Java tutorial
/* $Id: Rule.java 992060 2010-09-02 19:09:47Z simonetripodi $ * * 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.commons.digester; import org.xml.sax.Attributes; /** * Concrete implementations of this class implement actions to be taken when * a corresponding nested pattern of XML elements has been matched. * <p> * Writing a custom Rule is considered perfectly normal when using Digester, * and is encouraged whenever the default set of Rule classes don't meet your * requirements; the digester framework can help process xml even when the * built-in rules aren't quite what is needed. Creating a custom Rule is * just as easy as subclassing javax.servlet.http.HttpServlet for webapps, * or javax.swing.Action for GUI applications. * <p> * If a rule wishes to manipulate a digester stack (the default object stack, * a named stack, or the parameter stack) then it should only ever push * objects in the rule's begin method and always pop exactly the same * number of objects off the stack during the rule's end method. Of course * peeking at the objects on the stacks can be done from anywhere. * <p> * Rule objects should be stateless, ie they should not update any instance * member during the parsing process. A rule instance that changes state * will encounter problems if invoked in a "nested" manner; this can happen * if the same instance is added to digester multiple times or if a * wildcard pattern is used which can match both an element and a child of the * same element. The digester object stack and named stacks should be used to * store any state that a rule requires, making the rule class safe under all * possible uses. */ public abstract class Rule { // ----------------------------------------------------------- Constructors /** * Constructor sets the associated Digester. * * @param digester The digester with which this rule is associated * @deprecated The digester instance is now set in the {@link Digester#addRule} method. Use {@link #Rule()} instead. */ @Deprecated public Rule(Digester digester) { super(); setDigester(digester); } /** * <p>Base constructor. * Now the digester will be set when the rule is added.</p> */ public Rule() { } // ----------------------------------------------------- Instance Variables /** * The Digester with which this Rule is associated. */ protected Digester digester = null; /** * The namespace URI for which this Rule is relevant, if any. */ protected String namespaceURI = null; // ------------------------------------------------------------- Properties /** * Return the Digester with which this Rule is associated. */ public Digester getDigester() { return (this.digester); } /** * Set the <code>Digester</code> with which this <code>Rule</code> is associated. */ public void setDigester(Digester digester) { this.digester = digester; } /** * Return the namespace URI for which this Rule is relevant, if any. */ public String getNamespaceURI() { return (this.namespaceURI); } /** * Set the namespace URI for which this Rule is relevant, if any. * * @param namespaceURI Namespace URI for which this Rule is relevant, * or <code>null</code> to match independent of namespace. */ public void setNamespaceURI(String namespaceURI) { this.namespaceURI = namespaceURI; } // --------------------------------------------------------- Public Methods /** * This method is called when the beginning of a matching XML element * is encountered. * * @param attributes The attribute list of this element * @deprecated Use the {@link #begin(String,String,Attributes) begin} * method with <code>namespace</code> and <code>name</code> * parameters instead. */ @Deprecated public void begin(Attributes attributes) throws Exception { // The default implementation does nothing } /** * This method is called when the beginning of a matching XML element * is encountered. The default implementation delegates to the deprecated * method {@link #begin(Attributes) begin} without the * <code>namespace</code> and <code>name</code> parameters, to retain * backwards compatibility. * * @param namespace the namespace URI of the matching element, or an * empty string if the parser is not namespace aware or the element has * no namespace * @param name the local name if the parser is namespace aware, or just * the element name otherwise * @param attributes The attribute list of this element * @since Digester 1.4 */ public void begin(String namespace, String name, Attributes attributes) throws Exception { begin(attributes); } /** * This method is called when the body of a matching XML element * is encountered. If the element has no body, this method is * called with an empty string as the body text. * * @param text The text of the body of this element * @deprecated Use the {@link #body(String,String,String) body} method * with <code>namespace</code> and <code>name</code> parameters * instead. */ @Deprecated public void body(String text) throws Exception { // The default implementation does nothing } /** * This method is called when the body of a matching XML element is * encountered. If the element has no body, this method is * called with an empty string as the body text. * <p> * The default implementation delegates to the deprecated method * {@link #body(String) body} without the <code>namespace</code> and * <code>name</code> parameters, to retain backwards compatibility. * * @param namespace the namespace URI of the matching element, or an * empty string if the parser is not namespace aware or the element has * no namespace * @param name the local name if the parser is namespace aware, or just * the element name otherwise * @param text The text of the body of this element * @since Digester 1.4 */ public void body(String namespace, String name, String text) throws Exception { body(text); } /** * This method is called when the end of a matching XML element * is encountered. * * @deprecated Use the {@link #end(String,String) end} method with * <code>namespace</code> and <code>name</code> parameters instead. */ @Deprecated public void end() throws Exception { // The default implementation does nothing } /** * This method is called when the end of a matching XML element * is encountered. The default implementation delegates to the deprecated * method {@link #end end} without the * <code>namespace</code> and <code>name</code> parameters, to retain * backwards compatibility. * * @param namespace the namespace URI of the matching element, or an * empty string if the parser is not namespace aware or the element has * no namespace * @param name the local name if the parser is namespace aware, or just * the element name otherwise * @since Digester 1.4 */ public void end(String namespace, String name) throws Exception { end(); } /** * This method is called after all parsing methods have been * called, to allow Rules to remove temporary data. */ public void finish() throws Exception { // The default implementation does nothing } }