java

GraphQL provides flexible APIs where clients specify exact data requirements. Spring for GraphQL integrates GraphQL Java with Spring Boot. Schema-first approach defines types in .graphqls files. Resolvers map schema fields to Java methods using @Query

Spring Boot starters provide autoconfiguration for libraries. I create custom starters to standardize configurations across microservices. Starters contain @Configuration classes with @ConditionalOnClass, @ConditionalOnProperty annotations. spring.fac

Apache Kafka provides distributed messaging for event-driven architectures. Spring Kafka simplifies producer and consumer implementations. KafkaTemplate sends messages to topics. @KafkaListener consumes messages asynchronously. I configure serializers

Spring Boot handles multipart file uploads efficiently. MultipartFile represents uploaded files. I validate file types, sizes, and content. Files are stored locally, in cloud storage (S3, Azure Blob), or databases. Streaming large files prevents memor

Flyway manages database schema evolution through versioned SQL scripts. Migration files follow naming convention—V1__initial_schema.sql, V2__add_users_table.sql. Flyway tracks applied migrations in a schema history table. Migrations run automatically

WebSocket enables full-duplex communication between client and server. Spring WebSocket supports STOMP protocol over WebSocket. I configure message brokers for pub-sub messaging. @MessageMapping handles incoming messages. SimpMessagingTemplate sends m

The Builder pattern creates complex objects step-by-step, improving readability and flexibility. I implement builders with static inner classes—fluent methods return the builder for chaining. Required fields use constructor parameters, optional fields

Global exception handling in Spring uses @ControllerAdvice to centralize error responses across all controllers. I define @ExceptionHandler methods for specific exceptions, returning consistent error DTOs with HTTP status codes. Custom exceptions exte

Spring Data JPA eliminates boilerplate DAO code with repository interfaces. I extend JpaRepository to get CRUD methods automatically—save, findById, findAll, delete. Custom query methods use method naming conventions—findByEmailAndActiveTrue generates

Elasticsearch provides powerful full-text search capabilities. Spring Data Elasticsearch offers repository abstraction similar to JPA. @Document annotates entity classes with index mapping. @Field customizes field types and analyzers. Queries use meth

CompletableFuture enables non-blocking asynchronous programming in Java. I use supplyAsync() to run tasks in thread pools and thenApply() to chain transformations. thenCompose() flattens nested futures, while thenCombine() merges independent futures.

MapStruct generates type-safe bean mappers at compile-time, eliminating manual mapping code. I define mapper interfaces with @Mapper annotation—MapStruct generates implementations. @Mapping annotations handle different property names or custom convers