Overview

Relevant source files

• CHANGELOG.md
• README.md
• bom/pom.xml
• build-config/pom.xml
• code-parent/pom.xml
• components/pom.xml
• components/src/demo/java/PageDemo.java
• components/src/main/java/org/patternfly/component/page/PageGroup.java
• components/src/main/java/org/patternfly/component/page/PageMain.java
• core/pom.xml
• extensions/codeeditor/pom.xml
• extensions/finder/pom.xml
• gwt/pom.xml
• icons/pom.xml
• j2cl/pom.xml
• layouts/pom.xml
• pom.xml
• showcase/pom.xml
• showcase/src/doc/home.md

PatternFly Java is a pure Java implementation of the PatternFly design system for building enterprise web applications. It provides a comprehensive set of UI components, layouts, icons, and design tokens that can be compiled to JavaScript using either GWT (Google Web Toolkit) or J2CL (Java-to-Closure-Compiler). The library is built on top of Elemento utilizing its fluent builder API for type-safe HTML element construction.

This page introduces the project's purpose, architecture, and key characteristics. For detailed information about the multi-module Maven structure and dependency relationships, see Project Architecture. For instructions on adding PatternFly Java to your application, see Getting Started.

Sources: pom.xml1-599 README.md1-310

Core Characteristics

PatternFly Java distinguishes itself through several key design principles:

Characteristic	Description
Pure Java	All component logic implemented in Java with no manual JavaScript required
CSS Independence	Stylesheets are NOT bundled; developers must provide PatternFly CSS separately at runtime
Dual Compilation	Supports both GWT and J2CL compilation targets through dedicated integration modules
Type-Safe API	Leverages Elemento's builder pattern for compile-time safety and IDE autocomplete
Design Tokens	Includes ~1000 enum constants representing PatternFly design tokens as Token enum
Icon Generation	Icons generated at build time from Font Awesome and PatternFly NPM packages

Chart Exception: Chart components require the @patternfly-java/charts NPM package, which wraps PatternFly React Chart components as web components. This is the only JavaScript dependency in the project.

Sources: README.md84-86 README.md89-104 pom.xml78-89

Maven Module Structure

The project is organized as a multi-module Maven build with the following hierarchy:

Module Descriptions:

Module	Artifact ID	Packaging	Purpose
Parent	patternfly-java-parent	pom	Root aggregator POM with plugin management
Code Parent	patternfly-java-code-parent	pom	Parent for all code modules; manages dependencies
BOM	patternfly-java-bom	pom	Bill of materials for dependency management
Core	patternfly-java-core	gwt-lib	BaseComponent, BaseComponentSVG, utility classes
Icons	patternfly-java-icons	gwt-lib	Generated icon classes from Font Awesome & PatternFly
Tokens	patternfly-java-tokens	gwt-lib	Generated Token enum from PatternFly CSS variables
Layouts	patternfly-java-layouts	gwt-lib	Layout components (Grid, Flex, Stack, etc.)
Components	patternfly-java-components	gwt-lib	All UI components (Button, Menu, Modal, etc.)
Charts	patternfly-java-charts	gwt-lib	Java API for PatternFly chart web components
Code Editor	patternfly-java-codeeditor	gwt-lib	Code editor extension component
Finder	patternfly-java-finder	gwt-lib	MacOS-style finder extension component
GWT	patternfly-java-gwt	gwt-lib	GWT module descriptor and resources
J2CL	patternfly-java-j2cl	jar	J2CL externs for type safety
Showcase	patternfly-java-showcase	jar	Demo application (J2CL-based)

Sources: pom.xml113-126 README.md105-122 code-parent/pom.xml1-105

Dependency Flow

PatternFly Java builds upon several external libraries and follows a layered dependency structure:

Key Dependencies:

• Elemento `version.elemento=2.4.8`: Provides the foundational builder API (HTMLContainerBuilder, IsElement, etc.)
• Elemental2: Supplies browser DOM APIs (HTMLElement, Event, Promise, etc.)
• GWT User: Required only for GWT applications (provides gwt-user APIs)

