Java on OCI: Develop a REST-Based Microservice — Lesson 1: REST Resource Design, Java Framework Setup, DTOs, Validation, and Errors

Learning Objectives

• Explain the purpose and operating context of resource modeling, URIs, HTTP methods, status codes, and idempotency.
• Apply Helidon or Micronaut-style project structure, configuration, and dependency setup and DTOs, JSON binding, bean validation, and domain boundaries in a controlled environment.
• Validate outcomes and troubleshoot risks involving consistent error responses, logging context, and API tests.

Detailed Topics

• resource modeling, URIs, HTTP methods, status codes, and idempotency
• Helidon or Micronaut-style project structure, configuration, and dependency setup
• DTOs, JSON binding, bean validation, and domain boundaries
• consistent error responses, logging context, and API tests

Instructor Demonstration

Demonstrate resource modeling, URIs, HTTP methods, status codes, and idempotency for a small inventory microservice packaged, deployed, secured, and monitored on OCI; 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 Java on OCI: Develop a REST-Based Microservice exercise covering Helidon or Micronaut-style project structure, configuration, and dependency setup and DTOs, JSON binding, bean validation, and domain boundaries; introduce an exception involving consistent error responses, logging context, and API 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 resource modeling, URIs, HTTP methods, status codes, and idempotency, Helidon or Micronaut-style project structure, configuration, and dependency setup, DTOs, JSON binding, bean validation, and domain boundaries, consistent error responses, logging context, and API 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 REST Resource Design, Java Framework Setup, DTOs, Validation, and Errors in a realistic Java on OCI: Develop a REST-Based Microservice scenario and defend the result with documented evidence.