org.apache.druid.guice

Class ExtensionsLoader

java.lang.Object

org.apache.druid.guice.ExtensionsLoader

public class ExtensionsLoader
extends Object

Manages the loading of Druid extensions. Used in two cases: for CLI extensions from Main, and for DruidModule extensions during initialization. The design, however, should support any kind of extension that may be needed in the future. The extensions are cached so that they can be reported by various REST APIs.

Constructor Summary

Constructors

Constructor and Description
ExtensionsLoader(ExtensionsConfig config)

Method Summary

Modifier and Type	Method and Description
ExtensionsConfig	config()
URLClassLoader	getClassLoaderForExtension(File extension, boolean useExtensionClassloaderFirst)
File[]	getExtensionFilesToLoad() Find all the extension files that should be loaded by druid.
<T> Collection<T>	getFromExtensions(Class<T> serviceClass) Look for implementations for the given class from both classpath and extensions directory, using ServiceLoader.
<T> Collection<T>	getLoadedImplementations(Class<T> clazz) Returns a collection of implementations loaded.
Collection<DruidModule>	getLoadedModules()
Map<Pair<File,Boolean>,URLClassLoader>	getLoadersMap()
Collection<DruidModule>	getModules()
static List<URL>	getURLsForClasspath(String cp)
static ExtensionsLoader	instance(com.google.inject.Injector injector)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ExtensionsLoader

@Inject
public ExtensionsLoader(ExtensionsConfig config)

Method Detail

instance

public static ExtensionsLoader instance(com.google.inject.Injector injector)

config

public ExtensionsConfig config()

getLoadedImplementations

public <T> Collection<T> getLoadedImplementations(Class<T> clazz)

Returns a collection of implementations loaded.

Type Parameters:

T - the service type

Parameters:

clazz - service class

getLoadedModules

public Collection<DruidModule> getLoadedModules()

Returns:

a collection of implementations loaded.

getLoadersMap

public Map<Pair<File,Boolean>,URLClassLoader> getLoadersMap()

getFromExtensions

public <T> Collection<T> getFromExtensions(Class<T> serviceClass)

Look for implementations for the given class from both classpath and extensions directory, using ServiceLoader. A user should never put the same two extensions in classpath and extensions directory, if he/she does that, the one that is in the classpath will be loaded, the other will be ignored.

Parameters:

serviceClass - The class to look the implementations of (e.g., DruidModule)

Returns:

A collection that contains implementations (of distinct concrete classes) of the given class. The order of elements in the returned collection is not specified and not guaranteed to be the same for different calls to getFromExtensions().

getModules

public Collection<DruidModule> getModules()

getExtensionFilesToLoad

public File[] getExtensionFilesToLoad()

Find all the extension files that should be loaded by druid.

If user explicitly specifies druid.extensions.loadList, then it will look for those extensions under root extensions directory. If one of them is not found, druid will fail loudly.

If user doesn't specify druid.extension.toLoad (or its value is empty), druid will load all the extensions under the root extensions directory.

Returns:

an array of druid extension files that will be loaded by druid process

getClassLoaderForExtension

public URLClassLoader getClassLoaderForExtension(File extension,
                                                 boolean useExtensionClassloaderFirst)

Parameters:

extension - The File instance of the extension we want to load

Returns:

a URLClassLoader that loads all the jars on which the extension is dependent

getURLsForClasspath

public static List<URL> getURLsForClasspath(String cp)