android ARouter源码分析

背景:

随着项目越做越大，代码量越来越多，项目也随之改造成组件化的开发模式，组件化开发非常适合庞大的项目，将每个业务模块，功能模块解耦，抽离成组件的形式，各个组件遵循严格的依赖关系。因为这层严格的依赖关系，使得组件化比模块化结构更加简洁和清晰，以前的模块化开发，模块间常常相互依赖，形成闭环，改动模块的代码会牵一发而动全身，稳定性和可维护性就显得特别弱小。

组件化严格控制组件间的依赖关系，组件间相互依赖是不允许存在的，所以我们需要一个框架来解决组件间的通信的问题。

ARouter的几个常用功能：

1.组件间的页面跳转。

2.依赖注入

3.拦截器。

关于ARouter如何实现上面三个功能的？

ARouter源码主要由三个模块组成：

ARouter-compiler: 这个模块主要用于解析注解，然后生成路由业务代码的java文件，主要需要阅读的源码文件是

RouterProcessor

InterceptorProcessor

AutowiredProcessor

ARouter-api:这个模块主要暴露一些接口和方法给业务层调用，还封装了一个线程池和一些异常等等，建议需要阅读的源码文件

thread包下的文件，理解为什么需要用到线程池

launcher包下的文件，理解初始化过程中做了哪些工作

Warehouse

LogisticsCenter

InterceptorServiceImpl

ARouter-annotation:定义了一些注解。

先看下页面跳转是如何实现的:

// 页面跳转
ARouter.getInstance().build("/test/activity").navigation();

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

/*** Use router navigation.** @param context     Activity or null.* @param postcard    Route metas* @param requestCode RequestCode* @param callback    cb*/protected Object navigation(final Context context, final Postcard postcard, final int requestCode, final NavigationCallback callback) {PretreatmentService pretreatmentService = ARouter.getInstance().navigation(PretreatmentService.class);if (null != pretreatmentService && !pretreatmentService.onPretreatment(context, postcard)) {// Pretreatment failed, navigation canceled.return null;}// Set context to postcard.postcard.setContext(null == context ? mContext : context);try {LogisticsCenter.completion(postcard);} catch (NoRouteFoundException ex) {logger.warning(Consts.TAG, ex.getMessage());if (debuggable()) {// Show friendly tips for user.runInMainThread(new Runnable() {@Overridepublic void run() {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 {// No callback for this invoke, then we use the global degrade service.DegradeService degradeService = ARouter.getInstance().navigation(DegradeService.class);if (null != degradeService) {degradeService.onLost(context, postcard);}}return null;}if (null != callback) {callback.onFound(postcard);}if (!postcard.isGreenChannel()) {   // It must be run in async thread, maybe interceptor cost too mush time made ANR.interceptorService.doInterceptions(postcard, new InterceptorCallback() {/*** Continue process** @param postcard route meta*/@Overridepublic void onContinue(Postcard postcard) {_navigation(postcard, requestCode, callback);}/*** Interrupt process, pipeline will be destory when this method called.** @param exception Reson of interrupt.*/@Overridepublic void onInterrupt(Throwable exception) {if (null != callback) {callback.onInterrupt(postcard);}logger.info(Consts.TAG, "Navigation failed, termination by interceptor : " + exception.getMessage());}});} else {return _navigation(postcard, requestCode, callback);}return null;}

build方法传入path和group(可不传)，最后new一个postcard对象，Postcard对象可以理解为一个封装了页面跳转所需要的内容，它包含页面跳转的参数，动画，context等信息。

在navigation方法里面实现页面跳转的代码是

 LogisticsCenter.completion(postcard);

