Get ID of last inserted document in a mongoDB w/ Java driver

Is th开发者_开发百科ere an easy way to get the ID (ObjectID) of the last inserted document of a mongoDB instance using the Java driver?

I just realized you can do this:

BasicDBObject doc = new BasicDBObject( "name", "Matt" );
collection.insert( doc );
ObjectId id = (ObjectId)doc.get( "_id" );

To avoid casting from Object to ObjectId, given a com.mongodb.client.MongoCollection collection and a org.bson.Document doc, you can do the following:

collection.insert(doc);
ObjectId id = doc.getObjectId("_id");

It's safe to do

doc.set("_id", new ObjectId())

if you look at driver code

if ( ensureID && id == null ){
    id = ObjectId.get();
    jo.put( "_id" , id );       
}

public static ObjectId get(){
    return new ObjectId();
}

I do not know about the Java driver but for posterity, the getLastError command can be run to get the _id of a write, even an upsert (as of 1.5.4)

After a document is inserted into the MongoDB collection, the successful insertion should update required fields (viz. _id). You may query the inserted object for the _id.

In MongoTemplate.class has a method

protected <T> void doInsert(String collectionName, T objectToSave, MongoWriter<T> writer) {

    assertUpdateableIdIfNotSet(objectToSave);

    initializeVersionProperty(objectToSave);

    maybeEmitEvent(new BeforeConvertEvent<T>(objectToSave, collectionName));

    DBObject dbDoc = toDbObject(objectToSave, writer);

    maybeEmitEvent(new BeforeSaveEvent<T>(objectToSave, dbDoc, collectionName));
    Object id = insertDBObject(collectionName, dbDoc, objectToSave.getClass());

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

and the method will set id for us

protected void populateIdIfNecessary(Object savedObject, Object id) {

    if (id == null) {
        return;
    }

    if (savedObject instanceof BasicDBObject) {
        DBObject dbObject = (DBObject) savedObject;
        dbObject.put(ID_FIELD, id);
        return;
    }

    MongoPersistentProperty idProp = getIdPropertyFor(savedObject.getClass());

    if (idProp == null) {
        return;
    }

    ConversionService conversionService = mongoConverter.getConversionService();
    MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(savedObject.getClass());
    PersistentPropertyAccessor accessor = entity.getPropertyAccessor(savedObject);

    if (accessor.getProperty(idProp) != null) {
        return;
    }

    new ConvertingPropertyAccessor(accessor, conversionService).setProperty(idProp, id);
}

we can see if the entity is a sub-class of BasicDBObject,it will set a id for us.

I think the answer to this is "No".

What you can do is provide your the _id yourself, either manually, or implement the CollectibleCodec mechanism (which is exactly what BasicBDDocument does). However all these solutions involve generating the ID clientside.

Having said that, I don't think there's any problem with generating the _id clientside.

This is insert operation:

DBCollection table1 = db.getCollection("Collection name");
BasicDBObject document = new BasicDBObject();
document.put("_id",value);      
document.put("Name", name);
table1.insert(document);

After insert u get last inserted id:

DBCollection tableDetails = db.getCollection("collection name");
BasicDBObject queryDetails = new BasicDBObject();
queryDetails.put("_id", value);
DBCursor cursorDetails =tableDetails.find(queryDetails);
DBObject oneDetails;
oneDetails=cursorDetails.next();        
String data=oneDetails.get("_id").toString();
System.out.println(data);

after getting value convert to inter type.