Hopper Presentation Engine

Metadata-driven presentations and interactive dashboards for the Data Hopper ecosystem.

This project is the presentation engine behind server-side SVG reporting, data connectors, and a browser canvas editor. It is built to grow into simple interactive, dashboard-style UIs on the same metadata model.

Orientation

Hopper Presentation was not built to be a heavily productized commercial reporting suite. It is offered to the community as a possible open-source alternative to older reporting stacks that once filled the same niche—especially Pentaho Reporting and Jasper Reports.

Those projects could produce pixel-perfect PDFs (invoices, statements, formal print layout) and were widely used when open-source BI and reporting were stronger. Both have lost momentum: support and everyday use have thinned, and teams that need a web interface with serious print/PDF output often end up with closed-source tools or hand-coded PDF generation.

This engine aims at that gap with a different shape: server-side layout and SVG, metadata-driven pages, and print/PDF-capable rendering—without requiring a proprietary stack or a one-off PDF codebase for every document. Growth is intentionally slow and steady: solid output, clear APIs, and community usefulness over star-count campaigns. The implementation effort was modest relative to the value of having another option in the open, so this is a deliberate way to give back.

Modules

Module	Artifact	Role
hopper-presentation-core	JAR	Rendering, connectors, components, themes
hopper-presentation-swt	JAR	Hop GUI / SWT viewer (canvas; no web server)
hopper-presentation-rest	WAR	REST API + canvas editor / viewer

Naming

• Java packages: org.hopper.*
• Domain types use a short H prefix (e.g. HPresentation, HComponent, HConnector)
• HTTP context: /hopper/ — API base /hopper/api/
• Config file: hopper-presentation.properties

Build

mvn clean install

Requires Java 21 and Maven. Hop 2.20.0-SNAPSHOT is pulled from the ASF snapshots repository (or a local install of the Hop tree). Use 2.20.0 when that release is final.

Run (REST + editor)

Jetty is declared only on the REST module (the parent is a pom aggregator). Use one of:

# From the repository root: install modules, then run Jetty in the REST module
# (parent POM has no jetty plugin — bare "mvn jetty:run" at root fails with
# "No plugin found for prefix jetty")
mvn -pl hopper-presentation-rest -am install -DskipTests
cd hopper-presentation-rest && mvn jetty:run

# Or fully-qualified goal from the root:
# mvn -pl hopper-presentation-rest -am org.eclipse.jetty:jetty-maven-plugin:11.0.24:run

Point metadata.path at a folder with presentation/, connector/, theme/, hopper-database-connection/ (see hopper-presentation.properties).

Platform / Docker / SSO

Presentation joins the Data Hopper fleet (Keycloak realm hopper, role aliases, compose fragment) without Spring Boot. See docs/platform-sso-docker.md.

Then open:

http://localhost:8080/hopper/api/render/main/

Example property:

metadata.path=/data/hopper/metadata/
cors.allow.origin=true

Architecture (short)

1. Connectors load/transform row data (SQL, sample, chain, sort, filter, REST, …).
2. Components (table, crosstab, charts, Gantt, label, text block, group, composite, …) layout and draw SVG.
3. Presentations compose pages, themes, interactions, and parameter mappings as Hop metadata JSON.
4. REST serves render pages, edit forms (annotation-driven), undo history, and the JS canvas editor.

AI / automated authoring

Agents and tools should start from docs/ai/: wire-format notes, layout recipes, golden templates, JSON Schema export, validate/compile APIs (/hopper/api/ai/*), and a compact JSON DSL.

Core types: HMetadataCodec, HMetadataValidator, HAuthoringDsl in hopper-presentation-core.

SVG components (artwork)

HSvgComponent loads SVG via Hop/SvgCache and Apache Batik 1.19 (SVG 1.1). Artwork is embedded into the page SVG during server-side render.

Authoring tips

• Prefer SVG 1.1 primitives. Batik does not support SVG2-only filters such as feDropShadow (use feGaussianBlur + feOffset + feFlood + feMerge instead).
• Embedding composes with page/header/footer margin transforms so icons stay aligned with component bounds (including header logos).
• Scale types (NONE, MIN, MAX, FILL, …) control how natural SVG size maps into the layout box.

See hopper-presentation-core/docs/components.md.

Editor and view sessions

The canvas editor and read-only viewer use in-memory render IDs (POST /render/presentation returns a UUID).

• Edit → View (toolbar) opens a new tab using the current editor renderId, so the edit session is not discarded.
• Avoid reload: true on that path: reload removes the cached rendering for the presentation name and would leave the Edit tab with a dead id (Unable to find rendering with ID …).
• Soft re-render after save/apply (POST …/edit/presentation/{name}/render/) replaces the editor render and updates the page’s renderId in place.

See hopper-presentation-rest/README.md.

Icon

Project mark: assets/icons/hopper-presentation.svg — hopper funnel feeding a presentation canvas / chart. Packaged copies live under hopper-presentation-rest static resources (Batik-safe filters).

Documentation

Path	Content
AGENTS.md	Agent + developer guide: layout, requirements, schemas, authoring workflow
docs/ai/	AI authoring: wire format, templates, JSON Schema, validate/compile APIs
hopper-presentation-core/README.md	Core library overview
hopper-presentation-core/docs/	Architecture, API, components, connectors
docs/security-and-audit.md	Auth, action RBAC, usage audit plugins
hopper-presentation-rest/README.md	REST API, run, smoke test
hopper-presentation-rest/docs/smoke-test.md	End-to-end render checklist

License

Apache License 2.0 — see LICENSE.