前言

相信绝大多数公司项目都做了组件化。为了解耦，组件化势必要解决组件间的通信。其中阿里巴巴开源的Arouter很好的解决了组件间的通信，一直受到开发者的青睐。今天，我们来一步步揭开它的神秘面纱。

首先下载源代码，项目地址：

https://github.com/alibaba/ARouter

来讲一下项目结构

源代码

• app:项目主工程，演示代码
• module-java：java演示代码
• module-kotlin：kotlin演示代码
• arouter-annotation：所有注解以及注解涉及到的类
• arouter-compiler：注解处理器，APT
• arouter-gradle-plugin：路由表自动注册插件
• arouter-idea-plugin：路由跳转插件，搜索ARouter Helper插件安装即可。
• arouter-api：所有的api

第一步就是要生成注解类

@Route @Autowired Interceptor Provider都会生成如下面所示的对应注解类，java生成的注解类的位置在build-generated-sourse-apt中，kotlin生成的注解类的位置在build-generated-sourse-kapt

public class ARouter$$Group$$app implements IRouteGroup {
 @Override
 public void loadInto(Map atlas) {
 atlas.put("/app/degrade1", RouteMeta.build(RouteType.PROVIDER, DegradeServiceImpl.class, "/app/degrade1", "app", null, -1, -2147483648));
 atlas.put("/app/main", RouteMeta.build(RouteType.ACTIVITY, MainActivity.class, "/app/main", "app", null, -1, -2147483648));
 atlas.put("/app/path", RouteMeta.build(RouteType.PROVIDER, PathReplaceServiceImpl.class, "/app/path", "app", null, -1, -2147483648));
 }
}

这里需要重点关注一下RouteMeta这个类，这个类存储了目标对象的所有信息。包括路由类型、目标对象类、path、group、参数、优先级、额外参数。

涉及到的知识点:

1. apt
2. javapoet
3. auto-service

这里是我写的一个AptDemo，仅供参考：

https://github.com/liulingfeng/APT

关于AbstractProcessor的process多次执行可以通过下面方法处理

@Override
 public boolean process(Set annotations, RoundEnvironment roundEnvironment) {
 if (annotations != null && annotations.size() > 0) {
 
 }
 }

下面正式讲解api

先整体感受一下整个流程

整体流程

根据官方说明，首先在Application中调用如下api

if(BuildConfig.DEBUG){
 ARouter.openLog();//打开日志
 ARouter.openDebug();//打开路由调试
 }
 ARouter.init(this);

进入Arouter.init(this)

public static void init(Application application) {
 if (!hasInit) {
 logger = _ARouter.logger;
 hasInit = _ARouter.init(application);

 if (hasInit) {
 _ARouter.afterInit();
 }
 }
 }

hasInit保证只初始化一次，内部调用了_ARouter.init(application)，Arouter是门面， _Arouter是具体实现，有一点装饰模式的感觉。初始化之后调用 _ARouter.afterInit实例化拦截器（这个后面细讲）。继续跟进 _ARouter.init

protected static synchronized boolean init(Application application) {
 mContext = application;
 LogisticsCenter.init(mContext, executor);
 logger.info(Consts.TAG, "ARouter init success!");
 hasInit = true;
 return true;
 }

一眼就看到关键代码在LogisticsCenter.init中，executor是一个自定义的线程池(实现了一种抛出错误的方式)。

public synchronized static void init(Context context, ThreadPoolExecutor tpe) throws HandlerException {
 try {
 if (registerByPlugin) {
 logger.info(TAG, "Load router map by arouter-auto-register plugin.");
 } else {
 Set routerMap;
 if (ARouter.debuggable() || PackageUtils.isNewVersion(context)) {
 routerMap = ClassUtils.getFileNameByPackageName(mContext, ROUTE_ROOT_PAKCAGE);
 if (!routerMap.isEmpty()) {
 context.getSharedPreferences(AROUTER_SP_CACHE_KEY, Context.MODE_PRIVATE).edit().putStringSet(AROUTER_SP_KEY_MAP, routerMap).apply();
 }

