ARouter源码解析04-interceptor拦截器

布满荆棘的人生 2023-10-17 14:31 7阅读 0赞

上篇文章我们分析了ARouter的路由跳转，这篇文章我们来分析interceptor拦截器。

首先，同样在IDE编译过程中，拦截器也会产生相应的文件。(详见[ARouter源码解析01-编译生成文件][ARouter_01-])

public class ARouter$$Interceptors$$app implements IInterceptorGroup {
      @Override
      public void loadInto(Map<Integer, Class<? extends IInterceptor>> interceptors) {
        interceptors.put(3, Test2Interceptor.class);
        interceptors.put(5, Test3Interceptor.class);
        interceptors.put(7, Test1Interceptor.class);
      }
    }

可以看到，这里根据priority将Intercepter按照级别进行排序，级别从高到第依次put到interceptors集合中。那么，这些intercepter是在什么地方加载到内存中的呢？

同时，我们知道，拦截器有个init()方法，会在程序初始化的时候，进行调用，那么，是在哪里执行拦截器的init()方法的呢？  
再回到ARouter.init()来看

public static void init(Application application) {
    //...
    hasInit = _ARouter.init(application);
    if (hasInit) {
        _ARouter.afterInit();
    }
    //...

这里有个afterInit方法，我们跟进去看下

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

这里，通过路由跳转，调用了InterceptorServiceImpl，但是在路由app模块build文件中，并没有/arouter/service/interceptor这个路由表单，那么ARouter这里是通过怎么跳转的呢？

原来，在aroute-api中，还有个arouter的build文件，在这个文件下，有着和app模块下build包名相同的ARouter开头的几个文件(故ARouter.init的时候，也会把这几个路由表单加载进去)

package com.alibaba.android.arouter.routes;
    
    public class ARouter$$Group$$arouter implements IRouteGroup {
      @Override
      public void loadInto(Map<String, RouteMeta> atlas) {
        atlas.put("/arouter/service/autowired", RouteMeta.build(RouteType.PROVIDER, AutowiredServiceImpl.class, "/arouter/service/autowired", "arouter", null, -1, -2147483648));
        atlas.put("/arouter/service/interceptor", RouteMeta.build(RouteType.PROVIDER, InterceptorServiceImpl.class, "/arouter/service/interceptor", "arouter", null, -1, -2147483648));
      }
    }

我们再来在InterceptorServiceImpl，首先会在navigation的时候调用 LogisticsCenter.completion从而调用provider.init()方法进行初始化。

@Override
    public void init(final Context context) {
        LogisticsCenter.executor.execute(new Runnable() {
            @Override
            public void run() {
                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() + "]");
                        }
                    }
    
                    interceptorHasInit = true;
    
                    synchronized (interceptorInitLock) {
                        interceptorInitLock.notifyAll();
                    }
                }
            }
        });
    }

可以发现，大体的，就是通过线程池.execute()，在异步线程中，获取所有的拦截器IInterceptor，调用他们的init方法，并把拦截器添加到Warehouse.interceptors集合中。

知道了

接着，继续在navigation方法中，如果没有把postcard.isGreenChannel设为true，那么调用interceptorService.doInterceptions执行拦截器，处理是否拦截。

完成了拦截器的init()，再来看navigation的时候，拦截器的拦截，

final class _ARouter {
        protected Object navigation(final Context context, final Postcard postcard, final int requestCode, final NavigationCallback callback) {
            LogisticsCenter.completion(postcard);
            //isGreenChannel為ture，說明不需要interceptor，要跳過interceptor
            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);
                        }
                    }
                });
            } else {
                return _navigation(context, postcard, requestCode, callback);
            }
    
            return null;
        }
    }

来看doInterceptions()，这里进行拦截器的拦截，会遍历拦截器列表，并调用拦截器的process()，最终，根据结果回调onContinue或onInterrupt来继续navigation或终止navigation。

@Override
    public void doInterceptions(final Postcard postcard, final InterceptorCallback callback) {
        // 检查拦截器列表是否为空
        if (CollectionUtils.isNotEmpty(Warehouse.interceptors)) {
            // 等待拦截器服务完成初始化
            // ......
    
            LogisticsCenter.executor.execute(new Runnable() {
                @Override
                public void run() {
                    // CountDown倒数计数器
                    CancelableCountDownLatch interceptorCounter = new CancelableCountDownLatch(Warehouse.interceptors.size());
                    try {
                        // 在另一个线程中递归依次执行拦截器操作
                        _excute(0, interceptorCounter, postcard);
                        // 等待超时
                        interceptorCounter.await(postcard.getTimeout(), TimeUnit.SECONDS);
                        // 倒数计时器不为0,表示还有拦截器未执行完成
                        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(new HandlerException(postcard.getTag().toString()));
                        } else {
                            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) {
        if (index < Warehouse.interceptors.size()) {
            IInterceptor iInterceptor = Warehouse.interceptors.get(index);
            iInterceptor.process(postcard, new InterceptorCallback() {
                @Override
                public void onContinue(Postcard postcard) {
                    // Last interceptor excute over with no exception.
                    counter.countDown();
                    _excute(index + 1, counter, postcard);  // When counter is down, it will be execute continue ,but index bigger than interceptors size, then U know.
                }
    
                @Override
                public void onInterrupt(Throwable exception) {
                    // Last interceptor excute over with fatal exception.
    
                    postcard.setTag(null == exception ? new HandlerException("No message.") : exception.getMessage());    // save the exception message for backup.
                    counter.cancel();
                }
            });
        }
    }

至此，即完成了interceptor的拦截，下篇文章，我们来解析ARouter的自动注入参数的功能。

[ARouter_01-]: http://blog.csdn.net/ethanco/article/details/74858075