Streaming JSON (or any other content) with JAX-RS 2.0 is really easy to implement with the helper interface StreamingOutput:
I was asked the question "How to stream content with JAX-RS 2.0?" during the recent Warsaw JUG (wjug at twitter) meeting: Unorthodox Enterprise Practices. We were over time and the JUG leader repeatedly reminded me about this fact, so I rejected to answer this question. Now, as usual, or questions remain answered :-)
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Classic Java EE 7 Workshops: Bootstrap, Effective and Architectures, July, 13th-15th
Online workshop: Java EE 7 Bootstrap