Spring Boot Advanced Topics

Inter-service Communication in Microservice Architecture

• Direct Communication: Use RestTemplate for simple request/response interactions.
• Complex Interactions: Use FeignClient for cleaner and efficient code.
• Asynchronous Communication: Use message brokers like RabbitMQ or Kafka.

Caching Mechanism in Spring Boot

• Purpose: Stores frequently-used data to improve performance.
• Spring Cache Abstraction: A memory layer to save results of expensive operations.

Implementing Caching in Spring Boot

• Add Dependencies: Include spring-boot-starter-cache.
• Enable Caching: Add @EnableCaching annotation to the main class.
• Define Cachable Operations: Use @Cacheable on methods.
• Customize Cache Behavior: Use annotations like @CacheEvict and @CachePut.
• Choose Cache Provider: Options include Ehcache, Hazelcast, or a default concurrent map-based cache.

Handling Performance Issues Under High Load

• Identify Issues: Use monitoring tools like Spring Boot Actuator or Splunk.
• Analyze Logs and Metrics: Spot patterns and errors.
• Performance Testing: Replicate issues with tests and use profilers.
• Optimize: Database optimization, caching, scaling options.

Versioning REST APIs in Spring Boot

• URL Versioning: Include version number in the URL (e.g., /api/v1/products).
• Header Versioning: Use custom headers to specify version.
• Media Type Versioning: Use Accept header for content negotiation.
• Parameter Versioning: Specify version as a request parameter.

Simplifying Data Access Layer

• Auto-configuration: Automatic setup based on classpath dependencies.
• Repository Support: Use built-in repositories (like JpaRepository).
• Database Initialization: Auto-initialize schemas and seed data.
• Exception Handling: Translate SQL exceptions into Spring data exceptions.

Conditional Annotations in Spring Boot

• Purpose: Create beans or configurations only if certain conditions are met.
• Example: @ConditionalOnClass to create a bean if a specific class is present.

EnableAutoConfiguration in Spring Boot

• Role: Automatically sets up the application based on dependencies.
• Internal Mechanism: Uses conditional evaluation to determine configurations.

Spring Boot Actuator Endpoints

• Purpose: For monitoring and managing applications.
• Use Cases: Health checks, metrics, view configurations.
• Security Concerns: Protect sensitive information.

Securing Actuator Endpoints

• Limit Exposure: Control which endpoints are accessible over the web.
• Use Spring Security: Require authentication for access.
• Encrypt Communication: Use HTTPS instead of HTTP.
• Actuator Role: Create a specific role for accessing endpoints.

Optimizing Performance in Spring Boot Applications

• Caching: For frequently accessed data.
• Optimize Database Queries: Reduce load on the database.
• Asynchronous Methods: For non-critical operations.
• Load Balancer: Distribute high traffic.

Handling Multiple Beans of the Same Type

• Qualifier Annotation: Specify which bean to inject.
• Primary Annotation: Mark a default choice bean.

Managing Transactions

• Transactional Annotation: Used to handle methods as single transactions.
• Service Layer: Best to manage transactions at this level.

Testing Approaches in Spring Boot

• Unit Testing: Testing small pieces of code in isolation.
• Integration Testing: Testing how components interact together.

SpringBootTest and MockBean Annotations

• SpringBootTest: Used for integration testing, loads the full application context.
• MockBean: Create mock versions of components for isolated testing.

YAML vs Properties File

• Advantages: YAML supports hierarchical configuration, allows comments.
• Limitations: YAML is sensitive to spaces and indentations, less familiar to some developers.

Spring Boot Profiles

• Purpose: Different settings for different environments.
• Flexibility: Keeps application maintainable without code changes.

Aspect-Oriented Programming (AOP)

• Purpose: Separates cross-cutting concerns (e.g., logging, security).
• Implementation: Define aspects and apply them across the application.

Spring Cloud and Microservices

• Purpose: Simplifies microservices management.
• Features: Service discovery, load balancing, secure secrets.

