Semi-guided Enterprise-style Spring Boot Exercise - EmployeeVerse — Build a RESTful Directory of Employees

[akash-coded]

Designed to help your students internalize:

• n-tier architecture (Controller, Service, Repository, Model)
• Use of H2 Database
• Core Java concepts (e.g., String, List, JavaBeans)
• Spring Boot basics, gradually building towards a REST API
• Clean coding conventions, layered separation, and fun elements

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🧩 Exercise Title: EmployeeVerse — Build a RESTful Directory of Employees

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🧠 Story Context:

You’ve been hired by a fictional startup called EmployeeVerse. They want an internal app to store, retrieve, and manage employee data using modern Java practices and Spring Boot + H2. Right now, they have just a basic need — create a mini CRUD backend with layered architecture and test via Postman.

But there’s a twist: You’ll discover the app's purpose one feature at a time, and implement it layer by layer.

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🗂️ Project Setup

✅ Step 1: Generate the Spring Boot Project from [start.spring.io](https://start.spring.io/)

Project Settings:

• Group: com.employeeverse

• Artifact: employeeverse

• Name: EmployeeVerse

• Java Version: 17+

• Dependencies:

  • Spring Web
  • Spring Data JPA
  • H2 Database
  • Spring Boot DevTools (Optional but useful)

Download and import the project into Eclipse or IntelliJ.

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🔧 Step 2: Setup application.properties

# Enable H2 console
spring.h2.console.enabled=true
spring.h2.console.path=/h2-console

# H2 in-memory DB config
spring.datasource.url=jdbc:h2:mem:employeeverse
spring.datasource.driver-class-name=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=

# JPA settings
spring.jpa.database-platform=org.hibernate.dialect.H2Dialect
spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true

# Optional logging
logging.level.org.hibernate.SQL=DEBUG

💡 Pro Tip: Bookmark http://localhost:8080/h2-console for DB visualization (JDBC URL: jdbc:h2:mem:employeeverse)

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🧱 Step 3: Create the Folder Structure

src/main/java/com/employeeverse
├── controller
│   └── EmployeeController.java
├── model
│   └── Employee.java
├── repository
│   └── EmployeeRepository.java
├── service
│   ├── EmployeeService.java
│   └── EmployeeServiceImpl.java
└── EmployeeVerseApplication.java

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🏗️ Step 4: Create the Employee Entity Class (Model)

package com.employeeverse.model;

import jakarta.persistence.*;

@Entity
public class Employee {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

    private String name;
    private String department;
    private String email;

    // TODO: Add field validations if required

    // TODO: Generate constructor, getters and setters
}

✍️ Fill in the missing parts yourself using IDE shortcuts. Use good naming conventions!

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🧪 Step 5: Create the Repository Interface

package com.employeeverse.repository;

import org.springframework.data.jpa.repository.JpaRepository;
import com.employeeverse.model.Employee;

public interface EmployeeRepository extends JpaRepository<Employee, Integer> {
}

❓Q: Can you think of a method to search an employee by department later? (Hint: Spring Data naming)

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🧠 Step 6: Create the Service Layer

A. Interface

package com.employeeverse.service;

import java.util.List;
import com.employeeverse.model.Employee;

public interface EmployeeService {
    Employee addEmployee(Employee emp);
    List<Employee> getAllEmployees();
    Employee getEmployeeById(int id);
    void deleteEmployeeById(int id);
}

B. Implementation

package com.employeeverse.service;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.*;

import com.employeeverse.model.Employee;
import com.employeeverse.repository.EmployeeRepository;

@Service
public class EmployeeServiceImpl implements EmployeeService {

    @Autowired
    private EmployeeRepository repo;

    @Override
    public Employee addEmployee(Employee emp) {
        // TODO: Use String methods to format name (e.g., title case)
        return repo.save(emp);
    }

    @Override
    public List<Employee> getAllEmployees() {
        return repo.findAll();
    }

    @Override
    public Employee getEmployeeById(int id) {
        return repo.findById(id).orElse(null);
    }

    @Override
    public void deleteEmployeeById(int id) {
        repo.deleteById(id);
    }
}