然后继续跟

/*** Completion the postcard by route metas** @param postcard Incomplete postcard, should complete by this method.*/public synchronized static void completion(Postcard postcard) {if (null == postcard) {throw new NoRouteFoundException(TAG + "No postcard!");}RouteMeta routeMeta = Warehouse.routes.get(postcard.getPath());if (null == routeMeta) {// Maybe its does't exist, or didn't load.if (!Warehouse.groupsIndex.containsKey(postcard.getGroup())) {throw new NoRouteFoundException(TAG + "There is no route match the path [" + postcard.getPath() + "], in group [" + postcard.getGroup() + "]");} else {// Load route and cache it into memory, then delete from metas.try {if (ARouter.debuggable()) {logger.debug(TAG, String.format(Locale.getDefault(), "The group [%s] starts loading, trigger by [%s]", postcard.getGroup(), postcard.getPath()));}addRouteGroupDynamic(postcard.getGroup(), null);if (ARouter.debuggable()) {logger.debug(TAG, String.format(Locale.getDefault(), "The group [%s] has already been loaded, trigger by [%s]", postcard.getGroup(), postcard.getPath()));}} catch (Exception e) {throw new HandlerException(TAG + "Fatal exception when loading group meta. [" + e.getMessage() + "]");}completion(postcard);   // Reload}} else {postcard.setDestination(routeMeta.getDestination());postcard.setType(routeMeta.getType());postcard.setPriority(routeMeta.getPriority());postcard.setExtra(routeMeta.getExtra());Uri rawUri = postcard.getUri();if (null != rawUri) {   // Try to set params into bundle.Map<String, String> resultMap = TextUtils.splitQueryParameters(rawUri);Map<String, Integer> paramsType = routeMeta.getParamsType();if (MapUtils.isNotEmpty(paramsType)) {// Set value by its type, just for params which annotation by @Paramfor (Map.Entry<String, Integer> params : paramsType.entrySet()) {setValue(postcard,params.getValue(),params.getKey(),resultMap.get(params.getKey()));}// Save params name which need auto inject.postcard.getExtras().putStringArray(ARouter.AUTO_INJECT, paramsType.keySet().toArray(new String[]{}));}// Save raw uripostcard.withString(ARouter.RAW_URI, rawUri.toString());}switch (routeMeta.getType()) {case PROVIDER:  // if the route is provider, should find its instance// Its provider, so it must implement IProviderClass<? extends IProvider> providerMeta = (Class<? extends IProvider>) routeMeta.getDestination();IProvider instance = Warehouse.providers.get(providerMeta);if (null == instance) { // There's no instance of this providerIProvider provider;try {provider = providerMeta.getConstructor().newInstance();provider.init(mContext);Warehouse.providers.put(providerMeta, provider);instance = provider;} catch (Exception e) {logger.error(TAG, "Init provider failed!", e);throw new HandlerException("Init provider failed!");}}postcard.setProvider(instance);postcard.greenChannel();    // Provider should skip all of interceptorsbreak;case FRAGMENT:postcard.greenChannel();    // Fragment needn't interceptorsdefault:break;}}}

我们看到代码会从Warehouse类里面获取RouteMeta对象，如果为null，表示根据路由名找不到路由的目标页面，这个时候，做了一次对group的判断处理.

group是干嘛的？可以理解成分组的意思，因为各个组件交给各个人维护，所以很容易出现路由同名的情况，比如个人中心组件定义了相册选择页面的路由地址，购物车组件也有相册选择页面的路由地址，所以group的存在是为了做细分。

除了细分的作用以外，还可以减少内存的消耗，Warehouse.routes是一个static的map对象，如果一次性把所有路由信息全存放里面，有可能造成内存溢出。所以Group的第二个作用就是按组加载路由表。

根据group的特性不难理解为什么这里有个递归方法

completion(postcard);   // Reload

不知道有没有人跟我一样疑问，这里不会死循环吗？

public synchronized static void addRouteGroupDynamic(String groupName, IRouteGroup group) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {if (Warehouse.groupsIndex.containsKey(groupName)){// If this group is included, but it has not been loaded// load this group first, because dynamic route has high priority.Warehouse.groupsIndex.get(groupName).getConstructor().newInstance().loadInto(Warehouse.routes);Warehouse.groupsIndex.remove(groupName);}// cover old group.if (null != group) {group.loadInto(Warehouse.routes);}}

