DATAMONGO-1076 - Avoid resolving lazy-loading proxy for dbrefs during finalize.

We now handle intercepted finalize method invocations by not resolving the proxy. Previously the LazyLoadingProxy tried to resolve the proxy during finalisation which could lead to unnecessary database accesses.

Original pull request: #234.

Author: Thomas Darimont

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/DefaultDbRefResolver.java

@@ -178,7 +178,7 @@ private boolean isLazyDbRef(MongoPersistentProperty property) {
 	static class LazyLoadingInterceptor implements MethodInterceptor, org.springframework.cglib.proxy.MethodInterceptor,
 			Serializable {
 
-		private static final Method INITIALIZE_METHOD, TO_DBREF_METHOD;
+		private static final Method INITIALIZE_METHOD, TO_DBREF_METHOD, FINALIZE_METHOD;
 
 		private final DbRefResolverCallback callback;
 		private final MongoPersistentProperty property;
@@ -192,6 +192,7 @@ static class LazyLoadingInterceptor implements MethodInterceptor, org.springfram
 			try {
 				INITIALIZE_METHOD = LazyLoadingProxy.class.getMethod("getTarget");
 				TO_DBREF_METHOD = LazyLoadingProxy.class.getMethod("toDBRef");
+				FINALIZE_METHOD = Object.class.getDeclaredMethod("finalize");
 			} catch (Exception e) {
 				throw new RuntimeException(e);
 			}
@@ -255,6 +256,11 @@ public Object intercept(Object obj, Method method, Object[] args, MethodProxy pr
 				if (ReflectionUtils.isHashCodeMethod(method)) {
 					return proxyHashCode(proxy);
 				}
+
+				// DATAMONGO-1076 - finalize methods should not trigger proxy initialization
+				if (FINALIZE_METHOD.equals(method)) {
+					return null;
+				}
 			}
 
 			Object target = ensureResolved();

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/convert/DbRefMappingMongoConverterUnitTests.java

@@ -22,6 +22,7 @@
 import static org.springframework.data.mongodb.core.convert.LazyLoadingTestUtils.*;
 
 import java.io.Serializable;
+import java.lang.reflect.Method;
 import java.math.BigInteger;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -49,6 +50,7 @@
 import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
 import org.springframework.test.util.ReflectionTestUtils;
+import org.springframework.util.ReflectionUtils;
 import org.springframework.util.SerializationUtils;
 
 import com.mongodb.BasicDBObject;
@@ -541,6 +543,28 @@ public void shouldNotEagerlyResolveIdPropertyWithPropertyAccess() {
 		assertProxyIsResolved(proxy, false);
 	}
 
+	/**
+	 * @see DATAMONGO-1076
+	 */
+	@Test
+	public void shouldNotTriggerResolvingOfLazyLoadedProxyWhenFinalizeMethodIsInvoked() throws Exception {
+
+		MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(WithObjectMethodOverrideLazyDbRefs.class);
+		MongoPersistentProperty property = entity.getPersistentProperty("dbRefToConcreteTypeWithPropertyAccess");
+
+		String idValue = new ObjectId().toString();
+		DBRef dbRef = converter.toDBRef(new LazyDbRefTargetPropertyAccess(idValue), property);
+
+		WithObjectMethodOverrideLazyDbRefs result = converter.read(WithObjectMethodOverrideLazyDbRefs.class,
+				new BasicDBObject("dbRefToPlainObject", dbRef));
+
+		Method finalize = Object.class.getDeclaredMethod("finalize");
+		ReflectionUtils.makeAccessible(finalize);
+		ReflectionUtils.invokeMethod(finalize, result.dbRefToPlainObject);
+
+		assertProxyIsResolved(result.dbRefToPlainObject, false);
+	}
+
 	private Object transport(Object result) {
 		return SerializationUtils.deserialize(SerializationUtils.serialize(result));
 	}