Polish SpEL's Indexer and test

spring-expression/src/main/java/org/springframework/expression/spel/ast/Indexer.java

@@ -44,8 +44,21 @@
 import org.springframework.util.ReflectionUtils;
 
 /**
- * An Indexer can index into some proceeding structure to access a particular piece of it.
- * <p>Supported structures are: strings / collections (lists/sets) / arrays.
+ * An {@code Indexer} can index into some proceeding structure to access a
+ * particular element of the structure.
+ *
+ * <p>Numerical index values are zero-based, such as when accessing the
+ * n<sup>th</sup> element of an array in Java.
+ *
+ * <h3>Supported Structures</h3>
+ *
+ * <ul>
+ * <li>Arrays: the n<sup>th</sup> element</li>
+ * <li>Collections (list and sets): the n<sup>th</sup> element</li>
+ * <li>Strings: the n<sup>th</sup> character as a {@link String}</li>
+ * <li>Maps: the value for the specified key</li>
+ * <li>Objects: the property with the specified name</li>
+ * </ul>
  *
  * @author Andy Clement
  * @author Phillip Webb
@@ -58,6 +71,9 @@ public class Indexer extends SpelNodeImpl {
 	private enum IndexedType {ARRAY, LIST, MAP, STRING, OBJECT}
 
 
+	@Nullable
+	private IndexedType indexedType;
+
 	// These fields are used when the indexer is being used as a property read accessor.
 	// If the name and target type match these cached values then the cachedReadAccessor
 	// is used to read the property. If they do not match, the correct accessor is
@@ -86,12 +102,13 @@ private enum IndexedType {ARRAY, LIST, MAP, STRING, OBJECT}
 	@Nullable
 	private PropertyAccessor cachedWriteAccessor;
 
-	@Nullable
-	private IndexedType indexedType;
 
-
-	public Indexer(int startPos, int endPos, SpelNodeImpl expr) {
-		super(startPos, endPos, expr);
+	/**
+	 * Create an {@code Indexer} with the given start position, end position, and
+	 * index expression.
+	 */
+	public Indexer(int startPos, int endPos, SpelNodeImpl indexExpression) {
+		super(startPos, endPos, indexExpression);
 	}
 
 
@@ -146,6 +163,7 @@ protected ValueRef getValueRef(ExpressionState state) throws EvaluationException
 		if (target == null) {
 			throw new SpelEvaluationException(getStartPosition(), SpelMessage.CANNOT_INDEX_INTO_NULL_VALUE);
 		}
+
 		// At this point, we need a TypeDescriptor for a non-null target object
 		Assert.state(targetDescriptor != null, "No type descriptor");
 

spring-expression/src/test/java/org/springframework/expression/spel/IndexingTests.java

@@ -62,7 +62,6 @@ void indexIntoArrays() {
 		assertThat(expression.getValue(this)).isEqualTo(4);
 	}
 
-
 	@Test
 	@SuppressWarnings("unchecked")
 	void indexIntoGenericPropertyContainingMap() {
@@ -302,7 +301,7 @@ void indexIntoGenericPropertyContainingGrowingList2() {
 
 	@Test
 	void indexIntoGenericPropertyContainingArray() {
-		String[] property = new String[] { "bar" };
+		String[] property = { "bar" };
 		this.property = property;
 		SpelExpressionParser parser = new SpelExpressionParser();
 		Expression expression = parser.parseExpression("property");
@@ -357,17 +356,17 @@ void resolveMapKeyValueTypes() {
 
 	@Test
 	@SuppressWarnings("unchecked")
-	void testListOfScalar() {
+	void listOfScalars() {
 		listOfScalarNotGeneric = new ArrayList(1);
 		listOfScalarNotGeneric.add("5");
 		SpelExpressionParser parser = new SpelExpressionParser();
 		Expression expression = parser.parseExpression("listOfScalarNotGeneric[0]");
-		assertThat(expression.getValue(this, Integer.class)).isEqualTo(Integer.valueOf(5));
+		assertThat(expression.getValue(this, Integer.class)).isEqualTo(5);
 	}
 
 	@Test
 	@SuppressWarnings("unchecked")
-	void testListsOfMap() {
+	void listOfMaps() {
 		listOfMapsNotGeneric = new ArrayList();
 		Map map = new HashMap();
 		map.put("fruit", "apple");