null resolution support

spring-binding/src/main/java/org/springframework/binding/expression/el/ELExpression.java

@@ -44,9 +44,14 @@ public class ELExpression implements Expression {
 		try {
 			Object result = valueExpression.getValue(ctx);
 			if (result == null && !ctx.isPropertyResolved()) {
-				EvaluationAttempt attempt = new EvaluationAttempt(this, context);
-				throw new EvaluationException(attempt, attempt
-						+ " failed: the expression path did not resolve--is the base variable incorrect?", null);
+				if (getExpressionString().equals("null")) {
+					// special case for handling reserved null keyword
+					return null;
+				} else {
+					EvaluationAttempt attempt = new EvaluationAttempt(this, context);
+					throw new EvaluationException(attempt, attempt
+							+ " failed: the expression path did not resolve--is the base variable incorrect?", null);
+				}
 			}
 			return result;
 		} catch (javax.el.PropertyNotFoundException e) {

spring-binding/src/main/java/org/springframework/binding/expression/el/NullELResolver.java

@@ -1,60 +0,0 @@
-package org.springframework.binding.expression.el;
-
-import java.util.Iterator;
-
-import javax.el.ELContext;
-import javax.el.ELResolver;
-import javax.el.PropertyNotWritableException;
-
-/**
- * Resolves the special 'null' variable, indicating a null value.
- * 
- * @author Keith Donald
- */
-public class NullELResolver extends ELResolver {
-
-	private static final String NULL_VARIABLE_NAME = "null";
-
-	public Class getCommonPropertyType(ELContext context, Object base) {
-		return null;
-	}
-
-	public Iterator getFeatureDescriptors(ELContext context, Object base) {
-		return null;
-	}
-
-	public Class getType(ELContext context, Object base, Object property) {
-		if (base == null && NULL_VARIABLE_NAME.equals(property)) {
-			context.setPropertyResolved(true);
-			return null;
-		} else {
-			return null;
-		}
-	}
-
-	public Object getValue(ELContext context, Object base, Object property) {
-		if (base == null && NULL_VARIABLE_NAME.equals(property)) {
-			context.setPropertyResolved(true);
-			return null;
-		} else {
-			return null;
-		}
-	}
-
-	public boolean isReadOnly(ELContext context, Object base, Object property) {
-		if (base == null && NULL_VARIABLE_NAME.equals(property)) {
-			context.setPropertyResolved(true);
-			return true;
-		} else {
-			return false;
-		}
-	}
-
-	public void setValue(ELContext context, Object base, Object property, Object value) {
-		if (base == null && NULL_VARIABLE_NAME.equals(property)) {
-			context.setPropertyResolved(true);
-			throw new PropertyNotWritableException("The 'null' value cannot be set");
-		}
-	}
-
-}