 PackageUtils.updateVersion(context);
 } else {
 for (String className : routerMap) {
 if (className.startsWith(ROUTE_ROOT_PAKCAGE + DOT + SDK_NAME + SEPARATOR + SUFFIX_ROOT)) {
 ((IRouteRoot) (Class.forName(className).getConstructor().newInstance())).loadInto(Warehouse.groupsIndex);
 } else if (className.startsWith(ROUTE_ROOT_PAKCAGE + DOT + SDK_NAME + SEPARATOR + SUFFIX_INTERCEPTORS)) {
 ((IInterceptorGroup) (Class.forName(className).getConstructor().newInstance())).loadInto(Warehouse.interceptorsIndex);
 } else if (className.startsWith(ROUTE_ROOT_PAKCAGE + DOT + SDK_NAME + SEPARATOR + SUFFIX_PROVIDERS)) {
 ((IProviderGroup) (Class.forName(className).getConstructor().newInstance())).loadInto(Warehouse.providersIndex);
 }
 }
 }
 } catch (Exception e) {
 throw new HandlerException(TAG + "ARouter init logistics center exception! [" + e.getMessage() + "]");
 }
 }

代码比较长，我把它分解一下

• 1.判断是不是用插件自动注册路由表，插件注册的方式另说
• 2.从dex中加载指定路径（com.alibaba.android.arouter.routes）下的所有类名，其实就是注解生成类，然后根据版本号升级版本。非debuggable环境下从SharedPreferences缓存中读取（做的一个优化点）
• 3.反射调用loadInto把Group、Interceptor、Provider的映射关系添加到集合中

看一下各种类型的注解生成类
Root(这里做了优化先加载各个group，用到的时候再加载各个group下的路由)

public class ARouter$$Root$$app implements IRouteRoot {
 @Override
 public void loadInto(Map> routes) {
 routes.put("app", ARouter$$Group$$app.class);
 }
}

Interceptor

public class ARouter$$Interceptors$$app implements IInterceptorGroup {
 @Override
 public void loadInto(Map> interceptors) {
 interceptors.put(9, TestInterceptor2.class);
 interceptors.put(10, TestInterceptor.class);
 }
}

Provider

public class ARouter$$Providers$$app implements IProviderGroup {
 @Override
 public void loadInto(Map providers) {
 providers.put("com.xls.HelloService", RouteMeta.build(RouteType.PROVIDER, HelloServiceImpl.class, "/yourservicegroupname/hello", "yourservicegroupname", null, -1, -2147483648));
 }
}

init工作总结及知识点

• 1.把Group、Interceptor、Provider注解类的映射添加到Warehouse.groupsIndex、Warehouse.interceptorsIndex、Warehouse.providersIndex集合中
• 2.实例化所有的Interceptor添加到Warehouse.interceptors中
• 3.dex分析-多dex怎么查找-热修复的根本原理是什么
• 4.线程池-线程池各个参数-线程池抛出错误的方法-如何保证线程池线程名字唯一性-原子类

顺便补充一下插件自动注册路由表

首先目光移到PluginLaunch，这是自定义插件的入口。

public class PluginLaunch implements Plugin {
 @Override
 public void apply(Project project) {
 def android = project.extensions.getByType(AppExtension)
 def transformImpl = new RegisterTransform(project)

 ArrayList list = new ArrayList<>(3)
 list.add(new ScanSetting('IRouteRoot'))
 list.add(new ScanSetting('IInterceptorGroup'))
 list.add(new ScanSetting('IProviderGroup'))
 RegisterTransform.registerList = list
 android.registerTransform(transformImpl)
 }
 }
}

