# Run JBoss CLI-Client
$ java -jar wildfly/bin/client/jboss-cli-client.jar
You are disconnected at the moment. Type 'connect' to connect to the server or 'help' for the list of supported commands.

# Connect to WildFly Server
[disconnected /] connect localhost:9990
Warning! The CLI is running in a non-modular environment and cannot load commands from management extensions.

# Switch to JMS Dead-Letter-Queue (DLQ)
[standalone@localhost:9990 /] cd subsystem=messaging-activemq/server=default/jms-queue=DLQ

# Show all Messages in DLQ
[standalone@localhost:9990 jms-queue=DLQ] :list-messages
{
    "outcome" => "success",
    "result" => [
        {
            "JMSPriority" => 4,
            "JMSType" => "notification",
            "JMSMessageID" => "ID:196e2ba8-e4b6-11e6-b830-cf0c2e98a816",
            "address" => "jms.queue.DLQ",
            "JMSExpiration" => 0,
            "__AMQ_CID" => "adc19a1a-e3c4-11e6-b830-cf0c2e98a816",
            "_AMQ_ORIG_QUEUE" => "jms.queue.ApplicationInQueue",
            "JMSTimestamp" => 1485538144321L,
            "messageID" => 129422,
            "JMSDeliveryMode" => "PERSISTENT",
            "_AMQ_ORIG_MESSAGE_ID" => 129009,
            "_AMQ_ORIG_ADDRESS" => "jms.queue.ApplicationInQueue"
        }
    ]
}

# Remove all Messages from DLQ
[standalone@localhost:9990 jms-queue=DLQ] :remove-messages
{
    "outcome" => "success",
    "result" => 9
}
[standalone@localhost:9990 jms-queue=DLQ]