文章来源自作者的Android进阶计划(https://github.com/SusionSuc/AdvancedAndroid)
我前面其实已经分析过WMRouter的路由节点的生成原理: https://www.jianshu.com/p/116adb143970
其实ARouter的路由表的生成的步骤和WMRouter差不多,也是使用 : 注解处理 , Gradle Transfrom API, javapoet, asm。再贴一下相关文章技术文章以便了解:
注解 : https://blog.csdn.net/jeasonlzy/article/details/74273851
javapoet : https://blog.csdn.net/qq_18242391/article/details/77018155
gradle Transfrom api : https://www.jianshu.com/p/37df81365edf
我们来继续看ARouter的路由节点的生成原理, 我们先来看@Route的注解扫描处理器:
public class RouteProcessor extends AbstractProcessor {
private Map<String, Set<RouteMeta>> groupMap = new HashMap<>(); // ModuleName and routeMeta.
private Map<String, String> rootMap = new TreeMap<>(); // Map of root metas, used for generate class file in order.
@Override public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
for (Element element : routeElements) {
Route route = element.getAnnotation(Route.class);
RouteMeta routeMeta;
// 根据 @Route 的注解信息，生成一个 RouteMeta对象。
categories(routeMeta); //把这个 RouteMeta放到 groupMap 中， key 为组名
}
//atlas参数
ParameterSpec groupParamSpec = ParameterSpec.builder(inputMapTypeOfGroup, "atlas").build();
for (Map.Entry<String, Set<RouteMeta>> entry : groupMap.entrySet()) {
// 每个组，都要生成 loadInto 方法
MethodSpec.Builder loadIntoMethodOfGroupBuilder = MethodSpec.methodBuilder(“loadInto”)
.addAnnotation(Override.class)
.addModifiers(PUBLIC)
.addParameter(groupParamSpec);
// 产生 RouteMeta的注入方法 , 比如 ->
//atlas.put("/test/activity4", RouteMeta.build(RouteType.ACTIVITY, Test4Activity.class, "/test/activity4", "test", 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());
// 生成对应的组的文件，比如 : ARouter$$Group$$test.java
String groupFileName = "ARouter$$Group$$" + groupName;
JavaFile.builder(PACKAGE_OF_GENERATE_FILE,
TypeSpec.classBuilder(groupFileName)
.addJavadoc(WARNING_TIPS)
.addSuperinterface(ClassName.get(type_IRouteGroup))
.addModifiers(PUBLIC)
.addMethod(loadIntoMethodOfGroupBuilder.build())
.build()
).build().writeTo(mFiler);
rootMap.put(groupName, groupFileName); //把路由组文件信息保存起来
}
//加载每个路由组的类
if (MapUtils.isNotEmpty(rootMap)) {
for (Map.Entry<String, String> entry : rootMap.entrySet()) {
loadIntoMethodOfRootBuilder.addStatement("routes.put($S, $T.class)", entry.getKey(), ClassName.get(PACKAGE_OF_GENERATE_FILE, entry.getValue()));
}
}
//ARouter$$Root$$app.loadInto(Map<String, Class<? extends IRouteGroup>> routes) 方法
MethodSpec.Builder loadIntoMethodOfRootBuilder = MethodSpec.methodBuilder(METHOD_LOAD_INTO)
.addAnnotation(Override.class)
.addModifiers(PUBLIC)
.addParameter(rootParamSpec);
// 加载每个路由组的类
String rootFileName = “ARouter$$Root$$” + moduleName;
JavaFile.builder(PACKAGE_OF_GENERATE_FILE,
TypeSpec.classBuilder(rootFileName)
.addJavadoc(WARNING_TIPS)
.addSuperinterface(ClassName.get(elements.getTypeElement(ITROUTE_ROOT)))
.addModifiers(PUBLIC)
.addMethod(loadIntoMethodOfRootBuilder.build())
.build()
).build().writeTo(mFiler);
}
}
这里我不做详细解释了(注释写的很清楚了),我们这里直接举一个例子，比如我们这样标记了一个界面:
@Route(path = "/test/activity1")
public class Test1Activity extends AppCompatActivity {
}
那么按照RouteProcessor处理后将会生成以下类文件:
ARouter$$Group$$test.java
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", null, -1, -2147483648));
}
}
ARouter$$Root$$app.java:
public class ARouter$$Root$$app implements IRouteRoot {
@Override
public void loadInto(Map<String, Class<? extends IRouteGroup>> routes) {
routes.put("test", ARouter$$Group$$test.class);
}
}
参照上面这两个文件和RouteProcessor,应该大致可以理解。好，对应注册路由表与组的文件已经生成，那么这些文件是如何在ARouter运行的时候加载到内存的呢？
猜测：这些产生的类文件，在运行的时候，应该会被实例化，然后动态注册到Warehouse中。其实实现方式类似于WMRouter，也是gradle Transfrom api和asm, 下面来看一下 :
打开ARouter找到 gradle 插件。首先在插件启动的时候:
public class PluginLaunch implements Plugin<Project> {
@Override
public void apply(Project project) {
def isApp = project.plugins.hasPlugin(AppPlugin)
if (isApp) {
....
