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This page describes how patternfly-java supports two distinct Java-to-JavaScript compilation targets GWT and J2CL and how the project integrates with the JavaScript ecosystem for each. It covers the two platform-specific Maven modules, their packaging, their dependencies, and the key runtime difference: how Popper.js is delivered.
For GWT-specific details (module descriptor, EntryPoint, ScriptInjector), see GWT Integration. For J2CL-specific details (entry point annotation, Parcel bundler, showcase routing), see J2CL Integration. For JsInterop patterns and chart externs, see JavaScript Interop and Externs.
PatternFly Java's core code components, layouts, icons, tokens, charts is written once and compiled to JavaScript by two separate toolchains: the GWT compiler and the J2CL transpiler. To support both, the project provides two thin Maven modules that act as platform-facing entry points. All other modules (core, components, layouts, icons, tokens, charts) are shared between both targets and use gwt-lib packaging, which is compatible with both compilers.
| Attribute | GWT Module | J2CL Module |
|---|---|---|
| Artifact ID | patternfly-java-gwt | patternfly-java-j2cl |
| Packaging | gwt-lib | jar |
| GWT module name | org.patternfly.PatternFly | |
| Popper.js delivery | Inlined string + ScriptInjector | JS resource file included in jar |
| Primary dependency | gwt-user | |
| Shared dependencies | patternfly-java-components, patternfly-java-layouts | patternfly-java-components, patternfly-java-layouts |
Sources: gwt/pom.xml1-83 j2cl/pom.xml1-62
Platform module dependency graph
Sources: gwt/pom.xml46-83 j2cl/pom.xml35-61
The GWT module (patternfly-java-gwt) has two jobs: pull in the transitive gwt-user dependency and inject Popper.js at runtime.
The class PatternFly in gwt/src/main/java/org/patternfly/PatternFly.java21-40 implements com.google.gwt.core.client.EntryPoint. Its onModuleLoad() method injects the full Popper.js v2.11.8 code (held as a private static final String constant named POPPER_JS) using GWT's ScriptInjector.fromString(POPPER_JS).inject().
At the end of the injected IIFE, a GWT-specific export line is appended:
$wnd.Popper={createPopper:we};
This makes the createPopper function available on the GWT $wnd (browser window) object so that PopperBuilder can call it via JsInterop.
GWT runtime initialization flow
Sources: gwt/src/main/java/org/patternfly/PatternFly.java21-40
The gwt-maven-plugin in gwt/pom.xml72-80 declares the GWT module name as org.patternfly.PatternFly. GWT consumers must inherit this module in their own .gwt.xml descriptor:
The GWT module in the gwt directory also declares a dependency on sources JARs for patternfly-java-components and patternfly-java-layouts (via <classifier>sources</classifier> entries in gwt/pom.xml52-65). Source JARs are required for the GWT compiler to transpile the Java code.
Sources: gwt/pom.xml1-83 README.md56-81
The J2CL module (patternfly-java-j2cl) is a standard jar with no GWT-specific packaging. It depends on patternfly-java-components and patternfly-java-layouts and includes JavaScript resource files that are bundled alongside the compiled output.
Unlike GWT's ScriptInjector approach, J2CL includes Popper.js as a physical .js file on the classpath. The build configuration in j2cl/pom.xml46-61 adds two resource directories that copy all **/*.js files into the jar:
src/main/java for JS files co-located with Java sourcessrc/main/resources for standalone JS resourcesThis allows the J2CL build toolchain (via j2cl-maven-plugin) to discover and bundle these JavaScript resources along with the compiled Java code.
The root POM excludes **/src/main/java/org/patternfly/popper/popper.js from the license check (pom.xml225), confirming where the Popper.js file lives in the source tree.
The showcase (showcase/pom.xml201-218) demonstrates the canonical J2CL consumer setup. The j2cl-maven-plugin compiles the Java application to JavaScript:
| Property | Development Value | Production Value |
|---|---|---|
compilationLevel | BUNDLE_JAR | ADVANCED_OPTIMIZATIONS |
incrementalEnabled | true | false |
enableSourcemaps | true | true |
| Output filename | showcase.js | showcase.js |
Production builds use the Closure Compiler's ADVANCED_OPTIMIZATIONS mode, which requires that all JavaScript APIs called from Java have proper externs files.
Sources: j2cl/pom.xml1-62 showcase/pom.xml76-78 showcase/pom.xml201-218 pom.xml224-225
Popper.js integration by target
| Concern | GWT | J2CL |
|---|---|---|
| Popper.js source | Inline String in PatternFly.java | File at org/patternfly/popper/popper.js |
| Popper.js delivery | ScriptInjector.fromString(...).inject() | Bundled by j2cl-maven-plugin |
| Window export | $wnd.Popper={createPopper:we} | Standard ESM/CJS export |
| Module declaration | .gwt.xml with <inherits> | None; consumer configures j2cl-maven-plugin |
| Compilation tool | GWT compiler | J2CL transpiler + Closure compiler |
| Source JARs needed | Yes (in gwt module) | No |
| Entry point mechanism | com.google.gwt.core.client.EntryPoint | @GWT3EntryPoint annotation |
| Packaging | gwt-lib | jar |
Sources: gwt/src/main/java/org/patternfly/PatternFly.java21-40 j2cl/pom.xml46-61 showcase/pom.xml220-231
Neither platform module includes PatternFly CSS stylesheets. Consumers are expected to import or bundle the PatternFly CSS themselves. The showcase's package.json and Parcel configuration handle this for the showcase application; production consumers should follow the PatternFly getting started guide for stylesheet inclusion.
Sources: README.md83-87
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