Prevent ValueLoaderEntryProcessor to be created for each get call

Closes gh-31250

Author: snicoll

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

@@ -17,6 +17,7 @@
 package org.springframework.cache.jcache;
 
 import java.util.concurrent.Callable;
+import java.util.function.Function;
 
 import javax.cache.Cache;
 import javax.cache.processor.EntryProcessor;
@@ -42,6 +43,8 @@ public class JCacheCache extends AbstractValueAdaptingCache {
 
 	private final Cache<Object, Object> cache;
 
+	private final ValueLoaderEntryProcessor valueLoaderEntryProcessor;
+
 
 	/**
 	 * Create a {@code JCacheCache} instance.
@@ -60,6 +63,8 @@ public JCacheCache(Cache<Object, Object> jcache, boolean allowNullValues) {
 		super(allowNullValues);
 		Assert.notNull(jcache, "Cache must not be null");
 		this.cache = jcache;
+		this.valueLoaderEntryProcessor = new ValueLoaderEntryProcessor(
+				this::fromStoreValue, this::toStoreValue);
 	}
 
 
@@ -81,9 +86,10 @@ protected Object lookup(Object key) {
 
 	@Override
 	@Nullable
+	@SuppressWarnings("unchecked")
 	public <T> T get(Object key, Callable<T> valueLoader) {
 		try {
-			return this.cache.invoke(key, new ValueLoaderEntryProcessor<T>(), valueLoader);
+			return (T) this.cache.invoke(key, this.valueLoaderEntryProcessor, valueLoader);
 		}
 		catch (EntryProcessorException ex) {
 			throw new ValueRetrievalException(key, valueLoader, ex.getCause());
@@ -141,26 +147,37 @@ public Object process(MutableEntry<Object, Object> entry, Object... arguments) t
 	}
 
 
-	private class ValueLoaderEntryProcessor<T> implements EntryProcessor<Object, Object, T> {
+	private static final class ValueLoaderEntryProcessor implements EntryProcessor<Object, Object, Object> {
+
+		private final Function<Object, Object> fromStoreValue;
+
+		private final Function<Object, Object> toStoreValue;
+
+		private ValueLoaderEntryProcessor(Function<Object, Object> fromStoreValue,
+				Function<Object, Object> toStoreValue) {
+
+			this.fromStoreValue = fromStoreValue;
+			this.toStoreValue = toStoreValue;
+		}
 
-		@SuppressWarnings("unchecked")
 		@Override
 		@Nullable
-		public T process(MutableEntry<Object, Object> entry, Object... arguments) throws EntryProcessorException {
-			Callable<T> valueLoader = (Callable<T>) arguments[0];
+		@SuppressWarnings("unchecked")
+		public Object process(MutableEntry<Object, Object> entry, Object... arguments) throws EntryProcessorException {
+			Callable<Object> valueLoader = (Callable<Object>) arguments[0];
 			if (entry.exists()) {
-				return (T) fromStoreValue(entry.getValue());
+				return this.fromStoreValue.apply(entry.getValue());
 			}
 			else {
-				T value;
+				Object value;
 				try {
 					value = valueLoader.call();
 				}
 				catch (Exception ex) {
 					throw new EntryProcessorException("Value loader '" + valueLoader + "' failed " +
 							"to compute value for key '" + entry.getKey() + "'", ex);
 				}
-				entry.setValue(toStoreValue(value));
+				entry.setValue(this.toStoreValue.apply(value));
 				return value;
 			}
 		}