RestTestClient is used for WebMvc (servlet).

WebTestClient is used for WebFlux (Reactive).

Works with spring boot 4.0.0 RC1 as of today 07-11-2025

Switch between xml or json in application.yml file depending on the file format you want to write or read data.

@ConfigurationProperties(prefix="todo.file") Tells Spring Boot: Take all properties under todo.file in application.yml and bind them to this object For example: todo: file: path: data/todo.json format: json means: | YAML key | Java property | Value injected | | ------------------ | ------------- | ------------------ | | todo.file.path | path | "data/todo.json" | | todo.file.format | format | "json" |

WebTestClient has the following: bindToController() ---> unit test your REST endpoints bindToRouterFunction() ---> when using router-based handlers bindToApplicationContext() ---> used in integration tests (@SpringBootTest) bindToServer() ---> A real HTTP server, for end-to-end tests with actual networking Documentation page: https://docs.spring.io/spring-framework/reference/testing/webtestclient.html

Delete git branch in case of mistake:

Delete the branch locally

git branch -d branch-name

If the branch hasn't been merged, use force delete

git branch -D branch-name

Delete the branch remotely (if already pushed)

git push origin --delete branch-name

MongoDB can only autogenerate the following IDType:

String ✅ Yes Uses ObjectId

ObjectId✅ Yes Native MongoDB type

Long ❌ No You must set it manually

Integer ❌ No You must set it manually

UUID ❌ No You must set it manually

docker-compose down -v.

docker-compose up --build.

Very useful: https://medium.com/norsys-octogone/a-local-environment-for-mongodb-with-docker-compose-ba52445b93ed

Admin User(root user) vs Normal user (e.g., tjtechy) in mongodb

1. Admin (root user): This user is created by Docker when you define: MONGO_INITDB_ROOT_USERNAME: root MONGO_INITDB_ROOT_PASSWORD: rootpass It is created in the Admin Db. Has full privileges across all DBs Can create database, users, roles and run administrative commands Can authenticate with: --authenticationDatabase admin This user is not stored in the init.js script, MONGODB automatically creates it before executing the .js init script'

2. Normal User (tjetechy): It is created inside the init script. Lives in the todosdb database, NOT in admin. Has limited permissions (read/write only on todosdb) Cannot read or write other databases Cannot run admin commands such as: db.adminCommand('ping') listing all databases creating other users modifying indexes globally Can only authenticate using: mongodb://tjtechy:apppass@…/?authSource=todosdb

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USEFUL STEPS:

1. docker exec -it mongodb mongosh -u admin -p password --authenticationDatabase admin
2. use -->switched to the db
3. db.getUsers()
4. docker exec -it mongodb mongosh -u tjtechy -p apppass --authenticationDatabase todosdb todosdb --eval "db.todos.find().

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FEW TIPS ON MONGODB and Spring boot 4.0.0-rc1 bug? This is not confirmed yet. Dependencies for running integration test using test containers. Check pom.xml. To make doc looks more pretty, right click and check Render All Doc Comments.