plugincreaterule.java

JAVA 文章管理系统源码

     * the plugin class are then loaded into that new Rules object.
     * Finally, any custom rules that are associated with the current pattern
     * (such as SetPropertiesRules) have their begin methods executed.
     * 
     * @param namespace 
     * @param name 
     * @param attributes
     *
     * @throws ClassNotFoundException
     * @throws PluginInvalidInputException
     * @throws PluginConfigurationException
     */
    public void begin(String namespace, String name,
                      org.xml.sax.Attributes attributes)
                      throws java.lang.Exception {
        Log log = digester.getLogger();
        boolean debug = log.isDebugEnabled();
        if (debug) {
            log.debug("PluginCreateRule.begin" + ": pattern=[" + pattern + "]" + 
                  " match=[" + digester.getMatch() + "]");
        }

        if (initException != null) {
            // we had a problem during initialisation that we could
            // not report then; report it now.
            throw initException;
        }
        
        String path = digester.getMatch();

        // create a new Rules object and effectively push it onto a stack of
        // rules objects. The stack is actually a linked list; using the
        // PluginRules constructor below causes the new instance to link
        // to the previous head-of-stack, then the Digester.setRules() makes
        // the new instance the new head-of-stack.
        PluginRules oldRules = (PluginRules) digester.getRules();
        PluginRules newRules = new PluginRules(path, oldRules);
        digester.setRules(newRules);
        
        // load any custom rules associated with the plugin
        PluginManager pluginManager = newRules.getPluginManager();
        Declaration currDeclaration = null;
            
        if (debug) {
            log.debug("PluginCreateRule.begin: installing new plugin: " +
                "oldrules=" + oldRules.toString() +
                ", newrules=" + newRules.toString());
        }
              
        String pluginClassName; 
        if (pluginClassAttrNs == null) {
            // Yep, this is ugly.
            //
            // In a namespace-aware parser, the one-param version will 
            // return attributes with no namespace.
            //
            // In a non-namespace-aware parser, the two-param version will 
            // never return any attributes, ever.
            pluginClassName = attributes.getValue(pluginClassAttr);
        } else {
            pluginClassName = 
                attributes.getValue(pluginClassAttrNs, pluginClassAttr);
        }

        String pluginId; 
        if (pluginIdAttrNs == null) {
            pluginId = attributes.getValue(pluginIdAttr);
        } else {
            pluginId = 
                attributes.getValue(pluginIdAttrNs, pluginIdAttr);
        }
        
        if (pluginClassName != null) {
            // The user is using a plugin "inline", ie without a previous
            // explicit declaration. If they have used the same plugin class
            // before, we have already gone to the effort of creating a 
            // Declaration object, so retrieve it. If there is no existing
            // declaration object for this class, then create one.

            currDeclaration = pluginManager.getDeclarationByClass(
                pluginClassName);

            if (currDeclaration == null) {
                currDeclaration = new Declaration(pluginClassName);
                try {
                    currDeclaration.init(digester, pluginManager);
                } catch(PluginException pwe) {
                    throw new PluginInvalidInputException(
                        pwe.getMessage(), pwe.getCause());
                }
                pluginManager.addDeclaration(currDeclaration);
            }
        } else if (pluginId != null) {
            currDeclaration = pluginManager.getDeclarationById(pluginId);
                
            if (currDeclaration == null) {
                throw new PluginInvalidInputException(
                    "Plugin id [" + pluginId + "] is not defined.");
            }
        } else if (defaultPlugin != null) {
            currDeclaration = defaultPlugin;
        } else {
            throw new PluginInvalidInputException(
                "No plugin class specified for element " +
                pattern);
        }
            
        // now load up the custom rules
        currDeclaration.configure(digester, pattern);

        // and now create an instance of the plugin class
        Class pluginClass = currDeclaration.getPluginClass();
        
        Object instance = pluginClass.newInstance();
        getDigester().push(instance);
        if (debug) {
            log.debug(
                "PluginCreateRule.begin" + ": pattern=[" + pattern + "]" + 
                " match=[" + digester.getMatch() + "]" + 
                " pushed instance of plugin [" + pluginClass.getName() + "]");
        }
        
        // and now we have to fire any custom rules which would have
        // been matched by the same path that matched this rule, had
        // they been loaded at that time.
        List rules = newRules.getDecoratedRules().match(namespace, path);
        fireBeginMethods(rules, namespace, name, attributes); 
    }

    /**
     * Process the body text of this element.
     *
     * @param text The body text of this element
     */
    public void body(String namespace, String name, String text)
        throws Exception {

        // While this class itself has no work to do in the body method,
        // we do need to fire the body methods of all dynamically-added
        // rules matching the same path as this rule. During begin, we had
        // to manually execute the dynamic rules' begin methods because they
        // didn't exist in the digester's Rules object when the match begin.
        // So in order to ensure consistent ordering of rule execution, the
        // PluginRules class deliberately avoids returning any such rules
        // in later calls to the match method, instead relying on this
        // object to execute them at the appropriate time.
        //
        // Note that this applies only to rules matching exactly the path
        // which is also matched by this PluginCreateRule. 

