Remove duplicate LazyLoadingInterceptor code by reusing LazyLoadingProxyFactory.

Original pull request: #3647.
Closes #3602.

Author: mp911de

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

@@ -15,44 +15,25 @@
  */
 package org.springframework.data.mongodb.core.convert;
 
-import static org.springframework.util.ReflectionUtils.*;
-
-import java.io.IOException;
-import java.io.ObjectInputStream;
-import java.io.ObjectOutputStream;
-import java.io.Serializable;
-import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
-import org.aopalliance.intercept.MethodInterceptor;
-import org.aopalliance.intercept.MethodInvocation;
 import org.bson.Document;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
-import org.springframework.aop.framework.ProxyFactory;
-import org.springframework.cglib.proxy.Callback;
-import org.springframework.cglib.proxy.Enhancer;
-import org.springframework.cglib.proxy.Factory;
-import org.springframework.cglib.proxy.MethodProxy;
-import org.springframework.dao.DataAccessException;
+
 import org.springframework.dao.InvalidDataAccessApiUsageException;
-import org.springframework.dao.support.PersistenceExceptionTranslator;
-import org.springframework.data.mongodb.ClientSessionException;
-import org.springframework.data.mongodb.LazyLoadingException;
 import org.springframework.data.mongodb.MongoDatabaseFactory;
 import org.springframework.data.mongodb.MongoDatabaseUtils;
 import org.springframework.data.mongodb.core.convert.ReferenceLoader.DocumentReferenceQuery;
 import org.springframework.data.mongodb.core.mapping.BasicMongoPersistentProperty;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
 import org.springframework.lang.Nullable;
-import org.springframework.objenesis.ObjenesisStd;
 import org.springframework.util.Assert;
-import org.springframework.util.ReflectionUtils;
 import org.springframework.util.StringUtils;
 
 import com.mongodb.DBRef;
@@ -74,8 +55,6 @@ public class DefaultDbRefResolver extends DefaultReferenceResolver implements Db
 	private static final Logger LOGGER = LoggerFactory.getLogger(DefaultDbRefResolver.class);
 
 	private final MongoDatabaseFactory mongoDbFactory;
-	private final PersistenceExceptionTranslator exceptionTranslator;
-	private final ObjenesisStd objenesis;
 
 	/**
 	 * Creates a new {@link DefaultDbRefResolver} with the given {@link MongoDatabaseFactory}.
@@ -84,13 +63,11 @@ public class DefaultDbRefResolver extends DefaultReferenceResolver implements Db
 	 */
 	public DefaultDbRefResolver(MongoDatabaseFactory mongoDbFactory) {
 
-		super(new MongoDatabaseFactoryReferenceLoader(mongoDbFactory));
+		super(new MongoDatabaseFactoryReferenceLoader(mongoDbFactory), mongoDbFactory.getExceptionTranslator());
 
 		Assert.notNull(mongoDbFactory, "MongoDbFactory translator must not be null!");
 
 		this.mongoDbFactory = mongoDbFactory;
-		this.exceptionTranslator = mongoDbFactory.getExceptionTranslator();
-		this.objenesis = new ObjenesisStd(true);
 	}
 
 	/*
@@ -180,44 +157,9 @@ public List<Document> bulkFetch(List<DBRef> refs) {
 	private Object createLazyLoadingProxy(MongoPersistentProperty property, @Nullable DBRef dbref,
 			DbRefResolverCallback callback, DbRefProxyHandler handler) {
 
-		Class<?> propertyType = property.getType();
-		LazyLoadingInterceptor interceptor = new LazyLoadingInterceptor(property, dbref, exceptionTranslator, callback);
-
-		if (!propertyType.isInterface()) {
-
-			Factory factory = (Factory) objenesis.newInstance(getEnhancedTypeFor(propertyType));
-			factory.setCallbacks(new Callback[] { interceptor });
-
-			return handler.populateId(property, dbref, factory);
-		}
-
-		ProxyFactory proxyFactory = new ProxyFactory();
-
-		for (Class<?> type : propertyType.getInterfaces()) {
-			proxyFactory.addInterface(type);
-		}
-
-		proxyFactory.addInterface(LazyLoadingProxy.class);
-		proxyFactory.addInterface(propertyType);
-		proxyFactory.addAdvice(interceptor);
+		Object lazyLoadingProxy = getProxyFactory().createLazyLoadingProxy(property, callback, dbref);
 
