SpringBoot integrated pf4j code example to implement plug-in development functions

1.What is pf4j?

A plug-in framework for implementing plug-insDynamic loading, supported plug-in formats (zip, jar).

Core Components

• **Plugin: ** is the base class for all plugin types. Each plugin is loaded into a separate class loader to avoid conflicts.
• **PluginManager: ** Used for all aspects of plugin management (load, start, stop). You can use the built-in implementation as JarPluginManager, ZipPluginManager, DefaultPluginManager (it is a JarPluginManager + ZipPluginManager), or you can implement a custom plugin manager from AbstractPluginManager (implementing factory methods only).
• **PluginLoader: **All information (classes) required to load the plugin.
• **ExtensionPoint: ** is a point in the application where custom code can be called. This is a java interface tag. Any java interface or abstract class can be marked as an extension point (implementing the ExtensionPoint interface).
• **Extension: ** is the implementation of the extension point. It is a Java comment on a class

Scene

There is onespring-bootThe implemented web application provides an extension point on a certain business function. Users can implement function extension based on the SDK, require that plug-ins can be managed, and functions can be loaded dynamically at the business function extension point.

2. Code Engineering

Purpose of experiment

Implement dynamic loading of plug-ins, call unloading

Demo overall architecture

• pf4j-api: defines an extensible interface.
• pf4j-plugins-01: Plugin project, can contain multiple plugins, and the interface defined in plugin-api is required. All plug-in jar packages are placed in a unified folder for easy management. In the future, you only need to load the file directory path to start the plug-in.
• pf4j-app: The main program needs to rely on pf4j-api, load and execute pf4j-plugins-01.

pf4j-api

Import dependencies

<dependency>
    <groupId>org.pf4j</groupId>
    <artifactId>pf4j</artifactId>
    <version>3.0.1</version>
</dependency>

Custom extension interface, integrated ExtensionPoint, marked as extension point

package .pf4j;

import org.;

public interface Greeting extends ExtensionPoint {

    String getGreeting();

}

Package for other projects

pf4j-plugins-01

If you want to be able to control the life cycle of the plugin, you can customize the method inside the class integration plugin

/*
 * Copyright (C) 2012-present the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     /licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.;

import .;
import ;

import org.;
import org.;
import org.;
import org.;

/**
 * @author Decebal Suiu
 */
public class WelcomePlugin extends Plugin {

    public WelcomePlugin(PluginWrapper wrapper) {
        super(wrapper);
    }

    @Override
    public void start() {
        ("()");
        // for testing the development mode
        if ((())) {
            (("WelcomePlugin"));
        }
    }

    @Override
    public void stop() {
        ("()");
    }

    @Extension
    public static class WelcomeGreeting implements Greeting {

        @Override
        public String getGreeting() {
            return "Welcome ,my name is pf4j-plugin-01";
        }

    }

}

Make it into a jar or zip package to facilitate the loading of the main program

pf4j-app

Loading plugin packages

package .pf4j;

import org.;
import org.;
import ;

import ;
import ;

@SpringBootApplication
public class DemoApplication {

/* public static void main(String[] args) {
      (, args);
   }*/
   public static void main(String[] args) {


      // create the plugin manager
      PluginManager pluginManager = new JarPluginManager(); // or "new ZipPluginManager() / new DefaultPluginManager()"

      // start and load all plugins of application
      //();

      (("D:\\IdeaProjects\\ETFramework\\pf4j\\pf4j-plugin-01\\target\\pf4j-plugin-01-1."));
      ();
      /*
        // retrieves manually the extensions for the  extension point
        List<Greeting> greetings = ();
        ("() = " + ());
        */
      // retrieve all extensions for "Greeting" extension point
      List<Greeting> greetings = ();
      for (Greeting greeting : greetings) {
         (">>> " + ());
      }

      // stop and unload all plugins
      ();
      //();


   }
}

3. Test

Run the mian function inside to see the plug-in loading, calling and uninstalling situations

4. Quotation

/

/pf4j/pf4j-spring

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