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🌐 Step 7: Create the Controller

package com.employeeverse.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
import java.util.*;

import com.employeeverse.model.Employee;
import com.employeeverse.service.EmployeeService;

@RestController
@RequestMapping("/api/employees")
public class EmployeeController {

    @Autowired
    private EmployeeService service;

    @PostMapping
    public Employee create(@RequestBody Employee emp) {
        return service.addEmployee(emp);
    }

    @GetMapping
    public List<Employee> getAll() {
        return service.getAllEmployees();
    }

    @GetMapping("/{id}")
    public Employee getById(@PathVariable int id) {
        return service.getEmployeeById(id);
    }

    @DeleteMapping("/{id}")
    public String delete(@PathVariable int id) {
        service.deleteEmployeeById(id);
        return "Employee deleted successfully.";
    }
}

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🎯 Step 8: Challenges and Custom Practice

🧩 Challenge 1: Use StringUtils.capitalize() or create your own method to format names properly before saving.

🔍 "john doe" → "John Doe"

🧩 Challenge 2: Add a utility class in util/ to validate email addresses using regex.

🧩 Challenge 3: Add an endpoint /api/employees/filter?department=IT (Future task)

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🧪 Step 9: Test Using Postman

Test these endpoints:

• POST /api/employees
• GET /api/employees
• GET /api/employees/{id}
• DELETE /api/employees/{id}

✅ Validate JSON body, headers, and expected status codes.

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🏁 BONUS CHALLENGES

• Create DTO to hide internal fields
• Add a timestamp for creation
• Add a toString() override for meaningful log prints
• Write equals() and hashCode() based on ID

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Here’s the architecture of the EmployeeVerse Spring Boot application in Mermaid diagram syntax:

graph TD
  subgraph Web Layer
    A[Controller Layer<br>EmployeeController]
  end

  subgraph Business Layer
    B[Service Layer<br>EmployeeService + Impl]
  end

  subgraph Persistence Layer
    C[Repository Layer<br>EmployeeRepository]
  end

  subgraph Data Layer
    D[Model<br>Employee Entity]
    E[H2 Database]
  end

  A -->|calls| B
  B -->|calls| C
  C -->|uses| D
  C -->|executes queries on| E
  B -->|returns| D
  A -->|returns JSON of| D

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📌 Legend:

• Web Layer: Exposes REST APIs
• Business Layer: Contains all business logic
• Persistence Layer: Interacts with DB using Spring Data JPA
• Data Layer: Entity mappings and the actual database

[akash-coded]

Employee_Management_API.postman_collection.json

[akash-coded]

graph TD

  %% Client
  Client["Client (Browser or Postman)"]

  %% Web Layer
  Controller["EmployeeController - @RestController"]

  %% DTOs
  RequestDTO["EmployeeRequestDTO"]
  ResponseDTO["EmployeeResponseDTO"]

  %% Exception Handling
  ExceptionHandler["GlobalExceptionHandler - @ControllerAdvice"]

  %% Service Layer
  Service["EmployeeServiceImpl - @Service"]

  %% Pagination
  Pagination["Pagination Utils / Pageable Interface"]

  %% Repository Layer
  Repository["EmployeeRepository - @Repository"]

  %% Model Layer
  Model["Employee.java - @Entity"]

  %% DB
  DB["H2 Database"]

  %% Flow
  Client -->|"HTTP Request (JSON)"| Controller
  Controller -->|"Parses to DTO"| RequestDTO
  Controller -->|"Calls Service"| Service
  Service -->|"Handles Business Logic"| Pagination
  Service --> Repository
  Repository --> Model
  Repository --> DB
  Repository -->|"Returns Entity"| Service
  Service --> ResponseDTO
  ResponseDTO --> Controller
  Controller -->|"JSON Response"| Client

  Controller --> ExceptionHandler
  ExceptionHandler -->|"Handles Errors"| Client

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[Sdey0907]

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Task - EmployeeVerse — Build a RESTful API_Spring Boot_Sayan Dey_Completed

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employeeverse_REST-API_SB.zip