ArrayList<ScanSetting> list = new ArrayList<>(3)
list.add(new ScanSetting('IRouteRoot'))
list.add(new ScanSetting('IInterceptorGroup'))
list.add(new ScanSetting('IProviderGroup'))
RegisterTransform.registerList = list
//register this plugin
android.registerTransform(new RegisterTransform(project))
}
}
}
可以看到会注册RegisterTransform,并把RegisterTransform.registerList,加入几个ScanSetting定义的接口, 比如IRouteRoot。(注意,上面 ARouter$$Root$$app 实现的就是这个接口)
class RegisterTransform extends Transform {
static ArrayList<ScanSetting> registerList
@Override
void transform(Context context, Collection<TransformInput> inputs, Collection<TransformInput> referencedInputs, TransformOutputProvider outputProvider, boolean isIncremental) {
inputs.each { TransformInput input ->
input.jarInputs.each { JarInput jarInput -> // 扫描jar包
....
File src = jarInput.file // input file
File dest = outputProvider.getContentLocation(destName + "_" + hexName, jarInput.contentTypes, jarInput.scopes, Format.JAR) // output file
if (ScanUtil.shouldProcessPreDexJar(src.absolutePath)) {
ScanUtil.scanJar(src, dest)
}
}
input.directoryInputs.each { DirectoryInput directoryInput -> // 扫描指定目录
......
ScanUtil.scanClass(file)
....
}
}
}
}
static void scanJar(File jarFile, File destFile) {
if (jarFile) {
def file = new JarFile(jarFile)
Enumeration enumeration = file.entries()
while (enumeration.hasMoreElements()) {
String entryName = (JarEntry) enumeration.nextElement().getName()
if (entryName.startsWith("com/alibaba/android/arouter/routes/")) { //扫描这个目录下的文件
//如果这个文件实现了`RegisterTransform.registerList`的接口，就把这个类保存下来(保存类名)
scanClass(File file) // 使用 asm库，来访问class文件，完成这个操作
}
....
}
}
}
//scanClass(File file) 最终会调用下面的 visit方法
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) // 其实就是把 "com/alibaba/android/arouter/routes/" 目录下的文件加入到 RegisterTransform.registerList集合中
}
}
}
}
}
好经过上面的一顿操作，RegisterTransform.registerList已经保存了实现了IRouteRoot接口的类集合。
if (fileContainsInitClass) {
registerList.each { ext ->
RegisterCodeGenerator.insertInitCodeTo(ext)
}
}
RegisterCodeGenerator.insertInitCodeTo(ext)这里不仔细追了，其实就是通过asm库最终把路由表的初始化代码插入到了com/alibaba/android/arouter/core/LogisticsCenter.loadRouterMap方法中:
/**
* arouter-auto-register plugin will generate code inside this method
* call this method to register all Routers, Interceptors and Providers
*/
private static void loadRouterMap() {
registerByPlugin = false;
//auto generate register code by gradle plugin: arouter-auto-register
register("com.xxx.ARouter$$Root$$app")
}
看一下register()方法:
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) {
obj.loadInto(Warehouse.groupsIndex);
}
}
}
...
}
实例化ARouter$$Group$$test这种实现了IRouteRoot接口的类，然后把传入路由表，添加路由信息。
到这里@Route注册的页面，在程序运行时都以RouteMeta的形式放到了路由表中。方便路由使用。
一图胜千言, 我们用一张图来总结一下上面所做的操作:
路由节点的动态注入.png
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