Task Manager API

Introduction

Create a task manager backend — users, projects, tasks with status (TODO/IN_PROGRESS/DONE), due dates and assignees. A classic portfolio project that interviewers love because it maps to real sprint boards.

Informative example

Task entity and status workflow:

@Entity
public class Task {
    @Id @GeneratedValue Long id;
    String title;
    @Enumerated(STRING) TaskStatus status = TODO;
    LocalDate dueDate;
    @ManyToOne User assignee;
    @ManyToOne Project project;
}

@PatchMapping("/tasks/{id}/status")
public Task updateStatus(@PathVariable Long id, @RequestBody StatusUpdate req) {
    Task task = repo.findById(id).orElseThrow();
    task.transitionTo(req.status());  // enforce valid transitions
    return repo.save(task);
}

Best practices

• Enforce status transitions in the domain model, not the controller.
• Add filtering: GET /tasks?status=TODO&assignee=42.
• Use Testcontainers for integration tests.

Purpose of this lesson

Master Task Manager API so you can apply it confidently in production Java code, technical interviews, and code reviews.

Step-by-step explanation

1. Understand the core idea behind Task Manager API.
2. Walk through the runnable example and tweak it in the playground.
3. Apply the pattern in a small Spring Boot or CLI exercise of your own.
4. Re-read the common mistakes and interview Q&A to lock the concept in.

Interactive workflow diagram

Debugging tips

• Read the full stack trace — Java's exception messages name the offending class and line.
• Reproduce in the smallest possible main() method before fixing in the real app.
• Use IntelliJ's debugger breakpoints and 'Evaluate Expression' rather than scattering System.out.

Optimization strategies

• Profile before optimizing — JFR (Java Flight Recorder) and async-profiler reveal real hotspots.
• Prefer immutable data and stream pipelines over hand-rolled loops when readability matters.
• Reach for the right JDK collection (ArrayList vs LinkedList vs ArrayDeque) before writing custom data structures.

Enterprise example

Jira, Linear and Asana all started as task managers — yours demonstrates JPA relationships and status workflows.

Interview questions & answers

Summary

In this lesson you learned Task Manager API — the concept, syntax, a runnable example, and the production pitfalls to avoid. Apply it in the playground before moving on.