Cache.get(key, type) should also work in case of null value found in cache

Issue: SPR-11567

spring-context-support/src/main/java/org/springframework/cache/ehcache/EhCacheCache.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 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.
@@ -70,7 +70,7 @@ public class EhCacheCache implements Cache {
 	public <T> T get(Object key, Class<T> type) {
 		Element element = this.cache.get(key);
 		Object value = (element != null ? element.getObjectValue() : null);
-		if (type != null && !type.isInstance(value)) {
+		if (value != null && type != null && !type.isInstance(value)) {
 			throw new IllegalStateException("Cached value is not of required type [" + type.getName() + "]: " + value);
 		}
 		return (T) value;

spring-context-support/src/main/java/org/springframework/cache/guava/GuavaCache.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 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.
@@ -90,7 +90,7 @@ public class GuavaCache implements Cache {
 	@SuppressWarnings("unchecked")
 	public <T> T get(Object key, Class<T> type) {
 		Object value = fromStoreValue(this.cache.getIfPresent(key));
-		if (type != null && !type.isInstance(value)) {
+		if (value != null && type != null && !type.isInstance(value)) {
 			throw new IllegalStateException("Cached value is not of required type [" + type.getName() + "]: " + value);
 		}
 		return (T) value;

spring-context-support/src/main/java/org/springframework/cache/jcache/JCacheCache.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 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.
@@ -84,7 +84,7 @@ public class JCacheCache implements Cache {
 	@SuppressWarnings("unchecked")
 	public <T> T get(Object key, Class<T> type) {
 		Object value = fromStoreValue(this.cache.get(key));
-		if (type != null && !type.isInstance(value)) {
+		if (value != null && type != null && !type.isInstance(value)) {
 			throw new IllegalStateException("Cached value is not of required type [" + type.getName() + "]: " + value);
 		}
 		return (T) value;

spring-context-support/src/test/java/org/springframework/cache/ehcache/EhCacheCacheTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2013 the original author or authors.
+ * Copyright 2010-2014 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.
@@ -31,6 +31,7 @@ import static org.junit.Assert.*;
 
 /**
  * @author Costin Leau
+ * @author Juergen Hoeller
  */
 public class EhCacheCacheTests {
 
@@ -71,11 +72,20 @@ public class EhCacheCacheTests {
 		Object value = "george";
 
 		assertNull(cache.get(key));
+		assertNull(cache.get(key, String.class));
+		assertNull(cache.get(key, Object.class));
+
 		cache.put(key, value);
 		assertEquals(value, cache.get(key).get());
 		assertEquals(value, cache.get(key, String.class));
 		assertEquals(value, cache.get(key, Object.class));
 		assertEquals(value, cache.get(key, null));
+
+		cache.put(key, null);
+		assertNotNull(cache.get(key));
+		assertNull(cache.get(key).get());
+		assertNull(cache.get(key, String.class));
+		assertNull(cache.get(key, Object.class));
 	}
 
 	@Test

spring-context/src/main/java/org/springframework/cache/Cache.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 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.
@@ -24,6 +24,7 @@ package org.springframework.cache;
  * cache methods that return {@code null}).
  *
  * @author Costin Leau
+ * @author Juergen Hoeller
  * @since 3.1
  */
 public interface Cache {
@@ -59,11 +60,14 @@ public interface Cache {
 	 * between a cached {@code null} value and no cache entry found at all.
 	 * Use the standard {@link #get(Object)} variant for that purpose instead.
 	 * @param key the key whose associated value is to be returned
-	 * @param type the required type of the returned value
+	 * @param type the required type of the returned value (may be
+	 * {@code null} to bypass a type check; in case of a {@code null}
+	 * value found in the cache, the specified type is irrelevant)
 	 * @return the value to which this cache maps the specified key
 	 * (which may be {@code null} itself), or also {@code null} if
 	 * the cache contains no mapping for this key
 	 * @see #get(Object)
+	 * @since 4.0
 	 */
 	<T> T get(Object key, Class<T> type);
 

spring-context/src/main/java/org/springframework/cache/concurrent/ConcurrentMapCache.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 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.
@@ -110,7 +110,7 @@ public class ConcurrentMapCache implements Cache {
 	@SuppressWarnings("unchecked")
 	public <T> T get(Object key, Class<T> type) {
 		Object value = fromStoreValue(this.store.get(key));
-		if (type != null && !type.isInstance(value)) {
+		if (value != null && type != null && !type.isInstance(value)) {
 			throw new IllegalStateException("Cached value is not of required type [" + type.getName() + "]: " + value);
 		}
 		return (T) value;

spring-context/src/test/java/org/springframework/cache/concurrent/ConcurrentCacheTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2013 the original author or authors.
+ * Copyright 2010-2014 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.
@@ -28,6 +28,7 @@ import static org.junit.Assert.*;
 
 /**
  * @author Costin Leau
+ * @author Juergen Hoeller
  */
 public class ConcurrentCacheTests  {
 
@@ -62,11 +63,20 @@ public class ConcurrentCacheTests  {
 		Object value = "george";
 
 		assertNull(cache.get(key));
+		assertNull(cache.get(key, String.class));
+		assertNull(cache.get(key, Object.class));
+
 		cache.put(key, value);
 		assertEquals(value, cache.get(key).get());
 		assertEquals(value, cache.get(key, String.class));
 		assertEquals(value, cache.get(key, Object.class));
 		assertEquals(value, cache.get(key, null));
+
+		cache.put(key, null);
+		assertNotNull(cache.get(key));
+		assertNull(cache.get(key).get());
+		assertNull(cache.get(key, String.class));
+		assertNull(cache.get(key, Object.class));
 	}
 
 	@Test