Exploiting MongoDB together with Spring Data project: basic concepts

All of us are observing the explosion of NoSql solutions these days. I get used to RDBMS but those are not a solution for all kind of challenges you might have. In my recent experience I got a chance to work with MongoDB - document database. In this post I intent to cover some basics (and some advanced features in next post) of using MongoDB together with Spring Data project. Before we start, small disclaimer: at the moment Spring Data is still in milestone phase so some classes / interfaces may change.

Before we start, please download and run MongoDB for your operating system. It's very simple so I won't spend time on this and let's start with simple POM file for our project:

    4.0.0

    mongodb
    com.example.spring
    0.0.1-SNAPSHOT
    jar

    
        UTF-8
        3.0.5.RELEASE
    

    
        
            org.springframework.data
            spring-data-mongodb
            1.0.0.M3
        

        
            log4j
            log4j
            1.2.16
        

        
            org.mongodb
            mongo-java-driver
            2.5.3
        

        
            org.springframework
            spring-core
            ${spring.version}
        

        
            org.springframework
            spring-context
            ${spring.version}
        
    

    
        
            springsource-milestone
            Spring Framework Milestone Repository
            http://maven.springframework.org/milestone
        
    

There are two key dependencies here:
- MongoDB java driver
- Spring Data for MongoDB

There are few ways to define MongoDB inside your Spring application context. Let me show a bit verbose but more flexible one:

    
    
  
    
 
    
        <constructor-arg index="0" ref="mongo" />
        <constructor-arg index="1" value="elements-db"/>
    

        
      

    
        <constructor-arg name="mongoDbFactory" ref="mongoDbFactory" />
        <constructor-arg name="mappingContext" ref="mappingContext" />         
     

    
        <constructor-arg name="mongoDbFactory" ref="mongoDbFactory"/>
        <constructor-arg name="mongoConverter" ref="converter" />        
        <property name="writeResultChecking" value="EXCEPTION" />
        <property name="writeConcern" value="NORMAL"/>
    
 
    
        
    

The role of each bean here:

• mongo defines connection to MongoDB database (we rely on default settings, port 27027)
• converter is used to convert Java classes to/from MongoDB's DBObject (== JSON)
• mongoTemplate exposes operations we can do over MongoDB

So, we are ready to go!
Here are few code snippets to start with:

package com.example.mongodb;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.dao.DataAccessException;
import org.springframework.data.document.mongodb.CollectionCallback;
import org.springframework.data.document.mongodb.MongoOperations;
import org.springframework.data.document.mongodb.query.Index;
import org.springframework.data.document.mongodb.query.Index.Duplicates;
import org.springframework.data.document.mongodb.query.Order;
import org.springframework.stereotype.Service;

import com.mongodb.BasicDBObject;
import com.mongodb.DBCollection;
import com.mongodb.MongoException;

@Service
public class MongoService  {
    @Autowired private MongoOperations template;

    public void createCollection( final String name ) {
        template.createCollection( name  );
    }

    public void dropCollection( final String name ) {
        template.dropCollection( name  );
    }

    public void insert( final Object object, final String collection ) {
        template.insert( object, collection );
    }
   
    public void createIndex( final String name, final String collection ) {
        template.ensureIndex( 
            new Index()
                .on( name, Order.DESCENDING )
                .unique( Duplicates.DROP ), 
            collection  
        );
    }
 
    // Remove / save / ... operations here
}

That's it with basics. Next post will cover advanced features: using bulk inserts, update or insert operation and executing MongoDB commands. :)