How to display mongoDB array using java

Question

I want to fetch array elements from mongoDB and display it, here is my sample code.

String[] previliges = new String[20];
String g_name = (String)jComboBox2.getSelectedItem();
DBCursor f;
BasicDBObject query = new BasicDBObject("group_name", g_name);

connection.MongoConnection con = new MongoConnection();
con.createConnection();
con.selectDB("test", "user_group");

f = con.coll.find(query);
previliges = (String[])f.next().get("privileges");
System.out.println(previliges.length);

it is giving me an exception that -> com.mongodb.BasicDBList cannot be cast to [Ljava.lang.String;

my sample document from mongodb collection:

{    
    "_id" : ObjectId("51c7ebd9e4b096449a530024"),  
    "group_name" : "assss",  
    "privileges" : [  
        "View Log History",  
        "Communication"  
    ]  
}

See stackoverflow.com/questions/8957900/reading-an-array-in-mongodb — Shreyos Adikari
– Shreyos Adikari, Commented Jun 26, 2013 at 12:45

Trisha · Accepted Answer · 2013-07-01 14:21:45Z

1

The array of privileges will come back as a BasicDBList, not an array of Strings. So you can't cast it to a String[].

Instead of doing:

previliges=(String[]) f.next().get("privileges");
System.out.println(previliges.length);

Try:

BasicDBList privileges = (BasicDBList) f.next().get("privileges");
System.out.println(privileges.size());

You can iterate over this like you would over any List:

for (Object privilege : privileges) {
    String privilegeAsString = (String) privilege;
}

answered Jul 1, 2013 at 14:21

Trisha

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