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Get MongoDB document by ID on Java

I have a set of ID's of documents which I add previously in MongoDB.
Then I try to get Document from ID.
String idString = "57f8f50977c8a5b8757f261a";
BasicDBObject whereQuery = new BasicDBObject();
whereQuery.put("_id", idString);
DBCursor cursor = table.find(whereQuery);
if(cursor.hasNext())
{
System.out.println("FOUND!" + cursor.next());
}
I get zero results.
But, if I call another field
It works and return me document.
BasicDBObject whereQuery = new BasicDBObject();
whereQuery.put("datachain", "AA");
DBCursor cursor = table.find(whereQuery);
if(cursor.hasNext())
{
System.out.println("FOUND!" + cursor.next());
}
FOUND!{ "_id" : { "$oid" : "57f8f50977c8a5b8757f261b"} , "datachain" : "AA" , "createdDate" : { "$date" : "2016-10-08T13:30:49.588Z"}}
What I do wrong? Why I can't find document by ID's?
Thnx!
UPD:
BasicDBObject whereQuery = new BasicDBObject();
whereQuery.put("_id", new ObjectId("57f8f50977c8a5b8757f261a"));
DBCursor cursor = table.find(whereQuery);
Same, no result founded.

You have to pass the idString as an ObjectId.
whereQuery.put("_id", new ObjectId(idString));

How to use "$or" operator using documents in mongodb using java

Document query = new Document();
query.put("firstName", "abc");
query.put("firstName", "xyz");
Here,"abc" is overrided by the "xyz".So,in the query I'm getting only one value i.e,xyz.I don't know,why the query getting overrided.can u please help me out...
My code:
MongoClient mongo = new MongoClient("localhost",27017);
MongoDatabase db = mongo.getDatabase("sample");
MongoCollection<Document> coll = db.getCollection("users");
Document query = new Document();
query.put("firstName", "abc");
query.put("firstName", "xyz");
Document docStatus =new Document("$or",query );
try (MongoCursor<Document> cursor = coll.find(query).iterator()) {
while (cursor.hasNext()) {
System.out.println(cursor.next());
}
}

The arguments to the $or operator are a List, therefore you are just contructing a List of Document:
Document query = new Document(
"$or", Arrays.asList(
new Document("firstname", "abc"),
new Document("firstname", "xyz")
)
)
But really, when you want an $or condition on the same property, use $in instead. Which is of course another List but just of values:
Document query = new Document(
"firstname",
new Document(
"$in", Arrays.asList("abc","xyz")
)
)
Which is much shorter syntax for the selection of "either" value on the same document property.

You need to construct your query as below :
DBObject clause1 = new BasicDBObject("firstName", "abc");
DBObject clause2 = new BasicDBObject("firstName", "xyz");
BasicDBList or = new BasicDBList();
or.add(clause1);
or.add(clause2);
DBObject query = new BasicDBObject("$or", or);

BasicDBList orList = new BasicDBList();
orList.add(new BasicDBObject("FirstName","xxx"));
orList.add(new BasicDBObject("LastName","yyy"));
BasicDBObject dbObj = new BasicDBObject("$or",orList);

What's the update equivalent of insertMany in Mongo / Java

I am trying to do a bulk upsert, but am having problems to figure out how to do it. This does not work:
BasicDBObject filter = new BasicDBObject();
BasicDBObject update = new BasicDBObject("$set", list);
UpdateOptions options = new UpdateOptions().upsert(true);
collection.updateMany(filter, update, options);
Exception in thread "main" com.mongodb.MongoWriteException: Modifiers operate on fields but we found a Array instead.
Any examples would just be great!
UpsertMany items in one roundtrip
This is what I meant:
public static BulkWriteResult upsertAll(MongoCollection<Document> coll, List<Document> docs, String keyTag) {
List<UpdateOneModel<Document>> requests = new ArrayList<UpdateOneModel<Document>>();
UpdateOptions opt = new UpdateOptions().upsert(true);
for (Document doc : docs ) {
BasicDBObject filter = new BasicDBObject(keyTag, doc.get(keyTag));
BasicDBObject action = new BasicDBObject("$set", doc);
requests.add(new UpdateOneModel<Document>(filter, action, opt));
}
return coll.bulkWrite(requests);
}

You can perform bulk upsert using below code :
MongoClient mongo = new MongoClient("localhost", 27017);
DB db = (DB) mongo.getDB("testDB");
DBCollection collection = db.getCollection("collection");
BasicDBObject obj = new BasicDBObject();
obj.append("$set", new BasicDBObject("my_field", dbList));
BasicDBList dbList = new BasicDBList();
dbList.add(1);
dbList.add(2);
dbList.add(3);
BulkWriteOperation bwo = collection.initializeUnorderedBulkOperation();
bwo.find(new BasicDBObject()).upsert().update(obj);
bwo.execute();
For more details you can check : http://www.journaldev.com/6324/mongodb-upsert-example-using-mongo-shell-and-java-driver

This might work
db.collection.update({},{$set : {"my_field":[1, 2, 3]}},false,true)

