Spring Boot & MongoDB how to remove the '_class' column? - spring-data

Question

When inserting data into MongoDB Spring Data is adding a custom "_class" column, is there a way to eliminate the "class" column when using Spring Boot & MongoDB?
Or do i need to create a custom type mapper?
Any hints or advice?

Answer 1

Dave's answer is correct. However, we generally recommend not do this (that's why it's enabled by default in the first place) as you effectively throw away to persist type hierarchies or even a simple property set to e.g. Object. Assume the following type:
#Document
class MyDocument {
private Object object;
}
If you now set object to a value, it will be happily persisted but there's no way you can read the value back into it's original type.

Answer 2

A more up to date answer to that question, working with embedded mongo db for test cases:
I quote from http://mwakram.blogspot.fr/2017/01/remove-class-from-mongo-documents.html
Spring Data MongoDB adds _class in the mongo documents to handle
polymorphic behavior of java inheritance. If you want to remove _class
just drop following Config class in your code.
package com.waseem.config;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.mongodb.MongoDbFactory;
import org.springframework.data.mongodb.core.convert.DbRefResolver;
import org.springframework.data.mongodb.core.convert.DefaultDbRefResolver;
import org.springframework.data.mongodb.core.convert.DefaultMongoTypeMapper;
import org.springframework.data.mongodb.core.convert.MappingMongoConverter;
import org.springframework.data.mongodb.core.mapping.MongoMappingContext;
#Configuration
public class MongoConfig {
#Autowired MongoDbFactory mongoDbFactory;
#Autowired MongoMappingContext mongoMappingContext;
#Bean
public MappingMongoConverter mappingMongoConverter() {
DbRefResolver dbRefResolver = new DefaultDbRefResolver(mongoDbFactory);
MappingMongoConverter converter = new MappingMongoConverter(dbRefResolver, mongoMappingContext);
converter.setTypeMapper(new DefaultMongoTypeMapper(null));
return converter;
}
}

Answer 3

Here is a slightly simpler approach:
#Configuration
public class MongoDBConfig implements InitializingBean {
#Autowired
#Lazy
private MappingMongoConverter mappingMongoConverter;
#Override
public void afterPropertiesSet() throws Exception {
mappingMongoConverter.setTypeMapper(new DefaultMongoTypeMapper(null));
}
}

Answer 4

You can remove the _class by following code. You can use this in your mongo configuration class.
#Bean
public MongoTemplate mongoTemplate(MongoDatabaseFactory databaseFactory, MappingMongoConverter converter) {
converter.setTypeMapper(new DefaultMongoTypeMapper(null));
return new MongoTemplate(databaseFactory, converter);
}

Answer 5

I think you need to create a #Bean of type MongoTemplate and set the type converter explicitly. Details (non-Boot but just extract the template config): http://www.mkyong.com/mongodb/spring-data-mongodb-remove-_class-column/

Answer 6

Similar to RZet but avoids inheritance:
#Configuration
public class MongoConfiguration {
#Autowired
private MappingMongoConverter mappingMongoConverter;
// remove _class
#PostConstruct
public void setUpMongoEscapeCharacterConversion() {
mappingMongoConverter.setTypeMapper(new DefaultMongoTypeMapper(null));
}
}

Answer 7

A simple way (+ for ReactiveMongoTemplate):
#Configuration
public class MongoDBConfig {
#Autowired
private MongoClient mongoClient;
#Value("${spring.data.mongodb.database}")
private String dbName;
#Bean
public ReactiveMongoTemplate reactiveMongoTemplate() {
ReactiveMongoTemplate template = new ReactiveMongoTemplate(mongoClient, dbName);
MappingMongoConverter converter = (MappingMongoConverter) template.getConverter();
converter.setTypeMapper(new DefaultMongoTypeMapper(null));
converter.afterPropertiesSet();
return template;
}
}

Answer 8

Add a converter to remove class.
MappingMongoConverter converter =
new MappingMongoConverter(mongoDbFactory(), new MongoMappingContext());
converter.setTypeMapper(new DefaultMongoTypeMapper(null));
MongoTemplate mongoTemplate = new MongoTemplate(mongoDbFactory(), converter);
return mongoTemplate;
`

