Pass the previous one Tutorial on the use of centralized caching , We already know Redis Core functions ： As K、V High performance cache for storage .
Next, we will continue to talk about it in several chapters Redis Some other powerful uses of ！ If you're interested , You must pay attention to me ！
If you read what I wrote before About MQ Related articles of , So the publish subscribe function should not be strange . If I haven't seen , It doesn't matter , Here is a brief introduction , You can skip what you already know and go straight to the next section .
What is publish and subscribe mode ？
It plays an important role in the publish subscribe model , One is the publisher Publisher, Another subscriber Subscriber. In essence , The publish subscribe model is a producer consumer model ,Publisher Responsible for production information , and Subscriber Is responsible for consuming the messages it subscribes to . This mode is widely used in software and hardware system design . such as ： After a configuration change in the configuration center , It is delivered to subscribers who subscribe to this configuration through publish subscribe to realize automatic refresh .
It's the observer model ？
See here , Students who have studied design patterns may easily associate it with the observer pattern in design patterns , You will feel that the two concepts in publish subscribe mode and the two concepts in observer mode seem to do the same thing ？ therefore ：Publisher It's in the observer mode Subject？Subscriber It's in the observer mode Observer？
What are the important differences ？
The roles and tasks of these two modes are very similar , But there is a core difference in the implementation architecture ！
Let's understand it through the following diagram , It's clear ：
As you can see, there is a very big difference here ： Publish subscribe mode is a transition between two roles , Publishers don't interact directly with subscribers .
Think back to the producer consumer model , This intermediate transition area corresponds to a buffer . Because of this buffer , The work of publishers and subscribers can be decoupled to a greater extent . Publishers don't have to be slow by subscribers , And affect their own release tasks , It just needs to be produced quickly . And subscribers don't have to worry too much about not having time to deal with it , Because there are buffers in , You can line up a little bit （ That's what we often say “ Peak shaving and valley filling ” effect ）.
And what we know RabbitMQ、Kafka、RocketMQ The essence of these middleware is to implement the intermediate buffer in publish subscribe mode . and Redis It also provides a simple publish subscribe implementation , When we have some simple needs , It can also be used ！ If you already understand the concept , So let's move on to the next section , Let's make an example ！
The following hands-on tasks , We will be in Spring Boot Application , Realize the role of a message publisher through the interface , And then another one Service To subscribe to messages （ Print the message from the interface ）.
First step ： Create a basic Spring Boot application , If not yet Click here
The second step ：
pom.xml Add a few necessary dependencies to ：
The third step ： Create an interface , Used to send messages .
Here for simple implementation , public CHANNEL Name field , I wrote it all in the main application class .
Step four ： Continue to implement message subscription in the main class , Print the received message
Step six ： The verification results
- Start the application Spring Boot The main class
- adopt curl Or other tools to call the interface
- Observation console , You can see the print of the received message Parameters
2021-06-19 16:22:30.935 INFO 34351 --- [ioEventLoop-4-2] .c.Chapter55Application$MessageSubscribe : Receive message : hello
Okay , That's the end of today . If you're interested in this series of tutorials 《Spring Boot 2.x Basic course 》 Interested in , Sure Click through ！. If you encounter difficulties in the process of learning , It is suggested to join Spring Technology exchange group , Participate in communication and discussion , Better learning and progress ！
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