Responsive programming in Springboot Application (1)

一、Preliminary Knowledge

1. Functional Interface
2. Lambda expression
3. Stream API
   1. Intermediate operation
      1. filter：Used to filter elements in a stream
      2. map：One-to-one conversion
      3. flatMap：One-to-many conversion
      4. distinct、sorted、peek、limit、skip、takeWhile…
   2. Terminal operation
      1. collect：toList/toMap/groupingBy

二、Reactor Core

1、Reactive Stream

https://www.reactive-streams.org

Java’s Reactive Streams is a standardized API for asynchronously processing data streams, designed to support backpressure mechanisms to ensure that system resources are not over-consumed due to mismatches in the speeds of producers and consumers during asynchronous data processing. The main goal of Reactive Streams is to provide a compatible and unified API that allows different libraries and frameworks to work seamlessly together, especially when dealing with large-scale data streams.

For more information about the Backpressure mechanism, please visit the article: https://blog.youkuaiyun.com/Josh_scott/article/details/140398863

The Reactive Streams API is primarily composed of the following four core interfaces:

1. Publisher：A publisher, the source that produces the data stream.

   // The Publisher interface has only one method, subscribe, which is used to subscribe to the data stream.
   public interface Publisher<T> {
        
        
       void subscribe(Subscriber<? super T> s);
   }
   

2. Subscriber：A subscriber consumes the data stream at the terminal.

   public interface Subscriber<T> {
        
        
       // Called when a subscriber subscribes, passing a Subscription object.
       void onSubscribe(Subscription s);
       // Called when a new data item is produced.
       void onNext(T t);
       //  Called when an error occurs.
       void onError(Throwable t);
       // Called when the data stream ends.
       void onComplete();
   }
   

3. Subscription：A subscription manages the relationship between the publisher and the subscriber, including operations for requesting and canceling data.

   public interface Subscription {
        
        
       // Requesting the number of data items.
       void request(long n);
       // Canceling the subscription.
       void cancel();
   }
   

4. Processor<T, R>：A processor is both a publisher and a subscriber, used to process data within the data stream.

   // The Processor interface