revised scope inheritance: default scope is "" (empty String) now; consistent isPrototype checks

org.springframework.beans/src/main/java/org/springframework/beans/factory/config/BeanDefinition.java

@@ -211,9 +211,17 @@ public interface BeanDefinition extends AttributeAccessor, BeanMetadataElement {
 	/**
 	 * Return whether this a <b>Singleton</b>, with a single, shared instance
 	 * returned on all calls.
+	 * @see #SCOPE_SINGLETON
 	 */
 	boolean isSingleton();
 
+	/**
+	 * Return whether this a <b>Prototype</b>, with an independent instance
+	 * returned for each call.
+	 * @see #SCOPE_PROTOTYPE
+	 */
+	boolean isPrototype();
+
 	/**
 	 * Return whether this bean is "abstract", that is, not meant to be instantiated.
 	 */

org.springframework.beans/src/main/java/org/springframework/beans/factory/support/AbstractAutowireCapableBeanFactory.java

@@ -301,7 +301,7 @@ public abstract class AbstractAutowireCapableBeanFactory extends AbstractBeanFac
 		RootBeanDefinition bd = null;
 		if (mbd instanceof RootBeanDefinition) {
 			RootBeanDefinition rbd = (RootBeanDefinition) mbd;
-			if (SCOPE_PROTOTYPE.equals(rbd.getScope())) {
+			if (rbd.isPrototype()) {
 				bd = rbd;
 			}
 		}

org.springframework.beans/src/main/java/org/springframework/beans/factory/support/AbstractBeanDefinition.java

@@ -33,6 +33,7 @@ import org.springframework.core.io.Resource;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.ObjectUtils;
+import org.springframework.util.StringUtils;
 
 /**
  * Base class for concrete, full-fledged
@@ -54,6 +55,13 @@ import org.springframework.util.ObjectUtils;
 public abstract class AbstractBeanDefinition extends BeanMetadataAttributeAccessor
 		implements BeanDefinition, Cloneable {
 
+	/**
+	 * Constant for the default scope name: "", equivalent to singleton status
+	 * but to be overridden from a parent bean definition (if applicable).
+	 */
+	public static final String SCOPE_DEFAULT = "";
+
+
 	/**
 	 * Constant that indicates no autowiring at all.
 	 * @see #setAutowireMode
@@ -118,7 +126,7 @@ public abstract class AbstractBeanDefinition extends BeanMetadataAttributeAccess
 
 	private volatile Object beanClass;
 
-	private String scope;
+	private String scope = SCOPE_DEFAULT;
 
 	private boolean singleton = true;
 
@@ -273,16 +281,16 @@ public abstract class AbstractBeanDefinition extends BeanMetadataAttributeAccess
 	 * </ul>
 	 */
 	public void overrideFrom(BeanDefinition other) {
-		if (other.getBeanClassName() != null) {
+		if (StringUtils.hasLength(other.getBeanClassName())) {
 			setBeanClassName(other.getBeanClassName());
 		}
-		if (other.getFactoryBeanName() != null) {
+		if (StringUtils.hasLength(other.getFactoryBeanName())) {
 			setFactoryBeanName(other.getFactoryBeanName());
 		}
-		if (other.getFactoryMethodName() != null) {
+		if (StringUtils.hasLength(other.getFactoryMethodName())) {
 			setFactoryMethodName(other.getFactoryMethodName());
 		}
-		if (other.getScope() != null) {
+		if (StringUtils.hasLength(other.getScope())) {
 			setScope(other.getScope());
 		}
 		setAbstract(other.isAbstract());
@@ -306,11 +314,11 @@ public abstract class AbstractBeanDefinition extends BeanMetadataAttributeAccess
 			setDependsOn(otherAbd.getDependsOn());
 			setNonPublicAccessAllowed(otherAbd.isNonPublicAccessAllowed());
 			setLenientConstructorResolution(otherAbd.isLenientConstructorResolution());
-			if (otherAbd.getInitMethodName() != null) {
+			if (StringUtils.hasLength(otherAbd.getInitMethodName())) {
 				setInitMethodName(otherAbd.getInitMethodName());
 				setEnforceInitMethod(otherAbd.isEnforceInitMethod());
 			}
-			if (otherAbd.getDestroyMethodName() != null) {
+			if (StringUtils.hasLength(otherAbd.getDestroyMethodName())) {
 				setDestroyMethodName(otherAbd.getDestroyMethodName());
 				setEnforceDestroyMethod(otherAbd.isEnforceDestroyMethod());
 			}
@@ -405,14 +413,17 @@ public abstract class AbstractBeanDefinition extends BeanMetadataAttributeAccess
 
 	/**
 	 * Set the name of the target scope for the bean.
-	 * <p>Default is "singleton"; the out-of-the-box alternative is "prototype".
-	 * Extended bean factories might support further scopes.
+	 * <p>Default is singleton status, although this is only applied once
+	 * a bean definition becomes active in the containing factory. A bean
+	 * definition may eventually inherit its scope from a parent bean definitionFor this
+	 * reason, the default scope name is empty (empty String), with
+	 * singleton status being assumed until a resolved scope will be set.
 	 * @see #SCOPE_SINGLETON
 	 * @see #SCOPE_PROTOTYPE
 	 */
 	public void setScope(String scope) {
 		this.scope = scope;
-		this.singleton = SCOPE_SINGLETON.equals(scope);
+		this.singleton = SCOPE_SINGLETON.equals(scope) || SCOPE_DEFAULT.equals(scope);
 		this.prototype = SCOPE_PROTOTYPE.equals(scope);
 	}
 

org.springframework.beans/src/main/java/org/springframework/beans/factory/support/AbstractBeanFactory.java

@@ -1115,7 +1115,7 @@ public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport imp
 				}
 
 				// Set default singleton scope, if not configured before.
-				if (mbd.getScope() == null) {
+				if (!StringUtils.hasLength(mbd.getScope())) {
 					mbd.setScope(RootBeanDefinition.SCOPE_SINGLETON);
 				}