/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.compiler;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.net.JarURLConnection;
import java.net.URL;
import java.util.Collection;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.Map;
import java.util.Vector;
import java.util.jar.JarFile;
import java.util.zip.ZipEntry;

import javax.servlet.ServletContext;
import javax.servlet.jsp.tagext.FunctionInfo;
import javax.servlet.jsp.tagext.PageData;
import javax.servlet.jsp.tagext.TagAttributeInfo;
import javax.servlet.jsp.tagext.TagExtraInfo;
import javax.servlet.jsp.tagext.TagFileInfo;
import javax.servlet.jsp.tagext.TagInfo;
import javax.servlet.jsp.tagext.TagLibraryInfo;
import javax.servlet.jsp.tagext.TagLibraryValidator;
import javax.servlet.jsp.tagext.TagVariableInfo;
import javax.servlet.jsp.tagext.ValidationMessage;
import javax.servlet.jsp.tagext.VariableInfo;

import org.apache.jasper.Constants;
import org.apache.jasper.JasperException;
import org.apache.jasper.JspCompilationContext;
import org.apache.jasper.xmlparser.ParserUtils;
import org.apache.jasper.xmlparser.TreeNode;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;

/**
 * Implementation of the TagLibraryInfo class from the JSP spec.
 *
 * @author Anil K. Vijendran
 * @author Mandar Raje
 * @author Pierre Delisle
 * @author Kin-man Chung
 * @author Jan Luehe
 */
class TagLibraryInfoImpl extends TagLibraryInfo implements TagConstants {

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

    private JspCompilationContext ctxt;

    private PageInfo pi;

    private ErrorDispatcher err;

    private ParserController parserController;

    private final void print(String name, String value, PrintWriter w) {
        if (value != null) {
            w.print(name + " = {\n\t");
            w.print(value);
            w.print("\n}\n");
        }
    }

    public String toString() {
        StringWriter sw = new StringWriter();
        PrintWriter out = new PrintWriter(sw);
        print("tlibversion", tlibversion, out);
        print("jspversion", jspversion, out);
        print("shortname", shortname, out);
        print("urn", urn, out);
        print("info", info, out);
        print("uri", uri, out);
        print("tagLibraryValidator", "" + tagLibraryValidator, out);

        for (int i = 0; i < tags.length; i++)
            out.println(tags[i].toString());

        for (int i = 0; i < tagFiles.length; i++)
            out.println(tagFiles[i].toString());

        for (int i = 0; i < functions.length; i++)
            out.println(functions[i].toString());

        return sw.toString();
    }

    // XXX FIXME
    // resolveRelativeUri and/or getResourceAsStream don't seem to properly
    // handle relative paths when dealing when home and getDocBase are set
    // the following is a workaround until these problems are resolved.
    private InputStream getResourceAsStream(String uri)
            throws FileNotFoundException {
        try {
            // see if file exists on the filesystem first
            String real = ctxt.getRealPath(uri);
            if (real == null) {
                return ctxt.getResourceAsStream(uri);
            } else {
                return new FileInputStream(real);
            }
        } catch (FileNotFoundException ex) {
            // if file not found on filesystem, get the resource through
            // the context
            return ctxt.getResourceAsStream(uri);
        }

    }

    /**
     * Constructor.
     */
    public TagLibraryInfoImpl(JspCompilationContext ctxt, ParserController pc,
            PageInfo pi, String prefix, String uriIn, String[] location,
            ErrorDispatcher err, Mark mark)
            throws JasperException {
        super(prefix, uriIn);

        this.ctxt = ctxt;
        this.parserController = pc;
        this.pi = pi;
        this.err = err;
        InputStream in = null;
        JarFile jarFile = null;

        if (location == null) {
            // The URI points to the TLD itself or to a JAR file in which the
            // TLD is stored
            location = generateTLDLocation(uri, ctxt);
        }

        try {
            if (!location[0].endsWith("jar")) {
                // Location points to TLD file
                try {
                    in = getResourceAsStream(location[0]);
                    if (in == null) {
                        throw new FileNotFoundException(location[0]);
                    }
                } catch (FileNotFoundException ex) {
                    err.jspError(mark, "jsp.error.file.not.found", location[0]);
                }

