This is the first application I am creating using Spring Boot. I am recreating the backend for my Todo List project. I am focusing on learning Spring Boot and also on testing and TDD. The project will be tested using JUnit, and I am using the same MongoDB database as in the original version.
- Java
- Spring Boot
- Gradle
- MongoDB
- JUnit and Mockito
You will need to have MongoDB running locally at localhost:27017.
git clone https://github.com/sarahc-dev/todolist-java-spring-boot.gitTo run the application test server:
cd todolist-java-spring-boot
./gradlew bootRun --args='--spring.profiles.active=test'React frontend can be found here, and it is hosted on Vercel here (need to host API and MongoDB database locally).
Project set up using Spring Initializr.
I started off implementing a very simple test controller as this is the first time I am using Spring Boot to understand how it responds to GET requests. I then used hard-coded data and was enjoying seeing it working with my deployed frontend. I found implementing an API endpoint quite simple, the harder part was working out how to test it. I have been using both Postman and my tests to understand what the app is returning.
I tested and created each of the endpoints for my Todolist in the same structure so I can use the frontend I already created. Spring Boot combines the mapping and controller functionality and I have added a Service class that handles the business logic. This structure makes more sense to me, and I have found it much easier to understand unit testing the controller now I am able to mock the Service class.
Connecting the Spring Boot application to MongoDB was surprisingly simple, but I have struggled to either create a test database or embedded database to perform some integration tests. I ended up leaving this until the end. The MongoRepository built-in methods for performing CRUD operations on the database were also simple but (I think) there is no equivalence to some Mongoose methods, for example findOneAndDelete which returns the found item. In Java, you have to get the item by id as a separate request to return the deleted item. I suspect this isn't a common requirement, I am just comparing to functionality I have in the JavaScript version, but it's not necessary for the frontend to work.
I haven't implemented the test/deleteAll route as this is not necessary as I am not going to be testing on a test database and so do not need an API route to deleteAll from it.
After creating all the routes, I looked into how to handle exceptions and edge cases such as the todo title being an empty string. I have implemented an Exception class. I wanted to be able to return both server errors and client errors for edge cases, so I have two class initiations - one which uses a default value and one where it can be passed in as a parameter. Optional or default parameters for methods are not supported, so it was interesting to see how Java handles this case. But the event is kind of redundant in my implementation, so I think this could be improved.
I ended up doing the integration tests at the end. It was hard to find up-to-date information on using an embedded mongodb database (to use for tests instead of the production one) as it seems recent versions of Spring removed support for a commonly used version of this. Eventually I found this LinkedIn post which enabled me to get it working. Not without some difficulty though - it took me a while to understand the right combination of Annotations to get the application to run at all in the test. It also has some odd behaviour. I have set up @BeforeEach to reset the database before each test. This does work (in that if I mark a todo as completed for example, this is reset in the next test), however for some inexplicable reason running this editTodo functionality changes the order of the items in the embedded database for the test of the GET route. It does not do this in the real database. Also, the tests do not run in order, so I have had to force the testing of the GET route to occur first to avoid this quirk.
After thinking that I did not need to implement the api/test/deleteAll because my tests here are running on a separate embedded database, I have since realised I do need this because it is the e2e tests that utilise this. Which brings up the issue that I do not want the e2e tests to delete everything from my database (or anybody who accesses that route) - so I do need some way of also running the application in a 'test' environment. I have implemented a 'test' profile which connects to a different mongodb database. I also created another controller for this route and by adding the @Profile("test") annotation, it's access is limited to only when running the "test" profile. Confirmed that all my e2e tests in the todolist frontend are still passing.
I've really enjoyed the challenges of using Spring Boot for the first time. It's not been as daunting as anticipated and the hardest part has not been Java but the testing. I'm really happy I persevered and have a full suite of tests across my different test files (not just the Integration test as the screenshot suggests) that I can refer back to.
The original project description and planning along with the API in Express and Node.js is here.