Spring Samples

This is a sample project that demonstrates a couple of useful Spring maneuvers for reference purposes. It has all the trappings of an actual application that does actual work (namely, an API for creating and querying events) to make it easier to reason about how these techniques can be used.

Building the project

You'll need Java 8 installed.

Clone the project, and in the project directory run:

$ ./gradlew clean test

When working in an IDE, you'll need to have annotation processing enabled, and you'll probably need a Lombok plugin.

Points of interest

Multi-project Gradle build

The project consists of a core module containing high-level use cases, an api module containing a deployable Spring Boot app that provides the delivery mechanism, and a sql-backed-persistence module containing a database plugin. The gradle buildscripts define the dependencies between the modules.

In particular, the sql-backed-persistence module has a test dependency on the core module's test source set, because it needs access to an abstract repository test to extend for the implementation it provides. See the build.gradle file in the sql-backed-persistence module to see how that dependency is defined.

@Bean and @Import for building a Spring context without wide package scanning

The core module has no Spring dependency, so the use case classes are not annotated with @Component. Instead, the api module calls out the components it wants. See the Application class in the api module.

"Microcosm" Spring context for tests requiring Spring magic

Sometimes you have a test that needs to stand up a Spring context to make use of some Spring magic. However, this might be a unit test that doesn't need (and perhaps shouldn't know about) the whole application's context.

In this project, we have a SqlBackedEventRepositoryTest which needs Spring to implement a JPA repository. See that test for a way to create a tiny, test-specific Spring context.

Interface for configuration values

Spring has all kinds of mechanisms for accessing configuration values from the environment. Unfortunately, it can get unwieldy keeping track of what they all are, making sure you haven't missed any, and remembering the right techniques to make them available for a test.

Having a dedicated interface that defines what values the application expects to find in the environment can help with this. See the ConfigValues interface in the api module, and how test configuration is provided in the LocalFeatureTest.

Abstract feature tests

If you're careful, you can design the feature tests for a web application to run equally well against an app instance running locally as part of the test, as well as a deployed instance in an actual environment (like acceptance). This lets you run your test suite against the application after each deployment to ensure it's working well.

See the FeatureTest abstract class in the api module, along with the LocalFeatureTest and AcceptanceFeatureTest implementations.