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");
-		}
-	}
-
-}

spring-binding/src/test/java/org/springframework/binding/expression/el/ELExpressionParserTests.java

@@ -42,6 +42,11 @@ public class ELExpressionParserTests extends TestCase {
 		}
 	}
 
+	public void testParseNull() {
+		Expression exp = parser.parseExpression("null", null);
+		assertEquals(null, exp.getValue(null));
+	}
+
 	public void testParseEmptyExpressionString() {
 		String expressionString = "";
 		try {

spring-faces/src/main/java/org/springframework/faces/webflow/JsfManagedBeanAwareELExpressionParser.java

@@ -27,7 +27,6 @@ import javax.el.VariableMapper;
 import org.springframework.binding.expression.el.DefaultELResolver;
 import org.springframework.binding.expression.el.ELContextFactory;
 import org.springframework.binding.expression.el.ELExpressionParser;
-import org.springframework.binding.expression.el.NullELResolver;
 import org.springframework.webflow.execution.RequestContext;
 import org.springframework.webflow.expression.el.ActionMethodELResolver;
 import org.springframework.webflow.expression.el.ImplicitFlowVariableELResolver;
@@ -53,7 +52,6 @@ public class JsfManagedBeanAwareELExpressionParser extends ELExpressionParser {
 			RequestContext context = (RequestContext) target;
 			List customResolvers = new ArrayList();
 			customResolvers.add(new RequestContextELResolver(context));
-			customResolvers.add(new NullELResolver());
 			customResolvers.add(new ImplicitFlowVariableELResolver(context));
 			customResolvers.add(new ScopeSearchingELResolver(context));
 			customResolvers.add(new SpringBeanWebFlowELResolver(context));

spring-webflow/src/main/java/org/springframework/webflow/expression/el/WebFlowELExpressionParser.java

@@ -27,7 +27,6 @@ import javax.el.VariableMapper;
 import org.springframework.binding.expression.el.DefaultELResolver;
 import org.springframework.binding.expression.el.ELContextFactory;
 import org.springframework.binding.expression.el.ELExpressionParser;
-import org.springframework.binding.expression.el.NullELResolver;
 import org.springframework.webflow.execution.RequestContext;
 
 /**
@@ -55,7 +54,6 @@ public class WebFlowELExpressionParser extends ELExpressionParser {
 			RequestContext context = (RequestContext) target;
 			List customResolvers = new ArrayList();
 			customResolvers.add(new RequestContextELResolver(context));
-			customResolvers.add(new NullELResolver());
 			customResolvers.add(new ImplicitFlowVariableELResolver(context));
 			customResolvers.add(new ScopeSearchingELResolver(context));
 			customResolvers.add(new SpringBeanWebFlowELResolver(context));

spring-webflow/src/test/java/org/springframework/webflow/expression/el/WebFlowELExpressionParserTests.java

@@ -14,6 +14,7 @@ import org.springframework.webflow.core.collection.AttributeMap;
 import org.springframework.webflow.core.collection.LocalAttributeMap;
 import org.springframework.webflow.core.collection.MutableAttributeMap;
 import org.springframework.webflow.engine.AnnotatedAction;
+import org.springframework.webflow.execution.Event;
 import org.springframework.webflow.execution.RequestContext;
 import org.springframework.webflow.execution.TestAction;
 import org.springframework.webflow.test.MockRequestContext;
@@ -148,4 +149,20 @@ public class WebFlowELExpressionParserTests extends TestCase {
 		assertEquals("setupForm", action.getMethod());
 	}
 
+	public void testResolveEventAttributes() {
+		MockRequestContext context = new MockRequestContext();
+		LocalAttributeMap attributes = new LocalAttributeMap();
+		attributes.put("foo", "bar");
+		context.setCurrentEvent(new Event(this, "event", attributes));
+		Expression exp = parser.parseExpression("currentEvent.foo", new FluentParserContext()
+				.evaluate(RequestContext.class));
+		assertEquals("bar", exp.getValue(context));
+	}
+
+	public void testResolveNull() {
+		MockRequestContext context = new MockRequestContext();
+		Expression exp = parser.parseExpression("null", new FluentParserContext().evaluate(RequestContext.class));
+		assertEquals(null, exp.getValue(context));
+	}
+
 }