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ksef4j
Java client for Poland's KSeF 2.0 e-invoice API, with fluent builders and Spring Boot autoconfiguration.
What it does
Java client for KSeF 2.0, Poland's National e-Invoice System, for issuing FA(3) invoices: builds and validates them from YAML templates or builders, submits with token authentication, polls for the UPO and queries metadata. Java 21+, on Maven Central, with a Spring Boot 4 starter; a KSeF token is bound to one environment and one NIP. Apache 2.0; its live smoke tests submit real invoices.
Where it fits on the map
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