Migrating legacy JSP components to HTL in AEM 6.x

For years, Adobe Experience Manager projects in Australia ran on a familiar recipe: Java Server Pages stitched together by experienced back-end engineers, component dialogs storing values in the JCR, and a front-end team patching around the rough edges. That recipe served large ANZ publishers well through the AEM 5.6 era, but the shift to AEM 6.x has changed how templates and components are expected to behave. Sightly, now called the HTML Template Language (HTL), trades scriptlets for a clean separation between markup and logic, and teams that keep their old JSP files alive are starting to feel the weight of that legacy.

Sydney and Melbourne-based AEM centres of excellence have begun auditing their component libraries before the next platform upgrade. A typical engagement starts with a content audit, a dependency map, and a frank conversation about which JSP files deserve a rewrite and which can simply be retired.

Why JSP Became a Maintenance Burden

JSP files invite a kind of accidental complexity that grows quietly over time. A single component often bundles repository reads, business logic, helper tags, and inline HTML together, which means a small content change can ripple through a hundred lines of scriptlet. Once author-mode preview, publish-time rendering, and dispatcher caching each depend on different fragments of the same file, debugging becomes an exercise in archaeology.

Australian delivery teams, particularly those supporting banks and government departments around Sydney and Brisbane, have reported handover problems when experienced JSP authors leave and the next wave of developers reads scratch-built logic without documentation. The closure of certain component behaviours at the JSP layer also blocks tighter integration with the modern AEM 6.x stack, including the Sightly-style component export objects that connect straight into React and Angular front ends.

The licensing and security review process in regulated sectors, from ASIC-monitored finance to APRA-aligned insurance, makes any unmaintained JSP file a compliance liability. Patching a vulnerability in a custom taglib can stall a release for weeks.

How HTL Reshapes Templating Workflows

HTL was designed to remove the scriptlet problem at its root. The template file holds only markup and a small, readable set of special elements such as data-sly-use, data-sly-list, and data-sly-call. The JavaScript Use API pushes logic out into separate files that the front-end team can review in plain Git diffs. The same component can be reused across SPA, server-side rendering, and static export without rewriting the template.

A concrete win in Australian rollouts comes from cleaner component export. HTL can serialise a model into JSON that a React app on a mobile banking flow consumes directly, which suits teams in Melbourne and Sydney who have shifted toward headless publishing. Because HTL respects the dispatcher's security model by default, Express sessions and HMAC-signed tokens behave predictably during a CDN cache flush, something that previously required custom JSP filters.

Another gain is reuse. HTL templates behave like Lego, encouraging composition through templates and component inheritance. A page header built once can be re-used across the marketing site, the investor portal, and the intranet without forking source.

Planning a Phased Migration

A wholesale rewrite is rarely realistic inside a quarterly roadmap. The smarter approach is to draw a heat map of JSP usage by traffic, then migrate the cold edges first. Touch points such as footers, utility navigation, and disclaimer components are excellent training material because their behaviour is well understood and their failure modes are forgiving.

A useful starting ritual for ANZ teams is a brown-bag session with the Adobe User Group in Melbourne or the Sydney Adobe Community, where architects present the migration order and let authors flag components they consider politically sensitive. Building a published backlog inside Jira, ordered by blast radius rather than file size, helps align product, marketing, and engineering around a common schedule.

For large publishers, such as a national retailer with outlets in every capital from Perth to Darwin, the migration usually runs in tracks. Track one handles the public-facing homepages and category pages. Track two tackles authenticated portals. Track three cleans up internal tooling. Each track has its own code freeze and rollback plan.

Automating the Conversion with Helper Tools

Pure manual conversion works on small sites but tends to bog down once the component library passes a few hundred JSP files. A few open-source scripts can stub the first pass, copying the original markup into an HTL file, extracting scriptlet variables into a JavaScript Use API file, and replacing taglib imports with their HTL equivalents. The output is rarely ship-ready, but it gives developers a head start and surfaces the components that depend on hidden global state.

For deeper automation, teams at organisations such as IAG and Atlassian have leaned on internal codemod tools that pair with their CI pipelines. A typical pipeline runs the conversion, fails the build when the new component does not match the rendered output of the old JSP on a snapshot of test pages, and then opens a draft pull request with the diff for review.

When the migration intersects with form handling, it is worth revisiting the broader security posture at the same time. The Chicago talk titled securing AEM forms walked through drop-in replacements for old JSP validation snippets that hard-coded captcha secrets in tag libraries.

Testing Patterns That Catch Old Habits

HTL looks friendlier than JSP, which means testing can sometimes be skipped in the rush to retire the old stack. That is a mistake. Visual regression tools such as Percy or Chromatic, paired with HTML snapshots from both the JSP and HTL renderings of the same content tree, will flag subtle issues like missing aria attributes or whitespace changes that break a fragile layout.

Performance budgets also deserve a closer look once the JSP plumbing is gone. Removing inline scriptlets usually cuts the time to first byte, but a poorly designed HTL template can call a Use API too often per request. A quick profile in Chrome DevTools across a representative sample of pages, including the longest URL a real visitor can land on, gives a realistic baseline. Teams in Adelaide and across South Australia have reported double-digit improvements in Largest Contentful Paint after retiring their last batch of JSP includes.

Security scanning is the third leg of the stool. Tools such as OWASP ZAP and the AEM Security Scanner still apply, but the migration is also a clean moment to confirm that the dispatcher configuration matches the new template behaviour and that no path bypasses the sanitisation layers that HTL enforces.

Hardening the Platform After Migration

Once the component library runs entirely on HTL, the platform opens up to capabilities that the old JSP layer had quietly disabled. SPA Editor integration works without the bridge classes that JSP-heavy projects had to invent. Content fragments map more cleanly onto structured data fields, which suits data-driven teams analysing customer journeys across web and mobile.

Big data pipelines become easier to wire in. The Chicago AEM and Apache Spark recording covers how to feed component interaction events into a Spark cluster for campaign analytics, with a chapter on real-time dashboards that is directly relevant to Australian retailers measuring performance across states with different trading hours.

A few finishing touches make the migration stick. Rename old JSP files with a .deprecated extension during the transition so that any leftover reference is loud rather than silent. Keep a runbook of rollback paths for the first two releases after the cutover. Schedule a quarterly review with the architecture team based in Melbourne, Sydney or whichever capital owns the platform, and treat the migration not as a one-off project but as a permanent move toward template hygiene that will pay off through every AEM upgrade that follows.

The CIRCUIT newsletter carries Sydney and Melbourne meet-up invitations, speaker announcements, and recordings of every session from the 2015 and 2016 Chicago conferences. Subscribers who bring migration questions to the team are paired with an AEM architect who has handled a similar shelf of legacy Java files, often across regulated industries from banking to government services. Sign up to keep the migration roadmap on the table.