-		return handler.populateId(property, dbref, proxyFactory.getProxy(LazyLoadingProxy.class.getClassLoader()));
-	}
-
-	/**
-	 * Returns the CGLib enhanced type for the given source type.
-	 *
-	 * @param type
-	 * @return
-	 */
-	private Class<?> getEnhancedTypeFor(Class<?> type) {
-
-		Enhancer enhancer = new Enhancer();
-		enhancer.setSuperclass(type);
-		enhancer.setCallbackType(org.springframework.cglib.proxy.MethodInterceptor.class);
-		enhancer.setInterfaces(new Class[] { LazyLoadingProxy.class });
-
-		return enhancer.createClass();
+		return handler.populateId(property, dbref, lazyLoadingProxy);
 	}
 
 	/**
@@ -244,249 +186,6 @@ private static Stream<Document> documentWithId(Object identifier, Collection<Doc
 				.limit(1);
 	}
 
-	/**
-	 * A {@link MethodInterceptor} that is used within a lazy loading proxy. The property resolving is delegated to a
-	 * {@link DbRefResolverCallback}. The resolving process is triggered by a method invocation on the proxy and is
-	 * guaranteed to be performed only once.
-	 *
-	 * @author Thomas Darimont
-	 * @author Oliver Gierke
-	 * @author Christoph Strobl
-	 */
-	static class LazyLoadingInterceptor
-			implements MethodInterceptor, org.springframework.cglib.proxy.MethodInterceptor, Serializable {
-
-		private static final Method INITIALIZE_METHOD, TO_DBREF_METHOD, FINALIZE_METHOD;
-
-		private final DbRefResolverCallback callback;
-		private final MongoPersistentProperty property;
-		private final PersistenceExceptionTranslator exceptionTranslator;
-
-		private volatile boolean resolved;
-		private final @Nullable DBRef dbref;
-		private @Nullable Object result;
-
-		static {
-			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);
-			}
-		}
-
-		/**
-		 * Creates a new {@link LazyLoadingInterceptor} for the given {@link MongoPersistentProperty},
-		 * {@link PersistenceExceptionTranslator} and {@link DbRefResolverCallback}.
-		 *
-		 * @param property must not be {@literal null}.
-		 * @param dbref can be {@literal null}.
-		 * @param callback must not be {@literal null}.
-		 */
-		public LazyLoadingInterceptor(MongoPersistentProperty property, @Nullable DBRef dbref,
-				PersistenceExceptionTranslator exceptionTranslator, DbRefResolverCallback callback) {
-
-			Assert.notNull(property, "Property must not be null!");
-			Assert.notNull(exceptionTranslator, "Exception translator must not be null!");
-			Assert.notNull(callback, "Callback must not be null!");
-
-			this.dbref = dbref;
-			this.callback = callback;
-			this.exceptionTranslator = exceptionTranslator;
-			this.property = property;
-		}
-
-		/*
-		 * (non-Javadoc)
-		 * @see org.aopalliance.intercept.MethodInterceptor#invoke(org.aopalliance.intercept.MethodInvocation)
-		 */
-		@Override
-		public Object invoke(@Nullable MethodInvocation invocation) throws Throwable {
-			return intercept(invocation.getThis(), invocation.getMethod(), invocation.getArguments(), null);
-		}
-
-		/*
-		 * (non-Javadoc)
-		 * @see org.springframework.cglib.proxy.MethodInterceptor#intercept(java.lang.Object, java.lang.reflect.Method, java.lang.Object[], org.springframework.cglib.proxy.MethodProxy)
-		 */
-		@Nullable
-		@Override
-		public Object intercept(Object obj, Method method, Object[] args, @Nullable MethodProxy proxy) throws Throwable {
-
-			if (INITIALIZE_METHOD.equals(method)) {
-				return ensureResolved();
-			}
-
-			if (TO_DBREF_METHOD.equals(method)) {
-				return this.dbref;
-			}
-
-			if (isObjectMethod(method) && Object.class.equals(method.getDeclaringClass())) {
-
-				if (ReflectionUtils.isToStringMethod(method)) {
-					return proxyToString(proxy);
-				}
-
