JPA

Task Management API

Problem Statement

You are developing a simple Task Management API for a to-do list application. The API should allow users to Create, Read, Update, and Delete tasks stored in a relational database. Each task has a description and an optional priority level.

You are required to implement the backend API using Spring Boot, Spring Data JPA, and Hibernate, following RESTful principles. The application should return proper HTTP status codes and meaningful JSON error messages when something goes wrong. Incomplete code is given and task is to complete it.

Given

• Java: JDK 8

• Spring Boot: 2.0.5.RELEASE

• Hibernate: 5.2.17.Final

• Dependencies:

  • spring-boot-starter-data-jpa

  • spring-boot-starter-web

• The database schema is pre-configured and running.

• Table schema:

CREATE TABLE task (
  id BIGINT NOT NULL,
  description VARCHAR(200) NOT NULL,
  priority BIGINT,
  PRIMARY KEY (id)
);

Requirements

REST Endpoints

Create Task

• Method: POST /tasks

• Request Body:

  {
    "description": "Buy groceries",
    "priority": 2
  }

• Responses:

  • 201 Created: Task is successfully created.

  • 400 Bad Request: If the description is missing or null.

    {
      "message": "Task description is required",
      "status": 400
    }

Get Task by ID

• Method: GET /tasks/{id}

• Responses:

  • 200 OK: Returns the task object.

  • 404 Not Found: If task does not exist.

    {
      "message": "Cannot find task with given id",
      "status": 404
    }

Get All Tasks

• Method: GET /tasks

• Response:

  • 200 OK: Returns a list of all tasks.

Update Task

• Method: PUT /tasks/{id}

• Request Body:

  {
    "description": "Updated description",
    "priority": 5
  }

• Behavior:

  • Updates the task's description and priority.

• Responses:

  • 200 OK: Returns the updated task.

  • 400 Bad Request: If the description is missing or null.

    {
      "message": "Task description is required",
      "status": 400
    }

  • 404 Not Found: If task does not exist.

    {
      "message": "Cannot find task with given id",
      "status": 404
    }

Delete Task

• Method: DELETE /tasks/{id}

• Responses:

  • 204 No Content: If task is successfully deleted.

  • 404 Not Found: If task does not exist.

    {
      "message": "Cannot find task with given id",
      "status": 404
    }

Incomplete Code

The following code snippet has been provided:

package com.codility.tasks.hibernate.solution;

import org.springframework.data.jpa.repository.JpaRepository;
import java.util.logging.Logger;

class Task {
}

class TaskController {
  private static Logger log = Logger.getLogger("Solution");
  // log.info("You can use 'log' for debug messages");
}

interface TaskRepository extends JpaRepository<Task, Long> {
}

Solution

Task.java – Hibernate Entity

package com.codility.tasks.hibernate.solution;

import javax.persistence.*;

@Entity
@Table(name = "task")
class Task {

    @Id
    private Long id;

    @Column(nullable = false)
    private String description;

    private Long priority;

    // Getters and Setters
    public Long getId() { return id; }
    public void setId(Long id) { this.id = id; }

    public String getDescription() { return description; }
    public void setDescription(String description) { this.description = description; }

    public Long getPriority() { return priority; }
    public void setPriority(Long priority) { this.priority = priority; }
}

TaskRepository.java

package com.codility.tasks.hibernate.solution;

import org.springframework.data.jpa.repository.JpaRepository;

interface TaskRepository extends JpaRepository<Task, Long> {
}

TaskController.java

package com.codility.tasks.hibernate.solution;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.*;
import org.springframework.transaction.annotation.Transactional;
import org.springframework.web.bind.annotation.*;

import java.util.*;
import java.util.logging.Logger;

@RestController
@RequestMapping("/tasks")
@Transactional
class TaskController {

    private static Logger log = Logger.getLogger("Solution");

    @Autowired
    private TaskRepository taskRepository;

    @PostMapping
    public ResponseEntity<?> createTask(@RequestBody Map<String, Object> request) {
        if (!request.containsKey("description") || request.get("description") == null) {
            return ResponseEntity.badRequest().body(error("Task description is required", 400));
        }

        Task task = new Task();
        task.setId(new Random().nextLong());
        task.setDescription((String) request.get("description"));
        task.setPriority(request.get("priority") == null ? null : Long.valueOf(request.get("priority").toString()));
        taskRepository.save(task);
        return ResponseEntity.status(HttpStatus.CREATED).body(request);
    }

    @GetMapping("/{id}")
    public ResponseEntity<?> getTask(@PathVariable Long id) {
        return taskRepository.findById(id)
                .map(ResponseEntity::ok)
                .orElse(ResponseEntity.status(HttpStatus.NOT_FOUND)
                        .body(error("Cannot find task with given id", 404)));
    }

    @GetMapping
    public ResponseEntity<List<Task>> getAllTasks() {
        return ResponseEntity.ok(taskRepository.findAll());
    }

    @PutMapping("/{id}")
    public ResponseEntity<?> updateTask(@PathVariable Long id, @RequestBody Map<String, Object> request) {
        if (!request.containsKey("description") || request.get("description") == null) {
            return ResponseEntity.badRequest().body(error("Task description is required", 400));
        }

        Optional<Task> optionalTask = taskRepository.findById(id);
        if (!optionalTask.isPresent()) {
            return ResponseEntity.status(HttpStatus.NOT_FOUND).body(error("Cannot find task with given id", 404));
        }

        Task task = optionalTask.get();
        task.setDescription((String) request.get("description"));
        task.setPriority(request.get("priority") == null ? null : Long.valueOf(request.get("priority").toString()));
        taskRepository.save(task);
        return ResponseEntity.ok(request);
    }

    @DeleteMapping("/{id}")
    public ResponseEntity<?> deleteTask(@PathVariable Long id) {
        if (!taskRepository.existsById(id)) {
            return ResponseEntity.status(HttpStatus.NOT_FOUND).body(error("Cannot find task with given id", 404));
        }
        taskRepository.deleteById(id);
        return ResponseEntity.noContent().build();
    }

    private Map<String, Object> error(String message, int status) {
        Map<String, Object> error = new HashMap<>();
        error.put("message", message);
        error.put("status", status);
        return error;
    }
}