package com.example.demo.controller;
import com.example.demo.model.User;
import com.example.demo.service.UserService;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
import javax.validation.Valid;
import java.util.List;
@RestController
@RequestMapping("/api/users")
public class UserController {
private final UserService userService;
public UserController(UserService userService) {
this.userService = userService;
}
@GetMapping
public ResponseEntity<List<User>> getAllUsers() {
return ResponseEntity.ok(userService.findAll());
}
@GetMapping("/{id}")
public ResponseEntity<User> getUserById(@PathVariable Long id) {
return userService.findById(id)
.map(ResponseEntity::ok)
.orElse(ResponseEntity.notFound().build());
}
@PostMapping
public ResponseEntity<User> createUser(@Valid @RequestBody User user) {
User created = userService.save(user);
return ResponseEntity.status(HttpStatus.CREATED).body(created);
}
@PutMapping("/{id}")
public ResponseEntity<User> updateUser(
@PathVariable Long id,
@Valid @RequestBody User user
) {
return userService.findById(id)
.map(existing -> {
user.setId(id);
User updated = userService.save(user);
return ResponseEntity.ok(updated);
})
.orElse(ResponseEntity.notFound().build());
}
@DeleteMapping("/{id}")
public ResponseEntity<Void> deleteUser(@PathVariable Long id) {
if (userService.existsById(id)) {
userService.deleteById(id);
return ResponseEntity.noContent().build();
}
return ResponseEntity.notFound().build();
}
@GetMapping("/search")
public ResponseEntity<List<User>> searchUsers(@RequestParam String query) {
return ResponseEntity.ok(userService.search(query));
}
}
package com.example.demo.model;
import javax.persistence.*;
import javax.validation.constraints.Email;
import javax.validation.constraints.NotBlank;
import javax.validation.constraints.Size;
import java.time.LocalDateTime;
@Entity
@Table(name = "users")
public class User {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
@NotBlank(message = "Name is required")
@Size(min = 2, max = 100)
@Column(nullable = false)
private String name;
@NotBlank(message = "Email is required")
@Email(message = "Invalid email format")
@Column(unique = true, nullable = false)
private String email;
@Column(name = "created_at", nullable = false, updatable = false)
private LocalDateTime createdAt;
@Column(name = "updated_at")
private LocalDateTime updatedAt;
@PrePersist
protected void onCreate() {
createdAt = LocalDateTime.now();
updatedAt = LocalDateTime.now();
}
@PreUpdate
protected void onUpdate() {
updatedAt = LocalDateTime.now();
}
// Getters and setters
public Long getId() { return id; }
public void setId(Long id) { this.id = id; }
public String getName() { return name; }
public void setName(String name) { this.name = name; }
public String getEmail() { return email; }
public void setEmail(String email) { this.email = email; }
public LocalDateTime getCreatedAt() { return createdAt; }
public LocalDateTime getUpdatedAt() { return updatedAt; }
}
package com.example.demo.service;
import com.example.demo.model.User;
import com.example.demo.repository.UserRepository;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import java.util.List;
import java.util.Optional;
@Service
@Transactional
public class UserService {
private final UserRepository userRepository;
public UserService(UserRepository userRepository) {
this.userRepository = userRepository;
}
public List<User> findAll() {
return userRepository.findAll();
}
public Optional<User> findById(Long id) {
return userRepository.findById(id);
}
public User save(User user) {
return userRepository.save(user);
}
public void deleteById(Long id) {
userRepository.deleteById(id);
}
public boolean existsById(Long id) {
return userRepository.existsById(id);
}
public List<User> search(String query) {
return userRepository.findByNameContainingIgnoreCase(query);
}
}
Spring Boot simplifies building production-ready REST APIs with minimal configuration. I use @RestController to create RESTful endpoints and @RequestMapping to define routes. The @GetMapping, @PostMapping, @PutMapping, and @DeleteMapping annotations handle HTTP methods. @PathVariable extracts URL parameters, while @RequestBody deserializes JSON to Java objects. @Valid enables bean validation. Spring's dependency injection with @Autowired or constructor injection manages dependencies. Exception handling uses @ControllerAdvice and @ExceptionHandler for consistent error responses. ResponseEntity controls HTTP status codes and headers. Spring Boot's auto-configuration eliminates boilerplate, letting me focus on business logic. The embedded Tomcat server runs apps standalone without external deployment.