答案是不会，因为当某个group的路由表信息加载到内存的时候，这个group会从groupsIndex里面删除。

如果RouteMeta不为null，解析uri的相关参数，结合RouteMeta的路由信息设置Postcard的参数。然后调用

_navigation(postcard, requestCode, callback);

private Object _navigation(final Postcard postcard, final int requestCode, final NavigationCallback callback) {final Context currentContext = postcard.getContext();switch (postcard.getType()) {case ACTIVITY:// Build intentfinal Intent intent = new Intent(currentContext, postcard.getDestination());intent.putExtras(postcard.getExtras());// Set flags.int flags = postcard.getFlags();if (0 != flags) {intent.setFlags(flags);}// Non activity, need FLAG_ACTIVITY_NEW_TASKif (!(currentContext instanceof Activity)) {intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);}// Set ActionsString action = postcard.getAction();if (!TextUtils.isEmpty(action)) {intent.setAction(action);}// Navigation in main looper.runInMainThread(new Runnable() {@Overridepublic 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;}

最后在上面这个方法里面调用了startActvity方法实现跳转。

整个跳转过程中，离不开路由表，接下来分析下路由表的构建流程，即Warehouse类的初始化工作。拦截器的和provider的相关代码先忽略。

class Warehouse {// Cache route and metasstatic Map<String, Class<? extends IRouteGroup>> groupsIndex = new HashMap<>();static Map<String, RouteMeta> routes = new HashMap<>();
}

路由表的构建在初始化阶段。_ARouter的init方法会调用LogisticsCenter.init(mContext, executor);方法

public synchronized static void init(Context context, ThreadPoolExecutor tpe) throws HandlerException {mContext = context;executor = tpe;try {long startInit = System.currentTimeMillis();//load by plugin firstloadRouterMap();if (registerByPlugin) {logger.info(TAG, "Load router map by arouter-auto-register plugin.");} else {Set<String> routerMap;// It will rebuild router map every times when debuggable.if (ARouter.debuggable() || PackageUtils.isNewVersion(context)) {logger.info(TAG, "Run with debug mode or new install, rebuild router map.");// These class was generated by arouter-compiler.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);    // Save new version name when router map update finishes.} else {logger.info(TAG, "Load router map from cache.");routerMap = new HashSet<>(context.getSharedPreferences(AROUTER_SP_CACHE_KEY, Context.MODE_PRIVATE).getStringSet(AROUTER_SP_KEY_MAP, new HashSet<String>()));}logger.info(TAG, "Find router map finished, map size = " + routerMap.size() + ", cost " + (System.currentTimeMillis() - startInit) + " ms.");startInit = System.currentTimeMillis();for (String className : routerMap) {if (className.startsWith(ROUTE_ROOT_PAKCAGE + DOT + SDK_NAME + SEPARATOR + SUFFIX_ROOT)) {// This one of root elements, load root.((IRouteRoot) (Class.forName(className).getConstructor().newInstance())).loadInto(Warehouse.groupsIndex);} else if (className.startsWith(ROUTE_ROOT_PAKCAGE + DOT + SDK_NAME + SEPARATOR + SUFFIX_INTERCEPTORS)) {// Load interceptorMeta((IInterceptorGroup) (Class.forName(className).getConstructor().newInstance())).loadInto(Warehouse.interceptorsIndex);} else if (className.startsWith(ROUTE_ROOT_PAKCAGE + DOT + SDK_NAME + SEPARATOR + SUFFIX_PROVIDERS)) {// Load providerIndex((IProviderGroup) (Class.forName(className).getConstructor().newInstance())).loadInto(Warehouse.providersIndex);}}}logger.info(TAG, "Load root element finished, cost " + (System.currentTimeMillis() - startInit) + " ms.");if (Warehouse.groupsIndex.size() == 0) {logger.error(TAG, "No mapping files were found, check your configuration please!");}if (ARouter.debuggable()) {logger.debug(TAG, String.format(Locale.getDefault(), "LogisticsCenter has already been loaded, GroupIndex[%d], InterceptorIndex[%d], ProviderIndex[%d]", Warehouse.groupsIndex.size(), Warehouse.interceptorsIndex.size(), Warehouse.providersIndex.size()));}} catch (Exception e) {throw new HandlerException(TAG + "ARouter init logistics center exception! [" + e.getMessage() + "]");}}

