Inserting Java Object to MongoDB Collection Using Java

Question

I am trying to insert a whole Java object into a MongoDB Collection using Java. I am getting following error:

Error :

Exception in t         


        

Answer 1

Use BasicDBObjectBuilder to convert your POJO to an instance of DBObject which a DBCollection can save:

import com.mongodb.BasicDBObjectBuilder;
import com.mongodb.DBObject;

public class Employee {
    private long no;
    private String name;

    // Getters and Setters

    public DBObject toDBObject() {
        BasicDBObjectBuilder builder = BasicDBObjectBuilder
                .start("no", no)
                .append("name", name);
        return builder.get();
    }
}

In order to save, just call toDBObject() on POJO instance and provide it to collection:

public class test {

    public static void main(String[] args) throws UnknownHostException,
            MongoException {
        ...
        DBCollection dbCollection = db.getCollection("NameColl");

        Employee employee = new Employee();
        employee.setNo(1L);
        employee.setName("yogesh");

        dbCollection.save(employee.toDBObject());
    }
}

Using this approach:

• You don't need to manually create a DBObject every time
• You don't need to mess up your POJO by extending Mongo classes (what if your POJO is already extending a class?)
• You don't need a Json mapper [and its annotations on POJO fields]
• You only have dependency to java-mongo-driver jar

Answer 2

You can convert your java object into json string using the gson library and then insert it in mongodb.

Eg:

Gson gson = new Gson();
String json = gson.toJson(Employee);    
BasicDBObject basicDBObject = new BasicDBObject("Name", json );          
DBCollection dbCollection = db.getCollection("NameColl");          
dbCollection.save(basicDBObject);    

Answer 3

Just use "insertOne" method, not save.

    MongoCollection collection;
    String collectionName = "somename";
    String jsonObject = "{}";

    if (!mongoTemplate.collectionExists(collectionName)) {
        collection = mongoTemplate.createCollection(collectionName);
        logger.info("Collection %s was successfully created", collectionName);
    } else {
        collection = mongoTemplate.getCollection(collectionName);
    }

    collection.insertOne(Document.parse(jsonObject));

Answer 4

Highly recommend MongoJack, a decent library to map Java objects to/from MongoDB documents.

The code would be something like below:

import java.util.Arrays;
import org.mongojack.JacksonDBCollection;
import com.mongodb.DB;
import com.mongodb.MongoClient;
import com.mongodb.ServerAddress;

public class Test {

    public static void main(String[] args) {

        MongoClient mongoClient = new MongoClient(Arrays.asList(new ServerAddress("localhost", 27017)));
        DB db = mongoClient.getDB("test");

        Employee employee = new Employee();
        employee.setNo(1L);
        employee.setName("yogesh");

        JacksonDBCollection<Employee, String> collectionData = JacksonDBCollection.wrap(db.getCollection("NameColl"), Employee.class, String.class);
        collectionData.save(employee);
        mongoClient.close();
    }

}

(PS: Currently I'm using mongo-java-driver v3.2.2, and mongojack v2.6.1)

Answer 5

Hopefully this will work for you and you can get help from it. I performed database operations(insert,delete, update, get, getall) and used Person object for operations in MongoDB with java for demo purpose.

1. Database connection class

Connection.java

package test;
import org.bson.codecs.configuration.CodecRegistry;
import org.bson.codecs.pojo.PojoCodecProvider;
import static org.bson.codecs.configuration.CodecRegistries.fromProviders;
import static org.bson.codecs.configuration.CodecRegistries.fromRegistries;
import com.mongodb.MongoClient;
import com.mongodb.MongoClientOptions;
import com.mongodb.client.MongoDatabase;

public class Connection {
    public MongoClient mongo;
    private String db;
    public MongoDatabase database;
    private static Connection instance;

    private Connection() {
        db = "chatsystem";
        CodecRegistry pojoCodecRegistry = fromRegistries(MongoClient.getDefaultCodecRegistry(),
                fromProviders(PojoCodecProvider.builder().automatic(true).build()));
        mongo = new MongoClient("localhost", MongoClientOptions.builder().codecRegistry(pojoCodecRegistry).build());
        database = mongo.getDatabase(db);

    }

    public static Connection getInstance() {
        if (instance == null) {
            instance = new Connection();
            return instance;
        } else {
            return instance;
        }
    }

