一个简单的MongoDB操作类

import java.net.UnknownHostException;import java.util.Map;import java.util.concurrent.ConcurrentHashMap;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import com.mongodb.BasicDBObject;import com.mongodb.DB;import com.mongodb.DBCollection;import com.mongodb.DBCursor;import com.mongodb.DBObjec