Java Plugin for Action check

Summary:

We have a requirement of complex action check, where multiple trade transactions will be selected to create declaration and then we need to check each transactions in loop whether any specific refnum/remark is available or not at transaction level. Then only those valid transactions should be allowed to create declaration. The transaction which don’t have specific refnum/remark should not be allowed on that declaration (sample example). In normal action check, we can only write saved query, there is no option to validate in FOR loop.

Kindly advise, how to handled any such requirement in GTM. There is an option of using Java Plugin/Class for action check. Please help to advise, how we can use Java Plugin & Java Class for action check in GTM Cloud. Understood that, if we create a custom Java Plugin, then we can select that Plugin while creating an action check. But please guide, how and where to deploy the Java Class, which should be used in Java Plugin.