73 lines
3.5 KiB
Markdown
73 lines
3.5 KiB
Markdown
---
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description: 'Guidelines for building Java and Springboot base applications'
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applyTo: '**/*.java'
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---
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# Java and Spring Boot Development
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## General Instructions
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- Make only high confidence suggestions when reviewing code changes.
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- Write code with good maintainability practices, including comments on why certain design decisions were made.
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- Handle edge cases and write clear exception handling.
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- For libraries or external dependencies, mention their usage and purpose in comments.
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## Java Instructions
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- **Records**: For classes primarily intended to store data (e.g., DTOs, immutable data structures), **Java Records should be used instead of traditional classes**.
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- **Pattern Matching**: Utilize pattern matching for `instanceof` and `switch` expression to simplify conditional logic and type casting.
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- **Type Inference**: Use `var` for local variable declarations to improve readability, but only when the type is explicitly clear from the right-hand side of the expression.
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- **Immutability**: Favor immutable objects. Make classes and fields `final` where possible. Use collections from `List.of()`/`Map.of()` for fixed data. Use `Stream.toList()` to create immutable lists.
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- **Streams and Lambdas**: Use the Streams API and lambda expressions for collection processing. Employ method references (e.g., `stream.map(Foo::toBar)`).
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- **Null Handling**: Avoid returning or accepting `null`. Use `Optional<T>` for possibly-absent values and `Objects` utility methods like `equals()` and `requireNonNull()`.
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## Naming Conventions
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- Follow Google's Java style guide:
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- `UpperCamelCase` for class and interface names.
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- `lowerCamelCase` for method and variable names.
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- `UPPER_SNAKE_CASE` for constants.
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- `lowercase` for package names.
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- Use nouns for classes (`UserService`) and verbs for methods (`getUserById`).
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- Avoid abbreviations and Hungarian notation.
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## Spring Boot Instructions
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### Dependency Injection
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- Use constructor injection for all required dependencies.
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- Declare dependency fields as `private final`.
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### Configuration
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- Use YAML files (`application.yml`) for externalized configuration.
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- Environment Profiles: Use Spring profiles for different environments (dev, test, prod)
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- Configuration Properties: Use @ConfigurationProperties for type-safe configuration binding
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- Secrets Management: Externalize secrets using environment variables or secret management systems
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### Code Organization
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- Package Structure: Organize by feature/domain rather than by layer
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- Separation of Concerns: Keep controllers thin, services focused, and repositories simple
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- Utility Classes: Make utility classes final with private constructors
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### Service Layer
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- Place business logic in `@Service`-annotated classes.
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- Services should be stateless and testable.
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- Inject repositories via the constructor.
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- Service method signatures should use domain IDs or DTOs, not expose repository entities directly unless necessary.
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### Logging
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- Use SLF4J for all logging (`private static final Logger logger = LoggerFactory.getLogger(MyClass.class);`).
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- Do not use concrete implementations (Logback, Log4j2) or `System.out.println()` directly.
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- Use parameterized logging: `logger.info("User {} logged in", userId);`.
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## Build and Verification
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- After adding or modifying code, verify the project continues to build successfully.
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- If the project uses Maven, run `mvn clean install`.
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- If the project uses Gradle, run `./gradlew build` (or `gradlew.bat build` on Windows).
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- Ensure all tests pass as part of the build.
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