Backend Components

@Component
public class GatewayOriginFilter extends OncePerRequestFilter {
    @Override
    protected void doFilterInternal(HttpServletRequest request,
                                    HttpServletResponse response,
                                    FilterChain chain) {
        String gatewayHeader = request.getHeader("X-Gateway-Origin");
        if (isValidGatewayOrigin(gatewayHeader)) {
            chain.doFilter(request, response);
        } else {
            response.sendError(HttpStatus.FORBIDDEN.value());
        }
    }
}

api-module/
├── external/
│   ├── Interface.java      # Public API contract
│   └── DTO.java            # External data transfer
└── internal/
    ├── Interface.java      # Private API contract
    └── DTO.java            # Internal data transfer

service-module/
├── Controller.java         # REST endpoints
├── Service.java            # Business logic
├── Repository.java         # Database queries
└── Model.java              # Entity definitions

@Configuration
public class KafkaConfig {
    @Bean
    public ProducerFactory<String, Object> producerFactory() {
        Map<String, Object> props = new HashMap<>();
        props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
        props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, KafkaAvroSerializer.class);
        return new DefaultKafkaProducerFactory<>(props);
    }
}

@Configuration
public class RedisConfig {
    @Bean
    public RedisTemplate<String, Object> redisTemplate(RedisConnectionFactory factory) {
        RedisTemplate<String, Object> template = new RedisTemplate<>();
        template.setConnectionFactory(factory);
        template.setKeySerializer(new StringRedisSerializer());
        template.setValueSerializer(new GenericJackson2JsonRedisSerializer());
        return template;
    }
}