import org.apache.logging.log4j.core.config.plugins.Plugin; //导入依赖的package包/类

/**

* @since 2.1

*/

public Map>> loadFromPackage(final String pkg) {

if (Strings.isBlank(pkg)) {

// happens when splitting an empty string

return Collections.emptyMap();

}

Map>> existing = pluginsByCategoryByPackage.get(pkg);

if (existing != null) {

// already loaded this package

return existing;

}

final long startTime = System.nanoTime();

final ResolverUtil resolver = new ResolverUtil();

final ClassLoader classLoader = Loader.getClassLoader();

if (classLoader != null) {

resolver.setClassLoader(classLoader);

}

resolver.findInPackage(new PluginTest(), pkg);

final Map>> newPluginsByCategory = new HashMap<>();

for (final Class> clazz : resolver.getClasses()) {

final Plugin plugin = clazz.getAnnotation(Plugin.class);

final String categoryLowerCase = plugin.category().toLowerCase();

List> list = newPluginsByCategory.get(categoryLowerCase);

if (list == null) {

newPluginsByCategory.put(categoryLowerCase, list = new ArrayList<>());

}

final PluginEntry mainEntry = new PluginEntry();

final String mainElementName = plugin.elementType().equals(

Plugin.EMPTY) ? plugin.name() : plugin.elementType();

mainEntry.setKey(plugin.name().toLowerCase());

mainEntry.setName(plugin.name());

mainEntry.setCategory(plugin.category());

mainEntry.setClassName(clazz.getName());

mainEntry.setPrintable(plugin.printObject());

mainEntry.setDefer(plugin.deferChildren());

final PluginType> mainType = new PluginType<>(mainEntry, clazz, mainElementName);

list.add(mainType);

final PluginAliases pluginAliases = clazz.getAnnotation(PluginAliases.class);

if (pluginAliases != null) {

for (final String alias : pluginAliases.value()) {

final PluginEntry aliasEntry = new PluginEntry();

final String aliasElementName = plugin.elementType().equals(

Plugin.EMPTY) ? alias.trim() : plugin.elementType();

aliasEntry.setKey(alias.trim().toLowerCase());

aliasEntry.setName(plugin.name());

aliasEntry.setCategory(plugin.category());

aliasEntry.setClassName(clazz.getName());

aliasEntry.setPrintable(plugin.printObject());

aliasEntry.setDefer(plugin.deferChildren());

final PluginType> aliasType = new PluginType<>(aliasEntry, clazz, aliasElementName);

list.add(aliasType);

}

}

}

final long endTime = System.nanoTime();

final DecimalFormat numFormat = new DecimalFormat("#0.000000");

final double seconds = (endTime - startTime) * 1e-9;

LOGGER.debug("Took {} seconds to load {} plugins from package {}",

numFormat.format(seconds), resolver.getClasses().size(), pkg);

// Note multiple threads could be calling this method concurrently. Both will do the work,

// but only one will be allowed to store the result in the outer map.

// Return the inner map produced by whichever thread won the race, so all callers will get the same result.

existing = pluginsByCategoryByPackage.putIfAbsent(pkg, newPluginsByCategory);

if (existing != null) {

return existing;

}

return newPluginsByCategory;

}