Java MongoDB : Update document

In Java MongoDB API, you can use collection.update() to update an existing document. Here is some common use cases :

Note
Before proceed on this tutorial, you should understand how-to-do, update in mongoDB, list of supported update modifiers, and the Java DBCollection update() method.

1. Test Data

Assume following data / documents are saved into a collection.

{
	"hosting" : "hostA",
	"type" : "vps",
	"clients" : 1000
},
{
	"hosting" : "hostB",
	"type" : "dedicated server",
	"clients" : 100
},
{
	"hosting" : "hostC",
	"type" : "vps",
	"clients" : 900
}

{ "_id" : { "$oid" : "x"} , "hosting" : "hostA" , "type" : "vps" , "clients" : 1000}
{ "_id" : { "$oid" : "x"} , "hosting" : "hostB" , "type" : "dedicated server" , "clients" : 100}
{ "_id" : { "$oid" : "x"} , "hosting" : "hostC" , "type" : "vps" , "clients" : 900}

2. DBCollection.update() examples

See code snippets to update above saved document, with or without the modifiers.

Example 1

A normal way to update an existing document. Find hosting = hostB, and update it with a new document.

	BasicDBObject newDocument = new BasicDBObject();
	newDocument.put("hosting", "hostB");
	newDocument.put("type", "shared host");
	newDocument.put("clients", 111);
 
	collection.update(new BasicDBObject().append("hosting", "hostB"), newDocument);

Output

{ "_id" : { "$oid" : "x"} , "hosting" : "hostA" , "type" : "vps" , "clients" : 1000}
{ "_id" : { "$oid" : "x"} , "hosting" : "hostB" , "type" : "shared host" , "clients" : 111}
{ "_id" : { "$oid" : "x"} , "hosting" : "hostC" , "type" : "vps" , "clients" : 900}

Example 2

This example show the use of “$inc” modifier to increase a particular value. Find hosting = hostB, update the “clients” value by increasing its value from 100 to 199, (100 + 99) = 199.

	BasicDBObject newDocument = new BasicDBObject().append("$inc", 
		new BasicDBObject().append("total clients", 99));
 
	collection.update(new BasicDBObject().append("hosting", "hostB"), newDocument);

Output

{ "_id" : { "$oid" : "x"} , "hosting" : "hostA" , "type" : "vps" , "clients" : 1000}
{ "_id" : { "$oid" : "x"} , "hosting" : "hostB" , "type" : "dedicated server" , "clients" : 199}
{ "_id" : { "$oid" : "x"} , "hosting" : "hostC" , "type" : "vps" , "clients" : 900}

Example 3

This example show the use of “$set” modifier to update a particular value. Find hosting = hostA, update the “type” from “vps” to “dedicated server”.

	BasicDBObject newDocument3 = new BasicDBObject().append("$set", 
		new BasicDBObject().append("type", "dedicated server"));
 
	collection.update(new BasicDBObject().append("hosting", "hostA"), newDocument3);

Output

{ "_id" : { "$oid" : "x"} , "hosting" : "hostB" , "type" : "dedicated server" , "clients" : 100}
{ "_id" : { "$oid" : "x"} , "hosting" : "hostC" , "type" : "vps" , "clients" : 900}
{ "_id" : { "$oid" : "x"} , "hosting" : "hostA" , "clients" : 1000 , "type" : "dedicated server"}

Why need to use $set?

By default, if you update a document like this :

	BasicDBObject newDocument3 = new BasicDBObject().append("type", "dedicated server");
 
	collection.update(new BasicDBObject().append("hosting", "hostA"), newDocument3);

It will replaced the entire old document, see following result :

{"_id":{ "$oid" : "x"} , "type" : "dedicated server"}
{"_id":{ "$oid" : "x"} , "hosting" : "hostB" , "type" : "dedicated server" , "clients" : 100}
{"_id":{ "$oid" : "x"} , "hosting" : "hostC" , "type" : "vps" , "clients" : 900}

With “$set” modifier, only particular value is updated.

Example 4

This example show the use of “multi” parameter to update a set of matched documents. Find type = “vps”, update all the matched documents, “clients” value to 888.

	//find type = vps , update all matched documents , "clients" value to 888
	BasicDBObject updateQuery = new BasicDBObject().append("$set", 
		new BasicDBObject().append("clients", "888"));
 
	//both methods are doing the same thing.
	//collection.updateMulti(new BasicDBObject().append("type", "vps"), updateQuery);
	collection.update(new BasicDBObject().append("type", "vps"), updateQuery, false, true);

Output

{ "_id" : { "$oid" : "x"} , "hosting" : "hostA" , "clients" : "888" , "type" : "vps"}
{ "_id" : { "$oid" : "x"} , "hosting" : "hostB" , "type" : "dedicated server" , "clients" : 100}
{ "_id" : { "$oid" : "x"} , "hosting" : "hostC" , "clients" : "888" , "type" : "vps"}

Why need to use “multi”?

