Consistently support LoadingCache

This commits make sure that CaffeineCache handles consistently the
contract of LoadingCache.

Closes gh-25173

Author: snicoll

Diff for: spring-context-support/src/main/java/org/springframework/cache/caffeine/CaffeineCache.java

@@ -83,16 +83,6 @@ public final com.github.benmanes.caffeine.cache.Cache<Object, Object> getNativeC
 		return this.cache;
 	}
 
-	@Override
-	@Nullable
-	public ValueWrapper get(Object key) {
-		if (this.cache instanceof LoadingCache) {
-			Object value = ((LoadingCache<Object, Object>) this.cache).get(key);
-			return toValueWrapper(value);
-		}
-		return super.get(key);
-	}
-
 	@SuppressWarnings("unchecked")
 	@Override
 	@Nullable
@@ -103,6 +93,9 @@ public <T> T get(Object key, final Callable<T> valueLoader) {
 	@Override
 	@Nullable
 	protected Object lookup(Object key) {
+		if (this.cache instanceof LoadingCache) {
+			return ((LoadingCache<Object, Object>) this.cache).get(key);
+		}
 		return this.cache.getIfPresent(key);
 	}
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -21,9 +21,11 @@
 import org.junit.jupiter.api.Test;
 
 import org.springframework.cache.Cache;
+import org.springframework.cache.Cache.ValueWrapper;
 import org.springframework.context.testfixture.cache.AbstractValueAdaptingCacheTests;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
 
 /**
  * @author Ben Manes
@@ -61,6 +63,34 @@ protected Object getNativeCache() {
 		return nativeCache;
 	}
 
+	@Test
+	void testLoadingCacheGet() {
+		Object value = new Object();
+		CaffeineCache loadingCache = new CaffeineCache(CACHE_NAME, Caffeine.newBuilder()
+				.build(key -> value));
+		ValueWrapper valueWrapper = loadingCache.get(new Object());
+		assertThat(valueWrapper).isNotNull();
+		assertThat(valueWrapper.get()).isEqualTo(value);
+	}
+
+	@Test
+	void testLoadingCacheGetWithType() {
+		String value = "value";
+		CaffeineCache loadingCache = new CaffeineCache(CACHE_NAME, Caffeine.newBuilder()
+				.build(key -> value));
+		String valueWrapper = loadingCache.get(new Object(), String.class);
+		assertThat(valueWrapper).isNotNull();
+		assertThat(valueWrapper).isEqualTo(value);
+	}
+
+	@Test
+	void testLoadingCacheGetWithWrongType() {
+		String value = "value";
+		CaffeineCache loadingCache = new CaffeineCache(CACHE_NAME, Caffeine.newBuilder()
+				.build(key -> value));
+		assertThatIllegalStateException().isThrownBy(() -> loadingCache.get(new Object(), Long.class));
+	}
+
 	@Test
 	public void testPutIfAbsentNullValue() throws Exception {
 		CaffeineCache cache = getCache();