xmlresources.java

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package org.apache.james.util;

import org.apache.oro.text.perl.MalformedPerl5PatternException;
import org.apache.oro.text.perl.Perl5Util;
import org.w3c.dom.Attr;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.NodeList;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import java.io.File;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

/*
 * This is derived from the SQLResources.java class that we have been
 * using to provide SQL strings based upon the particular drive being
 * used.
 *
 * The format is indentical to the format used by SQLResources.  The
 * only difference are the names of the elements and attributes.  A
 * mapping is as follows:
 *
 *      sqlResources            xmlResources
 *      ------------            ------------
 *      sqlResources            resources
 *      dbMatchers              matchers
 *      dbMatcher               matcher
 *      db                      for
 *      databaseProductName     match
 *      sqlDefs                 group
 *      sql                     resource
 *
 * This class provides String resources defined in XML.  Resources are
 * organized into groups, and identified by name.  For each resource
 * there can be a standard value, and custom values matched by regular
 * expression.
 *
 * The structure of the XML file is:
 *
 *  <resources>
 *    <matchers>
 *      &lt;matcher for="<i>label</i>" match="<i>regular expression</i>"/&gt;
 *      ...
 *    &lt;/matchers&gt;
 *    &lt;group name="<i>group name</i>"&gt;
 *      &lt;resource name="<i>resouce name</i>" [for="<i>match label</i>"]&gt;<i>text, including ${placeholders}, which will be replaced at runtime.</i>&lt;/resource&gt;
 *      ...
 *    &lt;/group&gt;
 *    <i>... more &lt;group&gt; elements ...</i>
 *  &lt;/resources&gt;
 * 
 */
public class XMLResources
{
    /**
     * A map of statement types to resource strings
     */
    private Map m_resource = new HashMap();

    /**
     * A set of all used String values
     */
    static private Map stringTable = java.util.Collections.synchronizedMap(new HashMap());

    /**
     * A Perl5 regexp matching helper class
     */
    private Perl5Util m_perl5Util = new Perl5Util();

    /**
     * Configures an XMLResources object to provide string statements from a file.
     * 
     * Parameters encoded as $(parameter} in the input file are
     * replace by values from the parameters Map, if the named parameter exists.
     * Parameter values may also be specified in the resourceSection element.
     * 
     * @param xmlFile    the input file containing the string definitions
     * @param group      xml element containing the strings to be used
     * @param select     if customized elements exist for this value, use them instead of the default
     * @param configParameters a map of parameters (name-value string pairs) which are
     *                   replaced where found in the input strings
     */
    public void init(File xmlFile, String group,
                     String select, Map configParameters)
        throws Exception
    {
        // Parse the xmlFile as an XML document.
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        DocumentBuilder builder = factory.newDocumentBuilder();
        Document doc = builder.parse(xmlFile);

        // First process the matchers, to select the statements to use.
        Element matcherElement = 
            (Element)(doc.getElementsByTagName("matchers").item(0));
        String selectTag = null;
        if ( matcherElement != null ) {
            selectTag = match(select, matcherElement);
            m_perl5Util = null;     // release the PERL matcher!
        }

        // Now get the section defining strings for the group required.
        NodeList sections = doc.getElementsByTagName("group");
        int sectionsCount = sections.getLength();
        Element sectionElement = null;
        for (int i = 0; i < sectionsCount; i++ ) {
            sectionElement = (Element)(sections.item(i));
            String sectionName = sectionElement.getAttribute("name");
            if ( sectionName != null && sectionName.equals(group) ) {
                break;
            }

        }
        if ( sectionElement == null ) {
            StringBuffer exceptionBuffer =
                new StringBuffer(64)
                        .append("Error loading string definition file. ")
                        .append("The element named \'")
                        .append(group)
                        .append("\' does not exist.");
            throw new RuntimeException(exceptionBuffer.toString());
        }

        // Get parameters defined within the file as defaults,
        // and use supplied parameters as overrides.
        Map parameters = new HashMap();
        // First read from the <params> element, if it exists.
        Element parametersElement = 
            (Element)(sectionElement.getElementsByTagName("parameters").item(0));
        if ( parametersElement != null ) {
            NamedNodeMap params = parametersElement.getAttributes();
            int paramCount = params.getLength();
            for (int i = 0; i < paramCount; i++ ) {
                Attr param = (Attr)params.item(i);
                String paramName = param.getName();
                String paramValue = param.getValue();
                parameters.put(paramName, paramValue);
            }
        }
        // Then copy in the parameters supplied with the call.
        parameters.putAll(configParameters);

        // 2 maps - one for storing default statements,
        // the other for statements with a "for" attribute matching this 
        // connection.
        Map defaultStrings = new HashMap();
        Map selectTagStrings = new HashMap();

        // Process each string resource, replacing string parameters,
        // and adding to the appropriate map..
        NodeList resDefs = sectionElement.getElementsByTagName("resource");
        int resCount = resDefs.getLength();
        for ( int i = 0; i < resCount; i++ ) {
            // See if this needs to be processed (is default or product specific)
            Element resElement = (Element)(resDefs.item(i));
            String resSelect = resElement.getAttribute("for");
            Map resMap;
            if ( resSelect.equals("")) {
                // default
                resMap = defaultStrings;
            }
            else if (resSelect.equals(selectTag) ) {
                // Specific to this product
                resMap = selectTagStrings;
            }
            else {
                // for a different product
                continue;
            }

            // Get the key and value for this string resource.