Improve allowNullValue handling when a null value is provided

This commit improves `AbstractValueAdaptingCache` to throw a dedicated
exception if `allowNullValues` is `false` and a `null` value is provided
anyway. This avoid a lower-level exception from the cache library that
will miss some context.

Issue: SPR-15173

spring-context-support/src/test/java/org/springframework/cache/caffeine/CaffeineCacheManagerTests.java

@@ -102,14 +102,7 @@ public class CaffeineCacheManagerTests {
 		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");
 

spring-context-support/src/test/java/org/springframework/cache/caffeine/CaffeineCacheTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -20,7 +20,7 @@ import com.github.benmanes.caffeine.cache.Caffeine;
 import org.junit.Before;
 import org.junit.Test;
 
-import org.springframework.cache.AbstractCacheTests;
+import org.springframework.cache.AbstractValueAdaptingCacheTests;
 import org.springframework.cache.Cache;
 
 import static org.junit.Assert.*;
@@ -29,21 +29,31 @@ import static org.junit.Assert.*;
  * @author Ben Manes
  * @author Stephane Nicoll
  */
-public class CaffeineCacheTests extends AbstractCacheTests<CaffeineCache> {
+public class CaffeineCacheTests extends AbstractValueAdaptingCacheTests<CaffeineCache> {
 
 	private com.github.benmanes.caffeine.cache.Cache<Object, Object> nativeCache;
 
 	private CaffeineCache cache;
 
+	private CaffeineCache cacheNoNull;
+
 	@Before
 	public void setUp() {
 		nativeCache = Caffeine.newBuilder().build();
 		cache = new CaffeineCache(CACHE_NAME, nativeCache);
+		com.github.benmanes.caffeine.cache.Cache<Object, Object> nativeCacheNoNull
+				= Caffeine.newBuilder().build();
+		cacheNoNull =  new CaffeineCache(CACHE_NAME_NO_NULL, nativeCacheNoNull, false);
 	}
 
 	@Override
 	protected CaffeineCache getCache() {
-		return cache;
+		return getCache(true);
+	}
+
+	@Override
+	protected CaffeineCache getCache(boolean allowNull) {
+		return allowNull ? this.cache : this.cacheNoNull;
 	}
 
 	@Override

spring-context-support/src/test/java/org/springframework/cache/guava/GuavaCacheManagerTests.java

@@ -101,14 +101,7 @@ public class GuavaCacheManagerTests {
 		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");
 

spring-context-support/src/test/java/org/springframework/cache/jcache/JCacheEhCacheApiTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -25,12 +25,12 @@ import javax.cache.spi.CachingProvider;
 import org.junit.After;
 import org.junit.Before;
 
-import org.springframework.cache.AbstractCacheTests;
+import org.springframework.cache.AbstractValueAdaptingCacheTests;
 
 /**
  * @author Stephane Nicoll
  */
-public class JCacheEhCacheApiTests extends AbstractCacheTests<JCacheCache> {
+public class JCacheEhCacheApiTests extends AbstractValueAdaptingCacheTests<JCacheCache> {
 
 	private CacheManager cacheManager;
 
@@ -38,13 +38,19 @@ public class JCacheEhCacheApiTests extends AbstractCacheTests<JCacheCache> {
 
 	private JCacheCache cache;
 
+	private JCacheCache cacheNoNull;
+
 
 	@Before
 	public void setup() {
 		this.cacheManager = getCachingProvider().getCacheManager();
 		this.cacheManager.createCache(CACHE_NAME, new MutableConfiguration<>());
+		this.cacheManager.createCache(CACHE_NAME_NO_NULL, new MutableConfiguration<>());
 		this.nativeCache = this.cacheManager.getCache(CACHE_NAME);
 		this.cache = new JCacheCache(this.nativeCache);
+		Cache<Object, Object> nativeCacheNoNull =
+				this.cacheManager.getCache(CACHE_NAME_NO_NULL);
+		this.cacheNoNull = new JCacheCache(nativeCacheNoNull, false);
 	}
 
 	protected CachingProvider getCachingProvider() {
@@ -58,10 +64,14 @@ public class JCacheEhCacheApiTests extends AbstractCacheTests<JCacheCache> {
 		}
 	}
 
-
 	@Override
 	protected JCacheCache getCache() {
-		return this.cache;
+		return getCache(true);
+	}
+
+	@Override
+	protected JCacheCache getCache(boolean allowNull) {
+		return allowNull ? this.cache : this.cacheNoNull;
 	}
 
 	@Override