ActiveMQ 默认的 system 用户的密码是多少？

在 activemq.xml 中配置了身份验证，如下：

<plugins>
    <jaasAuthenticationPlugin configuration="activemq-domain"/>
</plugins>

当在 web 控制台上 browse Queue 时，data/activemq.log 有如下报错：

java.lang.SecurityException: User name [system] or password is invalid.
    at org.apache.activemq.security.JaasAuthenticationBroker.addConnection(JaasAuthenticationBroker.java:80)[activemq-broker-5.10.2.jar:5.10.2]
    at org.apache.activemq.broker.MutableBrokerFilter.addConnection(MutableBrokerFilter.java:102)[activemq-broker-5.10.2.jar:5.10.2]
    at org.apache.activemq.broker.TransportConnection.processAddConnection(TransportConnection.java:809)[activemq-broker-5.10.2.jar:5.10.2]
    at org.apache.activemq.command.ConnectionInfo.visit(ConnectionInfo.java:139)[activemq-client-5.10.2.jar:5.10.2]
    at org.apache.activemq.broker.TransportConnection.service(TransportConnection.java:334)[activemq-broker-5.10.2.jar:5.10.2]
    at org.apache.activemq.broker.TransportConnection$1.onCommand(TransportConnection.java:188)[activemq-broker-5.10.2.jar:5.10.2]
    at org.apache.activemq.transport.ResponseCorrelator.onCommand(ResponseCorrelator.java:116)[activemq-client-5.10.2.jar:5.10.2]
    at org.apache.activemq.transport.MutexTransport.onCommand(MutexTransport.java:50)[activemq-client-5.10.2.jar:5.10.2]
    at org.apache.activemq.transport.vm.VMTransport.iterate(VMTransport.java:248)[activemq-broker-5.10.2.jar:5.10.2]
    at org.apache.activemq.thread.DedicatedTaskRunner.runTask(DedicatedTaskRunner.java:112)[activemq-client-5.10.2.jar:5.10.2]
    at org.apache.activemq.thread.DedicatedTaskRunner$1.run(DedicatedTaskRunner.java:42)[activemq-client-5.10.2.jar:5.10.2]

该将 system 用户的密码设置为多少？

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看了下源码

是null