这里完成了自定义Transform的注册以及添加需要过滤的接口到ScanSetting，最主要的代码自然是在RegisterTransform中。直奔RegisterTransform的transform方法，首先遍历jar。

inputs.each { TransformInput input ->
 input.jarInputs.each {
 if (ScanUtil.shouldProcessPreDexJar(src.absolutePath)) {
 ScanUtil.scanJar(src, dest)
 }
 FileUtils.copyFile(src, dest)
 }

static void scanJar(File jarFile, File destFile) {
 if (jarFile) {
 def file = new JarFile(jarFile)
 Enumeration enumeration = file.entries()
 while (enumeration.hasMoreElements()) {
 JarEntry jarEntry = (JarEntry) enumeration.nextElement()
 String entryName = jarEntry.getName()
 if (entryName.startsWith("com/alibaba/android/arouter/routes/")) {
 InputStream inputStream = file.getInputStream(jarEntry)
 scanClass(inputStream)
 inputStream.close()
 } else if ("com/alibaba/android/arouter/core/LogisticsCenter.class" == entryName) {
 RegisterTransform.fileContainsInitClass = destFile
 }
 }
 file.close()
 }
 }

做到两步工作:1.把com/alibaba/android/arouter/routes包名下的交给scanClass处理（这个稍后会分析到） 2.找到LogisticsCenter.class类，对于这个类想必很熟悉吧。

接下来遍历directory

input.directoryInputs.each { DirectoryInput directoryInput ->
 directoryInput.file.eachFileRecurse { File file ->
 if(file.isFile() && ScanUtil.shouldProcessClass(path)){
 ScanUtil.scanClass(file)
 }
 }
 }

static void scanClass(InputStream inputStream) {
 ClassReader cr = new ClassReader(inputStream)
 ClassWriter cw = new ClassWriter(cr, 0)
 ScanClassVisitor cv = new ScanClassVisitor(Opcodes.ASM5, cw)
 cr.accept(cv, ClassReader.EXPAND_FRAMES)
 inputStream.close()
 }

把文件流丢给ScanClassVisitor

static class ScanClassVisitor extends ClassVisitor {

 ScanClassVisitor(int api, ClassVisitor cv) {
 super(api, cv)
 }

 void visit(int version, int access, String name, String signature,
 String superName, String[] interfaces) {
 super.visit(version, access, name, signature, superName, interfaces)
 RegisterTransform.registerList.each { ext ->
 if (ext.interfaceName && interfaces != null) {
 interfaces.each { itName ->
 if (itName == ext.interfaceName) {
 ext.classList.add(name)
 }
 }
 }
 }
 }
 }

一看就明白，就是把所有实现了IRouteRoot、IInterceptorGroup、IProviderGroup接口的类存到集合中。

接着看最后一步做了什么

if (fileContainsInitClass) {
 registerList.each { ext ->
 if (ext.classList.isEmpty()) {
 Logger.e("No class implements found for interface:" + ext.interfaceName)
 } else {
 RegisterCodeGenerator.insertInitCodeTo(ext)
 }
 }
 }

关键代码都在RegisterCodeGenerator这个类中，我只列关键代码。

private byte[] referHackWhenInit(InputStream inputStream) {
 ClassReader cr = new ClassReader(inputStream)
 ClassWriter cw = new ClassWriter(cr, 0)
 ClassVisitor cv = new MyClassVisitor(Opcodes.ASM5, cw)
 cr.accept(cv, ClassReader.EXPAND_FRAMES)
 return cw.toByteArray()
 }
 
MethodVisitor visitMethod(int access, String name, String desc,
 String signature, String[] exceptions) {
 MethodVisitor mv = super.visitMethod(access, name, desc, signature, exceptions)
 if (name == "loadRouterMap") {
 mv = new RouteMethodVisitor(Opcodes.ASM5, mv)
 }
 return mv
 }

找到hook点loadRouterMap。hook点的设计特别巧妙，增强了代码的可读性。

void visitInsn(int opcode) {
 if ((opcode >= Opcodes.IRETURN && opcode <= Opcodes.RETURN)) {
 extension.classList.each { name ->
 mv.visitMethodInsn(Opcodes.INVOKESTATIC
 , "com/alibaba/android/arouter/core/LogisticsCenter"
 , "register"
 , "(Ljava/lang/String;)V"
 , false)
 }
 }
 super.visitInsn(opcode)
 }

