From 23177fef0c0fe163e44d42543f17a621969d6e5f Mon Sep 17 00:00:00 2001
From: Christoph Strobl <cstrobl@vmware.com>
Date: Mon, 12 Jul 2021 10:32:13 +0200
Subject: [PATCH] Custom Converter should also be applicable for simple types.

This commit fixes a regression that prevented custom converters from being applied to types considered store native ones.

Original pull request: #3703.
Fixes #3670
---
 .../core/convert/MappingMongoConverter.java   |  6 ++++-
 .../MappingMongoConverterUnitTests.java       | 25 +++++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

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 aced009cd..83be993b9 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
@@ -1173,7 +1173,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	@SuppressWarnings({ "rawtypes", "unchecked" })
 	private Object getPotentiallyConvertedSimpleRead(Object value, @Nullable Class<?> target) {
 
-		if (target == null || ClassUtils.isAssignableValue(target, value)) {
+		if (target == null) {
 			return value;
 		}
 
@@ -1181,6 +1181,10 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 			return doConvert(value, target);
 		}
 
+		if (ClassUtils.isAssignableValue(target, value)) {
+			return value;
+		}
+
 		if (Enum.class.isAssignableFrom(target)) {
 			return Enum.valueOf((Class<Enum>) target, value.toString());
 		}
diff --git a/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/convert/MappingMongoConverterUnitTests.java b/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/convert/MappingMongoConverterUnitTests.java
index 369f6dbde..759be5c6b 100644
--- a/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/convert/MappingMongoConverterUnitTests.java
+++ b/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/convert/MappingMongoConverterUnitTests.java
@@ -30,6 +30,7 @@ import java.time.LocalDateTime;
 import java.time.temporal.ChronoUnit;
 import java.util.*;
 
+import org.bson.types.Binary;
 import org.bson.types.Code;
 import org.bson.types.Decimal128;
 import org.bson.types.ObjectId;
@@ -2568,6 +2569,21 @@ class MappingMongoConverterUnitTests {
 				.containsEntry("item3", "i3");
 	}
 
+	@Test // GH-3670
+	void appliesCustomConverterEvenToSimpleTypes() {
+
+		converter = new MappingMongoConverter(resolver, mappingContext);
+		converter.setCustomConversions(MongoCustomConversions.create(it -> {
+			it.registerConverter(new MongoSimpleTypeConverter());
+		}));
+		converter.afterPropertiesSet();
+
+		org.bson.Document source = new org.bson.Document("content", new Binary(new byte[] {0x00, 0x42}));
+
+		GenericType<Object> target = converter.read(GenericType.class, source);
+		assertThat(target.content).isInstanceOf(byte[].class);
+	}
+
 	static class GenericType<T> {
 		T content;
 	}
@@ -3136,6 +3152,15 @@ class MappingMongoConverterUnitTests {
 		}
 	}
 
+	@ReadingConverter
+	public static class MongoSimpleTypeConverter implements Converter<Binary, Object> {
+
+		@Override
+		public byte[] convert(Binary source) {
+			return source.getData();
+		}
+	}
+
 	static class TypeWrappingTypeImplementingMap {
 
 		String id;