环境

操作系统：window7
mongodb：3.4
IDE：eclipse Neon.1 Release RC3 (4.6.1RC3)

连接代码

错误代码

/**
     * 拿数据库的连接
     * @param collection
     * @return
     */
    public static MongoDatabase getDateBase(String db){
        MongoDatabase database = null;
        try {
            //连接数据库 start
//          MongoCredential credential = MongoCredential.createCredential("yutao", db, "yutao".toCharArray());
            MongoCredential credential = MongoCredential.createMongoCRCredential("yutao", db, "yutao".toCharArray());
            ServerAddress serverAddress;
            serverAddress = new ServerAddress("localhost", 27017);
            List<ServerAddress> addrs = new ArrayList<ServerAddress>();
            addrs.add(serverAddress);
            List<MongoCredential> credentials = new ArrayList<MongoCredential>();
            credentials.add(credential);
//          @SuppressWarnings("resource")
            MongoClient mongoClient = new MongoClient(addrs, credentials);
            if(mongoClient != null){
                database = mongoClient.getDatabase(db);
                System.out.println("Connect to database successfully");
            }
            System.out.println("Connect to database fails");
            //连接数据库 end
        } catch (Exception e) {
            System.err.println( e.getClass().getName() + ": " + e.getMessage() );
        }
        return database;
    }

上面这种写法会报错误：

com.mongodb.MongoSecurityException: Exception authenticating
    at com.mongodb.connection.NativeAuthenticator.authenticate(NativeAuthenticator.java:48) ~[mongodb-driver-core-3.4.2.jar:na]
    at com.mongodb.connection.InternalStreamConnectionInitializer.authenticateAll(InternalStreamConnectionInitializer.java:109) ~[mongodb-driver-core-3.4.2.jar:na]
    at com.mongodb.connection.InternalStreamConnectionInitializer.initialize(InternalStreamConnectionInitializer.java:46) ~[mongodb-driver-core-3.4.2.jar:na]
    at com.mongodb.connection.InternalStreamConnection.open(InternalStreamConnection.java:116) ~[mongodb-driver-core-3.4.2.jar:na]
    at com.mongodb.connection.DefaultServerMonitor$ServerMonitorRunnable.run(DefaultServerMonitor.java:113) ~[mongodb-driver-core-3.4.2.jar:na]
    at java.lang.Thread.run(Thread.java:745) [na:1.8.0_11]
Caused by: com.mongodb.MongoCommandException: Command failed with error 18: 'auth failed' on server localhost:27017. The full response is { "ok" : 0.0, "errmsg" : "auth failed", "code" : 18, "codeName" : "AuthenticationFailed" }
    at com.mongodb.connection.CommandHelper.createCommandFailureException(CommandHelper.java:170) ~[mongodb-driver-core-3.4.2.jar:na]
    at com.mongodb.connection.CommandHelper.receiveCommandResult(CommandHelper.java:123) ~[mongodb-driver-core-3.4.2.jar:na]
    at com.mongodb.connection.CommandHelper.executeCommand(CommandHelper.java:32) ~[mongodb-driver-core-3.4.2.jar:na]
    at com.mongodb.connection.NativeAuthenticator.authenticate(NativeAuthenticator.java:46) ~[mongodb-driver-core-3.4.2.jar:na]
    ... 5 common frames omitted

原因是3.0+连接数据库写法不一样啦。
比如第一句：

MongoCredential credential = MongoCredential.createMongoCRCredential("yutao", db, "yutao".toCharArray());

改为：

MongoCredential credential = MongoCredential.createCredential("yutao", db, "yutao".toCharArray());

正确代码

    /**
     * 拿数据库的连接
     * @param db 连接数据库的名称
     * @return
     */
    public static MongoDatabase getDateBase(String db){
        MongoDatabase database = null;
        try {
            //连接数据库 start
            MongoCredential credential = MongoCredential.createCredential("yutao", db, "yutao".toCharArray());
//          MongoCredential credential = MongoCredential.createMongoCRCredential("yutao", db, "yutao".toCharArray());
            ServerAddress serverAddress;
            serverAddress = new ServerAddress("localhost", 27017);
            List<ServerAddress> addrs = new ArrayList<ServerAddress>();
            addrs.add(serverAddress);
            List<MongoCredential> credentials = new ArrayList<MongoCredential>();
            credentials.add(credential);
//          @SuppressWarnings("resource")
            MongoClient mongoClient = new MongoClient(addrs, credentials);
            database = mongoClient.getDatabase(db);
            System.out.println("Connect to database successfully");
            //连接数据库 end
        } catch (Exception e) {
            System.err.println( e.getClass().getName() + ": " + e.getMessage() );
        }
        return database;
    }

这里我一个没搞懂的疑惑：

MongoSecurityException: Exception authenticating

这个异常，我代码都用try catch包裹啦，但是还是扑捉不到。没有走catch部分，直接扔出来啦，不懂。