User.java

@XmlRootElement
@Document(collection = "user")
@PersistenceCapable
@View
public class User {

    @Id
    @JsonIgnore(true)
    private String id;
    private String username;

}

UserAuth.java

@XmlRootElement
@Document(collection = "user")
@PersistenceCapable
public class UserAuth extends User {

    private String password;

}

UserContact.java

@XmlRootElement
@Document(collection = "user")
@PersistenceCapable
public class UserContact extends User {

    private String email;
    private String phone;
    private String address;

}

View.java

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Inherited
public @interface View {

}

ViewMongoTemplate.java

import com.mongodb.BasicDBObject;
import com.mongodb.DBObject;
import com.mongodb.Mongo;
import org.springframework.data.authentication.UserCredentials;
import org.springframework.data.mongodb.MongoDbFactory;
import org.springframework.data.mongodb.core.MongoTemplate;
import org.springframework.data.mongodb.core.convert.MongoConverter;
import org.springframework.data.mongodb.core.convert.MongoWriter;
import org.springframework.data.mongodb.core.mapping.event.AfterSaveEvent;
import org.springframework.data.mongodb.core.mapping.event.BeforeConvertEvent;
import org.springframework.data.mongodb.core.mapping.event.BeforeSaveEvent;
import org.springframework.data.mongodb.core.query.Criteria;
import org.springframework.data.mongodb.core.query.Query;
import org.springframework.data.mongodb.core.query.Update;

import java.util.Map;


public class ViewMongoTemplate extends MongoTemplate {

    private static final String ID_FIELD = "_id";
    private static final String CLASS_FIELD = "_class";

    public ViewMongoTemplate(Mongo mongo, String databaseName) {
        super(mongo, databaseName);
    }

    public ViewMongoTemplate(Mongo mongo, String databaseName, UserCredentials userCredentials) {
        super(mongo, databaseName, userCredentials);
    }


    public ViewMongoTemplate(MongoDbFactory mongoDbFactory) {
        super(mongoDbFactory);
    }

    public ViewMongoTemplate(MongoDbFactory mongoDbFactory, MongoConverter mongoConverter) {
        super(mongoDbFactory, mongoConverter);
    }

    @Override
    public void save(Object objectToSave, String collectionName) {
        if (objectToSave.getClass().isAnnotationPresent(View.class)) {
            doViewSave(collectionName, objectToSave, super.getConverter());
        } else {
            super.save(objectToSave, collectionName);
        }
    }

    protected <T> void doViewSave(final String collectionName, final T objectToSave,
                                  final MongoWriter<T> writer) {
        final BasicDBObject dbDoc = new BasicDBObject();

        maybeEmitEvent(new BeforeConvertEvent<T>(objectToSave));
        writer.write(objectToSave, dbDoc);

        // remove class field, views collection have many classes
        dbDoc.remove(CLASS_FIELD);

        final Object idValue = getDBObjectIdValue(dbDoc);
        if (idValue == null) {
            saveNewEntity(collectionName, objectToSave, dbDoc);
        } else {
            updateViewEntity(collectionName, objectToSave, dbDoc, idValue);
        }
    }

    private <T> void updateViewEntity(String collectionName, T objectToSave, BasicDBObject dbDoc, Object idValue) {
        final Query query = new Query().addCriteria(new Criteria(ID_FIELD).is(idValue));
        final Update update = new Update();
        for (Map.Entry<String, Object> entry : dbDoc.entrySet()) {
            final String field = entry.getKey();
            if (ID_FIELD.equals(field)) {
                continue;
            }
            final Object value = entry.getValue();
            if (value == null) {
                continue;
            }
            update.set(field, value);
        }
        // may check result
        doUpdate(collectionName, query, update, objectToSave.getClass(), true, false);
    }

    private <T> void saveNewEntity(String collectionName, T objectToSave, BasicDBObject dbDoc) {
        maybeEmitEvent(new BeforeSaveEvent<T>(objectToSave, dbDoc));
        final Object id = saveDBObject(collectionName, dbDoc, objectToSave.getClass());

        populateIdIfNecessary(objectToSave, id);
        maybeEmitEvent(new AfterSaveEvent<T>(objectToSave, dbDoc));
    }

    private Object getDBObjectIdValue(final DBObject dbDoc) {
        return dbDoc.get(ID_FIELD);
    }
}