我们看到初始化阶段，如果verson非新版本，那么会遍历所有dex文件，找出dex文件里面的ROUTE_ROOT_PAKCAGE = "com.alibaba.android.arouter.routes"的class。

如果已经是新版本了，就从shareprefrence里面读取了缓存，然后根据反射去创建了Class对象，然后将创建好的Group表放到内存中。

这时候又出现新的问题com.alibaba.android.arouter.routes是什么?

从上面的分析，我们知道所有group的class文件都在该package下里面，group的class文件都需要实现IRouteGroup的接口，当我们去看哪些class实现了这些接口的时候，发现都在build目录下。如下图所示。

显而易见，这个class是在编译阶段自动生成的，所以ARouter框架使用了AOP的编程模式。

我们接下来去compiler模块里面看下RouterProcessor类。

@Overridepublic boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {if (CollectionUtils.isNotEmpty(annotations)) {Set<? extends Element> routeElements = roundEnv.getElementsAnnotatedWith(Route.class);try {logger.info(">>> Found routes, start... <<<");this.parseRoutes(routeElements);} catch (Exception e) {logger.error(e);}return true;}return false;}

先找到Route注解的Elements，然后解析。

解析的代码比较多，这里分批贴代码分析

//  Follow a sequence, find out metas of group first, generate java file, then statistics them as root.for (Element element : routeElements) {TypeMirror tm = element.asType();Route route = element.getAnnotation(Route.class);RouteMeta routeMeta;// Activity or Fragmentif (types.isSubtype(tm, type_Activity) || types.isSubtype(tm, fragmentTm) || types.isSubtype(tm, fragmentTmV4)) {// Get all fields annotation by @AutowiredMap<String, Integer> paramsType = new HashMap<>();Map<String, Autowired> injectConfig = new HashMap<>();injectParamCollector(element, paramsType, injectConfig);if (types.isSubtype(tm, type_Activity)) {// Activitylogger.info(">>> Found activity route: " + tm.toString() + " <<<");routeMeta = new RouteMeta(route, element, RouteType.ACTIVITY, paramsType);} else {// Fragmentlogger.info(">>> Found fragment route: " + tm.toString() + " <<<");routeMeta = new RouteMeta(route, element, RouteType.parse(FRAGMENT), paramsType);}routeMeta.setInjectConfig(injectConfig);} else if (types.isSubtype(tm, iProvider)) {         // IProviderlogger.info(">>> Found provider route: " + tm.toString() + " <<<");routeMeta = new RouteMeta(route, element, RouteType.PROVIDER, null);} else if (types.isSubtype(tm, type_Service)) {           // Servicelogger.info(">>> Found service route: " + tm.toString() + " <<<");routeMeta = new RouteMeta(route, element, RouteType.parse(SERVICE), null);} else {throw new RuntimeException("The @Route is marked on unsupported class, look at [" + tm.toString() + "].");}categories(routeMeta);}

这里遍历了整个Elements，然后生成对应的RouteMeta。

最后的categories(routeMeta);会对生成的routeMeta做检验，只有合法的routeMeta才会被存入GroupMap里面。path不能为空且path必须是"/"开头才算合法。

