ARouter源码解析(五)

arouter-gradle-plugin version : 1.0.2

AutoRegister : https://github.com/luckybilly/AutoRegister

前言

====

在本系列的第一篇中讲过,ARouter 可以通过扫描 dex 文件中 class 的全类名,来加载 compiler 生成的路由类。但这种方式影响性能,并且效率也不高。所以在 ARouter v1.3.0 之后的版本中,加入了自动注册的方式进行路由表的加载,自动注册可以缩短初始化时间,解决应用加固导致无法直接访问 dex 文件从而初始化失败的问题。

那么自动注册到底是什么东东,为什么有这么强大的能力呢?

那么接下来,我们就来分析分析。

预先需要了解的知识点:

  • 自定义 gradle plugin

  • gradle transform api

  • 使用 asm 实现字节码插桩

arouter-register

================

arouter-register 的入口就在 PluginLaunch


public class PluginLaunch implements Plugin<Project> {

 @Override

 public void apply(Project project) {

 def isApp = project.plugins.hasPlugin(AppPlugin)

  //only application module needs this plugin to generate register code

 if (isApp) {

 Logger.make(project)

 Logger.i('Project enable arouter-register plugin')

 def android = project.extensions.getByType(AppExtension)

 def transformImpl = new RegisterTransform(project)

  //init arouter-auto-register settings

 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(transformImpl)

 }

 }

}

从上面的代码可知:

  • 只在 application module (一般都是 app module)生成自动注册的代码;

  • 初始化了自动注册的设置,这样自动注册就知道需要注册 IRouteRoot IInterceptorGroup IProviderGroup 这三者;

  • 注册 RegisterTransform ,字节码插桩将在 RegisterTransform 中完成;

可以看出,重点就在 RegisterTransform 里面。那我们重点就关注下 RegisterTransform 的代码,这里就贴出 transform 方法的源码了。(关于 Transform 的 InputTypes 和 Scopes 知识点在这就不讲了,如有需要了解的同学可以看 Android 热修复使用Gradle Plugin1.5改造Nuwa插件


class RegisterTransform extends Transform {

@Override

void transform(Context context, Collection<TransformInput> inputs

 , Collection<TransformInput> referencedInputs

 , TransformOutputProvider outputProvider

 , boolean isIncremental) throws IOException, TransformException, InterruptedException {

 Logger.i('Start scan register info in jar file.')

 long startTime = System.currentTimeMillis()

 boolean leftSlash = File.separator == '/'

 inputs.each { TransformInput input ->

  // 扫描所有的 jar 文件

 input.jarInputs.each { JarInput jarInput ->

 String destName = jarInput.name

  // rename jar files

 def hexName = DigestUtils.md5Hex(jarInput.file.absolutePath)

 if (destName.endsWith(".jar")) {

 destName = destName.substring(0, destName.length() - 4)

 }

  // 输入的 jar 文件

 File src = jarInput.file

  // 输出的 jar 文件

 File dest = outputProvider.getContentLocation(destName + "_" + hexName, jarInput.contentTypes, jarInput.scopes, Format.JAR)

  // 扫描 jar 文件,查找实现 IRouteRoot IInterceptorGroup IProviderGroup 接口的类,并且找到 LogisticsCenter 在哪个 jar 文件中

  // 不扫描 com.android.support 开头的 jar

 if (ScanUtil.shouldProcessPreDexJar(src.absolutePath)) {

  // ScanUtil.scanJar 的代码就不详细展开了,感兴趣的同学可以自己去看下

 ScanUtil.scanJar(src, dest)

 }

 FileUtils.copyFile(src, dest)

 }

  // 扫描所有的 class 文件,查找实现 IRouteRoot IInterceptorGroup IProviderGroup 接口的类

  // 和扫描 jar 做差不多类似的工作。不同的点就是不用再去找 LogisticsCenter 类

 input.directoryInputs.each { DirectoryInput directoryInput ->

 File dest = outputProvider.getContentLocation(directoryInput.name, directoryInput.contentTypes, directoryInput.scopes, Format.DIRECTORY)