调用LogisticsCenter的register方法，我们来看一下register方法做了什么。

 private static void register(String className) {
 if (!TextUtils.isEmpty(className)) {
 try {
 Class clazz = Class.forName(className);
 Object obj = clazz.getConstructor().newInstance();
 if (obj instanceof IRouteRoot) {
 registerRouteRoot((IRouteRoot) obj);
 } else if (obj instanceof IProviderGroup) {
 registerProvider((IProviderGroup) obj);
 } else if (obj instanceof IInterceptorGroup) {
 registerInterceptor((IInterceptorGroup) obj);
 } else {
 logger.info(TAG, "register failed, class name: " + className
 + " should implements one of IRouteRoot/IProviderGroup/IInterceptorGroup.");
 }
 } catch (Exception e) {
 logger.error(TAG,"register class error:" + className);
 }
 }
 }

所有实现了IRouteRoot、IInterceptorGroup、IProviderGroup接口的类都加入了Warehouse相对应的集合中。至此自动注册工作完成。

路由跳转

ARouter.getInstance().build("/home/test").withString("key3", "888")
 .withLong("key1", 666L)
 .navigation(this)

先看build，new一个Postcard对象并给Postcard设置path和group。Postcard构造方法中new了一个bundler对象。PathReplaceService提供了动态改path的方式，后面细讲。

protected Postcard build(String path, String group) {
 if (TextUtils.isEmpty(path) || TextUtils.isEmpty(group)) {
 throw new HandlerException(Consts.TAG + "Parameter is invalid!");
 } else {
 PathReplaceService pService = ARouter.getInstance().navigation(PathReplaceService.class);
 if (null != pService) {
 path = pService.forString(path);
 }
 return new Postcard(path, group);
 }
 }

.withString("key3", "888").withLong("key1", 666L)把参数设置给当前Postcard的bundle中。

再看navigation方法

protected Object navigation(final Context context, final Postcard postcard, final int requestCode, final NavigationCallback callback) {
 try {
 LogisticsCenter.completion(postcard);
 } catch (NoRouteFoundException ex) {
 if (debuggable()) {
 Toast.makeText(mContext, "There's no route matched!\n" +
 " Path = [" + postcard.getPath() + "]\n" +
 " Group = [" + postcard.getGroup() + "]", Toast.LENGTH_LONG).show();
 }

 if (null != callback) {
 callback.onLost(postcard);
 } else {
 DegradeService degradeService = ARouter.getInstance().navigation(DegradeService.class);
 if (null != degradeService) {
 degradeService.onLost(context, postcard);
 }
 }

 return null;
 }
 return null;
 }

先看第一部分，重点落在LogisticsCenter.completion(postcard)。内部主要做的是实例化当前group下的具体Route添加到Warehouse.routes，如果没找到就降级处理，两种方式（1.设置NavigationCallback 2.实现DegradeService）

public synchronized static void completion(Postcard postcard) {
 RouteMeta routeMeta = Warehouse.routes.get(postcard.getPath());
 if (null == routeMeta) {
 Class groupMeta = Warehouse.groupsIndex.get(postcard.getGroup());
 if (null == groupMeta) {
 throw new NoRouteFoundException(TAG + "There is no route match the path [" + postcard.getPath() + "], in group [" + postcard.getGroup() + "]");
 } else {
 try {
 IRouteGroup iGroupInstance = groupMeta.getConstructor().newInstance();
 iGroupInstance.loadInto(Warehouse.routes);
 Warehouse.groupsIndex.remove(postcard.getGroup());
 } catch (Exception e) {
 throw new HandlerException(TAG + "Fatal exception when loading group meta. [" + e.getMessage() + "]");
 }
 completion(postcard);
 }
 } else {
 postcard.setDestination(routeMeta.getDestination());
 postcard.setType(routeMeta.getType());
 postcard.setPriority(routeMeta.getPriority());
 postcard.setExtra(routeMeta.getExtra());