然后是通过代码生成java文件，具体生成规则在下面的代码，关键部分补充了注释了。

/** 遍历groupMap **/for (Map.Entry<String, Set<RouteMeta>> entry : groupMap.entrySet()) {String groupName = entry.getKey();/** 创建void loadInto(Map<String, RouteMeta> atlas);方法对象 **/MethodSpec.Builder loadIntoMethodOfGroupBuilder = MethodSpec.methodBuilder(METHOD_LOAD_INTO).addAnnotation(Override.class)     //注解.addModifiers(PUBLIC)              //方法访问属性.addParameter(groupParamSpec);     //方法参数List<RouteDoc> routeDocList = new ArrayList<>();// Build group method bodySet<RouteMeta> groupData = entry.getValue();/** 遍历每个groupMap下的routeMeta **/for (RouteMeta routeMeta : groupData) {RouteDoc routeDoc = extractDocInfo(routeMeta);ClassName className = ClassName.get((TypeElement) routeMeta.getRawType());switch (routeMeta.getType()) {case PROVIDER:  // Need cache provider's super classList<? extends TypeMirror> interfaces = ((TypeElement) routeMeta.getRawType()).getInterfaces();for (TypeMirror tm : interfaces) {routeDoc.addPrototype(tm.toString());if (types.isSameType(tm, iProvider)) {   // Its implements iProvider interface himself.// This interface extend the IProvider, so it can be used for mark providerloadIntoMethodOfProviderBuilder.addStatement("providers.put($S, $T.build($T." + routeMeta.getType() + ", $T.class, $S, $S, null, " + routeMeta.getPriority() + ", " + routeMeta.getExtra() + "))",(routeMeta.getRawType()).toString(),routeMetaCn,routeTypeCn,className,routeMeta.getPath(),routeMeta.getGroup());} else if (types.isSubtype(tm, iProvider)) {// This interface extend the IProvider, so it can be used for mark providerloadIntoMethodOfProviderBuilder.addStatement("providers.put($S, $T.build($T." + routeMeta.getType() + ", $T.class, $S, $S, null, " + routeMeta.getPriority() + ", " + routeMeta.getExtra() + "))",tm.toString(),    // So stupid, will duplicate only save class name.routeMetaCn,routeTypeCn,className,routeMeta.getPath(),routeMeta.getGroup());}}break;default:break;}// Make map body for paramsTypeStringBuilder mapBodyBuilder = new StringBuilder();Map<String, Integer> paramsType = routeMeta.getParamsType();Map<String, Autowired> injectConfigs = routeMeta.getInjectConfig();if (MapUtils.isNotEmpty(paramsType)) {List<RouteDoc.Param> paramList = new ArrayList<>();for (Map.Entry<String, Integer> types : paramsType.entrySet()) {mapBodyBuilder.append("put(\"").append(types.getKey()).append("\", ").append(types.getValue()).append("); ");RouteDoc.Param param = new RouteDoc.Param();Autowired injectConfig = injectConfigs.get(types.getKey());param.setKey(types.getKey());param.setType(TypeKind.values()[types.getValue()].name().toLowerCase());param.setDescription(injectConfig.desc());param.setRequired(injectConfig.required());paramList.add(param);}routeDoc.setParams(paramList);}String mapBody = mapBodyBuilder.toString();/*** loadInto方法里面加入具体的代码实现* 比如atlas.put("/module/2", RouteMeta.build(RouteType.ACTIVITY, TestModule2Activity.class, "/module/2", "m2", null, -1, -2147483648));* **/loadIntoMethodOfGroupBuilder.addStatement("atlas.put($S, $T.build($T." + routeMeta.getType() + ", $T.class, $S, $S, " + (StringUtils.isEmpty(mapBody) ? null : ("new java.util.HashMap<String, Integer>(){{" + mapBodyBuilder.toString() + "}}")) + ", " + routeMeta.getPriority() + ", " + routeMeta.getExtra() + "))",routeMeta.getPath(),routeMetaCn,routeTypeCn,className,routeMeta.getPath().toLowerCase(),routeMeta.getGroup().toLowerCase());routeDoc.setClassName(className.toString());routeDocList.add(routeDoc);}// Generate groups/**生成java文件**/String groupFileName = NAME_OF_GROUP + groupName;JavaFile.builder(PACKAGE_OF_GENERATE_FILE,  //指定java文件的包路径TypeSpec.classBuilder(groupFileName)  //java文件名.addJavadoc(WARNING_TIPS)  //java注解.addSuperinterface(ClassName.get(type_IRouteGroup))  //继承的接口.addModifiers(PUBLIC)   //类属性 公有.addMethod(loadIntoMethodOfGroupBuilder.build())  //加入方法.build()).build().writeTo(mFiler);logger.info(">>> Generated group: " + groupName + "<<<");rootMap.put(groupName, groupFileName);  //将组名和java文件名做映射关系docSource.put(groupName, routeDocList);  }

