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

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

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 2

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 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

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 5

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 6

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 7

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 8

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);
    }