SPR-6775

+ replace the vanilla hashmap with a quick-and-dirty, JDK based, fixed LRU cache

org.springframework.core/src/main/java/org/springframework/core/type/classreading/CachingMetadataReaderFactory.java

@@ -17,8 +17,9 @@
 package org.springframework.core.type.classreading;
 
 import java.io.IOException;
-import java.util.HashMap;
+import java.util.LinkedHashMap;
 import java.util.Map;
+import java.util.Map.Entry;
 
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.ResourceLoader;
@@ -33,8 +34,20 @@ import org.springframework.core.io.ResourceLoader;
  */
 public class CachingMetadataReaderFactory extends SimpleMetadataReaderFactory {
 
-	private final Map<Resource, MetadataReader> classReaderCache = new HashMap<Resource, MetadataReader>();
+	private static final int MAX_ENTRIES = 50;
 
+	@SuppressWarnings("serial")
+	private static final <K, V> Map<K, V> createLRUCache() {
+		return new LinkedHashMap<K, V>(MAX_ENTRIES, 0.75f, true) {
+
+			@Override
+			protected boolean removeEldestEntry(Entry<K, V> eldest) {
+				return size() > MAX_ENTRIES;
+			}
+		};
+	}
+
+	private final Map<Resource, MetadataReader> classReaderCache = createLRUCache();
 
 	/**
 	 * Create a new CachingMetadataReaderFactory for the default class loader.
@@ -60,7 +73,6 @@ public class CachingMetadataReaderFactory extends SimpleMetadataReaderFactory {
 		super(classLoader);
 	}
 
-
 	@Override
 	public MetadataReader getMetadataReader(Resource resource) throws IOException {
 		synchronized (this.classReaderCache) {
@@ -72,5 +84,4 @@ public class CachingMetadataReaderFactory extends SimpleMetadataReaderFactory {
 			return metadataReader;
 		}
 	}
-
 }

org.springframework.core/src/test/java/org/springframework/core/type/CachingMetadataReaderLeakTest.java

@@ -0,0 +1,75 @@
+/*
+ * Copyright 2006-2010 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.
+ * You may obtain a copy of the License at
+ * 
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.core.type;
+
+import static org.hamcrest.CoreMatchers.notNullValue;
+import static org.junit.Assert.assertThat;
+
+import java.net.URL;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.springframework.core.io.Resource;
+import org.springframework.core.io.UrlResource;
+import org.springframework.core.type.classreading.CachingMetadataReaderFactory;
+import org.springframework.core.type.classreading.MetadataReader;
+import org.springframework.core.type.classreading.MetadataReaderFactory;
+import org.springframework.core.type.classreading.SimpleMetadataReaderFactory;
+
+/**
+ * Unit test checking the behaviour of {@link CachingMetadataReaderFactory under load.
+ * If the cache is not controller, this test should fail with an out of memory exception around entry
+ * 5k. 
+ * 
+ * @author Costin Leau
+ */
+public class CachingMetadataReaderLeakTest {
+
+	private static int ITEMS_LOAD = 9999;
+	private MetadataReaderFactory mrf;
+
+	@Before
+	public void before() {
+		mrf = new CachingMetadataReaderFactory();
+	}
+
+	@Test
+	public void testSignificantLoad() throws Exception {
+		URL url = getClass().getResource("/org/springframework/beans/TestBean.class");
+		assertThat(url, notNullValue());
+
+		// look at a LOT of items
+		for (int i = 0; i < ITEMS_LOAD; i++) {
+			Resource resource = new UrlResource(url) {
+				private int counter = 0;
+
+				@Override
+				public boolean equals(Object obj) {
+					return (obj == this);
+
+				}
+
+				@Override
+				public int hashCode() {
+					return System.identityHashCode(this);
+				}
+			};
+
+			MetadataReader reader = mrf.getMetadataReader(resource);
+			assertThat(reader, notNullValue());
+		}
+	}
+}