What this book covers

Chapter 1, Getting Started with Reactive Streams, explains the Reactive Streams API and introduces the reactive paradigm and its benefits. The chapter also introduces Reactor as an implementation of Reactive Streams.

Chapter 2, The Publisher and Subscriber APIs in a Reactor, explains the Producer and Subscriber APIs and the corresponding Flux and Mono implications of Reactor. It also discusses use cases of Flux and Mono and the respective Sinks. We will also look into Hot and Cold variants of the components.

Chapter 3, Data and Stream Processing, tackles how we can process data generated by a Publisher before it gets consumed by a Subscriber, the possible operations available, and combining them to build a robust stream-processing pipeline. Stream processing also involves converting, pivoting, and aggregating data, and then generating new data.

Chapter 4, Processors, introduces the out-of-the-box processors available in Reactor. Processors are special Publishers, which are also Subscribers, and it is quite important to understand why we need them before jumping into putting one into practice. 

Chapter 5, SpringWebFlux for Microservices, introduces SpringWebFlux, a Reactor web extension. It explains the concepts of the RouterFunction, HandlerFunction, and FilterFunction. We will then build a REST-based microservice using Mongo as a store.

Chapter 6, Dynamic Rendering, integrates a templating engine into the REST-based microservice we introduced in the previous chapter, to render dynamic content. It also demonstrates request filters.

Chapter 7, Flow Control and Backpressure, discusses flow control, an important aspect of reactive programming, which is essentially required to control overruns by a fast Publisher. It also discusses various ways to control the complete pipeline processing.

Chapter 8, Handling Errors, as its title suggests, explains how to handle errors. All Java developers are accustomed to the try-catch-finally block of error handling. This chapter translates it for stream processing. It also covers how we can recover from an error and how can we go about generating errors. This is an essential requirement for all enterprise applications.

Chapter 9, Execution Control, looks at the various strategies available in Reactor for processing the built stream. It could be scheduled at some interval or batched in groups, or all operations can be performed in parallel. 

Chapter 10, Testing and Debugging, lists ways we can test a stream, because no development is complete without being tested. We will build JUnit tests that will use some of the testing utilities offered by Reactor to create robust tests. The chapter also lists ways to go about debugging asynchronous flows built over Reactor.