讀源碼-ARouter源碼解析

1-初始化

ARouter.init()開始，init方法的主要工作就是ARouter實例化，_ARouter的初始化。_ARouter是具體實現類。這裏用到了外觀模式，將所有API通過ARouter暴露，具體實現則交由_ARouter

//ARouter.java
public static void init(Application application) {
        if (!hasInit) {
            //日誌類
            logger = _ARouter.logger;
            _ARouter.logger.info(Consts.TAG, "ARouter init start.");
            //@1._ARouter初始化
            hasInit = _ARouter.init(application);

            if (hasInit) {
                //@4.通過路由開啓Service，預解析攔截器
                _ARouter.afterInit();
            }

            _ARouter.logger.info(Consts.TAG, "ARouter init over.");
        }
    }

@1._ARouter的初始化：

protected static synchronized boolean init(Application application) {
        mContext = application;
        //@2.LogisticsCenter初始化
        LogisticsCenter.init(mContext, executor);
        logger.info(Consts.TAG, "ARouter init success!");
        hasInit = true;
        //主線程Looper創建一個Handler
        mHandler = new Handler(Looper.getMainLooper());

        return true;
    }

@2.LogisticsCenter初始化。主要工作就是初始化所有類的map。在編譯期通過gradle插件（arouter-compiler）掃描文件，生成路由映射文件，apt生成路由映射關係文件。

public synchronized static void init(Context context, ThreadPoolExecutor tpe) throws HandlerException {
        mContext = context;
        executor = tpe;

        try {
            。。。
            if (registerByPlugin) {
                。。。
            } else {
                Set<String> routerMap;
                //debuggable模式或版本更新，重新獲取routerMap映射表
                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.
                    //遍歷arouter-compiler生成的包名下所有文件，讀取routerMap路由映射表，將routerMap存儲在sp中
                    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 {
                    //直接從sp中讀取routerMap。set<String>類型，存儲的是className
                    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();
                //@3.遍歷routerMap，根據文件類型存儲到Warehouse對應的字段。通過反射實例化對象，調用loadInto實現。
                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() + "]");
        }
    }

@3.這裏存儲到Warehose裏的主要是三個HashMap，分別是groupsIndex、interceptorsIndex、providersIndex

• interceptorsIndex-TreeMap實現，根據攔截器的優先級自平衡的有序結構，紅黑樹實現。key是優先級，value是攔截器類名
• groupsIndex-key是路由的group，value是該group下的路由映射關係類
• providersIndex-

存儲過程是通過routerMap拿到className，反射生成實例調用其loadInto方法，該方法是APT在@Route註解的類中自動生成的代碼

public class ARouter$$Root$$app implements IRouteRoot {
  @Override
  public void loadInto(Map<String, Class<? extends IRouteGroup>> routes) {
    //key爲分組名，即路徑的第一段，value爲分組中所有的映射關係
    routes.put("service", ARouter$$Group$$service.class);
    routes.put("test", ARouter$$Group$$test.class);
  }
}

//將module中使用@Route註解的activity或Fragment添加到集合中，這裏的方法會在之後調用
public class ARouter$$Group$$test implements IRouteGroup {
  @Override
  public void loadInto(Map<String, RouteMeta> atlas) {
    atlas.put("/test/activity1", RouteMeta.build(RouteType.ACTIVITY, Test1Activity.class, "/test/activity1", "test", new java.util.HashMap<String, Integer>(){{put("pac", 9); put("ch", 5); put("fl", 6); put("obj", 10); put("name", 8); put("dou", 7); put("boy", 0); put("objList", 10); put("map", 10); put("age", 3); put("url", 8); put("height", 3); }}, -1, -2147483648));
    atlas.put("/test/activity2", RouteMeta.build(RouteType.ACTIVITY, Test2Activity.class, "/test/activity2", "test", new java.util.HashMap<String, Integer>(){{put("key1", 8); }}, -1, -2147483648));
    atlas.put("/test/activity3", RouteMeta.build(RouteType.ACTIVITY, Test3Activity.class, "/test/activity3", "test", new java.util.HashMap<String, Integer>(){{put("name", 8); put("boy", 0); put("age", 3); }}, -1, -2147483648));
    atlas.put("/test/activity4", RouteMeta.build(RouteType.ACTIVITY, Test4Activity.class, "/test/activity4", "test", null, -1, -2147483648));
    atlas.put("/test/fragment", RouteMeta.build(RouteType.FRAGMENT, BlankFragment.class, "/test/fragment", "test", null, -1, -2147483648));
    atlas.put("/test/webview", RouteMeta.build(RouteType.ACTIVITY, TestWebview.class, "/test/webview", "test", null, -1, -2147483648));
  }
}

@4._ARouter.afterInit()方法。通過ARouter獲取管理攔截器的Service的實例，並開啓服務進行攔截器的一些初始化工作。

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

InterceptorServiceImpl服務主要是實例化攔截器，並將實例添加到Warehose的interceptors中

@Route(path = "/arouter/service/interceptor")
public class InterceptorServiceImpl implements InterceptorService {
    private static boolean interceptorHasInit;
    private static final Object interceptorInitLock = new Object();

