louisthomas / SpringBootRxJava

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SpringBootRxJava

This application implements a Spring Boot micro service using Rx-Java. All the external invocations are asynchronously done using RxJava components and programatic devices. This explains you how to bridge the gap between RxJava and Spring Boot while integrating them together.

First check out the project into your local file system. Then move into the JavaRxDemo directory (cd ./JavaRxDemo) Then execute the mvn clean install command to build the project. Once it is successfully built, enter this command while being at the same directory. mvn spring-boot:run

The above command will run the micro service project after deploying it to an embedded servlet container.

Now to get the swagger UI hit this url in your address bar. http://localhost:8080/swagger-ui.html#!/ You will be shown with all the REST methods exposed by the service with their definitions.

There are three main usecases pertaining to RxJava landscape is implemented by this application.

Usecase1: Calling an external Currency Conversion API asynchronously using RxJava to get the currency rates for given set of currencies.

This application gives you currency rates for the currencies you enter compared with a sensible base currency, which is Euro in this case.

Give following as the input query parameters in swagger ui. 'USD,GBP'

You should get the following as the response. { "base": "EUR", "date": "2016-12-20", "rates": { "GBP": 0.83978, "USD": 1.0364 } }

Alternatively you can just hit the following url in your browser address bar and see the same result. http://localhost:8080/api/currencyconverter/rates?symbol=USD,GBP

Usecase 2: Calling an exterenal NoSQL database asynchronously from within a Spring Boot microservice using RxJava.

This demonstrates calling a MongoDB database using RxJava asynchronously within the SpringBoot microservice. I assume that you have a MongoDB instance up and running in your local machine on default port. For some reason if you have a different configuration in your MongoDB instance to which you are planning to connect change the following peoperties in the application.properties file located under $PROJECT_ROOT/src/main/resources directory.

spring.data.mongodb.uri=mongodb://localhost:27017 spring.data.mongodb.database=studentdb

Start the micoservice and check out the swagger uri for the service definition as mentioned above. Now to create a new Student in our system POST the following JSON payload aiming at the url http://localhost:8080/api/students

{ "age": 28, "gpa": 3.7, "name": "Will", "stream": "Science" }

You get the following response, and the status code. "SUCCESS" HTTP_SC: 200

Then to fetch a student given the name send the following GET request. http://localhost:8080/api/students?name=Christina

You may get the response as below. { "name": "Christina", "age": 28, "gpa": 3.7, "stream": "Arts", "id": "586c98eff7df1a16e849c398" }

HTTP_SC: 200

Usecase 3: Combine the emissions of multiple Observables together using RxJava Zip operator.

This demonstrates the use of a powerful and advanced RxJava operataor called Zip. The use case we are going to use to demonstrate the RxJava Zip operator is an eCommerce system such as Amazon where people are purchasing things by placing orders online and getting them delivered at their door steps.

Suppose we have a simple REST API which returns us product information associated with our order. There is another REST API which computes shipping cost and returns all the necessary shipping information associated with this order. Our micro service is going to call both these services asynchronously and merge those information and return Order details to the end user. The product API [4] returns the price of the item while the shipping API [5] returns the shipping cost associated with it. Finally we sum them up to calculate the total price of the item and return it with all the other information about this order back to the user.

The response of the Product API is given below. GET: http://demo9514811.mockable.io/products/northfacehoodie { "name": "North Face Hoodie", "unitPrice": 100, "currency": "USD", "soldBy": "Amazon" }

The response of the Shipping API looks something like this. GET: http://demo9514811.mockable.io/shipping/northfacehoodie { "courierService": "FedEx", "cost": 20, "currency": "USD", "address": "8716, Vineyard Way #723 Germantown, TN 38138" }

When you send a get request to our Order API which we are planning to expose to the clients, you may get the following response. GET: http://localhost:8080/api/order { "itemName": "North Face Hoodie", "totalPrice": 120, "unitPrice": 100, "currency": "USD", "soldBy": "Amazon", "courierService": "FedEx", "shippingAddress": "8716, Vineyard Way #723 Germantown, TN 38138", "shippingCost": 20 }

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