From 1f07a3eb29768068e49f9d941720db99f98c4af7 Mon Sep 17 00:00:00 2001
From: Mark Paluch <mpaluch@pivotal.io>
Date: Thu, 23 Apr 2020 14:57:52 +0200
Subject: [PATCH] =?UTF-8?q?DATAMONGO-2529=20-=20Ensure=20that=20MappingMon?=
 =?UTF-8?q?goConverter.read(=E2=80=A6)=20is=20never=20called=20with=20null?=
 =?UTF-8?q?.?=
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Previously, various methods attempted to pass a null argument as source for the converter. The API is non-null and implementations relying on these constraints were easily breakable.

We now make sure that the source is never null.
---
 .../data/mongodb/core/MongoTemplate.java           |  9 ++++-----
 .../core/convert/MappingMongoConverter.java        | 14 +++++++-------
 2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/MongoTemplate.java b/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/MongoTemplate.java
index 915878978..5b6b3a80a 100644
--- a/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/MongoTemplate.java
+++ b/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/MongoTemplate.java
@@ -3029,12 +3029,13 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 		@Nullable
 		public T doWith(@Nullable Document object) {
 
+			T source = null;
+
 			if (null != object) {
 				maybeEmitEvent(new AfterLoadEvent<>(object, type, collectionName));
+				source = reader.read(type, object);
 			}
 
-			T source = reader.read(type, object);
-
 			if (null != source) {
 				maybeEmitEvent(new AfterConvertEvent<>(object, source, collectionName));
 			}
@@ -3074,9 +3075,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 			Class<?> typeToRead = targetType.isInterface() || targetType.isAssignableFrom(entityType) ? entityType
 					: targetType;
 
-			if (null != object) {
-				maybeEmitEvent(new AfterLoadEvent<>(object, targetType, collectionName));
-			}
+			maybeEmitEvent(new AfterLoadEvent<>(object, targetType, collectionName));
 
 			Object source = reader.read(typeToRead, object);
 			Object result = targetType.isInterface() ? projectionFactory.createProjection(targetType, source) : source;
diff --git a/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/MappingMongoConverter.java b/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/MappingMongoConverter.java
index e9eda4274..44d6f4921 100644
--- a/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/MappingMongoConverter.java
+++ b/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/MappingMongoConverter.java
@@ -200,11 +200,9 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 
 	@Nullable
 	@SuppressWarnings("unchecked")
-	private <S extends Object> S read(TypeInformation<S> type, @Nullable Bson bson, ObjectPath path) {
+	private <S extends Object> S read(TypeInformation<S> type, Bson bson, ObjectPath path) {
 
-		if (null == bson) {
-			return null;
-		}
+		Assert.notNull(bson, "Bson must not be null!");
 
 		TypeInformation<? extends S> typeToUse = typeMapper.readType(bson, type);
 		Class<? extends S> rawType = typeToUse.getType();
@@ -1562,17 +1560,19 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 
 		for (Document document : referencedRawDocuments) {
 
+			T target = null;
 			if (document != null) {
+
 				maybeEmitEvent(
 						new AfterLoadEvent<>(document, (Class<T>) (rawType != null ? rawType : Object.class), collectionName));
+				target = (T) read(type, document, path);
 			}
 
-			final T target = (T) read(type, document, path);
-			targeList.add(target);
-
 			if (target != null) {
 				maybeEmitEvent(new AfterConvertEvent<>(document, target, collectionName));
 			}
+
+			targeList.add(target);
 		}
 
 		return targeList;