If you update a document without the “multi” parameter like this :

	BasicDBObject updateQuery = new BasicDBObject().append("$set", 
		new BasicDBObject().append("total clients", "888"));
 
        //multi default to false
	collection.update(new BasicDBObject().append("type", "vps"), updateQuery);

You will noticed that only the first matched document is updated.

{"_id":{ "$oid" : "x"} , "hosting" : "hostA" , "clients" : "888" , "type" : "vps"}
{"_id":{ "$oid" : "x"} , "hosting" : "hostB" , "type" : "dedicated server" , "clients" : 100}
{"_id":{ "$oid" : "x"} , "hosting" : "hostC" , "type" : "vps" , "clients" : 900}

To update a set of matched documents, you need to set “multi” to true.

3. Full Example

Full example by combining above code snippets.

package com.mkyong.core;
 
import java.net.UnknownHostException;
import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBCursor;
import com.mongodb.Mongo;
import com.mongodb.MongoException;
 
/**
 * Java MongoDB : Update document
 *
 */
 
public class UpdateDocumentApp {
 
	public static void printAllDocuments(DBCollection collection){
		DBCursor cursor = collection.find();
		while (cursor.hasNext()) {
			System.out.println(cursor.next());
		}
	}
 
	public static void removeAllDocuments(DBCollection collection){
		collection.remove(new BasicDBObject());
	}
 
	public static void insertDummyDocuments(DBCollection collection){
		BasicDBObject document = new BasicDBObject();
		document.put("hosting", "hostA");
		document.put("type", "vps");
		document.put("clients", 1000);
 
		BasicDBObject document2 = new BasicDBObject();
		document2.put("hosting", "hostB");
		document2.put("type", "dedicated server");
		document2.put("clients", 100);
 
		BasicDBObject document3 = new BasicDBObject();
		document3.put("hosting", "hostC");
		document3.put("type", "vps");
		document3.put("clients", 900);
 
		collection.insert(document);
		collection.insert(document2);
		collection.insert(document3);
	}
 
	public static void main(String[] args) {
 
	try {
 
		Mongo mongo = new Mongo("localhost", 27017);
		DB db = mongo.getDB("yourdb");
 
		// get a single collection
		DBCollection collection = db.getCollection("dummyColl");
 
		System.out.println("Testing 1...");
		insertDummyDocuments(collection);
		//find hosting = hostB, and update it with new document
		BasicDBObject newDocument = new BasicDBObject();
		newDocument.put("hosting", "hostB");
		newDocument.put("type", "shared host");
		newDocument.put("clients", 111);
 
		collection.update(new BasicDBObject().append("hosting", "hostB"), newDocument);
 
		printAllDocuments(collection);
		removeAllDocuments(collection);
 
		System.out.println("Testing 2...");
		insertDummyDocuments(collection);
		//find hosting = hostB and increase its "clients" value by 99
		BasicDBObject newDocument2 = new BasicDBObject().append("$inc", 
				new BasicDBObject().append("clients", 99));
 
		collection.update(new BasicDBObject().append("hosting", "hostB"), newDocument2);
 
		printAllDocuments(collection);
		removeAllDocuments(collection);
 
		System.out.println("Testing 3...");
		insertDummyDocuments(collection);
		//find hosting = hostA and update type to from "vps" to "dedicated server"
		BasicDBObject newDocument3 = new BasicDBObject().append("$set", 
				new BasicDBObject().append("type", "dedicated server"));
 
		collection.update(new BasicDBObject().append("hosting", "hostA"), newDocument3);
		printAllDocuments(collection);
		removeAllDocuments(collection);
 
		System.out.println("Testing 4...");
		insertDummyDocuments(collection);
		//find type = vps , update all matched documents , clients value to 888
		BasicDBObject updateQuery = new BasicDBObject().append("$set", 
				new BasicDBObject().append("clients", "888"));
 
		//both method are same
		//collection.updateMulti(new BasicDBObject().append("type", "vps"), updateQuery);
 
		collection.update(
                        new BasicDBObject().append("type", "vps"), updateQuery, false, true);
 
		printAllDocuments(collection);
		removeAllDocuments(collection);
 
		System.out.println("Done");
 
	} catch (UnknownHostException e) {
		e.printStackTrace();
	} catch (MongoException e) {
		e.printStackTrace();
	}
 
    }
}