Server Selection in Spring Boot

• Decision Basis: Classpath dependencies.
• Default: Uses Tomcat if no other server dependencies are found.

Listing Beans in Spring Boot

• Method: Autowire ApplicationContext and use getBeanDefinitionNames method.

Improving Performance in a Spring Boot Project

• Optimizations: Database connection pooling, enabling HTTP response compression, using Actuator, asynchronous processing.

Embedded Servlet Containers

• Function: Embedded web server like Tomcat or Jetty.
• Advantage: Simplifies development and deployment.

Dependency Injection (DI) in Spring Boot

• Ease: Auto-configuration reduces need for XML or annotations setup.
• Focus: Application context and classpath dependencies determine configurations.

Managing Application Secrets

• Externalized Configuration: Keep configurations separate from code.
• Secure Storage: Use tools like Spring Cloud Config Server or HashiCorp Vault.

Handling Asynchronous Operations

• Annotation: Use @Async for asynchronous method execution.
• Enabling Async: Add @EnableAsync to configuration classes.

Securing Sensitive Data

• Authentication: Ensure users prove their identity.
• Authorization: Control access based on roles.
• Data Encryption: Secure data in storage and transit.
• Audit Trail: Keep track of access and changes.

Handling File Upload in Spring Boot

• Endpoint: Use @PostMapping.
• Method Handling: Accept MultipartFile as a parameter in the controller.

Authentication vs Authorization

• Authentication: Verifying identity (e.g., login).
• Authorization: Checking access rights after identity verification.

Sending Emails in Spring Boot

• Dependencies: Include spring-boot-starter-mail.
• Configuration: Set up mail server details in properties file.
• Service Class: Use JavaMailSender to send emails.

Spring Boot CLI

• Purpose: Tool for running Spring Boot applications easily.
• Execution: Install CLI, write application code in Groovy, run with spring [filename].groovy.

Implementing Spring Security

• Dependencies: Add spring-boot-starter-security.
• Configuration Class: Extend WebSecurityConfigurerAdapter.
• User Details Service: Load user information securely.
• Secure Endpoints: Use annotations like @PreAuthorize.

Disabling Auto Configuration

• Exclude Attribute: Use @SpringBootApplication(exclude = { DataSourceAutoConfiguration.class }).

Cache Eviction vs Cache Expiration

• Eviction: Removing data based on a policy like least recently used.
• Expiration: Removing data based on a time-to-live setting.

Scaling Spring Boot Applications

• Horizontal Scaling: Add more application instances.
• Microservices: Break up the application for independent scaling.
• Cloud Services: Automatically adjust resources.
• Caching: Store frequently accessed data.

Security in a Microservices Architecture

• Distributed Security: Each microservice has Spring Security.
• Central Authentication: Use a central service for token-based authentication.
• Secure Communication: Use SSL/TLS.
• API Gateway: Manage security at the gateway level.

Session Management in Distributed Systems

• Spring Session: Store session information in a shared location.
• Storage Options: Use a database or cache for session storage.

Handling API Rate Limits and Failures

• Circuit Breaker: Manage failures with resilience libraries.
• Rate Limiting: Protect APIs from abuse.
• Retry Mechanism: Handle temporary issues.
• Caching: Reduce repeated requests.
• API Gateway: Manage API request limits and security.

Externalized Configuration in Microservices

• Spring Cloud Config: Centralized configuration management.
• Encrypt Secrets: Use encrypted properties for sensitive data.

Non-Web Applications in Spring Boot

• Support: Spring Boot can be used for various application types, not just web.
• Execution: Use command-line features in Spring Boot.

SpringBootApplication Annotation

• Combination: Includes @Configuration, @EnableAutoConfiguration, and @ComponentScan.

Internationalization (i18n) in Spring Boot

• Properties Files: Use locale-specific properties files.
• Locale Resolver: Set rules for choosing user language.

Spring Boot DevTools

• Features: Auto-restart, live reload, and remote debugging.
• Purpose: Accelerate development process.

