With JAX-RS 2.0 client you can access whatever backend you like--it only has to speak HTTP. So you can use JAX-RS 2.0 client now from Java clients or to drive system tests:
Web Apps, SPA, PWA with vanilla Java Script (ES 6+), CSS 3 and WebStandards only. As simple as possible, but not simpler. See you at: (Progressive) Web apps, Single Page Apps and WebStandards airhacks workshops at MUC airport, Winter Edition
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