org.xchain.namespaces.core.IterateCommand.java Source code

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Here is the source code for org.xchain.namespaces.core.IterateCommand.java

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/**
 *    Copyright 2011 meltmedia
 *
 *    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.xchain.namespaces.core;

import org.apache.commons.jxpath.JXPathContext;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.xchain.Command;
import org.xchain.annotations.Attribute;
import org.xchain.annotations.AttributeType;
import org.xchain.annotations.Element;
import org.xchain.impl.ChainImpl;

import org.xchain.framework.jxpath.Scope;
import org.xchain.framework.jxpath.ScopedQNameVariables;

import java.util.Collection;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import javax.xml.namespace.QName;

/**
 * The <code>iterate</code> command will execute its child commands for each element in the object selected by the <code>select</code> attribute.
 *
 * <code class="source">
 * &lt;xchain:iterate xmlns:xchain="http://www.xchain.org/core/1.0" select="/some/xpath" variable="name"&gt;
 *   ...
 * &lt;/xchain:iterate&gt;
 * </code>
 *
 * @author Christian Trimble
 * @author Josh Kennedy
 */
@Element(localName = "iterate")
public abstract class IterateCommand extends ChainImpl {
    private static Logger log = LoggerFactory.getLogger(IterateCommand.class);

    /**
     * The QName of the variable.
     */
    @Attribute(localName = "variable", type = AttributeType.QNAME)
    public abstract QName getName(JXPathContext context);

    public abstract boolean hasName();

    /**
     * The JXPath of the java.util.Iterator object.  This method is provided for backwards compatiblity, the
     * select attribute should be used instead.
     */
    @Attribute(localName = "iterator", type = AttributeType.JXPATH_VALUE)
    public abstract Iterator getIterator(JXPathContext context);

    public abstract boolean hasIterator();

    /**
     * The JXPath of the object to iterate.  The object can be of type java.util.Iterator, java.util.Enumeration,
     * java.util.Collection, java.util.Map, or an array.
     */
    @Attribute(localName = "select", type = AttributeType.JXPATH_VALUE)
    public abstract Object getSelect(JXPathContext context);

    public abstract boolean hasSelect();

    /**
     * The scope of the variable.  Can either be the literal global or local. 
     */
    @Attribute(localName = "scope", type = AttributeType.LITERAL, defaultValue = "request")
    public abstract Scope getScope(JXPathContext context);

    public boolean execute(JXPathContext context) throws Exception {
        boolean result = false;
        try {
            if (log.isDebugEnabled()) {
                log.debug("Iterate command called. Has iterator:" + hasIterator() + " Has select:" + hasSelect());
            }

            Iterator iterator = null;
            Enumeration enumeration = null;
            Object[] objectArray = null;
            int index = -1;
            QName variableName = getName(context);

            if (log.isDebugEnabled()) {
                log.debug("Iterate variable:" + variableName);
            }

            // get the scope.
            Scope scope = getScope(context);

            ScopedQNameVariables variables = (ScopedQNameVariables) context.getVariables();

            if (log.isDebugEnabled()) {
                log.debug("Starting iteration process.");
            }

            if (hasIterator()) {
                iterator = getIterator(context);
            } else if (hasSelect()) {
                Object object = getSelect(context);
                if (object == null) {
                    if (log.isDebugEnabled()) {
                        log.debug("The selected iteration object is null.");
                    }
                } else if (object instanceof Iterator) {
                    if (log.isDebugEnabled()) {
                        log.debug("Iterator selected.");
                    }
                    iterator = (Iterator) object;
                } else if (object instanceof Enumeration) {
                    if (log.isDebugEnabled()) {
                        log.debug("Enumeration selected.");
                    }
                    enumeration = (Enumeration) object;
                } else if (object instanceof Collection) {
                    if (log.isDebugEnabled()) {
                        log.debug("Collection selected.");
                    }
                    iterator = ((Collection) object).iterator();
                } else if (object instanceof Map) {
                    if (log.isDebugEnabled()) {
                        log.debug("Map selected.");
                    }
                    iterator = ((Map) object).entrySet().iterator();
                } else if (object instanceof Object[]) {
                    objectArray = (Object[]) object;
                    index = 0;
                } else {
                    if (log.isDebugEnabled()) {
                        log.debug("The selected iteration object is not a supported type: "
                                + object.getClass().getName());
                    }
                }
            }

            if (iterator != null || enumeration != null || objectArray != null) {
                // if the variable has a value, then get it.
                while (((iterator != null && iterator.hasNext())
                        || (enumeration != null && enumeration.hasMoreElements())
                        || (objectArray != null && index < objectArray.length)) && !result) {
                    Object value = null;
                    if (iterator != null) {
                        value = iterator.next();
                    } else if (enumeration != null) {
                        value = enumeration.nextElement();
                    } else {
                        value = objectArray[index++];
                    }

                    if (log.isDebugEnabled()) {
                        log.debug("Setting variable name '" + variableName + "' to value '" + value + "' in scope '"
                                + scope + "'.");
                    }

                    variables.declareVariable(variableName, value, scope);
                    result = super.execute(context);
                }
            } else {
                if (log.isDebugEnabled()) {
                    log.debug("Skipping iteration due to a null iterator.");
                }
            }

            if (log.isDebugEnabled()) {
                log.debug("Iteration complete.");
            }

        } catch (Exception e) {
            if (log.isDebugEnabled()) {
                log.debug("Could not iterate due to exception.", e);
            }
            throw e;
        } catch (Error err) {
            if (log.isDebugEnabled()) {
                log.debug("Could not iterate due to exception.", err);
            }
            throw err;
        }

        // return false and allow other chains to execute.
        return result;
    }
}