Tech road one step 

1. Architecture

1. <POSA 2> chapter 1
2. <EIP> chapter
3. <SDP>

2. Message Transfer System

1. <depth in RabbitMQ> 
2. <Rabbitmq in action>
3. Gson, Jackson

3. Framework

1. Spring Ioc, AoP
2. log, exception

4.Extension

1. <Bob-ppp> chapter 19
2. <MS PPP> chapter2
3. <DDD> start
4. Java Stream, multiple compution
5. Java concurrency,
6. Java async.
7. JVM