                parseTLD(ctxt, location[0], in, null);
                // Add TLD to dependency list
                PageInfo pageInfo = ctxt.createCompiler().getPageInfo();
                if (pageInfo != null) {
                    pageInfo.addDependant(location[0]);
                }
            } else {
                // Tag library is packaged in JAR file
                try {
                    URL jarFileUrl = new URL("jar:" + location[0] + "!/");
                    JarURLConnection conn = (JarURLConnection) jarFileUrl
                            .openConnection();
                    conn.setUseCaches(false);
                    conn.connect();
                    jarFile = conn.getJarFile();
                    ZipEntry jarEntry = jarFile.getEntry(location[1]);
                    in = jarFile.getInputStream(jarEntry);
                    parseTLD(ctxt, location[0], in, jarFileUrl);
                } catch (Exception ex) {
                    err.jspError(mark, "jsp.error.tld.unable_to_read", location[0],
                            location[1], ex.toString());
                }
            }
        } finally {
            if (in != null) {
                try {
                    in.close();
                } catch (Throwable t) {
                }
            }
            if (jarFile != null) {
                try {
                    jarFile.close();
                } catch (Throwable t) {
                }
            }
        }

    }

    public TagLibraryInfo[] getTagLibraryInfos() {
        Collection coll = pi.getTaglibs();
        return (TagLibraryInfo[]) coll.toArray(new TagLibraryInfo[0]);
    }

    /*
     * @param ctxt The JSP compilation context @param uri The TLD's uri @param
     * in The TLD's input stream @param jarFileUrl The JAR file containing the
     * TLD, or null if the tag library is not packaged in a JAR
     */
    private void parseTLD(JspCompilationContext ctxt, String uri,
            InputStream in, URL jarFileUrl) throws JasperException {
        Vector tagVector = new Vector();
        Vector tagFileVector = new Vector();
        Hashtable functionTable = new Hashtable();

        ServletContext servletContext = ctxt.getServletContext();
        boolean validate = Boolean.parseBoolean(servletContext.getInitParameter(
                        Constants.XML_VALIDATION_TLD_INIT_PARAM));
        String blockExternalString = servletContext.getInitParameter(
                Constants.XML_BLOCK_EXTERNAL_INIT_PARAM);
        boolean blockExternal;
        if (blockExternalString == null) {
            blockExternal = true;
        } else {
            blockExternal = Boolean.parseBoolean(blockExternalString);
        }

        // Create an iterator over the child elements of our <taglib> element
        ParserUtils pu = new ParserUtils(validate, blockExternal);
        TreeNode tld = pu.parseXMLDocument(uri, in);

        // Check to see if the <taglib> root element contains a 'version'
        // attribute, which was added in JSP 2.0 to replace the <jsp-version>
        // subelement
        this.jspversion = tld.findAttribute("version");

        // Process each child element of our <taglib> element
        Iterator list = tld.findChildren();

        while (list.hasNext()) {
            TreeNode element = (TreeNode) list.next();
            String tname = element.getName();

            if ("tlibversion".equals(tname) // JSP 1.1
                    || "tlib-version".equals(tname)) { // JSP 1.2
                this.tlibversion = element.getBody();
            } else if ("jspversion".equals(tname)
                    || "jsp-version".equals(tname)) {
                this.jspversion = element.getBody();
            } else if ("shortname".equals(tname) || "short-name".equals(tname))
                this.shortname = element.getBody();
            else if ("uri".equals(tname))
                this.urn = element.getBody();
            else if ("info".equals(tname) || "description".equals(tname))
                this.info = element.getBody();
            else if ("validator".equals(tname))
                this.tagLibraryValidator = createValidator(element);
            else if ("tag".equals(tname))
                tagVector.addElement(createTagInfo(element, jspversion));
            else if ("tag-file".equals(tname)) {
                TagFileInfo tagFileInfo = createTagFileInfo(element, uri,
                        jarFileUrl);
                tagFileVector.addElement(tagFileInfo);
            } else if ("function".equals(tname)) { // JSP2.0
                FunctionInfo funcInfo = createFunctionInfo(element);
                String funcName = funcInfo.getName();
                if (functionTable.containsKey(funcName)) {
                    err.jspError("jsp.error.tld.fn.duplicate.name", funcName,
                            uri);

