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Developer 6 min read Published Updated Credibility 90/100

Language Briefing — Java 21 Long-Term Support Release

Oracle’s 19 September 2023 release of Java 21, the next LTS platform, requires governance committees to refresh runtime policies, engineering teams to execute staged upgrades, and privacy leaders to validate DSAR applications on the new language features and support timelines.

Zeph Tech Research Lead

Research lead, Zeph Tech

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Executive briefing: Oracle and the OpenJDK community released Java 21 (JDK 21) on 19 September 2023, ushering in the next long-term support (LTS) platform with eight features reaching production status and numerous previews. Highlights include the general availability of virtual threads (Project Loom), pattern matching enhancements, the sequenced collections API, record patterns, and generational mode for the Z Garbage Collector. The release is backed by at least eight years of Premier Support from Oracle (through September 2031) and community builds from Adoptium, Red Hat, and others. Enterprises must mobilise governance, engineering, and privacy teams to plan migrations from Java 11/17, update tooling, and ensure DSAR-critical services built on the JVM remain compliant during and after the upgrade.

Governance priorities

Runtime strategy falls under technology risk oversight. Boards and architecture review committees update evergreen platform policies to designate Java 21 as the target LTS for new development and long-term maintenance. They require business units to present migration roadmaps with funding estimates, testing milestones, and fallback strategies. Because Java 21 introduces new concurrency primitives (virtual threads) and preview features (string templates, structured concurrency), governance bodies insist on documented risk assessments detailing how teams will manage feature toggles, training, and production monitoring.

Audit and compliance teams examine licence implications. Oracle now distributes commercial binaries under the Oracle No-Fee Terms and Conditions (NFTC), while OpenJDK builds retain GPLv2 with Classpath Exception licensing. Procurement ensures support contracts (Oracle Java SE Subscription, Azul Platform, IBM Semeru) cover Java 21, and legal counsel documents obligations for third-party frameworks adopting the new release. Governance scorecards add metrics such as percentage of JVM workloads on supported LTS versions, completion status of migration pilots, and DSAR service readiness.

Feature overview and business impact

Virtual threads (JEP 444): Now GA, virtual threads dramatically reduce the cost of concurrency by decoupling task scheduling from OS threads. Call centre platforms, DSAR request processors, and API gateways can scale to thousands of concurrent requests without complex reactive frameworks, simplifying code maintenance.

Pattern matching for switch (JEP 441) and record patterns (JEP 440): These features streamline data-centric code, making it easier to safely deconstruct records or sealed hierarchies when parsing DSAR payloads or compliance rules.

Sequenced collections (JEP 431) and string templates (JEP 430, preview): Provide consistent iteration order guarantees and safer string interpolation. Privacy teams emphasise string templates for reducing injection risk when generating DSAR correspondence.

Generational ZGC (JEP 439) and Shenandoah updates: Improve garbage collection latency for large heaps, benefiting analytics platforms performing data discovery for subject access requests.

Vector API (JEP 448, 6th incubator) and Foreign Function & Memory API (JEP 442, 3rd preview): Offer performance and interoperability enhancements relevant to cryptography, data processing, and native integrations used in DSAR export pipelines.

Implementation roadmap

Assessment phase: Engineering teams inventory JVM workloads, categorising them by criticality (customer-facing DSAR portals, batch export jobs, analytics pipelines, internal tooling). They evaluate dependencies—application servers (Tomcat, Quarkus, Spring Boot), frameworks (Hibernate, Micronaut), and build tools (Maven, Gradle)—to confirm Java 21 compatibility. Vendors like Spring (Framework 6.1), Quarkus 3.5, and Micronaut 4 announced support windows; governance teams document release dependencies to avoid unsupported combinations.

Pilot phase: Selected services migrate to Java 21 in staging environments. Teams run comprehensive test suites—unit, integration, load, and regression—focusing on authentication, encryption, DSAR export generation, and workflow orchestration. Virtual threads pilots begin with non-critical workloads, with instrumentation capturing CPU utilisation, thread counts, and latency compared to Java 17 baselines. Observability pipelines (OpenTelemetry, Micrometer) are updated to ingest new runtime metrics, including virtual thread scheduling and garbage collection phases.

Rollout phase: After successful pilots, migrations progress service-by-service. CI/CD pipelines update toolchains (mvn -Djava.version=21, gradle toolchain definitions) and base container images. Infrastructure teams ensure Kubernetes clusters and application servers accept Java 21 images, adjusting resource limits for virtual thread adoption. Change management boards require backout plans and cutover communication strategies, particularly for DSAR portals where downtime must be minimal.

