使用Java在MongoDB中创建集合

Question

i want to create collection in mongodb using java.The below is the code i worked with.I can connect to database.But Collection is not happening..please help me

   import com.mongodb.MongoClient;
   import com.mongodb.DB;
   import com.mongodb.DBCollection;

   public class CreateCollection{

     public static void main( String args[] ){
       try{   

         // To connect to mongodb server
         MongoClient mongoClient = new MongoClient( "localhost" , 27017 );

         // Now connect to your databases
         DB db = mongoClient.getDB( "cms" );
         System.out.println("Connect to database successfully");

         DBCollection school = db.createCollection("college");
         System.out.println("Collection mycol created successfully");

       }catch(Exception e){
         System.err.println( e.getClass().getName() + ": " + e.getMessage() );
       }
    } 
  }

Answer 1

Indeed you have a compilation error.

You should use db.getCollection("college") which creates the collection if not exist.

Also, the collection is lazily created when you add something to it.

You can add:

school.save(new BasicDBObject("key" , "value"));

The collection with a single document will be created then.

Answer 2

Here I am sharing the working code

import com.mongodb.MongoClient;
import com.mongodb.MongoException;
import com.mongodb.WriteConcern;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.BasicDBObject;
import com.mongodb.DBObject;
import com.mongodb.DBCursor;
import com.mongodb.ServerAddress;
import java.util.Arrays;

public class MongoDBCollection
{

public static void main(String args[])
{
try
{
//Connect to Database
MongoClient mongoClient=new MongoClient("localhost",27017);
DB db=mongoClient.getDB("analytics");
System.out.println("Your connection to DB is ready for Use::"+db);

//Create Collection

DBCollection linked=db.createCollection("LinkedIn",new BasicDBObject()); 
System.out.println("Collection created successfully");

}

catch(Exception e)
{
System.out.println(e.getClass().getName()+":"+e.getMessage());

}

}


}

Answer 3

I just recently needed to do this very thing.

Here is what I used (adapted to your question):

String collectionName = "college");

if(!db.collectionExists(collectionName)
{
  //I can confirm that the collection is created at this point.
  DBCollection school = db.createCollection(collectionName, new BasicDBObject());      
  //I would highly recommend you check the 'school' DBCollection to confirm it was actually created
  System.out.println("Collection %s created successfully", collectionName);
}

Answer 4

Here is my way

        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));