Allow null params as advertised in Constants#toCode*

Even though the Javadoc for Constants#toCode and #toCodeForSuffix
specifies that a null value for the 'namePrefix' and 'nameSuffix'
parameters are respectively allowed, before this change passing a null
to either would result in a NullPointerException.

This change fixes constant name lookup for null values of these params
as if an empty string had been passed instead. This way of handling a
null value is consistent with the rest of Constants class API.

Issue: SPR-8278

spring-core/src/main/java/org/springframework/core/Constants.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2008 the original author or authors.
+ * Copyright 2002-2012 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -264,7 +264,7 @@ public class Constants {
 	 * @throws ConstantException if the value wasn't found
 	 */
 	public String toCode(Object value, String namePrefix) throws ConstantException {
-		String prefixToUse = (namePrefix != null ? namePrefix.trim().toUpperCase(Locale.ENGLISH) : null);
+		String prefixToUse = (namePrefix != null ? namePrefix.trim().toUpperCase(Locale.ENGLISH) : "");
 		for (Map.Entry<String, Object> entry : this.fieldCache.entrySet()) {
 			if (entry.getKey().startsWith(prefixToUse) && entry.getValue().equals(value)) {
 				return entry.getKey();
@@ -295,7 +295,7 @@ public class Constants {
 	 * @throws ConstantException if the value wasn't found
 	 */
 	public String toCodeForSuffix(Object value, String nameSuffix) throws ConstantException {
-		String suffixToUse = (nameSuffix != null ? nameSuffix.trim().toUpperCase(Locale.ENGLISH) : null);
+		String suffixToUse = (nameSuffix != null ? nameSuffix.trim().toUpperCase(Locale.ENGLISH) : "");
 		for (Map.Entry<String, Object> entry : this.fieldCache.entrySet()) {
 			if (entry.getKey().endsWith(suffixToUse) && entry.getValue().equals(value)) {
 				return entry.getKey();

spring-core/src/test/java/org/springframework/core/ConstantsTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2007 the original author or authors.
+ * Copyright 2002-2012 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -148,19 +148,28 @@ public class ConstantsTests extends TestCase {
 		assertEquals(c.toCode(new Integer(0), "D"), "DOG");
 		assertEquals(c.toCode(new Integer(0), "DO"), "DOG");
 		assertEquals(c.toCode(new Integer(0), "DoG"), "DOG");
+		assertEquals(c.toCode(new Integer(0), null), "DOG");
 		assertEquals(c.toCode(new Integer(66), ""), "CAT");
 		assertEquals(c.toCode(new Integer(66), "C"), "CAT");
 		assertEquals(c.toCode(new Integer(66), "ca"), "CAT");
 		assertEquals(c.toCode(new Integer(66), "cAt"), "CAT");
+		assertEquals(c.toCode(new Integer(66), null), "CAT");
 		assertEquals(c.toCode("", ""), "S1");
 		assertEquals(c.toCode("", "s"), "S1");
 		assertEquals(c.toCode("", "s1"), "S1");
+		assertEquals(c.toCode("", null), "S1");
 		try {
 			c.toCode("bogus", "bogus");
 			fail("Should have thrown ConstantException");
 		}
 		catch (ConstantException expected) {
 		}
+		try {
+			c.toCode("bogus", null);
+			fail("Should have thrown ConstantException");
+		}
+		catch (ConstantException expected) {
+		}
 
 		assertEquals(c.toCodeForProperty(new Integer(1), "myProperty"), "MY_PROPERTY_NO");
 		assertEquals(c.toCodeForProperty(new Integer(2), "myProperty"), "MY_PROPERTY_YES");
@@ -175,19 +184,28 @@ public class ConstantsTests extends TestCase {
 		assertEquals(c.toCodeForSuffix(new Integer(0), "G"), "DOG");
 		assertEquals(c.toCodeForSuffix(new Integer(0), "OG"), "DOG");
 		assertEquals(c.toCodeForSuffix(new Integer(0), "DoG"), "DOG");
+		assertEquals(c.toCodeForSuffix(new Integer(0), null), "DOG");
 		assertEquals(c.toCodeForSuffix(new Integer(66), ""), "CAT");
 		assertEquals(c.toCodeForSuffix(new Integer(66), "T"), "CAT");
 		assertEquals(c.toCodeForSuffix(new Integer(66), "at"), "CAT");
 		assertEquals(c.toCodeForSuffix(new Integer(66), "cAt"), "CAT");
+		assertEquals(c.toCodeForSuffix(new Integer(66), null), "CAT");
 		assertEquals(c.toCodeForSuffix("", ""), "S1");
 		assertEquals(c.toCodeForSuffix("", "1"), "S1");
 		assertEquals(c.toCodeForSuffix("", "s1"), "S1");
+		assertEquals(c.toCodeForSuffix("", null), "S1");
 		try {
 			c.toCodeForSuffix("bogus", "bogus");
 			fail("Should have thrown ConstantException");
 		}
 		catch (ConstantException expected) {
 		}
+		try {
+			c.toCodeForSuffix("bogus", null);
+			fail("Should have thrown ConstantException");
+		}
+		catch (ConstantException expected) {
+		}
 	}
 
 	public void testGetValuesWithNullPrefix() throws Exception {