 String root = directoryInput.file.absolutePath

 if (!root.endsWith(File.separator))

 root += File.separator

 directoryInput.file.eachFileRecurse { File file ->

 def path = file.absolutePath.replace(root, '')

 if (!leftSlash) {

 path = path.replaceAll("\\\\", "/")

 }

  // 只处理 com/alibaba/android/arouter/routes/ 开头的 class

 if(file.isFile() && ScanUtil.shouldProcessClass(path)){

 ScanUtil.scanClass(file)

 }

 }

  // copy to dest

 FileUtils.copyDirectory(directoryInput.file, dest)

 }

 }

 Logger.i('Scan finish, current cost time ' + (System.currentTimeMillis() - startTime) + "ms")

  // 这里开始字节码插桩操作

 if (fileContainsInitClass) {

  // 遍历之前找的 IRouteRoot IInterceptorGroup IProviderGroup

 registerList.each { ext ->

 Logger.i('Insert register code to file ' + fileContainsInitClass.absolutePath)

 if (ext.classList.isEmpty()) {

 Logger.e("No class implements found for interface:" + ext.interfaceName)

 } else {

 ext.classList.each {

 Logger.i(it)

 }

  // 对 LogisticsCenter.class 做字节码插桩

 RegisterCodeGenerator.insertInitCodeTo(ext)

 }

 }

 }

 Logger.i("Generate code finish, current cost time: " + (System.currentTimeMillis() - startTime) + "ms")

}

}

上面代码的逻辑很清晰,按照之前设置好的 IRouteRoot IInterceptorGroup IProviderGroup 这三个接口,然后扫描整个项目的代码,分别找到这三者各自的实现类,然后加入到集合中。最后在 LogisticsCenter 中实现字节码插桩。

我们来详细看下 RegisterCodeGenerator.insertInitCodeTo(ext) 的代码


static void insertInitCodeTo(ScanSetting registerSetting) {

 if (registerSetting != null && !registerSetting.classList.isEmpty()) {

 RegisterCodeGenerator processor = new RegisterCodeGenerator(registerSetting)

  // RegisterTransform.fileContainsInitClass 就是包含了 LogisticsCenter.class 的那个 jar 文件

 File file = RegisterTransform.fileContainsInitClass

 if (file.getName().endsWith('.jar'))

 // 开始处理

 processor.insertInitCodeIntoJarFile(file)

 }

}

插入的操作在 insertInitCodeIntoJarFile 中实现。


private File insertInitCodeIntoJarFile(File jarFile) {

 if (jarFile) {

 def optJar = new File(jarFile.getParent(), jarFile.name + ".opt")

 if (optJar.exists())

 optJar.delete()

 def file = new JarFile(jarFile)

 Enumeration enumeration = file.entries()

 JarOutputStream jarOutputStream = new JarOutputStream(new FileOutputStream(optJar))

  // 遍历 jar 文件中的 class

 while (enumeration.hasMoreElements()) {

 JarEntry jarEntry = (JarEntry) enumeration.nextElement()

 String entryName = jarEntry.getName()

 ZipEntry zipEntry = new ZipEntry(entryName)

 InputStream inputStream = file.getInputStream(jarEntry)

 jarOutputStream.putNextEntry(zipEntry)

  // 如果是 LogisticsCenter.class 的话

 if (ScanSetting.GENERATE_TO_CLASS_FILE_NAME == entryName) {

 Logger.i('Insert init code to class >> ' + entryName)

 // 插桩操作

 def bytes = referHackWhenInit(inputStream)

 jarOutputStream.write(bytes)

 } else {

 jarOutputStream.write(IOUtils.toByteArray(inputStream))

 }

 inputStream.close()

 jarOutputStream.closeEntry()

 }

 jarOutputStream.close()

 file.close()

  // 把字节码插桩的 jar 替换掉原来旧的 jar 文件

 if (jarFile.exists()) {

 jarFile.delete()

