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Trying to update a document using MongoDB Java Driver

Thank you
I just want to thank you for clicking on this question! I've tried my best to make this as thorough as possible.
but still, feel free to let me know if you need to clarify anything further!
if you think the question is too long. you can just read the third & fourth part and post your own solution down here!
Setup
Mongodb Java driver: org.mongodb:mongo-java-driver:3.11.0-rc0
What I want to do
find a specific document with a specific "name" field.
then update the other field or the whole document.
Example Document
// the document that I am trying to find in db
{
"_id":"5de6af7cfa42833bd9849477",
"name":"Richard Koba",
"skills":[]
}
// the document that I have
{
"name":"Richard Koba",
"skills":[jump, dance, sing]
}
// final result in db
{
"_id":"5de6af7cfa42833bd9849477",
"name":"Richard Koba",
"skills":[jump, dance, sing]
}
What I am doing now
// finding a document with same "name" field as input doc and update it with doc
public MongoCollection updateDocument(Document doc, String colName) {
MongoCollection collection;
// make sure collection exist
try {
collection = connectCollection(colName); // returns MongoCollection Obj
} catch (CollectionNotFoundException e) {
MessageHandler.errorMessage(e.getMessage());
return null;
}
// trying to find the document.
if (collection.find(eq("name", doc.get("name"))).first() == null) {
// if document not found, insert a new one
collection.insertOne(doc);
} else {
// if the document found, replace/update it with the one I have
collection.replaceOne(eq("name", doc.get("name")), doc);
}
return collection;
}
What I found about my false solution
collection.find(eq("name", doc.get("name"))).first() never returns null.
Java only tells me it returns an Object. MongoDB Documentation tells me it is a TResult, which point back to MongoIterable<TResult>. I am stuck here.
the code outcome is that none of the documents is inserted/updated in the end.
Reference
https://mongodb.github.io/mongo-java-driver/3.11/javadoc/com/mongodb/client/MongoIterable.html#first()

I tried some code and this works fine. This is not much different from your code.
Created a document from mongo shell:
MongoDB Enterprise > db.users.findOne()
{
"_id" : "5de6af7cfa42833bd9849477",
"name" : "Richard Koba",
"skills" : [ ]
}
My Java Code:
// Test input documents
private Document doc1 = new Document()
.append("name", "Richard Koba")
.append("skills", Arrays.asList("jump", "dance", "sing"));
private Document doc2 = new Document()
.append("name", "Richard K")
.append("skills", Arrays.asList("sings"));
When doc1 is passed to the following method the result is: "### Doc FOUND". And, with doc2 the result is "### Doc NOT found".
private void checkDocument(Document doc) {
MongoClient mongoClient = MongoClients.create("mongodb://localhost/");
MongoDatabase database = mongoClient.getDatabase("javadb");
MongoCollection<Document> collection = database.getCollection("users");
if (collection.find(eq("name", doc.get("name"))).first() == null) {
System.out.println("### Doc NOT found");
}
else {
System.out.println("### Doc FOUND");
}
}
I also tried this, with the same results.
Document d = collection.find(eq("name", doc.get("name"))).first();
if (d == null) { // ... }
I also tried this; works fine too.
if (collection.find(queryFilter).iterator().tryNext() == null) { // ... }
I think there might be some other issue with your code or the database / collection. Some debugging and testing with new data might reveal the real issue.
Did you check if the document already exists in the collection, from mongo shell or Compass tools?
Are you using the right database and collection names?
After each test run are you verifying the data in the database if it is updated / inserted?
collection.find(eq("name", doc.get("name"))).first() never returns
null.
With the code I posted above, the find query did return null when the users collection was empty.

collection.find() return an array of documents. What you actually want here is collection.findOneAndUpdate()
After you get a TDoucment object from findOneAndUpdate, you can use a ObjectMapper e.g.jackson to map it back to a java object

Mongo automatic POJO maps object with null values \

I'm trying to get documents from MongoDB and map them to my object. Inserting works well. Retrieving collection also seems have everything in it. But I can't figure out why deserializing object doesn't work as intented. I'm new to Java and I could've simply forget about something, didn't understand documentation properly. But from what I've read it should work properly.
I have this code
[...]
CodecProvider pojoCodecProvider = PojoCodecProvider.builder().automatic(true).build();
CodecRegistry pojoCodecRegistry = fromRegistries(MongoClientSettings.getDefaultCodecRegistry(), fromProviders(pojoCodecProvider));
_mongoClient = MongoClients.create(mongoClientURI);
_mongoDataBase = _mongoClient.getDatabase(dbName).withCodecRegistry(pojoCodecRegistry);
[...]
And in a fuction another function I get the collection and cast it to an ArrayList:
MongoCollection<Document> collection = _mongoDataBase.getCollection(collectionName);
Document query = new Document();
List<StockTakingItem> stockItems = collection.find(query, StockTakingItem.class).into(new ArrayList<StockTakingItem>());
Though if I display the values then:
For MongoCollection collection I got this (so the document with proper values is there).
{ "_id" : "asdfasdfasdf", "Description" : "aaaaaaaaaaaaaaaa description ", "Note" : "nnnnnnnnnnnnnnnn Another note " }
But my StockTakingItem has null values in it (except for an id)
StockTakingItem:id: 'asdfasdfasdf', Description: 'null', Note: 'null
EDIT:
StockTakingItem class:
public class StockTakingItem {
#BsonId
String _id;
String _description;
String _note;
[getters and setters]
}
This code for inserting is working:
var collection = _mongoDataBase.getCollection(collectionName);
collection.insertOne(docToInsert);
Why are there null values and how can I do it properly so it works as intended?