                }
                functionTable.put(funcName, funcInfo);
            } else if ("display-name".equals(tname) || // Ignored elements
                    "small-icon".equals(tname) || "large-icon".equals(tname)
                    || "listener".equals(tname)) {
                ;
            } else if ("taglib-extension".equals(tname)) {
                // Recognized but ignored
            } else {
                if (log.isWarnEnabled()) {
                    log.warn(Localizer.getMessage(
                            "jsp.warning.unknown.element.in.taglib", tname));
                }
            }

        }

        if (tlibversion == null) {
            err.jspError("jsp.error.tld.mandatory.element.missing",
                    "tlib-version", uri);
        }
        if (jspversion == null) {
            err.jspError("jsp.error.tld.mandatory.element.missing",
                    "jsp-version", uri);
        }

        this.tags = new TagInfo[tagVector.size()];
        tagVector.copyInto(this.tags);

        this.tagFiles = new TagFileInfo[tagFileVector.size()];
        tagFileVector.copyInto(this.tagFiles);

        this.functions = new FunctionInfo[functionTable.size()];
        int i = 0;
        Enumeration enumeration = functionTable.elements();
        while (enumeration.hasMoreElements()) {
            this.functions[i++] = (FunctionInfo) enumeration.nextElement();
        }
    }

    /*
     * @param uri The uri of the TLD @param ctxt The compilation context
     *
     * @return String array whose first element denotes the path to the TLD. If
     * the path to the TLD points to a jar file, then the second element denotes
     * the name of the TLD entry in the jar file, which is hardcoded to
     * META-INF/taglib.tld.
     */
    private String[] generateTLDLocation(String uri, JspCompilationContext ctxt)
            throws JasperException {

        int uriType = TldLocationsCache.uriType(uri);
        if (uriType == TldLocationsCache.ABS_URI) {
            err.jspError("jsp.error.taglibDirective.absUriCannotBeResolved",
                    uri);
        } else if (uriType == TldLocationsCache.NOROOT_REL_URI) {
            uri = ctxt.resolveRelativeUri(uri);
        }

        String[] location = new String[2];
        location[0] = uri;
        if (location[0].endsWith("jar")) {
            URL url = null;
            try {
                url = ctxt.getResource(location[0]);
            } catch (Exception ex) {
                err.jspError("jsp.error.tld.unable_to_get_jar", location[0], ex
                        .toString());
            }
            if (url == null) {
                err.jspError("jsp.error.tld.missing_jar", location[0]);
            }
            location[0] = url.toString();
            location[1] = "META-INF/taglib.tld";
        }

        return location;
    }

    private TagInfo createTagInfo(TreeNode elem, String jspVersion)
            throws JasperException {

        String tagName = null;
        String tagClassName = null;
        String teiClassName = null;

        /*
         * Default body content for JSP 1.2 tag handlers (<body-content> has
         * become mandatory in JSP 2.0, because the default would be invalid for
         * simple tag handlers)
         */
        String bodycontent = "JSP";

        String info = null;
        String displayName = null;
        String smallIcon = null;
        String largeIcon = null;
        boolean dynamicAttributes = false;

        Vector attributeVector = new Vector();
        Vector variableVector = new Vector();
        Iterator list = elem.findChildren();
        while (list.hasNext()) {
            TreeNode element = (TreeNode) list.next();
            String tname = element.getName();

