Arouter源码系列之拦截器原理详解
做过组件化开发的小伙伴应该都比较了解Arouter使用，那么Arouter的拦截器就更不用说了，一般用拦截器作用很多，比如在跳转之前做一些额外的操作（经典用法检查是否登陆，没登陆跳到登陆界面，实现一个拦截器也很简单，加一条注解就ok：@Interceptor(priority = 7)，priority代表的是优先级。既然加一条注解以后每次跳转都会回调到process方法，如下：
public class Interceptor1 implements IInterceptor {
/**
* The operation of this interceptor.
*
* @param postcard meta
* @param callback cb
*/
@Override
public void process(final Postcard postcard, final InterceptorCallback callback){}那么肯定有用编译期注解的方式，如下：
annotationProcessor 'com.google.auto.service:auto-service:1.0-rc7'
compileOnly 'com.google.auto.service:auto-service-annotations:1.0-rc7'在android中如果想在编译期根据注解产生新的java类的话，那么:auto-service是必不可少，然后你继承AbstractProcessor即可实现效果，这里处理拦截器的注解类的是InterceptorProcessor，实现处理的方法如下：
public boolean process(Set annotations, RoundEnvironment roundEnv) {
if (CollectionUtils.isNotEmpty(annotations)) {
Set elements = roundEnv.getElementsAnnotatedWith(Interceptor.class);
try {
parseInterceptors(elements);
} catch (Exception e) {
logger.error(e);
}
return true;
}
return false;
}
真正实现方法如下：
private void parseInterceptors(Set elements) throws IOException {
if (CollectionUtils.isNotEmpty(elements)) {
logger.info(">>> Found interceptors, size is " + elements.size() + " <<<");
// Verify and cache, sort incidentally.
for (Element element : elements) {
if (verify(element)) { // Check the interceptor meta
logger.info("A interceptor verify over, its " + element.asType());
Interceptor interceptor = element.getAnnotation(Interceptor.class);
Element lastInterceptor = interceptors.get(interceptor.priority());
if (null != lastInterceptor) { // Added, throw exceptions
throw new IllegalArgumentException(
String.format(Locale.getDefault(), "More than one interceptors use same priority [%d], They are [%s] and [%s].",
interceptor.priority(),
lastInterceptor.getSimpleName(),
element.getSimpleName())
);
}
interceptors.put(interceptor.priority(), element);
} else {
logger.error("A interceptor verify failed, its " + element.asType());
}
}
// Interface of ARouter.
TypeElement type_IInterceptor = elementUtils.getTypeElement(IINTERCEPTOR);
TypeElement type_IInterceptorGroup = elementUtils.getTypeElement(IINTERCEPTOR_GROUP);
/**
* Build input type, format as :
*
* ```Map>```
*/
ParameterizedTypeName inputMapTypeOfTollgate = ParameterizedTypeName.get(
ClassName.get(Map.class),
ClassName.get(Integer.class),
ParameterizedTypeName.get(
ClassName.get(Class.class),
WildcardTypeName.subtypeOf(ClassName.get(type_IInterceptor))
)
);
// Build input param name.
ParameterSpec tollgateParamSpec = ParameterSpec.builder(inputMapTypeOfTollgate, "interceptors").build();
// Build method : 'loadInto'
MethodSpec.Builder loadIntoMethodOfTollgateBuilder = MethodSpec.methodBuilder(METHOD_LOAD_INTO)
.addAnnotation(Override.class)
.addModifiers(PUBLIC)
.addParameter(tollgateParamSpec);
// Generate
if (null != interceptors && interceptors.size() > 0) {
// Build method body
for (Map.Entry entry : interceptors.entrySet()) {
loadIntoMethodOfTollgateBuilder.addStatement("interceptors.put(" + entry.getKey() + ", $T.class)", ClassName.get((TypeElement) entry.getValue()));
}
}
// Write to disk(Write file even interceptors is empty.)
