Basic modularity system: plugin preloading.
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package net.pingex.dcf.modularity;
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import org.apache.commons.configuration2.ImmutableConfiguration;
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/**
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* Basic declaration of a plugin
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*/
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public interface IPlugin
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{
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/**
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* Load basic parameters, instantiate some objects, load configuration
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* @param configuration Configuration from dcf.properties
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*/
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void load(ImmutableConfiguration configuration);
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/**
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* Power up objects, shedule tasks, and so on
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*/
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void run();
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/**
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* Stop everything, doesn't mean we'll unload the plugin
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*/
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void stop();
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/**
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* Unload the plugin, clean up, etc
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*/
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void unload();
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}
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package net.pingex.dcf.modularity;
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import java.lang.annotation.ElementType;
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import java.lang.annotation.Retention;
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import java.lang.annotation.RetentionPolicy;
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import java.lang.annotation.Target;
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/**
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* Annotation containing some details about annotated {@code IPlugin}.
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*/
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@Retention(RetentionPolicy.RUNTIME)
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@Target(ElementType.TYPE)
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public @interface Plugin
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{
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/**
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* Unique plugin id.
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*/
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String id();
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/**
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* Version of the plugin.
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*/
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String version();
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/**
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* Plugin short description
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*/
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String description() default "No description provided.";
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}
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package net.pingex.dcf.modularity;
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import net.pingex.dcf.core.Configuration;
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import org.apache.commons.io.FilenameUtils;
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import org.apache.logging.log4j.LogManager;
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import org.apache.logging.log4j.Logger;
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import java.io.IOException;
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import java.net.URL;
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import java.net.URLClassLoader;
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import java.nio.file.Files;
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import java.nio.file.Path;
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import java.nio.file.Paths;
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import java.util.HashMap;
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import java.util.Map;
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import java.util.jar.Attributes;
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import java.util.jar.JarFile;
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/**
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* Class that load the plugins, a very powerful thingy.
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*/
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public class PluginLoader
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{
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/**
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* Singleton instance
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*/
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private static PluginLoader INSTANCE = new PluginLoader();
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/**
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* Logger
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*/
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private static Logger LOGGER = LogManager.getLogger(PluginLoader.class);
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/**
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* All plugins
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*/
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Map<String, PluginWrapper> plugins;
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/**
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* Gives the singleton instance
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* @return The singleton instance
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*/
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public static PluginLoader getInstance()
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{
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return INSTANCE;
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}
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/**
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* Enforce singleton with a private constructor.
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*/
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private PluginLoader()
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{
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plugins = new HashMap<>();
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}
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/**
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* Discover all plugins contained in .jar files in the plugins directory.
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*/
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public void discoverPluginsDirectory()
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{
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LOGGER.debug("Discovering all IPlugin classes in plugins directory.");
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try
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{
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Files.walk(Paths.get(Configuration.PLUGINS_DIR))
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.filter(Files::isRegularFile)
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.filter(path -> FilenameUtils.getExtension(path.toString()).equals("jar"))
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.forEach(path -> {
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try
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{
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loadJarFile(path);
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}
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catch(IOException e)
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{
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LOGGER.catching(e);
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}
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});
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}
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catch(IOException e)
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{
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LOGGER.error("IO error while discovering plugins.", e);
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}
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}
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/**
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* Look in a .jar file for IPlugins.
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*/
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public void loadJarFile(Path target) throws IOException
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{
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LOGGER.debug("Looking up {} for plugins.", target.getFileName());
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// Get DCF-Plugins manifest attribute
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Attributes jarAttributes = new JarFile(target.toFile()).getManifest().getMainAttributes();
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LOGGER.trace("DCF-Plugins attribute: {}", jarAttributes.getValue("DCF-Plugins"));
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if(jarAttributes.getValue("DCF-Plugins") == null)
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{
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LOGGER.debug("Jar file has no `DCF-Plugins` attribute in its manifest. Ignoring archive.");
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return;
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}
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String[] pluginsToLoad = jarAttributes.getValue("DCF-Plugins").split(" ");
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LOGGER.debug("Manifest returned {} plugins to load.", pluginsToLoad.length);
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URLClassLoader classLoader = URLClassLoader.newInstance(new URL[]{target.toUri().toURL()});
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for(String item : pluginsToLoad)
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{
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LOGGER.debug("Attempting to load {}.", item);
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Class<?> clazz;
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try
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{
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clazz = Class.forName(item, true, classLoader);
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}
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catch(ClassNotFoundException e) // Class with that name doesn't exist.
