topictagplugin.java

这个weblogging 设计得比较精巧

/*
 * Copyright (c) 2004
 * Anil R. Gangolli. All rights reserved.
 *
 * Distributed with Roller Weblogger under the terms of the Roller license.
 */

package org.roller.presentation.velocity.plugins.topictag;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.velocity.context.Context;
import org.roller.RollerException;
import org.roller.config.RollerConfig;
import org.roller.model.BookmarkManager;
import org.roller.model.RollerFactory;
import org.roller.pojos.BookmarkData;
import org.roller.pojos.WeblogEntryData;
import org.roller.pojos.WebsiteData;
import org.roller.presentation.RollerRequest;
import org.roller.presentation.velocity.PagePlugin;

import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;
import java.text.FieldPosition;
import java.text.MessageFormat;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;

/**
 * Provides an easy way to write topic tag links for Technorati (or similar services).
 * <p/>
 * Looks for occurrences of topic tag specifiers of the form
 * <pre>
 * <code>topic:{topicbookmark}[tag]</code>  OR    <code>topic:[tag]</code>
 * </pre>
 * and replaces them with a topic tag link of the form:
 * <pre>
 * <code>&lt;a rel="tag" href="site/tag"&gt;tag&lt;/a&gt;</code>
 * </pre>
 * <p/>
 * More information on topic tag links can be found at <a href="http://www.technorati.com">Technorati</a>.
 * <p/>
 * <p/>
 * In the first form, the <code>topicbookmark</code> is used as the name of a bookmark, and the URL from that bookmark
 * entry is used as the <code>site</code> portion in the <code>href</code> of the link.
 * <p/>
 * All folders are searched to find a bookmark with the name specified by <code>topicbookmark</code>. A name must match
 * exactly, ignoring case.  The first matching bookmark is used, and folders may be searched in any order.  The
 * bookmark's URL value can end in a "/" or not; either will work.
 * <p/>
 * The second form is equivalent to using the string "Default Topic Site" as the value of <code>topicbookmark</code>.
 * <p/>
 * If the bookmark lookup fails, then "http://www.technorati.com/tag" is used as the site name in the topic tag link.
 * <p/>
 * You can specify some Roller site-wide properties in the roller.properties or roller-custom.properties to override
 * some of the defaults of this plugin. All of these are optional.
 * <p/>
 * <dl> <dt><code>org.roller.presentation.velocity.plugins.topictag.TopicTagPlugin.defaultTopicBookmarkName</code></dt>
 * <dd>Specify the name of the default topic bookmark instead of "Default Topic Site"</dd>
 * <p/>
 * <dt><code>org.roller.presentation.velocity.plugins.topictag.TopicTagPlugin.defaultTopicSite</code></dt> <dd>Specify
 * the default site name to be used instead of "http://www.technorati.com" for the case in which all of the lookups
 * fail.</dd>
 * <p/>
 * <dt><code>org.roller.presentation.velocity.plugins.topictag.TopicTagPlugin.tagPatternWithBookmark</code></dt> <dd>Can
 * be used to redefine the regular expression used to find a long-form topic tag specifiers in the input.  This pattern
 * corresponds to the "long form" and must have two matching groups.  Group 1 must correspond to the bookmark name.
 * Group 2 must correspond to the tag.</dd>
 * <p/>
 * <dt><code>org.roller.presentation.velocity.plugins.topictag.TopicTagPlugin.tagPatternDefaultBookmark</code></dt>
 * <dd>Can be used to redefine the regular expression used to find short-form topic tag specifiers in the input. This
 * pattern must have one matching group, which corresponds to the tag.</dd>
 * <p/>
 * <dt><code>org.roller.presentation.velocity.plugins.topictag.TopicTagPlugin.linkFormatString</code></dt> <dd>Can be
 * used to redefine the format of the generated link.  This string is a message format string with three positional
 * parameters.  Parameter <code>{0}</code> represents the site including a trailing "/",  parameter <code>{1}</code>
 * represents the url-encoded tag and parameter <code>{2}</code> represents the original unencoded tag text.</dd>
 * <p/>
 * </dl>
 *
 * @author <a href="mailto:[e-mail]">Anil Gangolli</a>
 * @version 0.3
 */
public class TopicTagPlugin implements PagePlugin
{
    private static final String version = "0.3";
    private static final Log mLogger = LogFactory.getFactory().getInstance(TopicTagPlugin.class);


    // Default values of properties that can be set from the web.xml configuration.
    private String defaultTopicBookmarkName = "Default Topic Site";
    private String defaultTopicSite = "http://www.technorati.com/tag";
    private String tagRegexWithBookmark = "topic:\\{(.*?)\\}\\[(.*?)\\]";
    private String tagRegexWithoutBookmark = "topic:\\[(.*?)\\]";
    private String linkFormatString = "<a rel=\"tag\" href=\"{0}{1}\">{2}</a>";