-				if (ReflectionUtils.isEqualsMethod(method)) {
-					return proxyEquals(proxy, args[0]);
-				}
-
-				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();
-
-			if (target == null) {
-				return null;
-			}
-
-			ReflectionUtils.makeAccessible(method);
-
-			return method.invoke(target, args);
-		}
-
-		/**
-		 * Returns a to string representation for the given {@code proxy}.
-		 *
-		 * @param proxy
-		 * @return
-		 */
-		private String proxyToString(@Nullable Object proxy) {
-
-			StringBuilder description = new StringBuilder();
-			if (dbref != null) {
-				description.append(dbref.getCollectionName());
-				description.append(":");
-				description.append(dbref.getId());
-			} else {
-				description.append(System.identityHashCode(proxy));
-			}
-			description.append("$").append(LazyLoadingProxy.class.getSimpleName());
-
-			return description.toString();
-		}
-
-		/**
-		 * Returns the hashcode for the given {@code proxy}.
-		 *
-		 * @param proxy
-		 * @return
-		 */
-		private int proxyHashCode(@Nullable Object proxy) {
-			return proxyToString(proxy).hashCode();
-		}
-
-		/**
-		 * Performs an equality check for the given {@code proxy}.
-		 *
-		 * @param proxy
-		 * @param that
-		 * @return
-		 */
-		private boolean proxyEquals(@Nullable Object proxy, Object that) {
-
-			if (!(that instanceof LazyLoadingProxy)) {
-				return false;
-			}
-
-			if (that == proxy) {
-				return true;
-			}
-
-			return proxyToString(proxy).equals(that.toString());
-		}
-
-		/**
-		 * Will trigger the resolution if the proxy is not resolved already or return a previously resolved result.
-		 *
-		 * @return
-		 */
-		@Nullable
-		private Object ensureResolved() {
-
-			if (!resolved) {
-				this.result = resolve();
-				this.resolved = true;
-			}
-
-			return this.result;
-		}
-
-		/**
-		 * Callback method for serialization.
-		 *
-		 * @param out
-		 * @throws IOException
-		 */
-		private void writeObject(ObjectOutputStream out) throws IOException {
-
-			ensureResolved();
-			out.writeObject(this.result);
-		}
-
-		/**
-		 * Callback method for deserialization.
-		 *
-		 * @param in
-		 * @throws IOException
-		 */
-		private void readObject(ObjectInputStream in) throws IOException {
-
-			try {
-				this.resolved = true;
-				this.result = in.readObject();
-			} catch (ClassNotFoundException e) {
-				throw new LazyLoadingException("Could not deserialize result", e);
-			}
-		}
-
-		/**
-		 * Resolves the proxy into its backing object.
-		 *
-		 * @return
-		 */
-		@Nullable
-		private synchronized Object resolve() {
-
-			if (resolved) {
-
-				if (LOGGER.isTraceEnabled()) {
-					LOGGER.trace("Accessing already resolved lazy loading property {}.{}",
-							property.getOwner() != null ? property.getOwner().getName() : "unknown", property.getName());
-				}
-				return result;
-			}
-
-			try {
-				if (LOGGER.isTraceEnabled()) {
-					LOGGER.trace("Resolving lazy loading property {}.{}",
-							property.getOwner() != null ? property.getOwner().getName() : "unknown", property.getName());
-				}
-
-				return callback.resolve(property);
-
-			} catch (RuntimeException ex) {
-
-				DataAccessException translatedException = this.exceptionTranslator.translateExceptionIfPossible(ex);
-
-				if (translatedException instanceof ClientSessionException) {
-					throw new LazyLoadingException("Unable to lazily resolve DBRef! Invalid session state.", ex);
-				}
-
-				throw new LazyLoadingException("Unable to lazily resolve DBRef!",
-						translatedException != null ? translatedException : ex);
-			}
-		}
-	}
-
 	/**
 	 * Customization hook for obtaining the {@link MongoCollection} for a given {@link DBRef}.
 	 *