            if ("name".equals(tname)) {
                tagName = element.getBody();
            } else if ("tagclass".equals(tname) || "tag-class".equals(tname)) {
                tagClassName = element.getBody();
            } else if ("teiclass".equals(tname) || "tei-class".equals(tname)) {
                teiClassName = element.getBody();
            } else if ("bodycontent".equals(tname)
                    || "body-content".equals(tname)) {
                bodycontent = element.getBody();
            } else if ("display-name".equals(tname)) {
                displayName = element.getBody();
            } else if ("small-icon".equals(tname)) {
                smallIcon = element.getBody();
            } else if ("large-icon".equals(tname)) {
                largeIcon = element.getBody();
            } else if ("icon".equals(tname)) {
                TreeNode icon = element.findChild("small-icon");
                if (icon != null) {
                    smallIcon = icon.getBody();
                }
                icon = element.findChild("large-icon");
                if (icon != null) {
                    largeIcon = icon.getBody();
                }
            } else if ("info".equals(tname) || "description".equals(tname)) {
                info = element.getBody();
            } else if ("variable".equals(tname)) {
                variableVector.addElement(createVariable(element));
            } else if ("attribute".equals(tname)) {
                attributeVector
                        .addElement(createAttribute(element, jspVersion));
            } else if ("dynamic-attributes".equals(tname)) {
                dynamicAttributes = JspUtil.booleanValue(element.getBody());
            } else if ("example".equals(tname)) {
                // Ignored elements
            } else if ("tag-extension".equals(tname)) {
                // Ignored
            } else {
                if (log.isWarnEnabled()) {
                    log.warn(Localizer.getMessage(
                            "jsp.warning.unknown.element.in.tag", tname));
                }
            }
        }

        TagExtraInfo tei = null;
        if (teiClassName != null && !teiClassName.equals("")) {
            try {
                Class teiClass = ctxt.getClassLoader().loadClass(teiClassName);
                tei = (TagExtraInfo) teiClass.newInstance();
            } catch (Exception e) {
                err.jspError("jsp.error.teiclass.instantiation", teiClassName,
                        e);
            }
        }

        TagAttributeInfo[] tagAttributeInfo = new TagAttributeInfo[attributeVector
                .size()];
        attributeVector.copyInto(tagAttributeInfo);

        TagVariableInfo[] tagVariableInfos = new TagVariableInfo[variableVector
                .size()];
        variableVector.copyInto(tagVariableInfos);

        TagInfo taginfo = new TagInfo(tagName, tagClassName, bodycontent, info,
                this, tei, tagAttributeInfo, displayName, smallIcon, largeIcon,
                tagVariableInfos, dynamicAttributes);
        return taginfo;
    }

    /*
     * Parses the tag file directives of the given TagFile and turns them into a
     * TagInfo.
     *
     * @param elem The <tag-file> element in the TLD @param uri The location of
     * the TLD, in case the tag file is specified relative to it @param jarFile
     * The JAR file, in case the tag file is packaged in a JAR
     *
     * @return TagInfo correspoding to tag file directives
     */
    private TagFileInfo createTagFileInfo(TreeNode elem, String uri,
            URL jarFileUrl) throws JasperException {

        String name = null;
        String path = null;

        Iterator list = elem.findChildren();
        while (list.hasNext()) {
            TreeNode child = (TreeNode) list.next();
            String tname = child.getName();
            if ("name".equals(tname)) {
                name = child.getBody();
            } else if ("path".equals(tname)) {
                path = child.getBody();
            } else if ("example".equals(tname)) {
                // Ignore <example> element: Bugzilla 33538
            } else if ("tag-extension".equals(tname)) {
                // Ignore <tag-extension> element: Bugzilla 33538
            } else if ("icon".equals(tname)
                    || "display-name".equals(tname)
                    || "description".equals(tname)) {
                // Ignore these elements: Bugzilla 38015
            } else {
                if (log.isWarnEnabled()) {
                    log.warn(Localizer.getMessage(
                            "jsp.warning.unknown.element.in.tagfile", tname));
                }
            }
        }

        if (path.startsWith("/META-INF/tags")) {
            // Tag file packaged in JAR
            // See https://bz.apache.org/bugzilla/show_bug.cgi?id=46471
            // This needs to be removed once all the broken code that depends on
            // it has been removed
            ctxt.setTagFileJarUrl(path, jarFileUrl);
        } else if (!path.startsWith("/WEB-INF/tags")) {
            err.jspError("jsp.error.tagfile.illegalPath", path);
        }

        TagInfo tagInfo = TagFileProcessor.parseTagFileDirectives(
                parserController, name, path, jarFileUrl, this);
        return new TagFileInfo(name, path, tagInfo);
    }

    TagAttributeInfo createAttribute(TreeNode elem, String jspVersion) {
        String name = null;
        String type = null;
        String expectedType = null;
        String methodSignature = null;
        boolean required = false, rtexprvalue = false, reqTime = false, isFragment = false, deferredValue = false, deferredMethod = false;

