jelly-tags/xml/src/java/org/apache/commons/jelly/tags/xml/SetTag.java

/*
 * Copyright 2002,2004 The Apache Software Foundation.
 *
 * Licensed 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.jelly.tags.xml;

import org.apache.commons.jelly.JellyTagException;
import org.apache.commons.jelly.MissingAttributeException;
import org.apache.commons.jelly.XMLOutput;
import org.apache.commons.jelly.xpath.XPathComparator;
import org.apache.commons.jelly.xpath.XPathTagSupport;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.dom4j.Node;

import org.jaxen.XPath;
import org.jaxen.JaxenException;

import java.util.ArrayList;
import java.util.List;
import java.util.Collections;

/** A tag which defines a variable from an XPath expression.
  * This function creates a variable of type {@link List} or {@link org.dom4j.Node}
  * (for example {@link org.dom4j.Element} or {@link org.dom4j.Attribute}).
  * Thus, the variable created from xml:set can be
  * used from the other xml library functions.
  *
  * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
  * @version $Revision: 1.12 $
  */
public class SetTag extends XPathTagSupport {

    /** The Log to which logging calls will be made. */
    private Log log = LogFactory.getLog(SetTag.class);

    /** The variable name to export. */
    private String var;

    /** The XPath expression to evaluate. */
    private XPath select;

    /** Xpath comparator for sorting */
    private XPathComparator xpCmp = null;

    private Boolean single = null;
    
    private Boolean asString = null;

    public SetTag() {

    }

    // Tag interface
    //-------------------------------------------------------------------------
    public void doTag(XMLOutput output) throws MissingAttributeException, JellyTagException {
        if (var == null) {
            throw new MissingAttributeException( "var" );
        }
        if (select == null) {
            throw new MissingAttributeException( "select" );
        }

        Object xpathContext = getXPathContext();
        Object value = null;
        try {
            if(single!=null && single.booleanValue()==true) {
                value = select.selectSingleNode(xpathContext);
            } else {
                value = select.evaluate(xpathContext);
            }
        }
        catch (JaxenException e) {
            throw new JellyTagException(e);
        }

        if (value instanceof List) {
            // sort the list if xpCmp is set.
            if (xpCmp != null && (xpCmp.getXpath() != null)) {
                Collections.sort((List)value, xpCmp);
            }
        }
        if (single!=null) {
            if (single.booleanValue()==true) {
                if(value instanceof List) {
                    List l = (List) value;
                    if (l.size()==0)
                        value=null;
                    else
                        value=l.get(0);
                }
                if(asString!=null && asString.booleanValue() && value instanceof Node)
                    value = ((Node) value).getStringValue();
            } else { // single == false
                if(! (value instanceof List) ) {
                    List l = null;
                    if (value==null) {
                        l = new ArrayList(0);
                    } else {
                        l = new ArrayList(1);
                        l.add(value);
                    }
                    value = l;
                }
            }
        }

        //log.info( "Evaluated xpath: " + select + " as: " + value + " of type: " + value.getClass().getName() );

        context.setVariable(var, value);
    }

    // Properties
    //-------------------------------------------------------------------------

    /** Sets the variable name to define for this expression
     */
    public void setVar(String var) {
        this.var = var;
    }

    /** Sets the XPath expression to evaluate. */
    public void setSelect(XPath select) {
        this.select = select;
    }

    /** If set to true will only take the first element matching.
        If set to false, guarantees that a list is returned.
        It then guarantees that the result is of type
        {@link org.dom4j.Node} thereby making sure that, for example,
        when an element is selected, one can directly call such methods
        as setAttribute.
        */
    public void setSingle(boolean single) {
        this.single = new Boolean(single);
    }
    
    /** If set to true, will ensure that the (XPath) text-value
      * of the selected node is taken instead of the node
      * itself.
      * This ensures that, thereafter, string manipulations
      * can be performed on the result.
      * Setting this attribute to true will also set the single
      * attribute to true.
      */
    public void setAsString(boolean asString) {
        if(asString)
            this.single = new Boolean(asString);
        this.asString = new Boolean(asString);
    }


    /** Sets the xpath expression to use to sort selected nodes.
     *  Ignored if single is true.
     */
    public void setSort(XPath sortXPath) throws JaxenException {
        if (xpCmp == null) xpCmp = new XPathComparator();
        xpCmp.setXpath(sortXPath);
    }

    /**
     * Set whether to sort ascending or descending.
     */
    public void setDescending(boolean descending) {
        if (xpCmp == null) xpCmp = new XPathComparator();
        xpCmp.setDescending(descending);
    }
}