全网最全面的Arouter源码解析

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

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

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:

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 extends TypeElement> 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

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

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 extends IRouteGroup> 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 extends IProvider> providerMeta = (Class extends IProvider>) 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

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 extends IInterceptor> 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

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 extends T> 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