src/main/java/org/apache/commons/scxml2/model/Var.java

/*
 * 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.scxml2.model;

import org.apache.commons.scxml2.ActionExecutionContext;
import org.apache.commons.scxml2.Context;
import org.apache.commons.scxml2.Evaluator;
import org.apache.commons.scxml2.SCXMLConstants;
import org.apache.commons.scxml2.SCXMLExpressionException;
import org.apache.commons.scxml2.TriggerEvent;
import org.apache.commons.scxml2.EventBuilder;
import org.apache.commons.scxml2.io.SCXMLWriter;

/**
 * The class in this SCXML object model that corresponds to the {@link CustomAction} <var> SCXML element.
 * <p>
 * When manually constructing or modifying a SCXML model using this custom action, either:
 * <ul>
 *     <li>derive from {@link CommonsSCXML}, or</li>
 *     <li>make sure to add the {@link SCXMLConstants#XMLNS_COMMONS_SCXML} namespace with
 *     the {@link SCXMLConstants#XMLNS_COMMONS_SCXML_PREFIX} prefix to the SCXML object, or</li>
 *     <li>wrap the {@link Var} instance in a {@link CustomActionWrapper} (for which the {@link #CUSTOM_ACTION}
 *     can be useful) before adding it to the object model</li>
 * </ul>
 * before write the SCXML model with {@link SCXMLWriter}. The writing will fail otherwise!
 */
public class Var extends Action {

    /**
     * Serial version UID.
     */
    private static final long serialVersionUID = 1L;

    public static final CustomAction CUSTOM_ACTION =
            new CustomAction(SCXMLConstants.XMLNS_COMMONS_SCXML, SCXMLConstants.ELEM_VAR, Var.class);

    /**
     * The name of the variable to be created.
     */
    private String name;

    /**
     * The expression that evaluates to the initial value of the variable.
     */
    private String expr;

    /**
     * Get the expression that evaluates to the initial value
     * of the variable.
     *
     * @return String Returns the expr.
     */
    public final String getExpr() {
        return expr;
    }

    /**
     * Set the expression that evaluates to the initial value
     * of the variable.
     *
     * @param expr The expr to set.
     */
    public final void setExpr(final String expr) {
        this.expr = expr;
    }

    /**
     * Get the name of the (new) variable.
     *
     * @return String Returns the name.
     */
    public final String getName() {
        return name;
    }

    /**
     * Set the name of the (new) variable.
     *
     * @param name The name to set.
     */
    public final void setName(final String name) {
        this.name = name;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void execute(ActionExecutionContext exctx) throws ModelException, SCXMLExpressionException {
        Context ctx = exctx.getContext(getParentEnterableState());
        Evaluator eval = exctx.getEvaluator();
        Object varObj = eval.eval(ctx, expr);
        ctx.setLocal(name, varObj);
        if (exctx.getAppLog().isDebugEnabled()) {
            exctx.getAppLog().debug("<var>: Defined variable '" + name
                + "' with initial value '" + String.valueOf(varObj) + "'");
        }
        TriggerEvent ev = new EventBuilder(name + ".change", TriggerEvent.CHANGE_EVENT).build();
        exctx.getInternalIOProcessor().addEvent(ev);
    }
}