Sources: pom.xml78-89 core/pom.xml39-51 code-parent/pom.xml35-64

Compilation Targets

PatternFly Java supports two Java-to-JavaScript compilation approaches:

GWT (Google Web Toolkit)

Applications using GWT compilation:

1. Depend on patternfly-java-gwt artifact (type: gwt-lib)
2. Inherit from org.patternfly.PatternFly module in their .gwt.xml file
3. Use gwt-maven-plugin for compilation
4. Automatically receive Popper.js injection via GWT resources

Module Descriptor: gwt/src/main/resources/org/patternfly/PatternFly.gwt.xml

Sources: gwt/pom.xml1-84 README.md75-81

J2CL (Java-to-Closure-Compiler)

Applications using J2CL compilation:

1. Depend on patternfly-java-j2cl artifact (type: jar)
2. Use j2cl-maven-plugin for compilation with Closure optimization
3. Benefit from incremental compilation and advanced optimizations
4. Receive type-safe chart integration via charts.externs.js

Externs File: j2cl/src/main/resources/META-INF/externs/charts.externs.js

Sources: j2cl/pom.xml1-63 showcase/pom.xml201-218

Component Architecture Overview

The component system follows a composition-based architecture with a common base class hierarchy:

Key Abstractions:

• BaseComponent<E extends HTMLElement, B>: Foundation for all HTML-based components
• BaseComponentSVG<E extends SVGElement, B>: Foundation for SVG-based components (icons)
• SubComponent<E, B>: Base for sub-components like PageMain, PageGroup
• Closeable: Components with popup/overlay behavior (Modal, Popover, Tooltip)
• Attachable: Components using Popper.js for positioning
• HasItems<B, S>: Parent components managing child items
• HasIdentifier: Child components with unique identifiers

Sources: components/src/main/java/org/patternfly/component/page/PageMain.java1-164 README.md194-207

Build-Time Code Generation

PatternFly Java generates several Java source files during the Maven build process:

Generated Files:

• IconSets.java: Static factory methods for Font Awesome (fab, far, fas) and PatternFly icons
• IconSpecs.java: SVG path data constants referenced by IconSets
• Token.java: Enum constants for all PatternFly design tokens (name, value, var)
• Version.java: Project version and PatternFly version constants

Build Plugins:

• frontend-maven-plugin: Executes Node.js scripts for icon and token generation
• jbang-maven-plugin: Executes JBang Java scripts for version generation

Sources: icons/pom.xml59-94 core/pom.xml81-101 pom.xml78-89

Application Integration Pattern

Applications integrate PatternFly Java by importing the BOM and depending on either the GWT or J2CL module:

Integration Steps:

1. Import patternfly-java-bom in <dependencyManagement>
2. Add dependency on patternfly-java-gwt (GWT apps) or patternfly-java-j2cl (J2CL apps)
3. For GWT: Inherit from org.patternfly.PatternFly in .gwt.xml
4. Use component factory methods (e.g., page(), button(), menu())
5. Provide PatternFly CSS stylesheets at runtime
6. Optional: Install @patternfly-java/charts NPM package for chart components

Sources: README.md38-87 bom/pom.xml83-201

Version Information

The project follows semantic versioning and tracks both PatternFly Java and upstream PatternFly versions:

Property	Value	Location
PatternFly Java Version	0.4.18-SNAPSHOT	pom.xml31
PatternFly Version	6.4.0	pom.xml88
Elemento Version	2.4.8	pom.xml81
Java Version	21	pom.xml106

Version Class: Generated at build time in core/src/main/java/org/patternfly/core/Version.java containing constants for programmatic access.

Sources: pom.xml31 pom.xml78-89 core/pom.xml81-101

Next Steps

• For detailed information about Maven module structure, dependencies, and plugin configurations, see Project Architecture
• For step-by-step instructions on adding PatternFly Java to your application, see Getting Started
• For information about building the project and CI/CD pipelines, see Build System and Development
• For component usage patterns and API documentation, see Component Library