updated Readme

Readme.md

@@ -1,32 +1,55 @@
 ## Java Implementation  
 
-#### 运行方式
+### 运行方式
 
 用./mvnw spring-boot:run运行
 h2 database在 localhost:8080/h2-console
 
-#### cURL测试
+docker compose file for redis,rocketmq nad nacos in the root directory.
 
-用cURL测试/api/v1/product/create
+#### Redis
-curl -X POST -H "Content-Type: application/json" --data '{"name":"product1","price":"1.0","stock":"5"}' http://localhost:8080/api/v1/product/create
+Redis acts as a caching service, increases application's ability to high traffic on the most popular products.
-返回
+<br>
-{"code":201,"name":"product1","message":"Product created"}
+It also reduces the number of database operations which can saves costs if using a pay per use database service.
+#### RocketMQ
+RocketMQ is a open source messaging service that separates message producers from message consumers.
+<br>
+Therefore reduces coupling between different services. 
+<br>
+It is similar to observer pattern but operates across different applications.
+#### Nacos
+Nacos is a registry that stores application properties and other variables that subject to change.
+<br>
+One of the use case is to act as some sort of environment variables manager.
+<br>
+It can also update those variables in real time without restarting the application.
 
-再次用cURL测试/api/v1/product/create使用相同的name
+### Test
-返回
+#### Redis
-{"code":409,"message":"Product with the same name already exists"}
+I logged in to redis-cli and checked the keys and values after creating products.
-
+<br>
-用cURL测试/api/v1/product/{id}
+Then I restart the application so that the H2 database is cleared.
-curl -X GET -H "Content-Type: application/json" http://localhost:8080/api/v1/product/product1
+However, the redis database continues to have the cached products.
-返回
+After restart the H2 database shouldn't have any products. If my GET request
-{"product":{"price":1.0,"name":"product1","stock":5},"code":200,"message":"Product retrieved"}
+got a 200 response then it means the response is from the redis cache (cache hit).
-用cURL测试/api/v1/product/{id}使用不存在的name
+#### RocketMQ
-返回
+After the product is created, a listener will print to the console the name of the product.
-{"code":404,"message":"Product not found"}
+#### Nacos
-
+When I change the value of product.service.welcome-message in the nacos web console and refresh
-#### 代码结构
+the page, the welcome message is updated without restarting the application.
-- controller: 接受请求parameters然后调用service
+### Thoughts
-- service: 调用repository，处理业务逻辑。在必要时throw exception
+The redis database setup is straightforward.
-- repository: 继承JpaRepository，和database交互存储数据
+<br>
-- product: Model class
+RocketMQ took a long time because I keep getting connection errors. 
-controller不直接调用repository,而是调用service负责业务逻辑。将来如要更改实现方式，只需更改service和repository，不用更改controller
+<br>
+I have RocketMQ set up in docker on my linux machine with ip 10.10.2.71. My application
+is on my Windows machine.
+<br>
+It turns out, although I set up the address of the nameserver correctly as 10.10.2.71:9876,
+the applications gets the address of the broker from the nameserver. Which is
+an internal ip used by docker container. There is no way for me to manually set the broker address.
+So I have to move my application to the same linux machine. It works fine afterward.
+<br>
+I ran in to compatibility issues when I tried to set up nacos. I initially
+used the version of "spring-cloud-starter-alibaba-nacos-config" in nacos documentation, 
+but it wasn't compatible with Spring Boot 3.5.4. I had to use the preview version of nacos