Legacy API – Java 17 Demo App

⚠️ This is a demo codebase with intentional legacy patterns for modernization demos.

What This App Is

A simple Spring Boot 3 REST API for managing Users and Products. It targets Java 17 and includes intentional legacy patterns that make it a realistic demo target for modernization.

Intentional Legacy Issues (Demo Points)

Issue	Location	Why It Matters
System.out.println logging	UserServiceImpl.java, ProductServiceImpl.java	Should use SLF4J / LoggerFactory
ObjectOutputStream serialization	ProductServiceImpl.java	Legacy Java serialization — use Jackson/JSON
Synchronous service methods	UserServiceImpl.java, ProductServiceImpl.java	No reactive/async patterns
Custom exception handler exposes internals	GlobalExceptionHandler.java	Raw exception messages sent to client
Hardcoded secrets in config	application.properties	Security risk — should use vault / env vars
Plain POJOs instead of records	model/	Java 17 supports record types
No input validation	Controllers, Models	No Bean Validation annotations
In-memory static storage	Services	No persistence layer

Running the App

Requires Java 17+ and Maven:

mvn spring-boot:run

Tests (8 tests, all green):

mvn test

Build fat JAR:

mvn package
java -jar target/legacy-api-1.0.0.jar