 Uri rawUri = postcard.getUri();
 if (null != rawUri) {
 Map resultMap = TextUtils.splitQueryParameters(rawUri);
 Map paramsType = routeMeta.getParamsType();

 if (MapUtils.isNotEmpty(paramsType)) {
 for (Map.Entry params : paramsType.entrySet()) {
 setValue(postcard,
 params.getValue(),
 params.getKey(),
 resultMap.get(params.getKey()));
 }
 postcard.getExtras().putStringArray(ARouter.AUTO_INJECT, paramsType.keySet().toArray(new String[]{}));
 }

 postcard.withString(ARouter.RAW_URI, rawUri.toString());
 }

 switch (routeMeta.getType()) {
 case PROVIDER: 
 Class providerMeta = (Class) routeMeta.getDestination();
 IProvider instance = Warehouse.providers.get(providerMeta);
 if (null == instance) {
 IProvider provider;
 try {
 provider = providerMeta.getConstructor().newInstance();
 provider.init(mContext);
 Warehouse.providers.put(providerMeta, provider);
 instance = provider;
 } catch (Exception e) {
 throw new HandlerException("Init provider failed! " + e.getMessage());
 }
 }
 postcard.setProvider(instance);
 postcard.greenChannel();
 break;
 case FRAGMENT:
 postcard.greenChannel(); 
 default:
 break;
 }
 }
 }

分析一下这段代码

• 1.判断Warehouse的routes中对应path的RouteMeta是否为空，看过注解生成类其实我们知道RouteMeta保存了类的具体信息
• 2.在集合中找到对应的group分组，然后实例化对应分组下的具体Route添加到集合中
• 3.把RouteMeta的各种信息设置给当前postcard对象
• 4.uri跳转的处理，uri跳转和普通跳转唯一的区别就是参数的剥离，普通跳转是直接设置的而uri是通过在链接中剥离的，其中参数的数据类型是在Routemeta的paramsType中设置的
• 5.根据跳转的类型不同做不同处理。如果是服务，直接实例化当前服务调用init方法并设置给postcard。设置绿色通道；如果是fragment，设置绿色通道。所谓绿色通道就是不被拦截器拦截。

第二个部分是处理拦截。我们稍后再讲
先看第三部分

private Object _navigation(final Context context, final Postcard postcard, final int requestCode, final NavigationCallback callback) {
 final Context currentContext = null == context ? mContext : context;

 switch (postcard.getType()) {
 case ACTIVITY:
 final Intent intent = new Intent(currentContext, postcard.getDestination());
 intent.putExtras(postcard.getExtras());

 int flags = postcard.getFlags();
 if (-1 != flags) {
 intent.setFlags(flags);
 } else if (!(currentContext instanceof Activity)) {
 intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
 }

 String action = postcard.getAction();
 if (!TextUtils.isEmpty(action)) {
 intent.setAction(action);
 }

 runInMainThread(new Runnable() {
 @Override
 public void run() {
 startActivity(requestCode, currentContext, intent, postcard, callback);
 }
 });

 break;
 case PROVIDER:
 return postcard.getProvider();
 case BOARDCAST:
 case CONTENT_PROVIDER:
 case FRAGMENT:
 Class fragmentMeta = postcard.getDestination();
 try {
 Object instance = fragmentMeta.getConstructor().newInstance();
 if (instance instanceof Fragment) {
 ((Fragment) instance).setArguments(postcard.getExtras());
 } else if (instance instanceof android.support.v4.app.Fragment) {
 ((android.support.v4.app.Fragment) instance).setArguments(postcard.getExtras());
 }

 return instance;
 } catch (Exception ex) {
 logger.error(Consts.TAG, "Fetch fragment instance error, " + TextUtils.formatStackTrace(ex.getStackTrace()));
 }
 case METHOD:
 case SERVICE:
 default:
 return null;
 }

 return null;
 }

看到这里是不是很亲切，这不就是我们平时常写的startActivity(intent,class)吗？如果是fragment的话反射调用Fragment构造方法返回fragment对象。provider也是返回 Provider对象。至此跳转这一块基本上都搞清楚了。

