This paper presents J-NVM, a framework to access efficiently Non-Volatile Main Memory (NVMM) in Java. J-NVM offers a fully-fledged interface to persist plain Java objects using failure-atomic blocks. This interface relies internally on proxy objects that intermediate direct off-heap access to NVMM. The framework also provides a library of highly-optimized persistent data types that resist reboots and power failures. We evaluate J-NVM by implementing a persistent backend for the Infinispan data store. Our experimental results, obtained with a TPC-B like benchmark and YCSB, show that J-NVM is consistently faster than other approaches at accessing NVMM in Java.