    @Override
    public void init(final Context context) {
       ... //省略子線程以及同步處理，下面的操作實際是在子線程處理的
        if (MapUtils.isNotEmpty(Warehouse.interceptorsIndex)) {
            for (Map.Entry<Integer, Class<? extends IInterceptor>> 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() + "]");
                }
            }
        ...
    }
}

總結初始化過程：

• (1)ARouter.init()–>_ARouter.init()–>LogisticsCenter.init()
• (2)debuggable()模式或新版本，則從指定的router-compiler生成的目錄遍歷文件加載路由映射表routerMap，並緩存到SP；否則直接讀取SP中的routerMap
• (3)遍歷routerMap，根據className的類型依次初始化並存儲到內存中。Warehose對應的三個map。groupsIndex(gourp名-該分組下的所有映射關係類名)、interceptorsIndex(優先級-攔截器名)、providersIndex()
• (4)_ARouter.afterInit().通過路由打開InterceptorService，遍歷Warehose中的interceptorsIndex，實例化對象並存儲到Warehose.interceptors
  

2-路由跳轉

跳轉的代碼從ARouter.getInstance()–>ARouter.build()

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

ARouter.build()–>_ARouter.getInstance().build()

protected Postcard build(String path) {
        if (TextUtils.isEmpty(path)) {
            throw new HandlerException(Consts.TAG + "Parameter is invalid!");
        } else {
            //PathReplaceService是實現路徑動態變化，也就是重定向功能。
            PathReplaceService pService = ARouter.getInstance().navigation(PathReplaceService.class);
            if (null != pService) {
                //拿到通過PathReplaceService修改後的path
                path = pService.forString(path);
            }
            //@1.extractGroup(path)解析出group名
            return build(path, extractGroup(path));
        }
    }

@1._ARouter.build方法。返回一個Postcard對象用於存儲跳轉信息。Postcard繼承RouteMeta，封裝了路由類型、@Autowired屬性集合Map(屬性名-屬性類型)等信息

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);
        }
    }

然後調用_ARouter.navigation方法

protected Object navigation(final Context context, final Postcard postcard, final int requestCode, final NavigationCallback callback) {
        。。。
        try {
            //@2.查找對應的路由信息
            LogisticsCenter.completion(postcard);
        } catch (NoRouteFoundException ex) {
            logger.warning(Consts.TAG, ex.getMessage());

            if (debuggable()) {
                // Show friendly tips for user.
                runInMainThread(new Runnable() {
                    @Override
                    public 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) {
                //調用onLost回調
                callback.onLost(postcard);
            } else {
                // 或者調用DegradeService全局降級的onLost處理
                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()) {   // 需要攔截處理
            //@3.調用InterceptorService攔截
            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);
                    }

                    logger.info(Consts.TAG, "Navigation failed, termination by interceptor : " + exception.getMessage());
                }
            });
        } else {//不需要攔截處理
            //@3.最終跳轉
            return _navigation(context, postcard, requestCode, callback);
        }

        return null;
    }

@2.LogisticsCenter.completion方法。主要工作就是從Warehouse中懶加載路由信息並緩存到Postcard，包括@Autowired註解的參數列表封裝到Postecard的mBundle中

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.
            Class<? extends IRouteGroup> groupMeta = Warehouse.groupsIndex.get(postcard.getGroup());  // Load route meta.
            if (null == groupMeta) {
                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()));
                    }
                    //從Warehouse.groupIndex讀取到對應的映射列表。並將列表中的路由加到Warehouse.routes
                    //同時已加載的group從groupIndex中移除
                    IRouteGroup iGroupInstance = groupMeta.getConstructor().newInstance();
                    iGroupInstance.loadInto(Warehouse.routes);
                    Warehouse.groupsIndex.remove(postcard.getGroup());

                    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() + "]");
                }
                //再次加載
                completion(postcard);   // Reload
            }
        } else {
            //將路由參數存儲到Postcard
            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 @Param
                    for (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 uri
                postcard.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 IProvider
                    Class<? extends IProvider> providerMeta = (Class<? extends IProvider>) routeMeta.getDestination();
                    IProvider instance = Warehouse.providers.get(providerMeta);
                    if (null == instance) { // There's no instance of this provider
                        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();    // Provider should skip all of interceptors
                    break;
                case FRAGMENT:
                    postcard.greenChannel();    // Fragment needn't interceptors
                default:
                    break;
            }
        }
    }

@3.跳轉_navigation

• Activity。則構建Intent，將相關信息封裝到Intent，包括action、bundle等。在主線程調用startActivity跳轉。
• Fragment。創建Fragment實例，設置bundle參數，返回該Fragment實例

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:
                // 構建intent
                final Intent intent = new Intent(currentContext, postcard.getDestination());
                intent.putExtras(postcard.getExtras());

