Develop Web Services and Microservices with Java — Lesson 1: RESTful Services, JAX-RS, HTTP Semantics, JSON, and API Contracts

Learning Objectives

• Explain the purpose and operating context of resources, URI design, methods, status codes, headers, and idempotency.
• Apply JAX-RS annotations, injection, routing, filters, interceptors, and providers and JSON binding, DTOs, content negotiation, validation, and error models in a controlled environment.
• Validate outcomes and troubleshoot risks involving OpenAPI awareness, examples, versioning, compatibility, and contract tests.

Detailed Topics

• resources, URI design, methods, status codes, headers, and idempotency
• JAX-RS annotations, injection, routing, filters, interceptors, and providers
• JSON binding, DTOs, content negotiation, validation, and error models
• OpenAPI awareness, examples, versioning, compatibility, and contract tests

Instructor Demonstration

Demonstrate resources, URI design, methods, status codes, headers, and idempotency for a customer and order integration exposed through REST, SOAP, and independently deployable Java services; capture the exact configuration, code, command, transaction, query, dashboard, model, schedule, or report evidence that proves the expected result.

Hands-On Exercise

Complete a controlled Develop Web Services and Microservices with Java exercise covering JAX-RS annotations, injection, routing, filters, interceptors, and providers and JSON binding, DTOs, content negotiation, validation, and error models; introduce an exception involving OpenAPI awareness, examples, versioning, compatibility, and contract tests, diagnose it from evidence, apply the smallest reversible correction, and rerun acceptance checks.

1. Confirm scope, prerequisites, identities, dependencies, data, risks, and expected outcome.
2. Perform the course-specific configuration, development, administration, analysis, or business-process workflow.
3. Capture commands, settings, records, logs, screenshots, reports, metrics, or test results.
4. Compare the observed result with acceptance criteria and document corrective or preventive action.

Scenario Analysis

• Identify the technical or business decision and the stakeholders affected by it.
• Compare security, performance, reliability, compliance, cost, usability, and support trade-offs.
• Define rollback, recovery, communication, evidence, ownership, and escalation requirements.

Troubleshooting Guidance

Diagnose issues involving resources, URI design, methods, status codes, headers, and idempotency, JAX-RS annotations, injection, routing, filters, interceptors, and providers, JSON binding, DTOs, content negotiation, validation, and error models, OpenAPI awareness, examples, versioning, compatibility, and contract tests without making an unverified production change. Separate symptoms from causes, gather time-correlated evidence, test a reversible hypothesis, validate the correction, and record recurrence controls.

Validation Checklist

• The requirement, environment, inputs, dependencies, and expected result are documented.
• The result is reproducible and supported by product-specific evidence.
• Normal, boundary, failure, security, performance, and operational conditions are reviewed.
• Exceptions, rollback, ownership, support actions, and the next improvement priority are recorded.

Lesson Outcome

Learners can apply RESTful Services, JAX-RS, HTTP Semantics, JSON, and API Contracts in a realistic Develop Web Services and Microservices with Java scenario and defend the result with documented evidence.