Support for nested path using field access

This commit adds a nested path support for DirectFieldAccessor that is
similar to what BeanWrapper provides. It is now possible to use
expressions such as "person.address.city.name" to access the name of
the city that a given person lives in using fields to traverse the
graph.

DirectFieldAccessor also now supports an auto-grow option to create
a default instance for a "null" intermediate path. This option is
false by default and leads to a NullValueInNestedPathException in such
a case.

This commit also harmonizes part of the tests suite so that core tests
are shared between BeanWrapperImpl and DirectFieldAccessor.

Note that map and list access is not implemented as part of this
commit.

Issue: SPR-9705

Author: snicoll

spring-beans/src/main/java/org/springframework/beans/AbstractPropertyAccessor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2014 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.
@@ -27,6 +27,7 @@
  * implementation of actual property access left to subclasses.
  *
  * @author Juergen Hoeller
+ * @author Stephane Nicoll
  * @since 2.0
  * @see #getPropertyValue
  * @see #setPropertyValue
@@ -35,6 +36,8 @@ public abstract class AbstractPropertyAccessor extends TypeConverterSupport impl
 
 	private boolean extractOldValueForEditor = false;
 
+	private boolean autoGrowNestedPaths = false;
+
 
 	@Override
 	public void setExtractOldValueForEditor(boolean extractOldValueForEditor) {
@@ -46,6 +49,16 @@ public boolean isExtractOldValueForEditor() {
 		return this.extractOldValueForEditor;
 	}
 
+	@Override
+	public void setAutoGrowNestedPaths(boolean autoGrowNestedPaths) {
+		this.autoGrowNestedPaths = autoGrowNestedPaths;
+	}
+
+	@Override
+	public boolean isAutoGrowNestedPaths() {
+		return this.autoGrowNestedPaths;
+	}
+
 
 	@Override
 	public void setPropertyValue(PropertyValue pv) throws BeansException {

spring-beans/src/main/java/org/springframework/beans/BeanWrapper.java

@@ -78,22 +78,6 @@ public interface BeanWrapper extends ConfigurablePropertyAccessor {
 	 */
 	PropertyDescriptor getPropertyDescriptor(String propertyName) throws InvalidPropertyException;
 
-	/**
-	 * Set whether this BeanWrapper should attempt to "auto-grow" a
-	 * nested path that contains a {@code null} value.
-	 * <p>If {@code true}, a {@code null} path location will be populated
-	 * with a default object value and traversed instead of resulting in a
-	 * {@link NullValueInNestedPathException}. Turning this flag on also enables
-	 * auto-growth of collection elements when accessing an out-of-bounds index.
-	 * <p>Default is {@code false} on a plain BeanWrapper.
-	 */
-	void setAutoGrowNestedPaths(boolean autoGrowNestedPaths);
-
-	/**
-	 * Return whether "auto-growing" of nested paths has been activated.
-	 */
-	boolean isAutoGrowNestedPaths();
-
 	/**
 	 * Specify a limit for array and collection auto-growing.
 	 * <p>Default is unlimited on a plain BeanWrapper.

spring-beans/src/main/java/org/springframework/beans/BeanWrapperImpl.java

@@ -115,8 +115,6 @@ public class BeanWrapperImpl extends AbstractPropertyAccessor implements BeanWra
 	 */
 	private Map<String, BeanWrapperImpl> nestedBeanWrappers;
 
-	private boolean autoGrowNestedPaths = false;
-
 	private int autoGrowCollectionLimit = Integer.MAX_VALUE;
 
 
@@ -252,25 +250,7 @@ public final Class<?> getRootClass() {
 		return (this.rootObject != null ? this.rootObject.getClass() : null);
 	}
 