    // Compiled form of the regular expressions above.  Compiled during the init()
    private Pattern tagPatternWithBookmark;
    private Pattern tagPatternWithoutBookmark;
    private MessageFormat linkFormat;

    // A map of the user's bookmarks (values of type BookmarkData) keyed by name (String).   If the user has multiple
    // bookmarks with the same name in different folders, only one gets used (the last encountered).
    private Map userBookmarks;


    public TopicTagPlugin()
    {
    }

    /**
     * Initialize the plugin instance.   This sets up the configurable properties and default topic site.
     *
     * @param rreq Plugins may need to access RollerRequest.
     * @param ctx  Plugins may place objects into the Velocity Context.
     * @see PagePlugin#init(org.roller.presentation.RollerRequest, org.apache.velocity.context.Context)
     */
    public void init(RollerRequest rreq, Context ctx) throws RollerException
    {
        if (mLogger.isDebugEnabled())
        {
            mLogger.debug("TopicTagPlugin v. " + version);
        }


        // Initialize property settings
        initializeProperties();

        // Build map of the user's bookmarks
        userBookmarks = buildBookmarkMap(rreq.getWebsite());

        // Determine default topic site from bookmark if present
        BookmarkData defaultTopicBookmark = (BookmarkData) userBookmarks.get(defaultTopicBookmarkName);
        if (defaultTopicBookmark != null) defaultTopicSite = defaultTopicBookmark.getUrl();

        // Append / to defaultTopicSite if it doesn't have it
        if (!defaultTopicSite.endsWith("/"))
        {
            defaultTopicSite += "/";
        }

        // Compile patterns and make sure they have the correct number of matching groups in them.
        try
        {
            tagPatternWithBookmark = Pattern.compile(tagRegexWithBookmark);
        }
        catch (PatternSyntaxException e)
        {
            throw new RollerException("Invalid regular expression for topic tags with bookmark '" +
                tagRegexWithBookmark + "': " + e.getMessage());
        }
        int groupCount = tagPatternWithBookmark.matcher("").groupCount();
        if (groupCount != 2)
        {
            throw new RollerException("Regular expression for topic tags with bookmark '" + tagRegexWithBookmark +
                "' contains wrong number of capture groups.  Must have exactly 2.  Contains " + groupCount);
        }

        try
        {
            tagPatternWithoutBookmark = Pattern.compile(tagRegexWithoutBookmark);
        }
        catch (PatternSyntaxException e)
        {
            throw new RollerException("Invalid regular expression for topic tags without bookmark '" +
                tagRegexWithoutBookmark + "': " + e.getMessage());
        }
        groupCount = tagPatternWithoutBookmark.matcher("").groupCount();
        if (groupCount != 1)
        {
            throw new RollerException("Regular expression for topic tags without bookmark '" + tagRegexWithoutBookmark +
                "' contains wrong number of capture groups.  Must have exactly 1.  Contains " + groupCount);
        }

        // Create link format from format string
        setLinkFormat(new MessageFormat(linkFormatString));
    }

    /**
     * Apply the plugin to the given entry.  Returns the entry text with topic tags expanded.
     *
     * @param entry           WeblogEntry to which plugin should be applied.
     * @param skipFlagIgnored the "skip flag" is ignored for this plugin
     * @return Results of applying plugin to entry.
     */
    public String render(WeblogEntryData entry, boolean skipFlagIgnored)
    {
        String entryText = entry.getText();
        StringBuffer result = new StringBuffer(entryText.length());
        MessageFormat fmt = getLinkFormat();

        // Replace all of the instances matching the pattern with bookmark specified.
        Matcher m = tagPatternWithBookmark.matcher(entryText);
        while (m.find())
        {
            String bookmark = m.group(1);
            String tag = m.group(2);
            String site = getBookmarkSite(bookmark);
            if (site == null)
            {
                site = getDefaultTopicSite();
            }
            if (!site.endsWith("/"))
            {
                site += "/";
            }
            String link = generateLink(fmt, site, tag);
            m.appendReplacement(result, link);
        }
        m.appendTail(result);

        // Now, in a second phase replace all of the instances matching the pattern without bookmark specified.
        entryText = result.toString();
        result = new StringBuffer(entryText.length());
        m = tagPatternWithoutBookmark.matcher(entryText);
        while (m.find())
        {
            String tag = m.group(1);
            String site = getDefaultTopicSite();
            String link = generateLink(fmt, site, tag);
            m.appendReplacement(result, link);
        }
        m.appendTail(result);

        return result.toString();