
    /*
     * No need to execute forward inside a privileged block, since it calls
     * ApplicationDispatcher forward, which in turn is executed inside a
     * privileged block
     */
    public void forward(String relativeUrlPath)
        throws ServletException, IOException{

        // JSP.4.5 If the buffer was flushed, throw IllegalStateException
        try {
            out.clear();
        } catch (IOException ex) {
            IllegalStateException ise =
                new IllegalStateException(Localizer.getMessage(
                            "jsp.error.attempt_to_clear_flushed_buffer"));
            ise.initCause(ex);
            throw ise;
        }

        // Make sure that the response object is not the wrapper for include
        while (response instanceof ServletResponseWrapperInclude) {
            response = ((ServletResponseWrapperInclude)response).getResponse();
        }

        final String path = getAbsolutePathRelativeToContext(relativeUrlPath);
        String includeUri
            = (String) request.getAttribute(Constants.INC_SERVLET_PATH);
            
        final ServletResponse fresponse = response;
        final ServletRequest frequest = request;
            
        if (includeUri != null)
            request.removeAttribute(Constants.INC_SERVLET_PATH);
        try {
            context.getRequestDispatcher(path).forward(request, response);
        } finally {
            if (includeUri != null)
                request.setAttribute(Constants.INC_SERVLET_PATH, includeUri);
            request.setAttribute(Constants.FORWARD_SEEN, "true");
        }
    }

    public BodyContent pushBody() {
	return (BodyContent) pushBody(null);
    }

    public JspWriter pushBody(Writer writer) {
        depth++;
        if (depth >= outs.length) {
            BodyContentImpl[] newOuts = new BodyContentImpl[depth + 1];
            for (int i=0; i<outs.length; i++) {
                newOuts[i] = outs[i];
            }
            newOuts[depth] = new BodyContentImpl(out);
            outs = newOuts;
        }

	outs[depth].setWriter(writer);
        out = outs[depth];

	// Update the value of the "out" attribute in the page scope
	// attribute namespace of this PageContext
	setAttribute(OUT, out);

        return outs[depth];
    }

    public JspWriter popBody() {
        depth--;
        if (depth >= 0) {
            out = outs[depth];
        } else {
            out = baseOut;
        }

	// Update the value of the "out" attribute in the page scope
	// attribute namespace of this PageContext
	setAttribute(OUT, out);

        return out;
    }

    /**
     * Provides programmatic access to the ExpressionEvaluator.
     * The JSP Container must return a valid instance of an
     * ExpressionEvaluator that can parse EL expressions.
     */
    public ExpressionEvaluator getExpressionEvaluator() {
        return new ExpressionEvaluatorImpl(this);
    }

    public void handlePageException(Exception ex)
        throws IOException, ServletException
    {
        // Should never be called since handleException() called with a
        // Throwable in the generated servlet.
        handlePageException((Throwable) ex);
    }

    public void handlePageException(final Throwable t)
        throws IOException, ServletException
    {
        if (t == null)
            throw new NullPointerException("null Throwable");

        if (SecurityUtil.isPackageProtectionEnabled()){
            try{
                AccessController.doPrivileged(new PrivilegedExceptionAction(){
                    public Object run() throws Exception{
                        doHandlePageException(t);
                        return null;
                    }
                });
            } catch (PrivilegedActionException e){
                Exception ex =  e.getException();
                if (ex instanceof IOException){
                    throw (IOException)ex;
                } else {
                    throw (ServletException)ex;
                }
            }
        } else {
            doHandlePageException(t);
        }

    }

    private void doHandlePageException(Throwable t)
        throws IOException, ServletException {

        if (errorPageURL != null && !errorPageURL.equals("")) {

            /*
             * Set request attributes.
             * Do not set the javax.servlet.error.exception attribute here
             * (instead, set in the generated servlet code for the error page)
             * in order to prevent the ErrorReportValve, which is invoked as
             * part of forwarding the request to the error page, from
             * throwing it if the response has not been committed (the response
             * will have been committed if the error page is a JSP page).
             */
            request.setAttribute("javax.servlet.jsp.jspException", t);
            request.setAttribute("javax.servlet.error.status_code",
                Integer.valueOf(HttpServletResponse.SC_INTERNAL_SERVER_ERROR));
            request.setAttribute("javax.servlet.error.request_uri",
            ((HttpServletRequest) request).getRequestURI());
            request.setAttribute("javax.servlet.error.servlet_name",
                     config.getServletName());
            try {
                forward(errorPageURL);
            } catch (IllegalStateException ise) {
                include(errorPageURL);
            }

            // The error page could be inside an include.