最后在生成root的java文件。

// Write root meta into disk.String rootFileName = NAME_OF_ROOT + SEPARATOR + moduleName;JavaFile.builder(PACKAGE_OF_GENERATE_FILE,TypeSpec.classBuilder(rootFileName).addJavadoc(WARNING_TIPS).addSuperinterface(ClassName.get(elementUtils.getTypeElement(ITROUTE_ROOT))).addModifiers(PUBLIC).addMethod(loadIntoMethodOfRootBuilder.build()).build()).build().writeTo(mFiler);

AOP阶段路由表的生成规则总结:

1.解析注解得到带有Route注解相关的Elements。

2.遍历所有Elements并解析Route注解的参数，生成对应的RouteMeta数据，并插入到groupMap中

3.遍历groupMap，将每个groupName下的所有的RouteMeta生成对应的java代码，然后写入该java文件到内存。此时一个groupName对应一个java文件。

4.并将每个groupName和生成的java文件做映射放在rootMap中。

5.最后再生成对应的root的java文件，该文件主要用于初始化的时候将groupName和java文件的映射关系加载进内存。

到这里，整个页面路由的逻辑都已经理清楚了。

接下来看下依赖注入实现。

AutowiredProcessor类和Autowired注解

@Overridepublic boolean process(Set<? extends TypeElement> set, RoundEnvironment roundEnvironment) {if (CollectionUtils.isNotEmpty(set)) {try {logger.info(">>> Found autowired field, start... <<<");categories(roundEnvironment.getElementsAnnotatedWith(Autowired.class));generateHelper();} catch (Exception e) {logger.error(e);}return true;}return false;}

private void categories(Set<? extends Element> elements) throws IllegalAccessException {if (CollectionUtils.isNotEmpty(elements)) {for (Element element : elements) {TypeElement enclosingElement = (TypeElement) element.getEnclosingElement();if (element.getModifiers().contains(Modifier.PRIVATE)) {throw new IllegalAccessException("The inject fields CAN NOT BE 'private'!!! please check field ["+ element.getSimpleName() + "] in class [" + enclosingElement.getQualifiedName() + "]");}if (parentAndChild.containsKey(enclosingElement)) { // Has categriesparentAndChild.get(enclosingElement).add(element);} else {List<Element> childs = new ArrayList<>();childs.add(element);parentAndChild.put(enclosingElement, childs);}}logger.info("categories finished.");}}

编译阶段会去解析Autowired注解，然后获取带有该注解的Elements，然后遍历，如果是私有属性，直接抛异常。然后将正确的elements存到parentAndChild map里面。

接着开始根据parentAndChild的数据里面的内容生成对应的java文件。

生成autowired的java文件步骤和生成ARouter的步骤相似；

1.创建inject方法对象。inject方法在ISyringe接口里面定义了，所以所有autowired类实现该接口。

2.先判断是否是provder，不是provider，然后去区分是activity还是fragment，activity情况下通过getintent去取参数，fragment情况下通过getArguments方法去取参数。

3.然后根据element属性生成对应的get代码，比如boolean对应getBooleanExtra()方法。

4.判断autowired注解里面的required是否是true，如果是true并且是非基本数据类型，则加入对象是否为null的判断代码。

5.此时autowired注解相关的java文件已经生成完毕。

当我们在某个地方调用如下方法的时候：依赖注入才开始生效。

ARouter.getInstance().inject(this);