Mocking External Services

• MockBean Annotation: Create mock services for testing.
• Mockito: Define mock behavior for external services.

Docker Images for Spring Boot Applications

• Dockerfile: Define base image, add JAR file, specify run command.
• Build Command: Use docker build to create the Docker image.

Configuring Spring Boot Security

• Form-Based Authentication: Login system for user verification.
• Authorization Rules: Control access based on roles.
• HTTPS: Secure data transmission.

JSON Web Tokens (JWT) for Security

• Token Generation: Authenticate user and generate JWT.
• Token Verification: Check JWT on each request for access control.

Resilience in Spring Boot Applications

• Circuit Breakers: Use libraries like Resilience4J.
• Retry Logic: Implement with exponential backoff.
• Timeouts: Avoid long waits for non-responsive services.
• Logging and Monitoring: Essential for quick issue resolution.

Serverless Functions with Spring Cloud Function

• Purpose: Write business logic as simple Java functions.
• Deployment: Run on cloud platforms without server management.

Spring Cloud Gateway Configuration

• Routing: Define paths and destinations.
• Security: Integrate with Spring Security for authentication and authorization.
• Monitoring: Use Spring Actuator for health and performance insights.

Managing Asynchronous Tasks

• Messaging System: Use RabbitMQ or Kafka.
• Enable Messaging: Add necessary dependencies and annotations.
• Send Messages: Use KafkaTemplate or equivalent.

Endpoint Security

• Form-Based Authentication: Set up with Spring Security.
• Custom Security Configuration: Use WebSecurityConfigurerAdapter.

Disabling Auto-configuration

• Conditional Annotation: Use @ConditionalOnMissingBean to prevent redundant configurations.

Packaging Spring Boot Applications

• Jar Files: Use embedded server.
• War Files: Deploy on external Java EE containers after modifying the project structure.

Relaxed Binding in Spring Boot

• Purpose: Flexible naming conventions for properties.
• Examples: server.port, server-port, server_port all recognized the same.

CI/CD Integration

• Tools: Use Jenkins, GitHub Actions for automated builds and deployments.
• Pipeline Steps: Compile code, run tests, deploy if tests pass.

Replacing Embedded Tomcat

• Exclude Dependency: Remove Tomcat from pom.xml or build.gradle.
• Include Another Server: Add preferred server dependency.

Resolving White Label Error Pages

• URL Mappings: Ensure correct URL mappings in controllers.
• Custom Error Pages: Use @ControllerAdvice for global error handling.

Implementing Pagination

• Pageable Interface: Modify repository methods to accept Pageable.
• Page Request: Use for specifying page number and size.

Handling 404 Errors

• Custom Error Controller: Implement ErrorController.
• Mapping Method: Use @RequestMapping to map error paths.

Event-Driven Architecture

• Event Creation: Extend ApplicationEvent.
• Event Publishing: Use ApplicationEventPublisher.
• Event Listening: Use @EventListener annotation.

Basic Spring Boot Annotations

• SpringBootApplication: Combines essential configuration annotations.
• RestController: Define controllers for RESTful web services.
• Service and Repository: Mark service and data access layers.
• Autowired: Enable dependency injection.

Distributed Tracing

• Purpose: Monitor and troubleshoot microservices.
• Tools: Spring Cloud Sleuth, Zipkin for tracking requests across services.

Cloud Storage Integration

• SDK: Use AWS SDK for S3 or Google Cloud Storage libraries.
• Service Class: Encapsulate storage operations.

Rate Limiting

• Libraries: Use Bucket4J or Spring Cloud Gateway.
• Configuration: Define rate limits as annotations or settings.

Soft Delete

• Database Column: Add deleted or deleteTimestamp columns.
• Custom Queries: Filter out deleted records in fetch operations.

Reactive REST API with Spring WebFlux

• Dependencies: Include spring-boot-starter-webflux.
• Return Types: Use Mono and Flux for reactive types.
• Reactive Repositories: Use for non-blocking database interactions.