I've looked for possible causes of this issue and for me it looks like the only way for getDefHostName() to return empty JID (BareJID with empty domain part) is caused by settings -Dtigase-primary-address to an empty value (adding -Dtigase-primary-address= to Tigase options in tigase.conf.

This is caused by the fact that InetAddress::getByName(tigasePrimaryHost) is NOT throwing an exception if tigasePrimaryHost is set to an empty string, causing Tigase to accept this empty string as default hostname.

Additionally, BareJID accepts domain of BareJID to be an empty string. In my opinion, this should not be allowed and we should:

• throw TigaseStringprepException for methods bareJIDInstance()
• return null for methods bareJIDInstanceNS (or throw NPE)

I think that we should also check if tigase-secondary-address does not have similar issues.

Andrzej Wójcik wrote:

I've looked for possible causes of this issue and for me it looks like the only way for getDefHostName() to return empty JID (BareJID with empty domain part) is caused by settings -Dtigase-primary-address to an empty value (adding -Dtigase-primary-address= to Tigase options in tigase.conf.

This is caused by the fact that InetAddress::getByName(tigasePrimaryHost) is NOT throwing an exception if tigasePrimaryHost is set to an empty string, causing Tigase to accept this empty string as default hostname.

Thank you for pointing this out - I fixed both places in stable and master.

Additionally, BareJID accepts domain of BareJID to be an empty string. In my opinion, this should not be allowed and we should:

• throw TigaseStringprepException for methods bareJIDInstance()
• return null for methods bareJIDInstanceNS (or throw NPE)

You are correct according to 2.2. Domainpart:

it is the primary identifier and is the only **REQUIRED** element of a JID (a mere domainpart is a valid JID)

I added checks in JIDInstance methods and accompanying tests.