Code walkthrough #1, restful communication
you will need
- Java 8
- Maven 3.3
- curl (recommended)
- MongoDB (admin-UI recommended, MongoHub for Mac, MongoVUE for Windows)
our goal is to build an online shop inluding
- login service
- customer service
- article service
(based on spring-boot)
- simple html/javascript frontend
(based on angular, bootstrap)
concepts shown
- client/server with device agnostic API
- stateless services
- usage of HTTP verbs (GET, POST)
- sending parameter via body (login), path (customer, article) and query (articlelist)
- hyperlinking (token -> customer, article-page -> prev/next)
- error codes (BAD REQUEST, NOT FOUND, UNAUTHORIZED)
homework & concepts for further study
- cart service: retrieve current/open cart if available; create a new cart if no current/open cart is available; update cart; checkout/buy everything in the shopping cart (cart will be closed then); store cart contents in DB for later retrieval and to survice service restart
- frontend: show shopping cart detail; add functionality to delete items from the cart
- idempotency: realize creating/updating a cart in an idempotent way; frontend should be able to do silent retries if service is not available
- caching: add cache information to article details to avoid the frontend hitting the service/database with each request
- content negotiation: add invoice service with one endpoint delivering an overview of all closed shopping carts of the customer; deliver content as raw JSON or PDF depending on accept header in the request
- (advanced) article service: add endpoint to send images of articles to the frontend
Tooling
build services: mvn clean intall from the toplevel directory will build all the projects
send POST data to service: curl -X POST localhost:9000/loginsrv/api/v1/login -H "Content-Type: application/json" -d '{"username":"dduck", "password":"secret"}' -vvv
start services: java -jar <service>.jar --server.port=<port> [--spring.active.profiles=<profile1,profile2,...>]
Usually, the services would be running on different machines and behind proxies/loadbalancers. For this demo they are intended to run on a single machine on different ports:
login-service: port 9000, launch from the toplevel directory with java -jar login-service/target/login-service-1.0-SNAPSHOT.jar --server.port=9000 --spring.profiles.active=remote
Please note that you have to provide --spring.profiles.active=remote or --spring.profiles.active=local for the login-service so that it knows whether it will do the customer lookup directly (local) or via customer service (remote).
customer-service: port 9100, launch from the toplevel directory with java -jar customer-service/target/customer-service-1.0-SNAPSHOT.jar --server.port=9100
article-service: port 9200, launch from the toplevel directory with java -jar article-service/target/article-service-1.0-SNAPSHOT.jar --server.port=9200
Populate MongoDB
You can insert data into the database with simple endpoints in the customer- and article service. Just enter their adresses in the browser:
http://localhost:9100/customersrv/api/v1/populate or http://localhost:9300/articlesrv/api/v1/populate (please use the ports you assigned to the services at startup)
If you have (security) problems while accessing the services from the HTML/JavaScript, this is most likely due to CORS (by default your browser might not allow you other URLs than the one where the initial page was loaded from). Please check how to override this feature in your browser for running the demo.