JavaFile.builder(PACKAGE_OF_GENERATE_FILE,
TypeSpec.classBuilder(NAME_OF_INTERCEPTOR + SEPARATOR + moduleName)
.addModifiers(PUBLIC)
.addJavadoc(WARNING_TIPS)
.addMethod(loadIntoMethodOfTollgateBuilder.build())
.addSuperinterface(ClassName.get(type_IInterceptorGroup))
.build()
).build().writeTo(mFiler);
logger.info(">>> Interceptor group write over. <<<");
}
} 这个方法的意思就是取得Interceptor所有注解，然后将优先级做为key，存到TreeMap中，因为key是Integer类型实现了Comparable接口，所以TreeMap是根据优先级排序的，排好序之后，用javaPoet去生成ARouter$$Interceptors$$（MoudleＮａｍｅ）类，这个类主要用来保存拦截器的真正实现类的ｃｌａｓｓ，如这句代码：loadIntoMethodOfTollgateBuilder.addStatement("interceptors.put(" + entry.getKey() + ",$T.class)", ClassName.get((TypeElement) entry.getValue()));
，ＪａｖａＰｏｅｔ链接。
这个拦截器什么时候被使用的呢？当然是在跳转前面，如下：
*/
protected Object navigation(final Context context, final Postcard postcard, final int requestCode, final NavigationCallback callback) {
／／去掉无用代码．．．．．．
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
*/
@Override
public void onContinue(Postcard postcard) {
_navigation(postcard, requestCode, callback);
}
/**
* Interrupt process, pipeline will be destory when this method called.
*
* @param exception Reson of interrupt.
*/
@Override
public 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;
}可以看到最终拦截器是通过interceptorService类调用，它的实现类是InterceptorServiceImpl，实现方法如下：
public 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() {
@Override
public 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);
}
} 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() {
@Override
public 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.
}
@Override
public 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());
// }
}
});
}
}_execute在内部一直调用的递归，遍历ｍａｐ中所有而编译器用的ＴｒｅｅＭａｐ保证了优先级，好了到这拦截器的流程基本走完了，那么还有一个问题就是拦截器的集合 Warehouse.interceptors是什么时候填充的呢？当然是ARouter初始化的时候,如下：
protected static synchronized boolean init(Application application) {
mContext = application;
LogisticsCenter.init(mContext, executor);
logger.info(Consts.TAG, "ARouter init success!");
hasInit = true;
mHandler = new Handler(Looper.getMainLooper());
return true;
}最终调用LogisticsCenter.init，如下：
public synchronized static void init(Context context, ThreadPoolExecutor tpe) throws HandlerException {
mContext = context;
executor = tpe;
try {
long startInit = System.currentTimeMillis();
//load by plugin first
loadRouterMap();
if (registerByPlugin) {
logger.info(TAG, "Load router map by arouter-auto-register plugin.");
} else {
Set 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()));
}
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() + "]");
}
} 其中getFileNameByPackageName真正实现了class的储存加载,如下代码：
public static Set getFileNameByPackageName(Context context, final String packageName) throws PackageManager.NameNotFoundException, IOException, InterruptedException {
final Set classNames = new HashSet<>();
List paths = getSourcePaths(context);
final CountDownLatch parserCtl = new CountDownLatch(paths.size());
for (final String path : paths) {
DefaultPoolExecutor.getInstance().execute(new Runnable() {
@Override
public void run() {
DexFile dexfile = null;
try {
if (path.endsWith(EXTRACTED_SUFFIX)) {
//NOT use new DexFile(path), because it will throw "permission error in /data/dalvik-cache"
dexfile = DexFile.loadDex(path, path + ".tmp", 0);
} else {
dexfile = new DexFile(path);
}
Enumeration dexEntries = dexfile.entries();
while (dexEntries.hasMoreElements()) {
String className = dexEntries.nextElement();
if (className.startsWith(packageName)) {
classNames.add(className);
}
}
} catch (Throwable ignore) {
Log.e("ARouter", "Scan map file in dex files made error.", ignore);
} finally {
if (null != dexfile) {
try {
dexfile.close();
} catch (Throwable ignore) {
}
}
parserCtl.countDown();
}
}
});
}
parserCtl.await();
Log.d(Consts.TAG, "Filter " + classNames.size() + " classes by packageName <" + packageName + ">");
return classNames;
}
用的DexFile加载所有编译期产生的新java类的class，然后将class反射实例化，实现如下：
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);
}
}
}最终InterceptorServiceImpl的init方法实现，如下：
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;
logger.info(TAG, "ARouter interceptors init over.");
synchronized (interceptorInitLock) {
interceptorInitLock.notifyAll();
}
}
}
});
}