然后跟下这个方法，会走到这里

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

这里用到一个AutowiredService，这个接口继承了IProvider的接口。然后在AutowiredServiceImpl类里面找到了该接口的具体实现。这个实现类也加了Router注解，那么这里有个新的问题，IProvider是干嘛的？

这里我们要回到RouteProcessor看下Provider的解析代码：

switch (routeMeta.getType()) {case PROVIDER:  // Need cache provider's super classList<? extends TypeMirror> interfaces = ((TypeElement) routeMeta.getRawType()).getInterfaces();for (TypeMirror tm : interfaces) {routeDoc.addPrototype(tm.toString());if (types.isSameType(tm, iProvider)) {   // Its implements iProvider interface himself.// This interface extend the IProvider, so it can be used for mark providerloadIntoMethodOfProviderBuilder.addStatement("providers.put($S, $T.build($T." + routeMeta.getType() + ", $T.class, $S, $S, null, " + routeMeta.getPriority() + ", " + routeMeta.getExtra() + "))",(routeMeta.getRawType()).toString(),routeMetaCn,routeTypeCn,className,routeMeta.getPath(),routeMeta.getGroup());} else if (types.isSubtype(tm, iProvider)) {// This interface extend the IProvider, so it can be used for mark providerloadIntoMethodOfProviderBuilder.addStatement("providers.put($S, $T.build($T." + routeMeta.getType() + ", $T.class, $S, $S, null, " + routeMeta.getPriority() + ", " + routeMeta.getExtra() + "))",tm.toString(),    // So stupid, will duplicate only save class name.routeMetaCn,routeTypeCn,className,routeMeta.getPath(),routeMeta.getGroup());}}break;default:break;}

这里看到如果是provider，会生成一段代码，这段代码会将定义的Interface和该interface的实现类做映射，前提条件是，该interface必须继承IProvider。

那做映射干嘛呢？

我们再去看下Provider的映射表使用的地方。也是在wareHouse类里面，发现和路由跳转一样，也是build()方法里面传入string，然后navigation跳转，其实到这里已经能猜到要干嘛了，为了实现跨组件间的方法调用嘛，比如组件A调用组件B里面的Class C的方法，那么就定义一个interface，然后interface下沉到底层组件，Class C继承该interface并实现该方法，接着按照ARouter的provder配置好后，就能在组件A中调用组件B的Class C的暴露的接口了，组件A也不需要去依赖组件B。

这样做得好处就是减少组件间依赖关系。

Provider已经理解了，我们继续AutowiredService分析。

 /*** Recursive injection** @param instance who call me.* @param parent   parent of me.*/private void doInject(Object instance, Class<?> parent) {Class<?> clazz = null == parent ? instance.getClass() : parent;ISyringe syringe = getSyringe(clazz);if (null != syringe) {syringe.inject(instance);}Class<?> superClazz = clazz.getSuperclass();// has parent and its not the class of framework.if (null != superClazz && !superClazz.getName().startsWith("android")) {doInject(instance, superClazz);}}private ISyringe getSyringe(Class<?> clazz) {String className = clazz.getName();try {if (!blackList.contains(className)) {ISyringe syringeHelper = classCache.get(className);if (null == syringeHelper) {  // No cache.syringeHelper = (ISyringe) Class.forName(clazz.getName() + SUFFIX_AUTOWIRED).getConstructor().newInstance();}classCache.put(className, syringeHelper);return syringeHelper;}} catch (Exception e) {blackList.add(className);    // This instance need not autowired.}return null;}

这段代码也好理解，获取传入object对象的class对象，通过类名找到编译阶段生成的实现ISyring接口的相关类，反射创建对象，然后调用该对象的inject方法。

