JExten Plugin

Runtime plugin management module for the JExten extension framework.

Overview

This module provides dynamic plugin loading capabilities, enabling applications to discover and load plugins at runtime from external sources. Key features:

• PluginManager for loading and managing plugin lifecycle
• PluginManifest for describing plugin metadata (YAML format)
• ArtifactStore SPI for custom plugin artifact resolution
• Isolated module layers per plugin for dependency isolation

Installation

<dependency>
    <groupId>org.myjtools.jexten</groupId>
    <artifactId>jexten-plugin</artifactId>
    <version>1.0.0</version>
</dependency>

Quick Start

Load Plugins

// Create plugin manager with a plugins directory
PluginManager pluginManager = new PluginManager(Path.of("plugins"));

// Load all plugins from the directory
pluginManager.loadPlugins();

// Create extension manager with plugin support
ExtensionManager extensions = ExtensionManager.create(pluginManager);

// Discover extensions from both application and plugins
extensions.getExtensions(MyExtensionPoint.class)
    .forEach(ext -> ext.execute());

Install a Plugin

// From a local file
pluginManager.install(Path.of("my-plugin-1.0.zip"));

// From a URL
pluginManager.install(new URL("https://example.com/plugins/my-plugin-1.0.zip"));

Remove a Plugin

pluginManager.remove(new PluginID("com.example", "my-plugin"));

Plugin Manifest

Each plugin requires a plugin.yaml manifest file:

group: com.example
name: my-plugin
version: 1.0.0
hostModule: com.example.myplugin

# Optional metadata
displayName: My Awesome Plugin
description: A plugin that does awesome things
application: MyApplication
url: https://example.com/my-plugin
licenseName: Apache-2.0

# Artifact dependencies (JAR files)
artifacts:
  main:
    - my-plugin-1.0.0.jar
    - dependency-lib-2.0.jar

# Extension declarations
extensions:
  com.example.api.MyExtensionPoint:
    - com.example.plugin.MyExtensionImpl

# Extension points provided by this plugin
extensionPoints:
  - com.example.plugin.api.PluginExtensionPoint

Required Fields

Plugin Package Formats

ZIP Bundle

A ZIP file containing:

my-plugin-1.0.zip
├── plugin.yaml
├── my-plugin-1.0.0.jar
├── dependency-lib-2.0.jar
└── other-dependency.jar

JAR with Embedded Manifest

A JAR file with plugin.yaml at the root:

my-plugin-1.0.jar
├── plugin.yaml
├── com/example/plugin/...
└── META-INF/...

Artifact Stores

Artifact stores resolve plugin dependencies. Built-in options:

Local Directory Store (Default)

Resolves artifacts from the plugin package itself.

Maven Artifact Store

Resolves artifacts from Maven repositories:

<dependency>
    <groupId>org.myjtools.jexten</groupId>
    <artifactId>jexten-maven-artifact-store</artifactId>
    <version>1.0.0</version>
</dependency>

ArtifactStore mavenStore = new MavenArtifactStore(
    Path.of("plugin-cache"),
    List.of("https://repo.maven.apache.org/maven2")
);

PluginManager pluginManager = new PluginManager(
    Path.of("plugins"),
    mavenStore
);

Custom Artifact Store

Implement the ArtifactStore interface:

public class MyArtifactStore implements ArtifactStore {
    @Override
    public List<Path> resolve(String artifact) {
        // Resolve artifact to local paths
    }
}

Plugin Lifecycle

┌─────────┐     ┌─────────┐     ┌────────┐     ┌──────────┐
│ Install │────▶│  Load   │────▶│ Active │────▶│ Unloaded │
└─────────┘     └─────────┘     └────────┘     └──────────┘
                     │               │
                     ▼               ▼
               ┌──────────┐    ┌─────────┐
               │  Failed  │    │ Removed │
               └──────────┘    └─────────┘

Module Layer Isolation

Each plugin runs in its own JPMS module layer, providing:

• Dependency isolation: Plugins can use different versions of the same library
• Security: Plugins cannot access internal APIs of other plugins
• Hot reload: Plugins can be loaded/unloaded without restarting the application

Documentation

For complete documentation, see the main JExten README.

License

Apache License 2.0