            Object newException = request.getAttribute("javax.servlet.error.exception");

            // t==null means the attribute was not set.
            if( (newException!= null) && (newException==t) ) {
                request.removeAttribute("javax.servlet.error.exception");
                request.setAttribute(Constants.JSP_ERROR_HANDLED, Boolean.TRUE);
            }

            // now clear the error code - to prevent double handling.
            request.removeAttribute("javax.servlet.error.status_code");
            request.removeAttribute("javax.servlet.error.request_uri");
            request.removeAttribute("javax.servlet.error.status_code");
            request.removeAttribute("javax.servlet.jsp.jspException");

        } else {

            // Otherwise throw the exception wrapped inside a ServletException.
            // Set the exception as the root cause in the ServletException
            // to get a stack trace for the real problem
            if (t instanceof IOException) throw (IOException)t;
            if (t instanceof ServletException) throw (ServletException)t;
            if (t instanceof RuntimeException) throw (RuntimeException)t;

            Throwable rootCause = null;
            if (t instanceof JspException) {
                rootCause = ((JspException) t).getRootCause();
            } else if (t instanceof ELException) {
                rootCause = t.getCause();
            }

            if (rootCause != null) {
                throw new ServletException(t.getMessage(), rootCause);
            }
                 
            throw new ServletException(t);
        }
    }

    private static ExpressionFactory getExpressionFactory(
            PageContext pageContext) {

        PageContextImpl pc =
            (PageContextImpl) JspContextWrapper.getRootPageContext(pageContext);
        return pc.getJspApplicationContext().getExpressionFactory();
    }

    /**
     * Evaluates an EL expression
     *
     * @param expression The expression to be evaluated
     * @param expectedType The expected resulting type
     * @param pageContext The page context
     * @param functionMap Maps prefix and name to Method
     * @return The result of the evaluation
     */
    public static Object evaluateExpression(final String expression, 
					    final Class expectedType,
					    final PageContext pageContext,
					    final ProtectedFunctionMapper functionMap)
	throws ELException
    {
	Object retValue;
        if (SecurityUtil.isPackageProtectionEnabled()){
            try {
                retValue = AccessController.doPrivileged(
			new PrivilegedExceptionAction(){

                    public Object run() throws Exception{
                        ELContextImpl elContext =
                            (ELContextImpl) pageContext.getELContext();
                        elContext.setFunctionMapper(functionMap);
                        ExpressionFactory expFactory = getExpressionFactory(pageContext);
                        ValueExpression expr =
                             expFactory.createValueExpression(
                                                   elContext,
                                                   expression,
                                                   expectedType);
                        return expr.getValue(elContext);
                    }
                });
            } catch (PrivilegedActionException ex) {
                Exception realEx = ex.getException();
		if (realEx instanceof ELException) {
		    throw (ELException) realEx;
		} else {
		    throw new ELException(realEx);
		}
            }
        } else {
            ELContextImpl elContext = (ELContextImpl)pageContext.getELContext();
            elContext.setFunctionMapper(functionMap);
            ExpressionFactory expFactory = getExpressionFactory(pageContext);
            ValueExpression expr = expFactory.createValueExpression(
                                           elContext,
                                           expression,
                                           expectedType);
            retValue = expr.getValue(elContext);
        }
	return retValue;
    }

    public static ValueExpression getValueExpression(String expression,
                                                     PageContext pageContext,
                                                     Class expectedType,
                                                     FunctionMapper functionMap)
    {
        // ELResolvers are not used in createValueExpression
        ELContextImpl elctxt = (ELContextImpl)pageContext.getELContext();
        elctxt.setFunctionMapper(functionMap);
        ExpressionFactory expFactory = getExpressionFactory(pageContext);
        return expFactory.createValueExpression(elctxt,
                                                expression,
                                                expectedType);
    }
                                                                                
    public static MethodExpression getMethodExpression(
                                               String expression,
                                               PageContext pageContext,
                                               FunctionMapper functionMap,
                                               Class expectedType,
                                               Class[] paramTypes) {
                                                                                
        ELContextImpl elctxt = (ELContextImpl)pageContext.getELContext();
        elctxt.setFunctionMapper(functionMap);
        ExpressionFactory expFactory = getExpressionFactory(pageContext);
        return expFactory.createMethodExpression(
                                    elctxt,
                                    expression,
                                    expectedType,
                                    paramTypes);
    }

    public static void setValueVariable(PageContext pageContext,
                                        String variable,
                                        ValueExpression expression) {
        ELContextImpl elctxt = (ELContextImpl)pageContext.getELContext();
        elctxt.getVariableMapper().setVariable(variable, expression);
    }

    public static void setMethodVariable(PageContext pageContext,
                                         String variable,
                                         MethodExpression expression) {
        ExpressionFactory expFactory = getExpressionFactory(pageContext);
        ValueExpression exp =
            expFactory.createValueExpression(expression, Object.class);
        setValueVariable(pageContext, variable, exp);
    }
}