Cannot find sub-field

I have this data on my mongodb database:
{
"_id" : BinData(3, "bU0bX4VEAMnW7AJ28wXcoA=="),
"online" : false,
"money" : 0,
"rank" : "USER",
"ban" : {
"end" : NumberLong("3027259780628"),
"reason" : "hello"
}
}
and I use this code to access to the ban.end sub-field saved in it:
final Document doc = collcetion.find(new Document("_id", myId)).
projection(Projections.include("ban.end"));
System.out.println(doc); // here is all ok.
// It print out the _id with the
// ban and the end values.
final long a = doc.getLong("ban.end"); // nullptr exception because
// I tryied to do this:
long a = (Long) null;
Is there any way to fix the null pointer reported above? I think I failed something with mongodb, I'm not sure in using ban.end as field name.
I already tried to get, for example, the money value and it works.

getLong returns a Long, not a long. See http://api.mongodb.org/java/current/org/bson/Document.html#getLong-java.lang.Object-.
In other words, you're getting the nullpointer because you're implicitly unboxing it. Just use
final long a = doc.getLong("ban.end");
instead, the handle the null case separately.

I'm not sure in using "ban.end" as field name.
Sadly, you are. You need to get the ban objcect first, before you could access its end attribute.
The logic remains the same for whatever versions.
code in 3.0.4 version of the java driver,
DBCursor docs = collection.find(new BasicDBObject("_id", myId),
new BasicDBObject("ban.end", 1));
while (docs.hasNext())
{
BasicDBObject banObj = (BasicDBObject) docs.next().get("ban");
long end = banObj.getLong("end");
System.out.println(end);
}

How to retrieve the value of a key(nested) in JSON which is stored in mongoDB using JAVA?

Below is the JSON file from which I want to retrieve the phone number:
"_data" : {
"Variable key" : {
"Name" : "Hello World",
"Phone" : "Phone : 123-456-6789 ",
"Region" : "New York",
"Description" : ""
}
}
My Java Code is:
BasicDBObject query = new BasicDBObject();
BasicDBObject field = new BasicDBObject();
field.put("_data.Phone", 1);
DBCursor cursor = table.find(query,field);
String str;
while (cursor.hasNext()) {
BasicDBObject obj = (BasicDBObject) cursor.next();
str=cursor.curr().get("_data.Phone").toString();
System.out.println(str);
}
which will return null as I'm not considering the variable key.
My problem is there are many JSON files present in the mongo database each having different "Variable Key" and this key may change after sometime. As this key may change over time, how can I retrieve the phone number ?
Thank You !!

Which phone numbers do you want? Your query will return all documents and you are trying to project out just the phone number, but with an incorrect projection specification. If you want all phone numbers, just leave out the projection specification entirely or project on { "_data" : 1 }. If you want the phone numbers associated with specific variable keys, project those out using dot notation like { "_data.key_name.Phone" : 1 }. If you don't know the names of the keys that you want to project on, then that is your root problem that you need to solve before you ask MongoDB to return something that you don't know that you want (or that you don't want).

Java MongoDB getting value for sub document

I am trying to get the value of a key from a sub-document and I can't seem to figure out how to use the BasicDBObject.get() function since the key is embedded two levels deep. Here is the structure of the document
File {
name: file_1
report: {
name: report_1,
group: RnD
}
}
Basically a file has multiple reports and I need to retrieve the names of all reports in a given file. I am able to do BasicDBObject.get("name") and I can get the value "file_1", but how do I do something like this BasicDBObject.get("report.name")? I tried that but it did not work.

You should first get the "report" object and then access its contents.You can see the sample code in the below.
DBCursor cur = coll.find();
for (DBObject doc : cur) {
String fileName = (String) doc.get("name");
System.out.println(fileName);
DBObject report = (BasicDBObject) doc.get("report");
String reportName = (String) report.get("name");
System.out.println(reportName);
}

I found a second way of doing it, on another post (didnt save the link otherwise I would have included that).
(BasicDBObject)(query.get("report")).getString("name")
where query = (BasicDBObject) cursor.next()

You can also use queries, as in the case of MongoTemplate and so on...
Query query = new Query(Criteria.where("report.name").is("some value"));

You can try this, this worked for me
BasicDBObject query = new BasicDBObject("report.name", "some value");