Java MongoDB : Delete document

In Java MongoDB API, you can use collection.remove() to delete document from collection. Here we show you different ways of doing it :

1. Test Data

Insert document number 1 to 10 for testing.

for (int i=1; i <= 10; i++) {
	collection.insert(new BasicDBObject().append("number", i));
}

2. DBCollection.remove()

See below code snippets to delete above saved document.

Example 1

Get first document and delete it. In this case, number = 1 is deleted.

	DBObject doc = collection.findOne(); //get first document
	collection.remove(doc);

Example 2

Puts query data in a BasicDBObject object. In this case, number = 2 is deleted.

	BasicDBObject document = new BasicDBObject();
	document.put("number", 2);
	collection.remove(document);

And Operator?

Two common mistakes :

1. Query like this only delete number = 3.

	BasicDBObject document = new BasicDBObject();
	document.put("number", 2);
        document.put("number", 3); //override above value 2
	collection.remove(document);

2. Nice try, but query like this will not work, it will delete NOTHING.

	BasicDBObject document = new BasicDBObject();
	List<Integer> list = new ArrayList<Integer>();
	list.add(7);
	list.add(8);
	document.put("number", list);
	collection.remove(document);

For “AND” query, you need to use “$in” operator as described in method 5.

Example 3

Use BasicDBObject directly. In this case, number = 3 is deleted.

	collection.remove(new BasicDBObject().append("number", 3));

Example 4

Puts a “greater than” operator in a BasicDBObject object. In this case, number = 10 is deleted.

	BasicDBObject query = new BasicDBObject();
	query.put("number", new BasicDBObject("$gt", 9));
	collection.remove(query);

Example 5

Puts a “in” operator in a BasicDBObject object, construct the query in ArrayList. In this case, number = 4 and number =5 are deleted.

	BasicDBObject query2 = new BasicDBObject();
	List<Integer> list = new ArrayList<Integer>();
	list.add(4);
	list.add(5);
	query2.put("number", new BasicDBObject("$in", list));
	collection.remove(query2);

More MongoDB Conditional Operators
For more operators, read this MongoDB supported conditional operators documentation.

Example 6

Use cursor to delete all available document. (not recommended, see example 7)

	DBCursor cursor = collection.find();
	while (cursor.hasNext()) {
		collection.remove(cursor.next());
	}

Example 7

Pass an empty BasicDBObject, and cause it delete all available document.

	collection.remove(new BasicDBObject());

3. Full Example

Full example to show the different ways to delete document with Java MongoDB API.

package com.mkyong.core;
 
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.List;
 
import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBCursor;
import com.mongodb.DBObject;
import com.mongodb.Mongo;
import com.mongodb.MongoException;
 
/**
 * Java MongoDB : Delete document
 * 
 */
 
public class App {
	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");
 
			//insert number 1 to 10 for testing
			for (int i=1; i <= 10; i++) {
				collection.insert(new BasicDBObject().append("number", i));
			}
 
			//remove number = 1
			DBObject doc = collection.findOne(); //get first document
			collection.remove(doc);
 
			//remove number = 2
			BasicDBObject document = new BasicDBObject();
			document.put("number", 2);
			collection.remove(document);
 
			//remove number = 3
			collection.remove(new BasicDBObject().append("number", 3));
 
			//remove number > 9 , means delete number = 10
			BasicDBObject query = new BasicDBObject();
			query.put("number", new BasicDBObject("$gt", 9));
			collection.remove(query);
 
			//remove number = 4 and 5
			BasicDBObject query2 = new BasicDBObject();
			List<Integer> list = new ArrayList<Integer>();
			list.add(4);
			list.add(5);
			query2.put("number", new BasicDBObject("$in", list));
			collection.remove(query2);
 
			//remove all documents
			//DBCursor cursor = collection.find();
			//while (cursor.hasNext()) {
			//	collection.remove(cursor.next());
			//}
 
			//remove all documents , no query means delete all
			//collection.remove(new BasicDBObject());
 
			//print out the document
			DBCursor cursor = collection.find();
	                while(cursor.hasNext()) {
	                     System.out.println(cursor.next());
	                }
 
	                System.out.println("Done");
 
		} catch (UnknownHostException e) {
			e.printStackTrace();
		} catch (MongoException e) {
			e.printStackTrace();
		}
 
	}
}

Output…

{ "_id" : { "$oid" : "4dc7a6989e3a66c5faeee757"} , "number" : 6}
{ "_id" : { "$oid" : "4dc7a6989e3a66c5faeee758"} , "number" : 7}
{ "_id" : { "$oid" : "4dc7a6989e3a66c5faeee759"} , "number" : 8}
{ "_id" : { "$oid" : "4dc7a6989e3a66c5faeee75a"} , "number" : 9}
Done