Security and compliance

Java 21 ships with TLS 1.3 support, updated cipher suites, and hardened default security providers. Security engineers validate mutual TLS configurations, FIPS 140-2/3 requirements, and hardware security module integrations. They review third-party libraries for compatibility with Java 21 and remove unsupported modules. Vulnerability management teams update scanners to recognise Java 21 builds and ensure SBOMs reflect new dependencies.

Privacy and compliance officers oversee DPIA updates for systems undergoing runtime migration. They verify that encryption used for DSAR files remains intact, that audit logs capture necessary context, and that any use of preview features complies with coding standards. Logging frameworks (Log4j 2.20+, Logback) and observability agents (New Relic, Dynatrace, AppDynamics) are upgraded to Java 21-compatible versions, ensuring DSAR access logs remain comprehensive.

Operational considerations

Performance tuning: Operations teams benchmark garbage collectors—G1, ZGC, Shenandoah—to select optimal settings. Virtual threads may require tuning of connection pools, scheduler configurations, and instrumentation. Capacity planning models incorporate new concurrency profiles to maintain DSAR SLA commitments.

Runtime management: SREs update JVM flag baselines (-XX:+UseZGC, -XX:MaxRAMPercentage, -XX:+EnableDynamicAgentLoading) and ensure startup scripts handle preview features (e.g., --enable-preview). They document support policies for preview APIs, limiting usage to services with clear rollback plans and risk acceptance.

Disaster recovery: Backup and restore procedures incorporate Java 21 runtimes. Container registries store signed images; infrastructure-as-code templates (Terraform, Ansible) reference new versions. Playbooks include steps to redeploy DSAR services on Java 17 should regressions occur, maintaining business continuity.

Developer enablement and training

Enablement teams provide workshops on Java 21 features, emphasising practical applications: using record patterns in Spring controllers, leveraging structured concurrency (preview) for DSAR batch jobs, and adopting sequenced collections for deterministic reporting. They update secure coding guidelines to cover string templates, emphasising placeholder validation to prevent injection. Code review checklists include considerations for virtual thread usage (thread-local storage, database driver compatibility) and guidelines for mixing traditional and virtual executors.

Tooling updates accompany training. IDEs (IntelliJ IDEA 2023.2+, Eclipse 2023-09, VS Code extensions) and static analysis tools (SpotBugs, SonarQube) are upgraded to parse Java 21 syntax. Build pipelines enable `--release 21` to compile to the new bytecode level while retaining cross-compilation options for legacy clients when required.

DSAR service assurance

Many DSAR workflows rely on JVM-based platforms (e.g., Spring Boot, Apache Camel, Camunda BPM). Privacy operations coordinate regression tests covering end-to-end DSAR scenarios: request intake, identity verification, data aggregation, export packaging, and secure delivery. They validate that PDF/CSV exports generated under Java 21 remain consistent with previous versions, that encryption (PGP, AES) works with updated security providers, and that automated retention policies execute correctly.

Monitoring dashboards track DSAR-specific KPIs (throughput, error rates, queue latency) before and after migration to detect performance regressions. Incident response plans include playbooks for rollbacks if DSAR SLAs degrade. Documentation packages prepared for regulators highlight the migration process, testing evidence, and controls ensuring uninterrupted rights fulfilment.

Third-party ecosystem

Vendors across the Java ecosystem issued compatibility statements. Organisations maintain a registry of critical dependencies—application servers (WebLogic 14.1.2, JBoss EAP 8 beta), workflow tools, identity providers—and their Java 21 support timelines. Procurement engages vendors lacking support to obtain roadmaps or negotiate extended maintenance for Java 17 until upgrades complete.

Open-source dependencies with native libraries (Netty, Apache Kafka, Lucene) must be updated to releases compiled against the new toolchain. Where DSAR solutions rely on commercial platforms (OneTrust, Securiti, BigID) that integrate with customer-hosted components, teams coordinate upgrade plans to avoid version skew.

Next steps

Within 90 days, organisations should deliver a Java 21 migration plan to executive sponsors, outlining inventory results, pilot candidates, resource needs, and target completion dates. Quarterly checkpoints track progress toward deprecating Java 11/17 workloads, with risk registers capturing blockers. Continuous monitoring ensures new Java 21 updates (Security Patch Updates and Patch Set Updates) are integrated into patch cycles.

By aligning governance, implementation, and DSAR operations with Java 21’s long-term support horizon, enterprises sustain security posture, leverage modern language features, and maintain trust with customers exercising their data rights.

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