        Iterator list = elem.findChildren();
        while (list.hasNext()) {
            TreeNode element = (TreeNode) list.next();
            String tname = element.getName();

            if ("name".equals(tname)) {
                name = element.getBody();
            } else if ("required".equals(tname)) {
                String s = element.getBody();
                if (s != null)
                    required = JspUtil.booleanValue(s);
            } else if ("rtexprvalue".equals(tname)) {
                String s = element.getBody();
                if (s != null)
                    rtexprvalue = JspUtil.booleanValue(s);
            } else if ("type".equals(tname)) {
                type = element.getBody();
                if ("1.2".equals(jspVersion)
                        && (type.equals("Boolean") || type.equals("Byte")
                                || type.equals("Character")
                                || type.equals("Double")
                                || type.equals("Float")
                                || type.equals("Integer")
                                || type.equals("Long") || type.equals("Object")
                                || type.equals("Short") || type
                                .equals("String"))) {
                    type = "java.lang." + type;
                }
            } else if ("fragment".equals(tname)) {
                String s = element.getBody();
                if (s != null) {
                    isFragment = JspUtil.booleanValue(s);
                }
            } else if ("deferred-value".equals(tname)) {
                deferredValue = true;
                type = "javax.el.ValueExpression";
                TreeNode child = element.findChild("type");
                if (child != null) {
                    expectedType = child.getBody();
                    if (expectedType != null) {
                        expectedType = expectedType.trim();
                    }
                } else {
                    expectedType = "java.lang.Object";
                }
            } else if ("deferred-method".equals(tname)) {
                deferredMethod = true;
                type = "javax.el.MethodExpression";
                TreeNode child = element.findChild("method-signature");
                if (child != null) {
                    methodSignature = child.getBody();
                    if (methodSignature != null) {
                        methodSignature = methodSignature.trim();
                    }
                } else {
                    methodSignature = "java.lang.Object method()";
                }
            } else if ("description".equals(tname) || // Ignored elements
            false) {
                ;
            } else {
                if (log.isWarnEnabled()) {
                    log.warn(Localizer.getMessage(
                            "jsp.warning.unknown.element.in.attribute", tname));
                }
            }
        }

        if (isFragment) {
            /*
             * According to JSP.C-3 ("TLD Schema Element Structure - tag"),
             * 'type' and 'rtexprvalue' must not be specified if 'fragment' has
             * been specified (this will be enforced by validating parser).
             * Also, if 'fragment' is TRUE, 'type' is fixed at
             * javax.servlet.jsp.tagext.JspFragment, and 'rtexprvalue' is fixed
             * at true. See also JSP.8.5.2.
             */
            type = "javax.servlet.jsp.tagext.JspFragment";
            rtexprvalue = true;
        }

        if (!rtexprvalue && type == null) {
            // According to JSP spec, for static values (those determined at
            // translation time) the type is fixed at java.lang.String.
            type = "java.lang.String";
        }

        return new TagAttributeInfo(name, required, type, rtexprvalue,
                isFragment, null, deferredValue, deferredMethod, expectedType,
                methodSignature);
    }

    TagVariableInfo createVariable(TreeNode elem) {
        String nameGiven = null;
        String nameFromAttribute = null;
        String className = "java.lang.String";
        boolean declare = true;
        int scope = VariableInfo.NESTED;

        Iterator list = elem.findChildren();
        while (list.hasNext()) {
            TreeNode element = (TreeNode) list.next();
            String tname = element.getName();
            if ("name-given".equals(tname))
                nameGiven = element.getBody();
            else if ("name-from-attribute".equals(tname))
                nameFromAttribute = element.getBody();
            else if ("variable-class".equals(tname))
                className = element.getBody();
            else if ("declare".equals(tname)) {
                String s = element.getBody();
                if (s != null)
                    declare = JspUtil.booleanValue(s);
            } else if ("scope".equals(tname)) {
                String s = element.getBody();
                if (s != null) {
                    if ("NESTED".equals(s)) {
                        scope = VariableInfo.NESTED;
                    } else if ("AT_BEGIN".equals(s)) {
                        scope = VariableInfo.AT_BEGIN;
                    } else if ("AT_END".equals(s)) {
                        scope = VariableInfo.AT_END;
                    }
                }
            } else if ("description".equals(tname) || // Ignored elements
            false) {
            } else {
                if (log.isWarnEnabled()) {
                    log.warn(Localizer.getMessage(
                            "jsp.warning.unknown.element.in.variable", tname));
                }
            }
        }
        return new TagVariableInfo(nameGiven, nameFromAttribute, className,
                declare, scope);
    }

    private TagLibraryValidator createValidator(TreeNode elem)
            throws JasperException {