分析一下拦截器怎么实现的

之前讲了Aroute.init之后会将所有的拦截器实例化。我们看看_ARouter.afterInit()做了什么

static void afterInit() {
 interceptorService = (InterceptorService) ARouter.getInstance().build("/arouter/service/interceptor").navigation();
 }

使用自己的路由方法初始化interceptorService服务，没毛病。该服务的实现类是InterceptorServiceImpl，从前面的分析可以知道navigation会调用服务的init方法。看看init里面做了什么

@Override
 public void init(final Context context) {
 LogisticsCenter.executor.execute(new Runnable() {
 @Override
 public void run() {
 if (MapUtils.isNotEmpty(Warehouse.interceptorsIndex)) {
 for (Map.Entry> entry : Warehouse.interceptorsIndex.entrySet()) {
 Class interceptorClass = entry.getValue();
 try {
 IInterceptor iInterceptor = interceptorClass.getConstructor().newInstance();
 iInterceptor.init(context);
 Warehouse.interceptors.add(iInterceptor);
 } catch (Exception ex) {
 throw new HandlerException(TAG + "ARouter init interceptor error! name = [" + interceptorClass.getName() + "], reason = [" + ex.getMessage() + "]");
 }
 }

 interceptorHasInit = true;
 }
 }
 });
 }

反射调用所有拦截器的构造函数实例化对象添加到Warehouse.interceptors并调用init方法，这里使用了object.wait和object.notifyAll保证子线程中的所有拦截器实例化完成。拦截的时机在前面已经提到过了，我们来看看具体的代码。

if (!postcard.isGreenChannel()) {
 interceptorService.doInterceptions(postcard, new InterceptorCallback() {
 @Override
 public void onContinue(Postcard postcard) {
 _navigation(context, postcard, requestCode, callback);
 }

 @Override
 public void onInterrupt(Throwable exception) {
 if (null != callback) {
 callback.onInterrupt(postcard);
 }
 }
 });

@Override
 public void doInterceptions(final Postcard postcard, final InterceptorCallback callback) {
 if (null != Warehouse.interceptors && Warehouse.interceptors.size() > 0) {
 LogisticsCenter.executor.execute(new Runnable() {
 @Override
 public void run() {
 CancelableCountDownLatch interceptorCounter = new CancelableCountDownLatch(Warehouse.interceptors.size());
 try {
 _excute(0, interceptorCounter, postcard);
 interceptorCounter.await(postcard.getTimeout(), TimeUnit.SECONDS);
 if (interceptorCounter.getCount() > 0) {
 callback.onInterrupt(new HandlerException("The interceptor processing timed out."));
 } else if (null != postcard.getTag()) { 
 callback.onInterrupt(new HandlerException(postcard.getTag().toString()));
 } else {
 callback.onContinue(postcard);
 }
 } catch (Exception e) {
 callback.onInterrupt(e);
 }
 }
 });
 } else {
 callback.onContinue(postcard);
 }
 }

private static void _excute(final int index, final CancelableCountDownLatch counter, final Postcard postcard) {
 if (index < Warehouse.interceptors.size()) {
 IInterceptor iInterceptor = Warehouse.interceptors.get(index);
 iInterceptor.process(postcard, new InterceptorCallback() {
 @Override
 public void onContinue(Postcard postcard) {
 counter.countDown();
 _excute(index + 1, counter, postcard);
 }

 @Override
 public void onInterrupt(Throwable exception) {
 postcard.setTag(null == exception ? new HandlerException("No message.") : exception.getMessage()); // save the exception message for backup.
 counter.cancel();
 }
 });
 }
 }

