2009/05/20 - Apache Shale has been retired.

 /*

  * 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.shale.dialog.scxml;

 import java.util.regex.Pattern;

 import javax.faces.context.FacesContext;

 import javax.faces.el.EvaluationException;

 import javax.faces.el.MethodBinding;

 import javax.faces.el.MethodNotFoundException;

 import javax.faces.el.ReferenceSyntaxException;

 import org.apache.commons.scxml.Context;

 import org.apache.commons.scxml.SCXMLExpressionException;

 import org.apache.commons.scxml.env.jsp.ELEvaluator;

 /**

  * <p>EL evaluator, for evaluating the expressions in SCXML documents used

  * to specify Shale dialogs.</p>

  *

  * <p>This evaluator uses the following premises for evaluation:

  *   <ol>

  *     <li>JSF method binding expressions will take the form:

  *         #{...}

  *         These will return a <code>java.lang.String</code> object as

  *         required by the methods associated with

  *         <code>org.apache.shale.dialog.ActionState</code></li>

  *     <li>JSP 2.0 EL expressions will take the form:

  *         ${...}</li>

  *   </ol>

  * </p>

  *

  * <p>This evaluator delegates to the following expression evaluators:

  *   <ol>

  *     <li>JSF method binding expressions get delegated to the JSF

  *         implementation (Ex: Apache MyFaces).</li>

  *     <li>JSP expressions get delegated to the Apache Jakarta Commons

  *         EL ExpressionEvaluator implementation. This evaluator adds

  *         ability to evaluate special predicates defined by SCXML.</li>

  *   </ol>

  * </p>

  *

  * @since 1.0.4

  *

  * $Id: ShaleDialogELEvaluator.java 481499 2006-12-02 03:47:39Z rahul $

  */

 public class ShaleDialogELEvaluator extends ELEvaluator {

     /**

      * Shale ActionState method parameters.

      */

     private static final Object[] PARAMETERS = new Object[0];

     /**

      * Shale ActionState method signature.

      */

     private static final Class[] SIGNATURE = new Class[0];

     // We do not have the privilege of having specific element attributes

     // associated with specific types of expressions

     /** Pattern for recognizing the method / value binding expression. */

     private static Pattern jsfBindingExpr =

         Pattern.compile("^\\s*#\\{.*\\}\\s*$");

     /** FacesContext for this request. */

     private transient FacesContext context;

     /**

      * Constructor.

      */

     public ShaleDialogELEvaluator() {

         super();

         this.context = null;

     }

     /**

      * Set per request context.

      *

      * @param context The FacesContext for this request.

      */

     public void setFacesContext(final FacesContext context) {

         this.context = context;

     }

     /**

      * Evaluate an expression.

      *

      * @param ctx variable context

      * @param expr expression

      * @return Object The result of the evaluation

      * @throws SCXMLExpressionException For a malformed expression

      * @see ELEvaluator#eval(Context, String)

      */

     public Object eval(final Context ctx, final String expr)

     throws SCXMLExpressionException {

         if (jsfBindingExpr.matcher(expr).matches()) {

             return invokeShaleActionStateMethod(expr);

         }

         return super.eval(ctx, expr);

     }

     /**

      * Invoke method binding expression for Shale <code>ActionState</code>.

      * Shale requires return type to be a <code>java.lang.String</code>.

      *

      * @param expr Method binding expression

      * @return String Method return value

      * @throws SCXMLExpressionException Re-throw potential Faces

      *                  exceptions as a SCXMLExpressionException.

      */

     private String invokeShaleActionStateMethod(final String expr)

     throws SCXMLExpressionException {

         try {

             MethodBinding mb = context.getApplication().

                 createMethodBinding(expr, SIGNATURE);

             return (String) mb.invoke(context, PARAMETERS);

         //Rethrow any exception as SCXMLExpressionException instance

         } catch (ReferenceSyntaxException rse) {

             throw new SCXMLExpressionException(rse.getMessage(), rse);

         } catch (MethodNotFoundException mnfe) {

             throw new SCXMLExpressionException(mnfe.getMessage(), mnfe);

         } catch (EvaluationException ee) {

             throw new SCXMLExpressionException(ee.getMessage(), ee);

         }

     }

 }