加载处理

@Override

public void loadPlugins() {

log.debug("Lookup plugins in '{}'", pluginsRoots);

// check for plugins roots

if (pluginsRoots.isEmpty()) {

log.warn("No plugins roots configured");

return;

}

pluginsRoots.forEach(path -> {

if (Files.notExists(path) || !Files.isDirectory(path)) {

log.warn("No '{}' root", path);

}

});

// get all plugin paths from repository

// 查找路径

List<Path> pluginPaths = pluginRepository.getPluginPaths();

// check for no plugins

if (pluginPaths.isEmpty()) {

("No plugins");

return;

}

log.debug("Found {} possible plugins: {}", pluginPaths.size(), pluginPaths);

// load plugins from plugin paths

for (Path pluginPath : pluginPaths) {

try {

// 加载发现到的插件，此方法比较重要

loadPluginFromPath(pluginPath);

} catch (PluginRuntimeException e) {

log.error(e.getMessage(), e);

}

}

// resolve plugins

try {

// 解析插件，主要是关于依赖，解析插件描述信息，然后进行插件状态的通知

resolvePlugins();

} catch (PluginRuntimeException e) {

log.error(e.getMessage(), e);

}

}

protected PluginWrapper loadPluginFromPath(Path pluginPath) {

// Test for plugin path duplication

String pluginId = idForPath(pluginPath);

if (pluginId != null) {

throw new PluginAlreadyLoadedException(pluginId, pluginPath);

}

// Retrieve and validate the plugin descriptor

PluginDescriptorFinder pluginDescriptorFinder = getPluginDescriptorFinder();

log.debug("Use '{}' to find plugins descriptors", pluginDescriptorFinder);

log.debug("Finding plugin descriptor for plugin '{}'", pluginPath);

PluginDescriptor pluginDescriptor = pluginDescriptorFinder.find(pluginPath);

validatePluginDescriptor(pluginDescriptor);

// Check there are no loaded plugins with the retrieved id

pluginId = pluginDescriptor.getPluginId();

if (plugins.containsKey(pluginId)) {

PluginWrapper loadedPlugin = getPlugin(pluginId);

throw new PluginRuntimeException("There is an already loaded plugin ({}) "

+ "with the same id ({}) as the plugin at path '{}'. Simultaneous loading "

+ "of plugins with the same PluginId is not currently supported.\n"

+ "As a workaround you may include PluginVersion and PluginProvider "

+ "in PluginId.",

loadedPlugin, pluginId, pluginPath);

}

log.debug("Found descriptor {}", pluginDescriptor);

String pluginClassName = pluginDescriptor.getPluginClass();

log.debug("Class '{}' for plugin '{}'",  pluginClassName, pluginPath);

// load plugin

log.debug("Loading plugin '{}'", pluginPath);

// 此处，保证每个插件会有一个不同的classloader，这个后续会介绍

ClassLoader pluginClassLoader = getPluginLoader().loadPlugin(pluginPath, pluginDescriptor);

log.debug("Loaded plugin '{}' with class loader '{}'", pluginPath, pluginClassLoader);

PluginWrapper pluginWrapper = createPluginWrapper(pluginDescriptor, pluginPath, pluginClassLoader);

// test for disabled plugin

if (isPluginDisabled(pluginDescriptor.getPluginId())) {

("Plugin '{}' is disabled", pluginPath);

pluginWrapper.setPluginState(PluginState.DISABLED);

}

// validate the plugin

if (!isPluginValid(pluginWrapper)) {

log.warn("Plugin '{}' is invalid and it will be disabled", pluginPath);

pluginWrapper.setPluginState(PluginState.DISABLED);

}

log.debug("Created wrapper '{}' for plugin '{}'", pluginWrapper, pluginPath);

pluginId = pluginDescriptor.getPluginId();

// add plugin to the list with plugins

plugins.put(pluginId, pluginWrapper);

getUnresolvedPlugins().add(pluginWrapper);

// add plugin class loader to the list with class loaders

getPluginClassLoaders().put(pluginId, pluginClassLoader);

return pluginWrapper;

}