Apply type conversion to id types.

This commit makes sure to convert the generated query into the target type.

Closes #4709
Original pull request: #4721

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/support/SpringDataMongodbSerializer.java

@@ -26,6 +26,7 @@
 import org.springframework.data.mongodb.core.mapping.FieldName;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
+import org.springframework.data.util.TypeInformation;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
@@ -137,10 +138,30 @@ protected String asDBKey(@Nullable Operation<?> expr, int index) {
 		return property.isIdProperty() ? key.replaceAll("." + ID_KEY + "$", "") : key;
 	}
 
+	@Override
+	protected boolean isId(Path<?> arg) {
+		MongoPersistentProperty propertyFor = getPropertyFor(arg);
+		return propertyFor == null ? super.isId(arg) : propertyFor.isIdProperty();
+	}
+
 	protected Object convert(@Nullable Path<?> path, @Nullable Constant<?> constant) {
 
 		if (!isReference(path)) {
-			return super.convert(path, constant);
+
+			MongoPersistentProperty property = getPropertyFor(path);
+			if(property == null) {
+				return super.convert(path, constant);
+			}
+
+			if(property.isIdProperty()) {
+				return mapper.convertId(constant.getConstant(), property.getFieldType());
+			}
+
+			if(property.hasExplicitWriteTarget()) {
+				return converter.convertToMongoType(constant.getConstant(), TypeInformation.of(property.getFieldType()));
+			}
+
+			return converter.convertToMongoType(constant.getConstant());
 		}
 
 		MongoPersistentProperty property = getPropertyFor(path);

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/repository/support/SpringDataMongodbSerializerUnitTests.java

@@ -30,17 +30,21 @@
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.mockito.Mock;
 import org.mockito.junit.jupiter.MockitoExtension;
+
 import org.springframework.core.convert.converter.Converter;
+import org.springframework.data.annotation.Id;
 import org.springframework.data.convert.WritingConverter;
 import org.springframework.data.mongodb.core.convert.DbRefResolver;
 import org.springframework.data.mongodb.core.convert.MappingMongoConverter;
 import org.springframework.data.mongodb.core.convert.MongoConverter;
 import org.springframework.data.mongodb.core.convert.MongoCustomConversions;
 import org.springframework.data.mongodb.core.mapping.Field;
+import org.springframework.data.mongodb.core.mapping.MongoId;
 import org.springframework.data.mongodb.core.mapping.MongoMappingContext;
 import org.springframework.data.mongodb.repository.Person.Sex;
 import org.springframework.data.mongodb.repository.QAddress;
 import org.springframework.data.mongodb.repository.QPerson;
+import org.springframework.data.mongodb.repository.User;
 
 import com.querydsl.core.types.Ops;
 import com.querydsl.core.types.Predicate;
@@ -50,7 +54,6 @@
 import com.querydsl.core.types.dsl.PathBuilder;
 import com.querydsl.core.types.dsl.SimplePath;
 import com.querydsl.core.types.dsl.StringPath;
-import org.springframework.data.mongodb.repository.User;
 
 /**
  * Unit tests for {@link SpringDataMongodbSerializer}.
@@ -115,15 +118,15 @@ public void returnsEmptyStringIfNoPathExpressionIsGiven() {
 	}
 
 	@Test // DATAMONGO-467, DATAMONGO-1798
-	public void retainsIdPropertyType() {
+	public void appliesImplicitIdConversion() {
 
 		ObjectId id = new ObjectId();
 
 		PathBuilder<Address> builder = new PathBuilder<Address>(Address.class, "address");
 		StringPath idPath = builder.getString("id");
 
 		Document result = (Document) serializer.visit((BooleanOperation) idPath.eq(id.toString()), null);
-		assertThat(result.get("_id")).isNotNull().isInstanceOf(String.class).isEqualTo(id.toString());
+		assertThat(result.get("_id")).isNotNull().isInstanceOf(ObjectId.class);
 	}
 
 	@Test // DATAMONGO-761
@@ -246,6 +249,41 @@ void parsesDocumentReferenceOnId() {
 		assertThat(serializer.handle(predicate)).isEqualTo(Document.parse("{ 'spiritAnimal' : '007' }"));
 	}
 
+	@Test // GH-4709
+	void appliesConversionToIdType() {
+
+		Predicate predicate = QSpringDataMongodbSerializerUnitTests_Outer.outer.embeddedObject.id
+				.eq("64268a7b17ac6a00018bf312");
+
+		assertThat(serializer.handle(predicate))
+				.isEqualTo(new Document("embedded_object._id", new ObjectId("64268a7b17ac6a00018bf312")));
+	}
+
+	@Test // GH-4709
+	void appliesConversionToIdTypeForExplicitTypeRef() {
+
+		Predicate predicate = QQuerydslRepositorySupportTests_WithMongoId.withMongoId.id.eq("64268a7b17ac6a00018bf312");
+
+		assertThat(serializer.handle(predicate)).isEqualTo(new Document("_id", "64268a7b17ac6a00018bf312"));
+	}
+
+	@org.springframework.data.mongodb.core.mapping.Document(collection = "record")
+	class Outer {
+
+		@Id private String id;
+
+		@Field("embedded_object") private Inner embeddedObject;
+	}
+
+	@org.springframework.data.mongodb.core.mapping.Document(collection = "embedded_object")
+	class Inner {
+		@Id private String id;
+	}
+
+	public class WithMongoId {
+		@MongoId private String id;
+	}
+
 	class Address {
 		String id;
 		String street;