Virtual Host is not set when calling setUri() from ConnectionFactory when URI as a trailing slash

[ahmed-debbech]

Describe the bug

We noticed that when using setUri(String uri) method from ConnectionFactory class and the URI for example is amqp://guest:guest@localhost:5672/ (with a trailing slash) the Virtual Host is not getting set to the default value / but rather to an empty string.
Which leads to not being able to connect to RabbitMQ server.

Config:

• RabbitMQ server 4.3.1
• Erlang 27.3.4.11
• Debian 12
• Rabbitmq Java Client 5.31.0
• No RabbitMQ plugins

Reproduction steps

To reproduce this bug you can simply use the client like this

class App {
    public static void main(String[] args) {
        String s = "amqp://guest:guest@localhost:5672/";
        try {
            ConnectionFactory factory = new ConnectionFactory();
            factory.setUri(s);

            // you can uncomment the line below to check virtualhost before it crashes.
            //System.out.println(factory.getVirtualHost());

            Connection connection = factory.newConnection();
            // .... rest of code
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

When running the code we get the following stack trace:

java.io.IOException
        at com.rabbitmq.client.impl.AMQChannel.wrap(AMQChannel.java:140)
        at com.rabbitmq.client.impl.AMQChannel.wrap(AMQChannel.java:136)
        at com.rabbitmq.client.impl.AMQChannel.exnWrappingRpc(AMQChannel.java:158)
        at com.rabbitmq.client.impl.AMQConnection.start(AMQConnection.java:459)
        at com.rabbitmq.client.impl.recovery.RecoveryAwareAMQConnectionFactory.newConnection(RecoveryAwareAMQConnectionFactory.java:71)
        at com.rabbitmq.client.impl.recovery.AutorecoveringConnection.init(AutorecoveringConnection.java:165)
        at com.rabbitmq.client.ConnectionFactory.newConnection(ConnectionFactory.java:1350)
        at com.rabbitmq.client.ConnectionFactory.newConnection(ConnectionFactory.java:1299)
        at com.rabbitmq.client.ConnectionFactory.newConnection(ConnectionFactory.java:1254)
        at com.rabbitmq.client.ConnectionFactory.newConnection(ConnectionFactory.java:1629)
        at com.debbech.test.App.main(App.java:30)
Caused by: com.rabbitmq.client.ShutdownSignalException: connection error; protocol method: #method<connection.close>(reply-code=530, reply-text=NOT_ALLOWED - vhost  not found, class-id=10, method-id=40)
        at com.rabbitmq.utility.ValueOrException.getValue(ValueOrException.java:66)
        at com.rabbitmq.utility.BlockingValueOrException.uninterruptibleGetValue(BlockingValueOrException.java:36)
        at com.rabbitmq.client.impl.AMQChannel$BlockingRpcContinuation.getReply(AMQChannel.java:552)
        at com.rabbitmq.client.impl.AMQChannel.privateRpc(AMQChannel.java:316)
        at com.rabbitmq.client.impl.AMQChannel.exnWrappingRpc(AMQChannel.java:152)
        ... 8 more

And the RabbitMQ server logs show this:

2026-06-01 22:26:13.964685+00:00 [info] <0.672.0> accepting AMQP connection 172.17.0.1:42988 -> 172.17.0.2:5672
2026-06-01 22:26:13.982722+00:00 [error] <0.672.0> Error on AMQP connection <0.672.0> (172.17.0.1:42988 -> 172.17.0.2:5672, user: 'guest', state: opening):
2026-06-01 22:26:13.982722+00:00 [error] <0.672.0> vhost  not found
2026-06-01 22:26:13.983938+00:00 [info] <0.672.0> closing AMQP connection (172.17.0.1:42988 -> 172.17.0.2:5672, vhost: 'none', user: 'guest', duration: '33ms')
2026-06-01 22:26:13.984865+00:00 [info] <0.681.0> accepting AMQP connection 172.17.0.1:42994 -> 172.17.0.2:5672
2026-06-01 22:26:13.986469+00:00 [error] <0.681.0> Error on AMQP connection <0.681.0> (172.17.0.1:42994 -> 172.17.0.2:5672, user: 'guest', state: opening):
2026-06-01 22:26:13.986469+00:00 [error] <0.681.0> vhost  not found
2026-06-01 22:26:13.986839+00:00 [info] <0.681.0> closing AMQP connection (172.17.0.1:42994 -> 172.17.0.2:5672, vhost: 'none', user: 'guest', duration: '2ms')

Expected behavior

The setUri() method should be indifferent when there is a or isn't a trailing slash only as a virtual host in the URI provided and therefor it should set it to default which is /.
Note: that amqp://guest:guest@localhost:5672 is parsed just fine and any explicit names after / are set correctly as virtual host.

Additional context

No response

[lukebakken]

The current behavior does follow the AMQP URI spec, though it may not be very intuitive. As soon as you have a trailing /, the spec says a virtual host must be present.

In your case, this should be the URI string:

amqp://guest:guest@localhost:5672/%2f