创建 MongoClient 实例时如何捕获异常

Question

我正在使用 Mongo DB java 驱动程序连接到 mongo 实例。下面是我用来创建 MongoClient 实例的代码。

try {
            new MongoClient("localhost", 1111);

        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

如果主机名或端口号不正确，我将得到以下异常。我想知道如何捕获这些异常。MongoDB 连接发生在内部线程中，客户端代码无法捕获。我想知道 MongoClient 是否已正确连接。我怎样才能得到这些信息？

INFO: Exception in monitor thread while connecting to server localhost:0
com.mongodb.MongoSocketOpenException: Exception opening socket
    at com.mongodb.connection.SocketStream.open(SocketStream.java:63)
    at com.mongodb.connection.InternalStreamConnection.open(InternalStreamConnection.java:115)
    at com.mongodb.connection.DefaultServerMonitor$ServerMonitorRunnable.run(DefaultServerMonitor.java:116)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.net.ConnectException: Can't assign requested address (connect failed)
    at java.net.PlainSocketImpl.socketConnect(Native Method)
    at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
    at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
    at java.net.Socket.connect(Socket.java:589)
    at com.mongodb.connection.SocketStreamHelper.initialize(SocketStreamHelper.java:50)
    at com.mongodb.connection.SocketStream.open(SocketStream.java:58)
    ... 3 more

编辑1

我的代码没有捕获上面显示的异常。它可能会被 Mongo 代码捕获。所以我不知道实例是否创建正确。

Answer 1

服务器连接是在守护线程上创建的。长话短说，您在创建 Mongo 客户端时将无法检查与连接相关的错误。

当您创建第一个涉及读取或写入的真实数据库时，您将不得不延迟连接检查。

只是为了演示目的，让您有一个想法。

MongoClient mongoClient = new MongoClient("127.0.34.1", 89);
DB db = mongoClient.getDB("test");
try {
   db.addUser("user", new char[] {'p', 'a', 's', 's'});
} catch(Exception e) { MongoTimeoutException exception}

来自守护线程的 MongoSocketOpenException

INFO: Exception in monitor thread while connecting to server 127.0.34.1:89
com.mongodb.MongoSocketOpenException: Exception opening socket
at com.mongodb.connection.SocketStream.open(SocketStream.java:63)
at com.mongodb.connection.InternalStreamConnection.open(InternalStreamConnection.java:115)
at com.mongodb.connection.DefaultServerMonitor$ServerMonitorRunnable.run(DefaultServerMonitor.java:116)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.net.ConnectException: Connection refused: connect

主线程中的 MongoTimeoutException

Exception in thread "main" com.mongodb.MongoTimeoutException: Timed out after 30000 ms while waiting for a server that matches ReadPreferenceServerSelector{readPreference=primary}. Client view of cluster state is {type=UNKNOWN, servers=[{address=127.0.34.1:89, type=UNKNOWN, state=CONNECTING, exception={com.mongodb.MongoSocketOpenException: Exception opening socket}, 
caused by {java.net.ConnectException: Connection refused: connect}}]
at com.mongodb.connection.BaseCluster.createTimeoutException(BaseCluster.java:375)

因此，将代码包装在 try catch 块中MongoTimeoutException，它可以很好地检查与连接相关的错误。