java - Mongo Java 连接到无效的主机/端口，它真的连接了吗？

Question

我有以下代码

public class MongoService {

    private final Mongo mongo;
    private static final Logger LOGGER = LoggerFactory.getLogger(MongoService.class);

    public MongoService() throws UnknownHostException {
        mongo = new Mongo("localhot", 2707);
        DB db = mongo.getDB("contract");
        LOGGER.info(db.getCollection("Test").getName());
    }

    public Mongo getMongoInstance() {
        return mongo;
    }

    public void insert() {
        LOGGER.info("will run mongo insert now");
    }

    public void query() {
        LOGGER.info("will run query now");
    }

    public static void main(String args[]) throws UnknownHostException {
        MongoService mongoService = new MongoService();
        mongoService.insert();
        mongoService.query();

    }
}

输出

15:26:07.509 [main] INFO  c.s.s.business.persist.MongoService - Test
15:26:07.514 [main] INFO  c.s.s.business.persist.MongoService - will run mongo insert now
15:26:07.514 [main] INFO  c.s.s.business.persist.MongoService - will run query now

• 主机(应该是 localhost)和端口(应该是 27017)显然是错误的，但是当我运行这个程序时，它运行并且没有给出任何异常

• 真的连接了吗？我肯定不会，那么遇到这种情况该如何处理呢？

Answer 1

mongo.getDB("contract") 只是创建一个数据库对象并将其放入 mongo-java-driver 内部缓存中。

据我所知，只有当请求(即查找、插入等操作)发送到数据库时，才会从池中获取连接。

尝试执行 findOne 操作，并且应该发生 IOException:

java.io.IOException: couldn't connect to [/127.0.0.1:2017] bc:java.net.ConnectException: Connection refused
    at com.mongodb.DBPort._open(DBPort.java:228)
    at com.mongodb.DBPort.go(DBPort.java:112)
    at com.mongodb.DBPort.go(DBPort.java:93)
    at com.mongodb.DBPort.findOne(DBPort.java:146)
    at com.mongodb.DBPort.runCommand(DBPort.java:157)
    at com.mongodb.DBTCPConnector.fetchMaxBsonObjectSize(DBTCPConnector.java:457)
    at com.mongodb.DBTCPConnector.checkMaster(DBTCPConnector.java:444)
    at com.mongodb.DBTCPConnector.call(DBTCPConnector.java:209)
    at com.mongodb.DBApiLayer$MyCollection.__find(DBApiLayer.java:305)
    at com.mongodb.DBCollection.findOne(DBCollection.java:647)
    at com.mongodb.DBCollection.findOne(DBCollection.java:626)
    at com.mongodb.DBCollection.findOne(DBCollection.java:615)