dubbo SPI扩展点，通过扩展点名称获取实例的详细流程图

if cachedAdaptiveClass is null or the same as the clazz

load all the extension classes to global variableExtensionLoader.loadExtensionClasses()

no

get instance from EXTENSION_INSTANCESby class type

getHolder from cachedInstances

extensionClasses

check all fields which are not be annotated by DisableInject and has setter function

yes

return extension classes

obtain the instance by extension nameExtensionLoader.getExtensionLoader(Class type).getExtension(String name)

if clazz isAnnotationPresent(Adaptive.class)

getOrCreateHolder

Dubbo SPIThe Process of Getting an Instance by Instance Name

get clazz extension name

cacheDefaultExtensionName

wrap instance by cachedWrapperClasses

if name eqauls \"true\"

instance is null

injectExtension in the instance

createHolderthen put into cachedInstances

load all extention classes of this type by strategies（actually load the classes in \"META-INF/dubbo/internal/\" \"META-INF/dubbo/\" \"META-INF/services/\" of this type）

get instance

instanceis null

validate extension name

getInstance

get instance from holder

if the interface type is annotated by @SPIfont color=\"#000000\

get class type by name

return the name of default extention class

noreturn instance

set of cachedWrapperClasses add this clazz

if clazz is annotated by Activate

get extension classes 

return instance

cache ActivateClass

set cachedAdaptiveClass

if class type is null

if cachedInstances containsKey(name)

inject by reflective method

if name is empty

validate cached extension classesExtensionLoader.getExtensionClasses()

if clazz extension name is empty

put into EXTENSION_INSTANCES 

create extension instance

get clazz simple name and toLowerCase

saveExtensionClasses

return classes then cache

load extension class include(adaptive / wrapper / activate / normal)

if cachedClassesis empty

set cachedDefaultName in global variable

throw exception(More than 1 adaptive class found)

initExtension(lifecycle.initialize)

cachedActivates.put(font color=\"#ff3333\

if clazz isWrapperClass(has a constructor with only one param of interface type)

throw exception

getDefaultExtension

get cached default extensionExtensionLoader.getExtension(String name)