/* $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.

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.

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.

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.
/**
 * 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.
Params:
digester – The digester with which this rule is associated
Deprecated:
The digester instance is now set in the Digester.addRule method. Use Rule() instead./**
     * 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);

    }
    
    
Base constructor.
Now the digester will be set when the rule is added.
/**
     * <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.
/**
     * The Digester with which this Rule is associated.
     */
    protected Digester digester = null;


    
The namespace URI for which this Rule is relevant, if any.
/**
     * 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.
/**
     * Return the Digester with which this Rule is associated.
     */
    public Digester getDigester() {

        return (this.digester);

    }
    
    
Set the Digester with which this Rule is associated.
/**
     * 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.
/**
     * 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.
Params:
namespaceURI – Namespace URI for which this Rule is relevant,
 or null to match independent of namespace./**
     * 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.
Params:
attributes – The attribute list of this element
Deprecated:
Use the begin method with namespace and name
  parameters instead./**
     * 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 begin without the namespace and name parameters, to retain 
backwards compatibility.
Params:
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
name – the local name if the parser is namespace aware, or just 
  the element name otherwise
attributes – The attribute list of this element
Since:
Digester 1.4/**
     * 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.
Params:
text – The text of the body of this element
Deprecated:
Use the body method with namespace and name parameters
  instead./**
     * 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.
 The default implementation delegates to the deprecated method body without the namespace and
name parameters, to retain backwards compatibility.
Params:
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
name – the local name if the parser is namespace aware, or just 
  the element name otherwise
text – The text of the body of this element
Since:
Digester 1.4/**
     * 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 end method with namespace and name parameters instead./**
     * 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 end without the namespace and name parameters, to retain 
backwards compatibility.
Params:
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
name – the local name if the parser is namespace aware, or just 
  the element name otherwise
Since:
Digester 1.4/**
     * 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.
/**
     * 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

    }


}