bkpawlowski / development-showcase

A simple app showing my development capabilities

Development showcase project

This showcase was meant to show implementation of sort of service that meets following requirements:

• Uses JDK 8/11
• Uses gradle or maven as build managers
• It should process data from multiple data sources
• Data sources returns numbers - type and precision is not relevant
• Data source 1: should fetch numbers from https://www.random.org via its REST API
• Data source 2: should be random features provided by Java Platform
• Data source 3: it could be either in-memory database or standalone
• Optionally data source could be different - it's developers choice
• Data(numbers) from given data sources should be aggregated(sumed up together) and returned
• Fetch/aggregation process trigger is up to developer (REST-API, scheduled task/job, etc.)
• Framework choice is up to developer
• Source code should be provided either as a zip/rar package or as a link to publicly available repository

Techstack

• Java 11 (platform)
• SpringBoot (framework)
• Jackson (json/xml serializer/deserializer)
• Hibernate (persistence api provider)
• Retrofit (http resource facade util library)
• OkHttp (http client)
• H2 (in memory database)
• Hikari-CP (jdbc datasource connection pooling library)
• Logback + SLF4J (logger and logging facade)
• Lombok (boiler plate code)
• Spock Framework (testing framework) + groovy (test source code language)
• WireMock (mocking http resources)
• Gradle (project manager)

Solution

• Aggregation process is triggered via REST-API by GET calling endpoint /number/v1/random.
• Endpoints are NOT secured for convenience
• Business logic and provider components are framework-dependency-free
• Business logic beans are created manually(without component-scan on purpose) - framework-dependency-free, it makes business logic components to be easily adapted to different frameworks
• Business logic provides an interface NumberProvider that is implemented by various providers(java_random, random_org, persistence)
• NumberProvider operates on BigDecimal number representation so it supports not only huge numbers but also numbers with huge precision
• Business logic provides an implementation of NumberProvider - SummingCompositeNumberProvider - that aggregates NumberProviders and performs add operation on returned results
• Requesting /number/v1/random resource triggers number fetch process from SummingCompositeNumberProvider; if any of the given provider fails while fetching number SERVICE_UNAVAILABLE status code is returned in response
• Unit tests are implemented
• Simple E2E test of process trigger is implemented
• Swagger docs are exposed
• Health indicators are exposed
• application.properties file is neither externalized nor profiled (profiles works out of the box actually)

Requirements

• JDK 11
• A bit of gradle knowledge

Running unit tests

gradlew test

Running integration tests

gradlew testIntegration

Building executable jar

gradlew bootJar

Running directly from gradle

gradlew bootRun

Running from previously build executable jar

it will work as long as nobody touched gradle project descriptor

java -jar build/libs/development-showcase-1.0.jar

Accessing app endpoints

These are unsecured for ease of access purpose

Random number sum

curl localhost:8200/number/v1/random

Swagger

REST API documentation

curl localhost:8200/v2/api-docs

Health

Application health indicators

curl localhost:8200/actuator/health