Answer 9

The correct answer above seems to be using a number of deprecated dependencies. For example if you check the code, it mentions MongoDbFactory which is deprecated in the latest Spring release. If you happen to be using MongoDB with Spring-Data in 2020, this solution seems to be older. For instant results, check this snippet of code. Works 100%.
Just Create a new AppConfig.java file and paste this block of code. You'll see the "_class" property disappearing from the MongoDB document.
package com.reddit.redditmain.Configuration;
import org.apache.naming.factory.BeanFactory;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.convert.CustomConversions;
import org.springframework.data.mongodb.MongoDatabaseFactory;
import org.springframework.data.mongodb.core.MongoTemplate;
import org.springframework.data.mongodb.core.convert.DbRefResolver;
import org.springframework.data.mongodb.core.convert.DefaultDbRefResolver;
import org.springframework.data.mongodb.core.convert.DefaultMongoTypeMapper;
import org.springframework.data.mongodb.core.convert.MappingMongoConverter;
import org.springframework.data.mongodb.core.mapping.MongoMappingContext;
#Configuration
public class AppConfig {
#Autowired
MongoDatabaseFactory mongoDbFactory;
#Autowired
MongoMappingContext mongoMappingContext;
#Bean
public MappingMongoConverter mappingMongoConverter() {
DbRefResolver dbRefResolver = new DefaultDbRefResolver(mongoDbFactory);
MappingMongoConverter converter = new MappingMongoConverter(dbRefResolver, mongoMappingContext);
converter.setTypeMapper(new DefaultMongoTypeMapper(null));
return converter;
}
}

Answer 10

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.data.mongodb.MongoDatabaseFactory;
import org.springframework.data.mongodb.core.MongoTemplate;
import
org.springframework.data.mongodb.core.convert.DefaultMongoTypeMapper;
import
org.springframework.data.mongodb.core.convert.MappingMongoConverter;
#Configuration
public class MongoConfigWithAuditing {
#Bean
#Primary
public MongoTemplate mongoTemplate(MongoDatabaseFactory
mongoDatabaseFactory, MappingMongoConverter mappingMongoConverter) {
// this is to avoid saving _class to db
mappingMongoConverter.setTypeMapper(new DefaultMongoTypeMapper(null));
MongoTemplate mongoTemplate = new MongoTemplate(mongoDatabaseFactory, mappingMongoConverter);
return mongoTemplate;
}
}

Answer 11

Spring Boot 3 with reactive mongo.
package es.dmunozfer.trading.config;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.mongo.MongoProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.mongodb.ReactiveMongoDatabaseFactory;
import org.springframework.data.mongodb.config.AbstractReactiveMongoConfiguration;
import org.springframework.data.mongodb.core.convert.DefaultMongoTypeMapper;
import org.springframework.data.mongodb.core.convert.MappingMongoConverter;
import org.springframework.data.mongodb.core.convert.MongoCustomConversions;
import org.springframework.data.mongodb.core.mapping.MongoMappingContext;
import org.springframework.data.mongodb.repository.config.EnableReactiveMongoRepositories;
import lombok.extern.slf4j.Slf4j;
#Slf4j
#Configuration
#EnableReactiveMongoRepositories("es.dmunozfer.trading.repository")
public class MongoConfig extends AbstractReactiveMongoConfiguration {
#Autowired
private MongoProperties mongoProperties;
#Override
protected String getDatabaseName() {
return mongoProperties.getDatabase();
}
#Bean
#Override
public MappingMongoConverter mappingMongoConverter(ReactiveMongoDatabaseFactory databaseFactory, MongoCustomConversions customConversions,
MongoMappingContext mappingContext) {
MappingMongoConverter converter = super.mappingMongoConverter(databaseFactory, customConversions, mappingContext);
converter.setTypeMapper(new DefaultMongoTypeMapper(null));
return converter;
}
}

Answer 12

I'm leaving this answer here in case someone wants to remove the _class from kotlin and update it a bit since the previous answers have several deprecated dependencies.
import org.springframework.beans.factory.BeanFactory
import org.springframework.context.annotation.Bean
import org.springframework.context.annotation.Configuration
import org.springframework.data.mongodb.MongoDatabaseFactory
import org.springframework.data.mongodb.core.convert.DbRefResolver
import org.springframework.data.mongodb.core.convert.DefaultDbRefResolver
import org.springframework.data.mongodb.core.convert.DefaultMongoTypeMapper
import org.springframework.data.mongodb.core.convert.MappingMongoConverter
import org.springframework.data.mongodb.core.mapping.MongoMappingContext
#Configuration
internal class SpringMongoConfig {
#Bean
fun mappingMongoConverter(
factory: MongoDatabaseFactory, context: MongoMappingContext,
beanFactory: BeanFactory
): MappingMongoConverter {
val dbRefResolver: DbRefResolver = DefaultDbRefResolver(factory)
val mappingConverter = MappingMongoConverter(dbRefResolver, context)
mappingConverter.setTypeMapper(DefaultMongoTypeMapper(null))
return mappingConverter
}
}