/* $Id: ObjectParamRule.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;

Rule implementation that saves a parameter for use by a surrounding
CallMethodRule.

This parameter may be:

an arbitrary Object defined programatically, assigned when the element pattern associated with the Rule is matched. See ObjectParamRule(int paramIndex, Object param). 
an arbitrary Object defined programatically, assigned if the element pattern AND specified attribute name are matched. See ObjectParamRule(int paramIndex, String attributeName, Object param). 

Since:
1.4/**
 * <p>Rule implementation that saves a parameter for use by a surrounding
 * <code>CallMethodRule<code>.</p>
 *
 * <p>This parameter may be:
 * <ul>
 * <li>an arbitrary Object defined programatically, assigned when the element 
 *  pattern associated with the Rule is matched. See 
 * {@link #ObjectParamRule(int paramIndex, Object param)}.
 * <li>an arbitrary Object defined programatically, assigned if the element 
 * pattern AND specified attribute name are matched. See 
 * {@link #ObjectParamRule(int paramIndex, String attributeName, Object param)}.
 * </ul>
 * </p>
 *
 * @since 1.4
 */

public class ObjectParamRule extends Rule {
    // ----------------------------------------------------------- Constructors
    
Construct a "call parameter" rule that will save the given Object as
the parameter value.
Params:
paramIndex – The zero-relative parameter number
param – the parameter to pass along/**
     * Construct a "call parameter" rule that will save the given Object as
     * the parameter value.
     *
     * @param paramIndex The zero-relative parameter number
     * @param param the parameter to pass along
     */
    public ObjectParamRule(int paramIndex, Object param) {
        this(paramIndex, null, param);
    }


    
Construct a "call parameter" rule that will save the given Object as
the parameter value, provided that the specified attribute exists.
Params:
paramIndex – The zero-relative parameter number
attributeName – The name of the attribute to match
param – the parameter to pass along/**
     * Construct a "call parameter" rule that will save the given Object as
     * the parameter value, provided that the specified attribute exists.
     *
     * @param paramIndex The zero-relative parameter number
     * @param attributeName The name of the attribute to match
     * @param param the parameter to pass along
     */
    public ObjectParamRule(int paramIndex, String attributeName, Object param) {
        this.paramIndex = paramIndex;
        this.attributeName = attributeName;
        this.param = param;
    }


    // ----------------------------------------------------- Instance Variables

    
The attribute which we are attempting to match
/**
     * The attribute which we are attempting to match
     */
    protected String attributeName = null;

    
The zero-relative index of the parameter we are saving.
/**
     * The zero-relative index of the parameter we are saving.
     */
    protected int paramIndex = 0;

    
The parameter we wish to pass to the method call
/**
     * The parameter we wish to pass to the method call
     */
    protected Object param = null;


    // --------------------------------------------------------- Public Methods

    
Process the start of this element.
Params:
attributes – The attribute list for this element/**
     * Process the start of this element.
     *
     * @param attributes The attribute list for this element
     */
    @Override
    public void begin(String namespace, String name,
                      Attributes attributes) throws Exception {
        Object anAttribute = null;
        Object parameters[] = (Object[]) digester.peekParams();

        if (attributeName != null) {
            anAttribute = attributes.getValue(attributeName);
            if(anAttribute != null) {
                parameters[paramIndex] = param;
            }
            // note -- if attributeName != null and anAttribute == null, this rule
            // will pass null as its parameter!
        }else{
            parameters[paramIndex] = param;
        }
    }

    
Render a printable version of this Rule.
/**
     * Render a printable version of this Rule.
     */
    @Override
    public String toString() {
        StringBuffer sb = new StringBuffer("ObjectParamRule[");
        sb.append("paramIndex=");
        sb.append(paramIndex);
        sb.append(", attributeName=");
        sb.append(attributeName);
        sb.append(", param=");
        sb.append(param);
        sb.append("]");
        return (sb.toString());
    }
}