        String validatorClass = null;
        Map initParams = new Hashtable();

        Iterator list = elem.findChildren();
        while (list.hasNext()) {
            TreeNode element = (TreeNode) list.next();
            String tname = element.getName();
            if ("validator-class".equals(tname))
                validatorClass = element.getBody();
            else if ("init-param".equals(tname)) {
                String[] initParam = createInitParam(element);
                initParams.put(initParam[0], initParam[1]);
            } else if ("description".equals(tname) || // Ignored elements
            false) {
            } else {
                if (log.isWarnEnabled()) {
                    log.warn(Localizer.getMessage(
                            "jsp.warning.unknown.element.in.validator", tname));
                }
            }
        }

        TagLibraryValidator tlv = null;
        if (validatorClass != null && !validatorClass.equals("")) {
            try {
                Class tlvClass = ctxt.getClassLoader()
                        .loadClass(validatorClass);
                tlv = (TagLibraryValidator) tlvClass.newInstance();
            } catch (Exception e) {
                err.jspError("jsp.error.tlvclass.instantiation",
                        validatorClass, e);
            }
        }
        if (tlv != null) {
            tlv.setInitParameters(initParams);
        }
        return tlv;
    }

    String[] createInitParam(TreeNode elem) {
        String[] initParam = new String[2];

        Iterator list = elem.findChildren();
        while (list.hasNext()) {
            TreeNode element = (TreeNode) list.next();
            String tname = element.getName();
            if ("param-name".equals(tname)) {
                initParam[0] = element.getBody();
            } else if ("param-value".equals(tname)) {
                initParam[1] = element.getBody();
            } else if ("description".equals(tname)) {
                 // Do nothing
            } else {
                if (log.isWarnEnabled()) {
                    log.warn(Localizer.getMessage(
                            "jsp.warning.unknown.element.in.initParam", tname));
                }
            }
        }
        return initParam;
    }

    FunctionInfo createFunctionInfo(TreeNode elem) {

        String name = null;
        String klass = null;
        String signature = null;

        Iterator list = elem.findChildren();
        while (list.hasNext()) {
            TreeNode element = (TreeNode) list.next();
            String tname = element.getName();

            if ("name".equals(tname)) {
                name = element.getBody();
            } else if ("function-class".equals(tname)) {
                klass = element.getBody();
            } else if ("function-signature".equals(tname)) {
                signature = element.getBody();
            } else if ("display-name".equals(tname) || // Ignored elements
                    "small-icon".equals(tname) || "large-icon".equals(tname)
                    || "description".equals(tname) || "example".equals(tname)) {
            } else {
                if (log.isWarnEnabled()) {
                    log.warn(Localizer.getMessage(
                            "jsp.warning.unknown.element.in.function", tname));
                }
            }
        }

        return new FunctionInfo(name, klass, signature);
    }

    // *********************************************************************
    // Until javax.servlet.jsp.tagext.TagLibraryInfo is fixed

    /**
     * The instance (if any) for the TagLibraryValidator class.
     *
     * @return The TagLibraryValidator instance, if any.
     */
    public TagLibraryValidator getTagLibraryValidator() {
        return tagLibraryValidator;
    }

    /**
     * Translation-time validation of the XML document associated with the JSP
     * page. This is a convenience method on the associated TagLibraryValidator
     * class.
     *
     * @param thePage
     *            The JSP page object
     * @return A string indicating whether the page is valid or not.
     */
    public ValidationMessage[] validate(PageData thePage) {
        TagLibraryValidator tlv = getTagLibraryValidator();
        if (tlv == null)
            return null;

        String uri = getURI();
        if (uri.startsWith("/")) {
            uri = URN_JSPTLD + uri;
        }

        return tlv.validate(getPrefixString(), uri, thePage);
    }

    protected TagLibraryValidator tagLibraryValidator;
}