 }

 optJar.renameTo(jarFile)

 }

 return jarFile

}

字节码插桩的代码还在 referHackWhenInit 方法中。


//refer hack class when object init

private byte[] referHackWhenInit(InputStream inputStream) {

 ClassReader cr = new ClassReader(inputStream)

 ClassWriter cw = new ClassWriter(cr, 0)

 ClassVisitor cv = new MyClassVisitor(Opcodes.ASM5, cw)

 cr.accept(cv, ClassReader.EXPAND_FRAMES)

 return cw.toByteArray()

}

class MyClassVisitor extends ClassVisitor {

 MyClassVisitor(int api, ClassVisitor cv) {

 super(api, cv)

 }

 void visit(int version, int access, String name, String signature,

 String superName, String[] interfaces) {

 super.visit(version, access, name, signature, superName, interfaces)

 }

 @Override

 MethodVisitor visitMethod(int access, String name, String desc,

 String signature, String[] exceptions) {

 MethodVisitor mv = super.visitMethod(access, name, desc, signature, exceptions)

  // 对 loadRouterMap 这个方法进行代码插入

 if (name == ScanSetting.GENERATE_TO_METHOD_NAME) {

 mv = new RouteMethodVisitor(Opcodes.ASM5, mv)

 }

 return mv

 }

}

class RouteMethodVisitor extends MethodVisitor {

 RouteMethodVisitor(int api, MethodVisitor mv) {

 super(api, mv)

 }

 @Override

 void visitInsn(int opcode) {

  // 插入的代码在 return 之前

 if ((opcode >= Opcodes.IRETURN && opcode <= Opcodes.RETURN)) {

 extension.classList.each { name ->

 name = name.replaceAll("/", ".")

 mv.visitLdcInsn(name)//这里的name就是之前扫描出来的 IRouteRoot IInterceptorGroup IProviderGroup 实现类名

  // 生成 LogisticsCenter.register(name) 代码

 mv.visitMethodInsn(Opcodes.INVOKESTATIC

 , ScanSetting.GENERATE_TO_CLASS_NAME

 , ScanSetting.REGISTER_METHOD_NAME

 , "(Ljava/lang/String;)V"

 , false)

 }

 }

 super.visitInsn(opcode)

 }

 @Override

 void visitMaxs(int maxStack, int maxLocals) {

 super.visitMaxs(maxStack + 4, maxLocals)

 }

}

最终,生成的代码会像下面所示:


private static void loadRouterMap() {

 registerByPlugin = false;

  //auto generate register code by gradle plugin: arouter-auto-register

  // looks like below:

 register("com.alibaba.android.arouter.routes.ARouter$$Root$$app");

 register("com.alibaba.android.arouter.routes.ARouter$$Interceptors$$app");

 register("com.alibaba.android.arouter.routes.ARouter$$Group$$arouter");

}

那么顺便来跟踪一下 register 方法的代码,看看里面是如何完成路由表注册的。


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) {

 registerRouteRoot((IRouteRoot) obj);

 } else if (obj instanceof IProviderGroup) {

 registerProvider((IProviderGroup) obj);

 } else if (obj instanceof IInterceptorGroup) {

 registerInterceptor((IInterceptorGroup) obj);

 } else {

 logger.info(TAG, "register failed, class name: " + className

 + " should implements one of IRouteRoot/IProviderGroup/IInterceptorGroup.");

 }

 } catch (Exception e) {

 logger.error(TAG,"register class error:" + className);

 }

 }

}

// 注册 IRouteRoot 类型

private static void registerRouteRoot(IRouteRoot routeRoot) {

 markRegisteredByPlugin();

 if (routeRoot != null) {

 routeRoot.loadInto(Warehouse.groupsIndex);

 }

}

// 注册 IInterceptorGroup 类型

private static void registerInterceptor(IInterceptorGroup interceptorGroup) {

 markRegisteredByPlugin();

 if (interceptorGroup != null) {

 interceptorGroup.loadInto(Warehouse.interceptorsIndex);