                // 設置Activity啓動模式
                int flags = postcard.getFlags();
                if (-1 != flags) {
                    intent.setFlags(flags);
                } else if (!(currentContext instanceof Activity)) {    // Non activity, need less one flag.
                    intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                }

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

                // 主線程調用startActivity跳轉
                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 {
                    //生成fragment實例
                    Object instance = fragmentMeta.getConstructor().newInstance();
                    //設置bundle參數
                    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());
                    }
                    //返回fragment實例
                    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;
    }

跳轉過程總結：封裝Postcard -> 查找信息集合，實例化目標類 -> 返回實例或者跳轉。

• (1)ARouter.getInstance().build()–>_ARouter.getInstance().build()
• (2)PathReplaceService執行path重定向
• (3)_ARouter.navigation–>LogisticsCenter.completion。
• (4)Warehouse的routes中取路由參數，獲取失敗則解析groupsIndex中對應group的路由列表，添加到routes中。
• (5)添加完畢再次從routes獲取，將路由參數封裝到Poster並返回
• (6)啓動InterceptorService執行攔截器
• (7)執行_navigation。若是Activity，則將poster信息封裝到Intent，通過在主線程startActivity跳轉。若是Fragment，根據poster信息創建Fragment實例並返回
  

3-@Interceptor攔截

@4.InterceptorService的doInterceptions進行攔截處理。通過CountDownLatch實現計數阻塞。計數初始值爲攔截器個數，每執行一個攔截器操作計數-1。計數爲0或timeout則取消線程阻塞

@Override
public void doInterceptions(final Postcard postcard, final InterceptorCallback callback) {
    if (null != Warehouse.interceptors && Warehouse.interceptors.size() > 0) {
        ... //省略同步等待初始化
        LogisticsCenter.executor.execute(new Runnable() {
            @Override
            public void run() {
                //攔截器個數作爲計數初始值
                CancelableCountDownLatch interceptorCounter = new CancelableCountDownLatch(Warehouse.interceptors.size());
                try {
                    _excute(0, interceptorCounter, postcard);
                    //阻塞線程直到超時，或者計數歸0
                    interceptorCounter.await(postcard.getTimeout(), TimeUnit.SECONDS);
                    if (interceptorCounter.getCount() > 0) { //攔截超時
                        callback.onInterrupt(new HandlerException("The interceptor processing timed out."));
                    } else if (null != postcard.getTag()) {  // 被攔截
                        callback.onInterrupt(new HandlerException(postcard.getTag().toString()));
                    } else { //放行
                        callback.onContinue(postcard);
                    }
                } catch (Exception e) {
                    callback.onInterrupt(e);
                }
            }
        });
    } else {
        callback.onContinue(postcard);
    }
}

/**
 * Excute interceptor
 *
 * @param index    current interceptor index
 * @param counter  interceptor counter
 * @param postcard routeMeta
 */
private static void _excute(final int index, final CancelableCountDownLatch counter, final Postcard postcard) {
    //有下一個攔截器
    if (index < Warehouse.interceptors.size()) {
        IInterceptor iInterceptor = Warehouse.interceptors.get(index);
        iInterceptor.process(postcard, new InterceptorCallback() {
            @Override
            public void onContinue(Postcard postcard) {
                // 如果放行，則計數減1，執行後一個攔截器
                counter.countDown();
                _excute(index + 1, counter, postcard); 
            }

            @Override
            public void onInterrupt(Throwable exception) {
                // 攔截，將exception存入postcard的tag字段，計數歸零
                postcard.setTag(null == exception ? new HandlerException("No message.") : exception.getMessage());
                counter.cancel();
            });
        }
    }

4-@Autowired參數註解

@Route(path = "/arouter/service/autowired")
public class AutowiredServiceImpl implements AutowiredService {
    private LruCache<String, ISyringe> classCache;
    private List<String> blackList;

    @Override
    public void init(Context context) {
        classCache = new LruCache<>(66);
        blackList = new ArrayList<>();
    }

    @Override
    public void autowire(Object instance) {
        String className = instance.getClass().getName();
        try {
            if (!blackList.contains(className)) {
                ISyringe autowiredHelper = classCache.get(className);
                if (null == autowiredHelper) {  // No cache.
                    autowiredHelper = (ISyringe) Class.forName(instance.getClass().getName() + SUFFIX_AUTOWIRED).getConstructor().newInstance();
                }
                //從mBundle中取出參數賦值
                autowiredHelper.inject(instance);
                classCache.put(className, autowiredHelper);
            }
        } catch (Exception ex) {
            blackList.add(className);    // This instance need not autowired.
        }
    }
}

ISyringe是apt在註解@Autowired時自動生成一個對應的ISyringe實現。將bundle中的數據取出，賦值給@Autowired註解的屬性。

總的參數注入過程：

• ARouter.inject–>_ARouter.inject
• AutowiredServiceImpl.autowire
• 生成apt自動生成的ISyringe類的實例
• ISyringe。inject將Poster中的mBundle參數賦值給具體的屬性
  先通過開啓AutowiredService來實現