Shulou(Shulou.com)06/01 Report--

Explain the basic operation of database and examples in detail

Don't talk too much nonsense, go directly to the code, the comments are relatively clear, please refer to it.

Sample code:

/ * insert a DB object * / public static void addDBObject (DBCollection collection,BasicDBObject object) {collection.insert (object);} / * query DBObject * / public static DBObject getDBObjectById (String value) throws UnknownHostException according to id, MongoException {dbc = getDBCollection ("company", "users"). Find (new BasicDBObject ("_ id", new ObjectId (value)); DBObject ob = null; int i = 0; while (dbc.hasNext ()) {ob = dbc.next () IDefinder;} if (I = = 1) {return ob;} else {return null;}} / * query * / public static DBObject getDBObject (String key,String value) throws UnknownHostException based on key and value values, MongoException {dbc = getDBCollection ("company", "users") .find (new BasicDBObject (key,value)); DBObject ob = null; int i = 0; while (dbc.hasNext ()) {ob = dbc.next (); iSum + } if (I = = 1) {return ob;} else {return null;}} / * get (add) all the following aggregate names (table names) * / public static Set getCollectionsNames (String DBName) throws MongoException, UnknownHostException {return getDB (DBName). GetCollectionNames () } / * traverse the collection of db objects in the aggregation (equivalent to data in a relational database) * / public static Set getDBObjects (DBCollection collection) {Set dbObjects = new HashSet (); DBCursor cursor = collection.find (); while (cursor.hasNext ()) {DBObject object = cursor.next (); dbObjects.add (object);} return dbObjects } / * get / add aggregations (equivalent to relational database tables) * / public static DBCollection getDBCollection (String DBName,String collectionName) throws UnknownHostException, MongoException {return getDB (DBName) .getCollection (collectionName);} / * acquire / add databases * / public static DB getDB (String DBName) throws UnknownHostException, MongoException {return getMongo (). GetDB (DBName) } / * Connect database * / public static Mongo getMongo () throws UnknownHostException, MongoException {Mongo mg = null; if (mg = = null) {mg = new Mongo ();} return mg;} / * close connection * / public static void destory (Mongo mg) {if (mg! = null) {mg.close (); mg = null;} System.gc () } / * get database name * / public static List getDBNames () throws MongoException, UnknownHostException {return getMongo (). GetDatabaseNames ();} / * Delete database * / public static void deleteDB (String DBName) throws MongoException, UnknownHostException {getMongo (). DropDatabase (DBName);}

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