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<document>

 <properties>
  <title>Commons SCXML Usage - API notes - EL</title>
  <author email="dev@commons.apache.org">Commons Documentation Team</author>
 </properties>

 <body>

  <section name="Commons SCXML - Trying out EL without the servlet container">
   <p>Someone asked about Commons EL:<br/>
   &quot;<i>Is there no way to test this stuff outside of a Servlet/JSP
   container?</i>&quot;</p>

   <p>Commons SCXML supports EL as an expression language that may be used
   within the expressions in an SCXML document. As a side-effect, a simple
   API may be available for anyone who has the need to test without wanting
   to deal with a Servlet/JSP container. <i>We understand this has limited
   use.</i>
   </p>

   <p>To test an expression language implementation, one minimally needs a
   context of evaluation and an evaluator, which gives us the following
   usage:</p>
   <pre>
   //import org.apache.commons.scxml.Context;
   //import org.apache.commons.scxml.Evaluator;
   //import org.apache.commons.scxml.SCXMLExpressionException;
   //import org.apache.commons.scxml.env.jsp.ELContext;
   //import org.apache.commons.scxml.env.jsp.ELEvaluator;

   Context context = new ELContext();
   // Say we have an instance 'foo' of type Foo which
   // has a property 'bar' of type String
   context.set("foo", foo);

   Evaluator evaluator = new ELEvaluator();

   String bar = null;
   try {
     bar = (String) evaluator.eval(context, "${foo.bar}");
   } catch (SCXMLExpressionException see) {
     // Commons SCXML wraps the underlying exception,
     // in this case, a javax.servlet.jsp.el.ELException
   }
   </pre>
  </section> 

 </body>

</document>