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{
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LOGGER.debug("No class with name {} was found.", item);
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return;
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}
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// Class doesn't implement IPlugin, or doesn't have @Plugin annotation.
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if(!clazz.isAnnotationPresent(Plugin.class) || !IPlugin.class.isAssignableFrom(clazz))
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{
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LOGGER.debug("Class does not implement IPlugin or doesn't gave @Plugin annotation.");
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return;
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}
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LOGGER.debug("Plugin {} {} preloaded.", clazz.getAnnotation(Plugin.class).id(), clazz.getAnnotation(Plugin.class).version());
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plugins.put(clazz.getAnnotation(Plugin.class).id(), new PluginWrapper(clazz.asSubclass(IPlugin.class), classLoader));
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}
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}
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}
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package net.pingex.dcf.modularity;
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/**
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* Every possible plugin states
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*/
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public enum PluginState
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{
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/**
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* The plugin does not have an associated {@code IPlugin} instance.
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*/
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VOID,
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/**
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* The plugin is unloaded, ie. the loader did not run {@code load()}, or executed {@code unload()} on the associated instance.
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*/
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UNLOADED,
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/**
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* The loader ran {@code load()}.
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*/
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LOADED,
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/**
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* The loader ran {@code run()}.
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*/
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RUNNING,
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/**
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* The plugin has been running once, but has now stopped.
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*/
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STOPPED,
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/**
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* The plugin fucked up somewhere.
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*/
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FAILED
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}
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@ -0,0 +1,104 @@
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package net.pingex.dcf.modularity;
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import java.net.URLClassLoader;
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/**
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* A class wrapping a {@code IPlugin} class.
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*/
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public class PluginWrapper
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{
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/**
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* Unique ID of the plugin.
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*/
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private String id;
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/**
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* Version of this plugin.
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*/
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private String version;
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/**
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* Plugin short description
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*/
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private String description;
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/**
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* Matching plugin class.
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*/
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private Class<? extends IPlugin> pluginClass;
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/**
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* The associated class loader.
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*/
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private URLClassLoader classLoader;
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/**
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* The plugin main instance.
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*/
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private IPlugin instance;
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/**
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* The current state of this plugin.
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*/
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private PluginState state;
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public PluginWrapper(Class<? extends IPlugin> pluginClass, URLClassLoader classLoader)
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{
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this.id = pluginClass.getAnnotation(Plugin.class).id();
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this.version = pluginClass.getAnnotation(Plugin.class).version();
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this.description = pluginClass.getAnnotation(Plugin.class).description();
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this.pluginClass = pluginClass;
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this.classLoader = classLoader;
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this.instance = null;
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this.state = PluginState.VOID;
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}
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// GETTERS
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public String getId()
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{
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return id;
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}
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public String getVersion()
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{
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return version;
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}
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public String getDescription()
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{
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return description;
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}
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public Class<? extends IPlugin> getPluginClass()
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{
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return pluginClass;
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}
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public URLClassLoader getClassLoader()
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{
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return classLoader;
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}
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public IPlugin getInstance()
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{
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return instance;
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}
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public PluginState getState()
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{
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return state;
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}
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// SETTERS
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public void setInstance(IPlugin instance)
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{
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this.instance = instance;
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}
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public void setState(PluginState state)
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{
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this.state = state;
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}
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}
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@ -0,0 +1,4 @@
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/**
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* Contains all classes needed to load modules
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*/
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package net.pingex.dcf.modularity;
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