Java Spring Boot Skill#

Build production-ready Spring Boot applications with modern best practices.

Overview#

This skill covers Spring Boot development including REST APIs, security configuration, data access, actuator monitoring, and cloud integration. Follows Spring Boot 3.x patterns with emphasis on production readiness.

When to Use This Skill#

Use when you need to:

• Create REST APIs with Spring MVC/WebFlux
• Configure Spring Security (OAuth2, JWT)
• Set up database access with Spring Data
• Enable monitoring with Actuator
• Integrate with Spring Cloud

Topics Covered#

Spring Boot Core#

• Auto-configuration and starters
• Application properties and profiles
• Bean lifecycle and configuration
• DevTools and hot reload

REST API Development#

• @RestController and @RequestMapping
• Request/response handling
• Validation with Bean Validation
• Exception handling with @ControllerAdvice

Spring Security#

• SecurityFilterChain configuration
• OAuth2 and JWT authentication
• Method security (@PreAuthorize)
• CORS and CSRF configuration

Spring Data JPA#

• Repository pattern
• Query methods and @Query
• Pagination and sorting
• Auditing and transactions

Actuator & Monitoring#

• Health checks and probes
• Metrics with Micrometer
• Custom endpoints
• Prometheus integration

Quick Reference#

java

// REST Controller
@RestController
@RequestMapping("/api/users")
@Validated
public class UserController {

    @GetMapping("/{id}")
    public ResponseEntity<User> getUser(@PathVariable Long id) {
        return userService.findById(id)
            .map(ResponseEntity::ok)
            .orElse(ResponseEntity.notFound().build());
    }

    @PostMapping
    public ResponseEntity<User> createUser(@Valid @RequestBody UserRequest request) {
        User user = userService.create(request);
        URI location = URI.create("/api/users/" + user.getId());
        return ResponseEntity.created(location).body(user);
    }
}

// Security Configuration
@Configuration
@EnableWebSecurity
public class SecurityConfig {

    @Bean
    public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
        return http
            .csrf(csrf -> csrf.disable())
            .sessionManagement(s -> s.sessionCreationPolicy(STATELESS))
            .authorizeHttpRequests(auth -> auth
                .requestMatchers("/actuator/health/**").permitAll()
                .requestMatchers("/api/public/**").permitAll()
                .anyRequest().authenticated())
            .oauth2ResourceServer(oauth2 -> oauth2.jwt(Customizer.withDefaults()))
            .build();
    }
}

// Exception Handler
@RestControllerAdvice
public class GlobalExceptionHandler {

    @ExceptionHandler(EntityNotFoundException.class)
    public ProblemDetail handleNotFound(EntityNotFoundException ex) {
        return ProblemDetail.forStatusAndDetail(NOT_FOUND, ex.getMessage());
    }
}

Configuration Templates#

yaml

# application.yml
spring:
  application:
    name: ${APP_NAME:my-service}
  profiles:
    active: ${SPRING_PROFILES_ACTIVE:local}
  jpa:
    open-in-view: false
    properties:
      hibernate:
        jdbc.batch_size: 50

management:
  endpoints:
    web:
      exposure:
        include: health,info,metrics,prometheus
  endpoint:
    health:
      probes:
        enabled: true

server:
  error:
    include-stacktrace: never

Common Patterns#

Layer Architecture#

text

Controller → Service → Repository → Database
     ↓           ↓          ↓
   DTOs      Entities    Entities

Validation Patterns#

java

public record CreateUserRequest(
    @NotBlank @Size(max = 100) String name,
    @Email @NotBlank String email,
    @NotNull @Min(18) Integer age
) {}

Troubleshooting#

Common Issues#

ProblemCauseSolutionBean not foundMissing @ComponentAdd annotation or @BeanCircular dependencyConstructor injectionUse @Lazy or refactor401 UnauthorizedSecurity configCheck permitAll pathsSlow startupHeavy auto-configExclude unused starters

Debug Properties#

properties

debug=true
logging.level.org.springframework.security=DEBUG
spring.jpa.show-sql=true

Debug Checklist#

text

□ Check /actuator/conditions
□ Verify active profiles
□ Review security filter chain
□ Check bean definitions
□ Test health endpoints

Usage#

text

Skill("java-spring-boot")

Related Skills#

• java-testing - Spring test patterns
• java-jpa-hibernate - Data access