ConcurrentMapCacheManager recreates caches in case of setAllowNullValues change

Issue: SPR-12026

spring-context/src/main/java/org/springframework/cache/concurrent/ConcurrentMapCacheManager.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.
@@ -19,6 +19,7 @@ package org.springframework.cache.concurrent;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 
@@ -70,6 +71,8 @@ public class ConcurrentMapCacheManager implements CacheManager {
 	 * Specify the set of cache names for this CacheManager's 'static' mode.
 	 * <p>The number of caches and their names will be fixed after a call to this method,
 	 * with no creation of further cache regions at runtime.
+	 * <p>Calling this with a {@code null} collection argument resets the
+	 * mode to 'dynamic', allowing for further creation of caches again.
 	 */
 	public void setCacheNames(Collection<String> cacheNames) {
 		if (cacheNames != null) {
@@ -78,6 +81,9 @@ public class ConcurrentMapCacheManager implements CacheManager {
 			}
 			this.dynamic = false;
 		}
+		else {
+			this.dynamic = true;
+		}
 	}
 
 	/**
@@ -85,9 +91,17 @@ public class ConcurrentMapCacheManager implements CacheManager {
 	 * in this cache manager.
 	 * <p>Default is "true", despite ConcurrentHashMap itself not supporting {@code null}
 	 * values. An internal holder object will be used to store user-level {@code null}s.
+	 * <p>Note: A change of the null-value setting will reset all existing caches,
+	 * if any, to reconfigure them with the new null-value requirement.
 	 */
 	public void setAllowNullValues(boolean allowNullValues) {
+		if (allowNullValues != this.allowNullValues) {
 			this.allowNullValues = allowNullValues;
+			// Need to recreate all Cache instances with the new null-value configuration...
+			for (Map.Entry<String, Cache> entry : this.cacheMap.entrySet()) {
+				entry.setValue(createConcurrentMapCache(entry.getKey()));
+			}
+		}
 	}
 
 	/**

spring-context/src/test/java/org/springframework/cache/concurrent/ConcurrentMapCacheManagerTests.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.
@@ -56,7 +56,7 @@ public class ConcurrentMapCacheManagerTests {
 
 	@Test
 	public void testStaticMode() {
-		CacheManager cm = new ConcurrentMapCacheManager("c1", "c2");
+		ConcurrentMapCacheManager cm = new ConcurrentMapCacheManager("c1", "c2");
 		Cache cache1 = cm.getCache("c1");
 		assertTrue(cache1 instanceof ConcurrentMapCache);
 		Cache cache1again = cm.getCache("c1");
@@ -76,6 +76,36 @@ public class ConcurrentMapCacheManagerTests {
 		assertNull(cache1.get("key3").get());
 		cache1.evict("key3");
 		assertNull(cache1.get("key3"));
+
+		cm.setAllowNullValues(false);
+		Cache cache1x = cm.getCache("c1");
+		assertTrue(cache1x instanceof ConcurrentMapCache);
+		assertTrue(cache1x != cache1);
+		Cache cache2x = cm.getCache("c2");
+		assertTrue(cache2x instanceof ConcurrentMapCache);
+		assertTrue(cache2x != cache2);
+		Cache cache3x = cm.getCache("c3");
+		assertNull(cache3x);
+
+		cache1x.put("key1", "value1");
+		assertEquals("value1", cache1x.get("key1").get());
+		cache1x.put("key2", 2);
+		assertEquals(2, cache1x.get("key2").get());
+		try {
+			cache1x.put("key3", null);
+			fail("Should have thrown NullPointerException");
+		}
+		catch (NullPointerException ex) {
+			// expected
+		}
+
+		cm.setAllowNullValues(true);
+		Cache cache1y = cm.getCache("c1");
+
+		cache1y.put("key3", null);
+		assertNull(cache1y.get("key3").get());
+		cache1y.evict("key3");
+		assertNull(cache1y.get("key3"));
 	}
 
 }