}

2. Model Class

Person.java

package test;

import org.bson.types.ObjectId;

public class Person {

    public Person() {
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getFname() {
        return fname;
    }

    public void setFname(String fname) {
        this.fname = fname;
    }

    public String getLname() {
        return lname;
    }

    public void setLname(String lname) {
        this.lname = lname;
    }

    private ObjectId id;

    public Person(String username, String email, String password, String fname, String lname) {
        super();
        this.username = username;
        this.email = email;
        this.password = password;
        this.fname = fname;
        this.lname = lname;
    }

    public ObjectId getId() {
        return id;
    }

    public void setId(ObjectId id) {
        this.id = id;
    }

    private String username;
    private String email;
    private String password;
    private String fname;
    private String lname;
}

3. Main class

test.java

package test;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import static com.mongodb.client.model.Filters.*;
import com.mongodb.client.FindIterable;
import com.mongodb.client.MongoCollection;

public class test {
    private MongoCollection<Person> person;
    Connection conn;
    public void getCollection() {
        conn = Connection.getInstance();
        person = conn.database.getCollection("person", Person.class);
    }
    public static void main(String[] args) throws Exception {
        test t = new test();
        t.getCollection();
        Person p = new Person();
        p.setEmail("test@test.com");
        p.setFname("ftest");
        p.setLname("ltest");
        p.setPassword("testtest");
        p.setUsername("test123");


        // insert person type objects in database
        t.insertPerson(p);


        // get all persons from database
        List<Person> pp = t.getAllPersons();
        Person pt = pp.get(0);
        System.out.println(pt.getEmail());
        System.out.println(pt.getId());


        // get one person from database by username filter

                 // pass username of person in method argument
        Person ph = t.getOnePerson("test123");
        System.out.println(ph.getEmail());
        System.out.println(ph.getId());


        // update/edit person by username filter
                // pass username of person in method argument
        t.updatePerson("test123");


        // delete person by username filter
               // pass username of person in method argument
        t.removePerson("updatetest123");

    }

    public void insertPerson(Person p) {

        person.insertOne(p);
    }

    public List<Person> getAllPersons() {
        FindIterable<Person> iterable = person.find();
        Iterator it = iterable.iterator();
        List<Person> allPersons = new ArrayList<>();
        while (it.hasNext()) {
            Person per = (Person) it.next();
            allPersons.add(per);
        }
        return allPersons;
    }

    public Person getOnePerson(String username) {
        return person.find(eq("username", username)).first();
    }

    public void updatePerson(String username) {
        Person p = new Person();
        p.setEmail("update@test.com");
        p.setFname("updateftest");
        p.setLname("updateltest");
        p.setPassword("updatetesttest");
        p.setUsername("updatetest123");
        person.replaceOne(eq("username", username), p);

    }

    public void removePerson(String username) {
        person.deleteOne(eq("username", username));
    }



}

Answer 6

There have been several changes since this question was asked. Using test.java in the question, here is what worked for me using Google's Gson:

import com.google.gson.Gson;
import com.mongodb.Block;
import com.mongodb.MongoClient;
import com.mongodb.client.FindIterable;
import com.mongodb.client.MongoDatabase;
import org.bson.Document;

public class test {
  public static void main(String[] args) {
    MongoClient mongoClient = new MongoClient(); // Connect with default settings i.e. localhost:27017
    MongoDatabase db = mongoClient.getDatabase("test"); // Get database "test". Creates one if it doesn't exist
    Employee employee = new Employee(); // Create java object
    employee.setNo(1L);
    employee.setName("yogesh");
    // Deserialize object to json string
    Gson gson = new Gson();
    String json = gson.toJson(employee);
    // Parse to bson document and insert
    Document doc = Document.parse(json);
    db.getCollection("NameColl").insertOne(doc);

    // Retrieve to ensure object was inserted
    FindIterable<Document> iterable = db.getCollection("NameColl").find();
    iterable.forEach(new Block<Document>() {
      @Override
      public void apply(final Document document) {
        System.out.println(document); // See below to convert document back to Employee
      }
    });

  }
}

You can also use Gson to convert retrieved bson document back to Java object:

Gson gson = new Gson();
Employee emp = gson.fromJson(document.toJson(), Employee.class);