Juel Getting Started

Getting Started

The JUEL distribution contains the following JAR files:

1. juel-api-2.2.x.jar - contains the javax.el API classes.
2. juel-impl-2.2.x.jar
3. juel-spi-2.2.x.jar 

1. Factory and Context

   // the ExpressionFactory implementation is de.odysseus.el.ExpressionFactoryImpl
   ExpressionFactory factory = new de.odysseus.el.ExpressionFactoryImpl();
   
   // package de.odysseus.el.util provides a ready-to-use subclass of ELContext
   de.odysseus.el.util.SimpleContext context = new de.odysseus.el.util.SimpleContext();

2. Functions and Variables

   // map function math:max(int, int) to java.lang.Math.max(int, int)
   context.setFunction("math", "max", Math.class.getMethod("max", int.class, int.class));
   
   // map variable foo to 0
   context.setVariable("foo", factory.createValueExpression(0, int.class));

3. Parse and Evaluate

   // parse our expression
   ValueExpression e = factory.createValueExpression(context, "${math:max(foo,bar)}", int.class);
   
   // set value for top-level property "bar" to 1
   factory.createValueExpression(context, "${bar}", int.class).setValue(context, 1);
   
   // get value for our expression
   System.out.println(e.getValue(context)); // --> 1