Restore lenient null return value for ConditionContext.getBeanFactory()

Includes nullable return value for getClassLoader() with corresponding notes in applicable javadoc.

Issue: SPR-16866

spring-beans/src/main/java/org/springframework/beans/factory/config/ConfigurableBeanFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -89,7 +89,9 @@ public interface ConfigurableBeanFactory extends HierarchicalBeanFactory, Single
 	void setBeanClassLoader(@Nullable ClassLoader beanClassLoader);
 
 	/**
-	 * Return this factory's class loader for loading bean classes.
+	 * Return this factory's class loader for loading bean classes
+	 * (only {@code null} if even the system ClassLoader isn't accessible).
+	 * @see org.springframework.util.ClassUtils#forName(String, ClassLoader)
 	 */
 	@Nullable
 	ClassLoader getBeanClassLoader();

spring-context/src/main/java/org/springframework/context/annotation/ConditionContext.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -20,6 +20,7 @@ import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
 import org.springframework.beans.factory.support.BeanDefinitionRegistry;
 import org.springframework.core.env.Environment;
 import org.springframework.core.io.ResourceLoader;
+import org.springframework.lang.Nullable;
 
 /**
  * Context information for use by {@link Condition}s.
@@ -33,13 +34,17 @@ public interface ConditionContext {
 	/**
 	 * Return the {@link BeanDefinitionRegistry} that will hold the bean definition
 	 * should the condition match.
+	 * @throws IllegalStateException if no registry is available (which is unusual:
+	 * only the case with a plain {@link ClassPathScanningCandidateComponentProvider})
 	 */
 	BeanDefinitionRegistry getRegistry();
 
 	/**
 	 * Return the {@link ConfigurableListableBeanFactory} that will hold the bean
-	 * definition should the condition match.
+	 * definition should the condition match, or {@code null} if the bean factory is
+	 * not available (or not downcastable to {@code ConfigurableListableBeanFactory}).
 	 */
+	@Nullable
 	ConfigurableListableBeanFactory getBeanFactory();
 
 	/**
@@ -53,8 +58,11 @@ public interface ConditionContext {
 	ResourceLoader getResourceLoader();
 
 	/**
-	 * Return the {@link ClassLoader} that should be used to load additional classes.
+	 * Return the {@link ClassLoader} that should be used to load additional classes
+	 * (only {@code null} if even the system ClassLoader isn't accessible).
+	 * @see org.springframework.util.ClassUtils#forName(String, ClassLoader)
 	 */
+	@Nullable
 	ClassLoader getClassLoader();
 
 }

spring-context/src/main/java/org/springframework/context/annotation/ConditionEvaluator.java

@@ -120,7 +120,7 @@ class ConditionEvaluator {
 		return (List<String[]>) (values != null ? values : Collections.emptyList());
 	}
 
-	private Condition getCondition(String conditionClassName, ClassLoader classloader) {
+	private Condition getCondition(String conditionClassName, @Nullable ClassLoader classloader) {
 		Class<?> conditionClass = ClassUtils.resolveClassName(conditionClassName, classloader);
 		return (Condition) BeanUtils.instantiateClass(conditionClass);
 	}
@@ -202,8 +202,8 @@ class ConditionEvaluator {
 		}
 
 		@Override
+		@Nullable
 		public ConfigurableListableBeanFactory getBeanFactory() {
-			Assert.state(this.beanFactory != null, "No ConfigurableListableBeanFactory available");
 			return this.beanFactory;
 		}
 
@@ -218,8 +218,8 @@ class ConditionEvaluator {
 		}
 
 		@Override
+		@Nullable
 		public ClassLoader getClassLoader() {
-			Assert.state(this.classLoader != null, "No ClassLoader available");
 			return this.classLoader;
 		}
 	}

spring-core/src/main/java/org/springframework/core/io/ResourceLoader.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -72,7 +72,9 @@ public interface ResourceLoader {
 	 * in a uniform manner with the ResourceLoader, rather than relying
 	 * on the thread context ClassLoader.
 	 * @return the ClassLoader
+	 * (only {@code null} if even the system ClassLoader isn't accessible)
 	 * @see org.springframework.util.ClassUtils#getDefaultClassLoader()
+	 * @see org.springframework.util.ClassUtils#forName(String, ClassLoader)
 	 */
 	@Nullable
 	ClassLoader getClassLoader();