Complex Mongo DB query - Sub documents

I have the document structured as shown
I would like to get a collection of moduleDataItems which has version say more than 0.
This is my attempt :
Query qu = Query.query(Criteria.where("appKey")
.is("MOCK_APP").and("modules._id")
.is("APP_1_MOD_1")
.and("modules.moduleDataItems.version")
.gt(0));
List<DataItem> dList = mongoTemplate.find(qu,
DataItem.class,
ApplicationConstants.MONGO_APPLICATION_COLLECTION_NAME);
I m pretty sure I'm not doing the right thing. I do not get any DataItem in the result.
The classes represent the json structure.
Any help is appreciated.
Thanks

Finally solved it using this -
DBObject unwindParam = new BasicDBObject("$unwind","$dataItems");
DBObject matchParam = new BasicDBObject("$match",
new BasicDBObject("dataItems.version",
new BasicDBObject("$gt",requestedModule.getVersion())));
DBObject fields = new BasicDBObject("dataItems", 1);
DBObject projectParam = new BasicDBObject("$project", fields);
AggregationOutput output = mongoTemplate.getCollection(
"appModules").aggregate(
unwindParam, matchParam,projectParam);
CommandResult updatedData = output.getCommandResult();
BasicDBList resList = (BasicDBList) updatedData.get("result");

Query fields in a MongoDB Collection.

I am trying to query specific fields in a mongodb collection. Here is my code and output:
Mongo m = new Mongo();
DB db = m.getDB( "mydb" );
DBCollection coll = db.getCollection("student") ;
// adding data
BasicDBObject moz = new BasicDBObject();
moz.put("Name", "Mozammil");
coll.insert(moz);
DBCursor cursor = coll.find();
while (cursor.hasNext()) {
System.out.println(cursor.next());
}
This returns the following:
{ "_id" : { "$oid" : "4f5a4477c5e80f71ece56797"} , "Name" : "Mozammil"}
However, i want only the Name part. Googling around, this should do the job.
DBCursor cursor = coll.find({}, {'Name':1});
while (cursor.hasNext()) {
System.out.println(cursor.next());
}
But it is not working. Help please?

You can use get on the returned document by the cursor to get the field you are looking for. Like this:
System.out.println(cursor.next().get("key"));

I know you already accepted an answer, but it isn't exactly what you were asking for.
Here is some working code:
// get Mongo set up...
Mongo m = new Mongo();
DB db = m.getDB( "test" );
DBCollection coll = db.getCollection("test");
// insert a test record
coll.insert(new BasicDBObject("Name","Wes").append("x", "to have a second field"));
// create an empty query
BasicDBObject query = new BasicDBObject();
// configure fields to be returned (true/1 or false/0 will work)
// YOU MUST EXPLICITLY CONFIGURE _id TO NOT SHOW
BasicDBObject fields = new BasicDBObject("Name",true).append("_id",false);
// do a query without specifying fields (and print results)
DBCursor curs = coll.find(query);
while(curs.hasNext()) {
DBObject o = curs.next();
System.out.println(o.toString());
}
// do a query specifying the fields (and print results)
curs = coll.find(query, fields);
while(curs.hasNext()) {
DBObject o = curs.next();
System.out.println(o.toString());
}
The first query outputs:
{ "_id" : { "$oid" : "4f5a6c1603647d34f921f967"} , "Name" : "Wes" , "x" : "to have a second field"}
And the second query outputs:
{ "Name" : "Wes"}

Take a look at DBCollection.find
BasicDBObject query = new BasicDBObject(); // because you have no conditions
BasicDBObject fields = new BasicDBObject("Name",1);
coll.find(query, fields);

collection.find().projection(Projections.include("Name"))
this worked such well!!!

BasicDBObject query = new BasicDBObject();
BasicDBObject fields = new BasicDBObject();
fields.put("name", 1);
DBCursor cursor = collection.find(query, fields);
while (cursor.hasNext()) {
System.out.println(cursor.next());
}

To get all nested keys:
public static ArrayList<String> getKeys(Document it1) throws JSONException {
ArrayList<String> result = new ArrayList<String>();
ArrayList<String> resultTemp;
String temp;
Document doc;
JSONArray jsa;
int len, i;
System.out.println(it1);
String js = it1.toJson();
JSONObject js1 = new JSONObject(js);
Iterator<String> keys = js1.keys();
while (keys.hasNext()) {
String key = keys.next();
if (key.equals("_id")) {
result.add(key);
continue;
}
System.out.println(key);
temp = js1.get(key).toString();
if (temp.contains(":")) {
jsa = new JSONArray(temp);
len = jsa.length();
for (i = 0; i < len; i++) {
JSONObject object = jsa.getJSONObject(i);
doc = Document.parse(object.toString());
System.out.println(doc);
resultTemp = getKeys(doc);
for (String keyTemp : resultTemp) {
if (!result.contains(key + "." + keyTemp))
result.add(key + "." + keyTemp);
}
}
} else {
result.add(key);
}
}
return result;
}

db.getCollection('users').aggregate([
{"$project":{"arrayofkeyvalue":{"$objectToArray":"$$ROOT"}}},
{"$unwind":"$arrayofkeyvalue"},
{"$group":{"_id":null,"columns":{"$addToSet":"$arrayofkeyvalue.k"}}}
])
Use the above query it will give you all the fields of a document. In this you will get nested field also.