ernyoke / completable-future

Completable Future Workshop

• delete the package 'solution'
• run the tests and make them pass
• Follow the hints you find in the source code of the exercises, for example Combining.java
• good luck

Basics

• completing with value
• completing with exception

Combining

• thenApply
• thenRun
• compose (aka flatMap)
• CF0.fork{CF1,CF2}->join{cfResult}
• anyOf and Either

Exceptions

• catch() {log}
• catch() {wrap exception in new one}
• catch() {default value}
• catch() {call another CF} / retry
• finally {cleanup}

Thread Pools

• launch on ForkJoinPool.commonPool
• launch on dedicated thread pool
• launch in parallel 2 steps
• Complete a CF after a delay
• Combine 2 CF, change what thread executes the BiFunction

Testing

• mocks returning a CF: then complete/fail
• mocks delaying response
• integration testing with WireMock

Enrich Data

(sequential, or parallel ||)

• a() || b() ==> AB(a,b)
• a(), then b1(a) ==> AB(a,b)
• a(), then b1(a) || c1(a) ==> ABC(a,b,c)
• a(), then b1(a), then c2(a,b) ==> ABC(a,b,c)
• a() || b() || c() ==> ABC(a,b,c)

Complex Real-Life Scenarios

• HTTP-Message Bridge
  • from a HTTP request send message on request MQ
  • keep the connection open
  • complete the pending HTTP request
    • with the corresponding reply message received on a reply MQ (hint: CorrelationID pattern), or
    • with a message "Order in processing" if no reply message arrives in 3 seconds
• Bidding
  • You receive a HTTP request with a List clientIDs
  • Within 5 seconds,
  • Every five seconds emit (log) a signal.
  • If a http req arrives with the next n 5 sec
• merge data: get/put async
• rate limiting over WebClient adapter
• profiling