详解MongoDB数据库基础操作及实例

/**  * 插入一条DB对象  */ public static void addDBObject(DBCollection collection,BasicDBObject object){   collection.insert(object); }  /**  * 根据id查询DBObject  */ public static DBObject getDBObjectById(String value) throws UnknownHostException, MongoException{   dbc = getDBCollection("company", "users").find(new BasicDBObject("_id",new ObjectId(value)));   DBObject ob = null;   int i = 0;   while(dbc.hasNext()){     ob = dbc.next();     i++;   }   if(i == 1){     return ob;   }else{     return null;   } }  /**  * 根据key和value值查询  */ public static DBObject getDBObject(String key,String value) throws UnknownHostException, MongoException{   dbc = getDBCollection("company", "users").find(new BasicDBObject(key,value));   DBObject ob = null;   int i = 0;   while(dbc.hasNext()){     ob = dbc.next();     i++;   }   if(i == 1){     return ob;   }else{     return null;   } }  /**  * 根据数据库名获取(新增)下面所有聚集名（表名）  */ public static Set<String> getCollectionsNames(String DBName) throws MongoException, UnknownHostException{   return getDB(DBName).getCollectionNames(); }  /**  * 遍历聚集中的db对象集合(相当于关系数据库中的数据)  */ public static Set<DBObject> getDBObjects(DBCollection collection){   Set<DBObject> dbObjects = new HashSet<DBObject>();   DBCursor cursor = collection.find();   while(cursor.hasNext()){     DBObject object = cursor.next();     dbObjects.add(object);   }   return dbObjects; }  /**  * 获取/新增聚集（相当于关系数据库表）  */ public static DBCollection getDBCollection(String DBName,String collectionName) throws UnknownHostException, MongoException{   return getDB(DBName).getCollection(collectionName); }  /**  * 获取/新增数据库  */ public static DB getDB(String DBName) throws UnknownHostException, MongoException{   return getMongo().getDB(DBName); }  /**  * 连接数据库  */ public static Mongo getMongo() throws UnknownHostException, MongoException{   Mongo mg = null;   if(mg == null){     mg = new Mongo();   }   return mg; }  /**  * 关闭连接  */ public static void destory(Mongo mg) {   if (mg != null){     mg.close();     mg = null;    }   System.gc();   }  /**  * 获取数据库名  */ public static List<String> getDBNames() throws MongoException, UnknownHostException{   return getMongo().getDatabaseNames(); }  /**  * 删除数据库  */ public static void deleteDB(String DBName) throws MongoException, UnknownHostException{   getMongo().dropDatabase(DBName); }