-	/**
-	 * Set whether this BeanWrapper should attempt to "auto-grow" a nested path that contains a null value.
-	 * <p>If "true", a null path location will be populated with a default object value and traversed
-	 * instead of resulting in a {@link NullValueInNestedPathException}. Turning this flag on also
-	 * enables auto-growth of collection elements when accessing an out-of-bounds index.
-	 * <p>Default is "false" on a plain BeanWrapper.
-	 */
-	@Override
-	public void setAutoGrowNestedPaths(boolean autoGrowNestedPaths) {
-		this.autoGrowNestedPaths = autoGrowNestedPaths;
-	}
 
-	/**
-	 * Return whether "auto-growing" of nested paths has been activated.
-	 */
-	@Override
-	public boolean isAutoGrowNestedPaths() {
-		return this.autoGrowNestedPaths;
-	}
 
 	/**
 	 * Specify a limit for array and collection auto-growing.
@@ -570,7 +550,7 @@ private BeanWrapperImpl getNestedBeanWrapper(String nestedProperty) {
 		String canonicalName = tokens.canonicalName;
 		Object propertyValue = getPropertyValue(tokens);
 		if (propertyValue == null) {
-			if (this.autoGrowNestedPaths) {
+			if (isAutoGrowNestedPaths()) {
 				propertyValue = setDefaultValue(tokens);
 			}
 			else {
@@ -761,7 +741,7 @@ public Object run() throws Exception {
 
 			if (tokens.keys != null) {
 				if (value == null) {
-					if (this.autoGrowNestedPaths) {
+					if (isAutoGrowNestedPaths()) {
 						value = setDefaultValue(tokens.actualName);
 					}
 					else {
@@ -851,7 +831,7 @@ else if (value instanceof Map) {
 	}
 
 	private Object growArrayIfNecessary(Object array, int index, String name) {
-		if (!this.autoGrowNestedPaths) {
+		if (!isAutoGrowNestedPaths()) {
 			return array;
 		}
 		int length = Array.getLength(array);
@@ -874,7 +854,7 @@ private Object growArrayIfNecessary(Object array, int index, String name) {
 	private void growCollectionIfNecessary(Collection<Object> collection, int index, String name,
 			PropertyDescriptor pd, int nestingLevel) {
 
-		if (!this.autoGrowNestedPaths) {
+		if (!isAutoGrowNestedPaths()) {
 			return;
 		}
 		int size = collection.size();
@@ -951,7 +931,7 @@ private void setPropertyValue(PropertyTokenHolder tokens, PropertyValue pv) thro
 			String key = tokens.keys[tokens.keys.length - 1];
 			if (propValue == null) {
 				// null map value case
-				if (this.autoGrowNestedPaths) {
+				if (isAutoGrowNestedPaths()) {
 					// TODO: cleanup, this is pretty hacky
 					int lastKeyIndex = tokens.canonicalName.lastIndexOf('[');
 					getterTokens.canonicalName = tokens.canonicalName.substring(0, lastKeyIndex);

spring-beans/src/main/java/org/springframework/beans/ConfigurablePropertyAccessor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2009 the original author or authors.
+ * Copyright 2002-2014 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.
@@ -26,6 +26,7 @@
  * <p>Serves as base interface for {@link BeanWrapper}.
  *
  * @author Juergen Hoeller
+ * @author Stephane Nicoll
  * @since 2.0
  * @see BeanWrapper
  */
@@ -54,4 +55,19 @@ public interface ConfigurablePropertyAccessor extends PropertyAccessor, Property
 	 */
 	boolean isExtractOldValueForEditor();
 
+	/**
+	 * Set whether this instance should attempt to "auto-grow" a
+	 * nested path that contains a {@code null} value.
+	 * <p>If {@code true}, a {@code null} path location will be populated
+	 * with a default object value and traversed instead of resulting in a
+	 * {@link NullValueInNestedPathException}.
+	 * <p>Default is {@code false} on a plain instance.
+	 */
+	void setAutoGrowNestedPaths(boolean autoGrowNestedPaths);
+
+	/**
+	 * Return whether "auto-growing" of nested paths has been activated.
+	 */
+	boolean isAutoGrowNestedPaths();
+
 }