 }

}

// 注册 IProviderGroup 类型

private static void registerProvider(IProviderGroup providerGroup) {

 markRegisteredByPlugin();

 if (providerGroup != null) {

 providerGroup.loadInto(Warehouse.providersIndex);

 }

}

// 标记通过gradle plugin完成自动注册

private static void markRegisteredByPlugin() {

 if (!registerByPlugin) {

 registerByPlugin = true;

 }

}

这样相比之下,自动注册的方式确实比扫描 dex 文件更高效,扫描 dex 文件是在 app 运行时操作的,这样会影响 app 的性能,对用户造成不好的体验。而自动注册是在 build 的时候完成字节码插桩的,对运行时不产生影响。

学了今天这招,以后 compiler 生成的代码需要注册的步骤都可以通过自动注册来完成了,赞一个👍

番外

====

之前看到自动注册这么神奇,所以想看下插入字节码之后 LogisticsCenter 代码的效果,所以反编译了一下 ARouter demo apk,可以看到 LogisticsCenter.smali 的 loadRouterMap 方法:


.method private static loadRouterMap()V

  .locals  1

 .line 64

 const/4 v0, 0x0

 sput-boolean v0, Lcom/alibaba/android/arouter/core/LogisticsCenter;->registerByPlugin:Z

 .line 69

  const-string v0, "com.alibaba.android.arouter.routes.ARouter$$Root$$modulejava"

 invoke-static {v0}, Lcom/alibaba/android/arouter/core/LogisticsCenter;->register(Ljava/lang/String;)V

  const-string v0, "com.alibaba.android.arouter.routes.ARouter$$Root$$modulekotlin"

 invoke-static {v0}, Lcom/alibaba/android/arouter/core/LogisticsCenter;->register(Ljava/lang/String;)V

  const-string v0, "com.alibaba.android.arouter.routes.ARouter$$Root$$arouterapi"

 invoke-static {v0}, Lcom/alibaba/android/arouter/core/LogisticsCenter;->register(Ljava/lang/String;)V

  const-string v0, "com.alibaba.android.arouter.routes.ARouter$$Root$$app"

 invoke-static {v0}, Lcom/alibaba/android/arouter/core/LogisticsCenter;->register(Ljava/lang/String;)V

  const-string v0, "com.alibaba.android.arouter.routes.ARouter$$Interceptors$$modulejava"

 invoke-static {v0}, Lcom/alibaba/android/arouter/core/LogisticsCenter;->register(Ljava/lang/String;)V

  const-string v0, "com.alibaba.android.arouter.routes.ARouter$$Interceptors$$app"

 invoke-static {v0}, Lcom/alibaba/android/arouter/core/LogisticsCenter;->register(Ljava/lang/String;)V

  const-string v0, "com.alibaba.android.arouter.routes.ARouter$$Providers$$modulejava"

 invoke-static {v0}, Lcom/alibaba/android/arouter/core/LogisticsCenter;->register(Ljava/lang/String;)V

  const-string v0, "com.alibaba.android.arouter.routes.ARouter$$Providers$$modulekotlin"

 invoke-static {v0}, Lcom/alibaba/android/arouter/core/LogisticsCenter;->register(Ljava/lang/String;)V

  const-string v0, "com.alibaba.android.arouter.routes.ARouter$$Providers$$arouterapi"

 invoke-static {v0}, Lcom/alibaba/android/arouter/core/LogisticsCenter;->register(Ljava/lang/String;)V

  const-string v0, "com.alibaba.android.arouter.routes.ARouter$$Providers$$app"

 invoke-static {v0}, Lcom/alibaba/android/arouter/core/LogisticsCenter;->register(Ljava/lang/String;)V

  return-void

.end method

确实符合我们的预期啊,真好!

References

==========

    原文作者:yyyuqirong
    原文地址: https://www.jianshu.com/p/8ad636fbfcc6
    本文转自网络文章,转载此文章仅为分享知识,如有侵权,请联系博主进行删除。
点赞