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

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Here is the source code for org.xchain.namespaces.core.VariableCommand.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.framework.jxpath.Scope;
import org.xchain.framework.jxpath.ScopedQNameVariables;

import java.util.List;

import javax.xml.namespace.QName;

/**
 * <p>The <code>variable</code> command will declare and set a variable in the context.
 * The <code>name</code> attribute is the QName of the variable.
 * The <code>select</code>, <code>select-nodes</code>, or <code>select-single-node</code> attribute will be the value of the variable.
 * The <code>scope</code> attribute will determine the scope of the variable.  A 'chain' scope variable will only exist if the current
 * context.  A 'request' scope variable will exist for every context.  A request scope is assumed if no scope attribute is
 * provided.</p>
 *
 * <code class="source">
 * &lt;xchain:variable xmlns:xchain="http://www.xchain.org/core/1.0" name="/some/xpath" select="/some/xpath"/ scope="chain"/&gt;
 * </code>
 *
 * @author Christian Trimble
 * @author Devon Tackett
 * @author Josh Kennedy
 */
@Element(localName = "variable")
public abstract class VariableCommand implements Command {
    public static Logger log = LoggerFactory.getLogger(VariableCommand.class);

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

    public abstract boolean hasName();

    /**
     * The value of the variable. 
     */
    @Attribute(localName = "select", type = AttributeType.JXPATH_VALUE)
    public abstract Object getSelect(JXPathContext context) throws Exception;

    public abstract boolean hasSelect();

    /**
     * The value of the variable. 
     */
    @Attribute(localName = "select-nodes", type = AttributeType.JXPATH_SELECT_NODES)
    public abstract List getSelectNodes(JXPathContext context) throws Exception;

    public abstract boolean hasSelectNodes();

    /**
     * The value of the variable. 
     */
    @Attribute(localName = "select-single-node", type = AttributeType.JXPATH_SELECT_SINGLE_NODE)
    public abstract Object getSelectSingleNode(JXPathContext context) throws Exception;

    public abstract boolean hasSelectSingleNode();

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

    public boolean execute(JXPathContext context) throws Exception {
        QName variableName = getName(context);
        Object variableValue = null;

        if (hasSelect()) {
            variableValue = getSelect(context);
        } else if (hasSelectNodes()) {
            variableValue = getSelectNodes(context);
        } else if (hasSelectSingleNode()) {
            variableValue = getSelectSingleNode(context);
        } else {
            throw new Exception("Variable '" + variableName
                    + "' must have a select attribute (select, select-nodes, or select-single-node)");
        }

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

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

        // declare the variable.
        ((ScopedQNameVariables) context.getVariables()).declareVariable(variableName, variableValue, scope);

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