        String path = digester.getMatch();
        PluginRules newRules = (PluginRules) digester.getRules();
        List rules = newRules.getDecoratedRules().match(namespace, path);
        fireBodyMethods(rules, namespace, name, text);
    }

    /**
     * Invoked by the digester when the closing tag matching this Rule's
     * pattern is encountered.
     * </p>
     * 
     * @param namespace Description of the Parameter
     * @param name Description of the Parameter
     * @exception Exception Description of the Exception
     *
     * @see #begin
     */
    public void end(String namespace, String name)
                    throws Exception {


        // see body method for more info
        String path = digester.getMatch();
        PluginRules newRules = (PluginRules) digester.getRules();
        List rules = newRules.getDecoratedRules().match(namespace, path);
        fireEndMethods(rules, namespace, name);
        
        // pop the stack of PluginRules instances, which
        // discards all custom rules associated with this plugin
        digester.setRules(newRules.getParent());
        
        // and get rid of the instance of the plugin class from the
        // digester object stack.
        digester.pop();
    }

    /**
     * Return the pattern that this Rule is associated with.
     * <p>
     * In general, Rule instances <i>can</i> be associated with multiple
     * patterns. A PluginCreateRule, however, will only function correctly
     * when associated with a single pattern. It is possible to fix this, but
     * I can't be bothered just now because this feature is unlikely to be
     * used.
     * </p>
     * 
     * @return The pattern value
     */
    public String getPattern() {
        return pattern;
    }
    
    /**
     * Duplicate the processing that the Digester does when firing the
     * begin methods of rules. It would be really nice if the Digester
     * class provided a way for this functionality to just be invoked
     * directly.
     */
    public void fireBeginMethods(List rules,
                      String namespace, String name,
                      org.xml.sax.Attributes list)
                      throws java.lang.Exception {
        
        if ((rules != null) && (rules.size() > 0)) {
            Log log = digester.getLogger();
            boolean debug = log.isDebugEnabled();
            for (int i = 0; i < rules.size(); i++) {
                try {
                    Rule rule = (Rule) rules.get(i);
                    if (debug) {
                        log.debug("  Fire begin() for " + rule);
                    }
                    rule.begin(namespace, name, list);
                } catch (Exception e) {
                    throw digester.createSAXException(e);
                } catch (Error e) {
                    throw e;
                }
            }
        }
    }

    /**
     * Duplicate the processing that the Digester does when firing the
     * body methods of rules. It would be really nice if the Digester
     * class provided a way for this functionality to just be invoked
     * directly.
     */
    private void fireBodyMethods(List rules,
                    String namespaceURI, String name,
                    String text) throws Exception {

        if ((rules != null) && (rules.size() > 0)) {
            Log log = digester.getLogger();
            boolean debug = log.isDebugEnabled();
            for (int i = 0; i < rules.size(); i++) {
                try {
                    Rule rule = (Rule) rules.get(i);
                    if (debug) {
                        log.debug("  Fire body() for " + rule);
                    }
                    rule.body(namespaceURI, name, text);
                } catch (Exception e) {
                    throw digester.createSAXException(e);
                } catch (Error e) {
                    throw e;
                }
            }
        }
    }
    
    /**
     * Duplicate the processing that the Digester does when firing the
     * end methods of rules. It would be really nice if the Digester
     * class provided a way for this functionality to just be invoked
     * directly.
     */
    public void fireEndMethods(List rules,
                    String namespaceURI, String name)
                    throws Exception {

        // Fire "end" events for all relevant rules in reverse order
        if (rules != null) {
            Log log = digester.getLogger();
            boolean debug = log.isDebugEnabled();
            for (int i = 0; i < rules.size(); i++) {
                int j = (rules.size() - i) - 1;
                try {
                    Rule rule = (Rule) rules.get(j);
                    if (debug) {
                        log.debug("  Fire end() for " + rule);
                    }
                    rule.end(namespaceURI, name);
                } catch (Exception e) {
                    throw digester.createSAXException(e);
                } catch (Error e) {
                    throw e;
                }
            }
        }
    }
}