至此:依赖注入也分析完了。

接下来看下拦截器

拦截器是什么，参考OKHttp的实现，拦截器就是在处理一个任务的时候，在该任务之前或者之后加入自己的业务逻辑。拦截器设计模式可以有效减少耦合度。

IntercepterProcessor的注解解析其实和前面两个差不多，拦截器表也在Warehouse类里维护。

区别是拦截器提供了手动注册的方法，不一定要通过Aop的方式去注册。

if (!postcard.isGreenChannel()) {   // It must be run in async thread, maybe interceptor cost too mush time made ANR.interceptorService.doInterceptions(postcard, new InterceptorCallback() {/*** Continue process** @param postcard route meta*/@Overridepublic void onContinue(Postcard postcard) {_navigation(postcard, requestCode, callback);}/*** Interrupt process, pipeline will be destory when this method called.** @param exception Reson of interrupt.*/@Overridepublic void onInterrupt(Throwable exception) {if (null != callback) {callback.onInterrupt(postcard);}logger.info(Consts.TAG, "Navigation failed, termination by interceptor : " + exception.getMessage());}});} else {return _navigation(postcard, requestCode, callback);}

这里我们看到如果是绿色通道，则会调用拦截器的方法。

那什么时候是绿色通道呢？

 switch (routeMeta.getType()) {case PROVIDER:  // if the route is provider, should find its instance// Its provider, so it must implement IProviderClass<? extends IProvider> providerMeta = (Class<? extends IProvider>) routeMeta.getDestination();IProvider instance = Warehouse.providers.get(providerMeta);if (null == instance) { // There's no instance of this providerIProvider provider;try {provider = providerMeta.getConstructor().newInstance();provider.init(mContext);Warehouse.providers.put(providerMeta, provider);instance = provider;} catch (Exception e) {logger.error(TAG, "Init provider failed!", e);throw new HandlerException("Init provider failed!");}}postcard.setProvider(instance);postcard.greenChannel();    // Provider should skip all of interceptorsbreak;case FRAGMENT:postcard.greenChannel();    // Fragment needn't interceptorsdefault:break;}

这里我们看到如果是fragment或者provider的时候，打开了绿色通道，所以这两个不会经过拦截器。

然后我们到InterceptorServiceImpl看下拦截器的执行过程

@Overridepublic void doInterceptions(final Postcard postcard, final InterceptorCallback callback) {if (MapUtils.isNotEmpty(Warehouse.interceptorsIndex)) {checkInterceptorsInitStatus();if (!interceptorHasInit) {callback.onInterrupt(new HandlerException("Interceptors initialization takes too much time."));return;}LogisticsCenter.executor.execute(new Runnable() {@Overridepublic void run() {CancelableCountDownLatch interceptorCounter = new CancelableCountDownLatch(Warehouse.interceptors.size());try {_execute(0, interceptorCounter, postcard);interceptorCounter.await(postcard.getTimeout(), TimeUnit.SECONDS);if (interceptorCounter.getCount() > 0) {    // Cancel the navigation this time, if it hasn't return anythings.callback.onInterrupt(new HandlerException("The interceptor processing timed out."));} else if (null != postcard.getTag()) {    // Maybe some exception in the tag.callback.onInterrupt((Throwable) postcard.getTag());} else {callback.onContinue(postcard);}} catch (Exception e) {callback.onInterrupt(e);}}});} else {callback.onContinue(postcard);}}

1.校验拦截器是否初始化。

2.开启线程执行拦截器内部代码。

private static void _execute(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() {@Overridepublic void onContinue(Postcard postcard) {// Last interceptor excute over with no exception.counter.countDown();_execute(index + 1, counter, postcard);  // When counter is down, it will be execute continue ,but index bigger than interceptors size, then U know.}@Overridepublic void onInterrupt(Throwable exception) {// Last interceptor execute over with fatal exception.postcard.setTag(null == exception ? new HandlerException("No message.") : exception);    // save the exception message for backup.counter.cancel();// Be attention, maybe the thread in callback has been changed,// then the catch block(L207) will be invalid.// The worst is the thread changed to main thread, then the app will be crash, if you throw this exception!
//                    if (!Looper.getMainLooper().equals(Looper.myLooper())) {    // You shouldn't throw the exception if the thread is main thread.
//                        throw new HandlerException(exception.getMessage());
//                    }}});}}

按照从0--n的顺序执行拦截器。

这里拦截器的代码也分析完了。