使用CountDownLatch.await使得代码阻塞直到所有拦截器执行完成或者超时。拦截器process方法中需要调用callback.onContinue才能调用到counter.countDown()移交到下一个拦截器，这就解释了自定义的拦截器为什么一定要调用counter.countDown()

涉及知识点

• 1.线程间通信
• 2.CountDownLatch
• 3.Object.wait/Object.notify

降级处理

两种方式：1.navigation的时候添加NavigationCallback回调 2.写一个类实现DegradeService别忘了添加@Route path可以随意 第一种比较简单我么不讲，讲一下第二种方式

@Route(path = "/app/degrade1")
class DegradeServiceImpl : DegradeService {
 override fun onLost(context: Context?, postcard: Postcard?) {
 Log.e("降级处理","自定义降级处理")
 }

 override fun init(context: Context?) {
 }
}

生成的注解类在ARouter$$Providers$$app中，也是init的时候就把映射关系添加到集合中。调用的地方是在navigation中，这段代码也间接的说明了NavigationCallback的优先级高于全局降级处理。

if (null != callback) {
 callback.onLost(postcard);
 } else {
 DegradeService degradeService = ARouter.getInstance().navigation(DegradeService.class);
 if (null != degradeService) {
 degradeService.onLost(context, postcard);
 }
 }

关键代码是下面一段代码，诠释了服务的navigation是如何运行的

protected  T navigation(Class service) {
 try {
 Postcard postcard = LogisticsCenter.buildProvider(service.getName());
 if (null == postcard) {
 postcard = LogisticsCenter.buildProvider(service.getSimpleName());
 }

 LogisticsCenter.completion(postcard);
 return (T) postcard.getProvider();
 } catch (NoRouteFoundException ex) {
 logger.warning(Consts.TAG, ex.getMessage());
 return null;
 }
 }

buildProvider是根据service的名字从集合中找到对应的RouteMeta并把path和group设置给postcard，接下来也是给postcard设置其他各种参数，和上面分析的大同小异。

path动态改变

调用的方式和降级处理一模一样，时机是在build的时候。

参数自动获取

@Autowired
 @JvmField
 var key3: String? = null
 @Autowired
 @JvmField
 var key1: Long = 0L
 
 ARouter.getInstance().inject(this)

从文档中可以知道，按照上面的方式就可以自动获取各个参数。关键代码肯定是在inject方法中，调用的还是服务。

static void inject(Object thiz) {
 AutowiredService autowiredService = ((AutowiredService) ARouter.getInstance().build("/arouter/service/autowired").navigation());
 if (null != autowiredService) {
 autowiredService.autowire(thiz);
 }
 }

看看AutowiredService的autowire方法

@Override
 public void autowire(Object instance) {
 String className = instance.getClass().getName();
 try {
 if (!blackList.contains(className)) {
 ISyringe autowiredHelper = classCache.get(className);
 if (null == autowiredHelper) {
 autowiredHelper = (ISyringe) Class.forName(instance.getClass().getName() + SUFFIX_AUTOWIRED).getConstructor().newInstance();
 }
 autowiredHelper.inject(instance);
 classCache.put(className, autowiredHelper);
 }
 } catch (Exception ex) {
 blackList.add(className);
 }
 }

最关键的方法是XXclass_$$ARouter$$Autowired.inject，其实这个类还是在注解生成类中

public class TestOneActivity$$ARouter$$Autowired implements ISyringe {
 private SerializationService serializationService;

 @Override
 public void inject(Object target) {
 serializationService = ARouter.getInstance().navigation(SerializationService.class);
 TestOneActivity substitute = (TestOneActivity)target;
 substitute.key3 = substitute.getIntent().getStringExtra("girl");
 substitute.key1 = substitute.getIntent().getLongExtra("key1", substitute.key1);
 }
}

还是通过getIntent().getExtra方法获取的参数，然后把获取的参数设置给当前类。

分析完源码之后扪心自问一下下面问题是否能回答上来

个人的一些思考，大家可以讨论一下