一.Arouter框架分析

2024-01-24 20:39:28

Arouter框架结构

Arouter框架结构中有注解定义和注解处理器相关的内容，Arouter本身也可以算是一个示例。

arouter-api对Arouter初始化

Arouter框架使用的静态注解处理，为适应多模块，使用moduleName后缀生成了一组统一规则的注册类。这些注册类分布在各自的module内部，需要一个管理类把他们聚合在一起，提供统一的注册和调用入口。

初始化入口

集成Arouter路由框架，需要在Application初始化过程中调用下面的方法对Arouter框架进行初始化。

ARouter.init(sInstance);

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;
}

动态扫描路由注册类

其中路由表初始化在 LogisticsCenter.init(mContext, executor); 中完成。需要注意下面的这个判断：

ARouter.debuggable() || PackageUtils.isNewVersion(context)，在debug或者更新app版本的条件下才会更新路由表，扫描的路由文件列表在SharedPreference中保存。

registerByPlugin 是 com.alibaba.arouter 插件标记，标明是否在编译阶段已经进行了路由表注册工作，直接跳过；
使用 ClassUtils 扫描package(com.alibaba.android.arouter.routes)中所有类文件 - 因为所有模块的路由都创建在这个包路径中；
把所有扫描到的文件，按照规则生成实例，注册到管理器 Warehouse 中；

/**
 * LogisticsCenter init, load all metas in memory. Demand initialization
 */
public synchronized static void init(Context context, ThreadPoolExecutor tpe) throws HandlerException {
    // 有删减
    loadRouterMap();
    if (!registerByPlugin) {
	Set<String> routerMap;
        if (ARouter.debuggable() || PackageUtils.isNewVersion(context)) {
            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 {
            routerMap = new HashSet<>(context.getSharedPreferences(AROUTER_SP_CACHE_KEY, Context.MODE_PRIVATE).getStringSet(AROUTER_SP_KEY_MAP, new HashSet<String>()));
        }
        for (String className : routerMap) {
            if (className.startsWith(ROUTE_ROOT_PAKCAGE + DOT + SDK_NAME + SEPARATOR + SUFFIX_ROOT)) {
            	((IRouteRoot) (Class.forName(className).getConstructor().newInstance())).loadInto(Warehouse.groupsIndex);
            } else if (className.startsWith(ROUTE_ROOT_PAKCAGE + DOT + SDK_NAME + SEPARATOR + SUFFIX_INTERCEPTORS)) {
                ((IInterceptorGroup) (Class.forName(className).getConstructor().newInstance())).loadInto(Warehouse.interceptorsIndex);
            } else if (className.startsWith(ROUTE_ROOT_PAKCAGE + DOT + SDK_NAME + SEPARATOR + SUFFIX_PROVIDERS)) {
            	((IProviderGroup) (Class.forName(className).getConstructor().newInstance())).loadInto(Warehouse.providersIndex);
            }
        }
    }
}

使用arouter-register插件

Arouter-register是AutoRegister插件在Arouter框架中的实现，主要目的是在编译阶段完成路由表的初始化操作，降低Arouter初始化耗时。

路由文件和初始化类扫描

@Override
void transform(Context context, Collection<TransformInput> inputs , Collection<TransformInput> referencedInputs,
               TransformOutputProvider outputProvider, boolean isIncremental) throws IOException, TransformException, InterruptedException {

    // 有删减
    boolean leftSlash = File.separator == '/'
    if (!isIncremental){
        outputProvider.deleteAll()
    }

    inputs.each { TransformInput input ->

        // scan all jars
        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)
            }
            // input file
            File src = jarInput.file
            // output file
            File dest = outputProvider.getContentLocation(destName + "_" + hexName, jarInput.contentTypes, jarInput.scopes, Format.JAR)

            //scan jar file to find classes
            if (ScanUtil.shouldProcessPreDexJar(src.absolutePath)) {
                ScanUtil.scanJar(src, dest)
            }
            FileUtils.copyFile(src, dest)

        }
        // scan class files
        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("\\", "/")
                }
                if(file.isFile() && ScanUtil.shouldProcessClass(path)){
                    ScanUtil.scanClass(file)
                }
            }

            // copy to dest
            FileUtils.copyDirectory(directoryInput.file, dest)
        }
    }

    if (fileContainsInitClass) {
        registerList.each { ext ->
            if (!ext.classList.isEmpty()) {
                ext.classList.each {
                    Logger.i(it)
                }
                RegisterCodeGenerator.insertInitCodeTo(ext)
            }
        }
    }
}

static void scanJar(File jarFile, File destFile) {
    if (jarFile) {
        def file = new JarFile(jarFile)
        Enumeration enumeration = file.entries()
        while (enumeration.hasMoreElements()) {
            JarEntry jarEntry = (JarEntry) enumeration.nextElement()
            String entryName = jarEntry.getName()
            if (entryName.startsWith(ScanSetting.ROUTER_CLASS_PACKAGE_NAME)) {
                InputStream inputStream = file.getInputStream(jarEntry)
                scanClass(inputStream)
                inputStream.close()
            } else if (ScanSetting.GENERATE_TO_CLASS_FILE_NAME == entryName) {
				// com/alibaba/android/arouter/core/LogisticsCenter
                RegisterTransform.fileContainsInitClass = destFile
            }
        }
        file.close()
    }
}

/**
 * scan class file
 * @param class file
 */
static void scanClass(File file) {
    scanClass(new FileInputStream(file))
}

static void scanClass(InputStream inputStream) {
    ClassReader cr = new ClassReader(inputStream)
    ClassWriter cw = new ClassWriter(cr, 0)
    ScanClassVisitor cv = new ScanClassVisitor(Opcodes.ASM5, cw)
    cr.accept(cv, ClassReader.EXPAND_FRAMES)
    inputStream.close()
}

static class ScanClassVisitor extends ClassVisitor {

    ScanClassVisitor(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)
        RegisterTransform.registerList.each { ext ->
            if (ext.interfaceName && interfaces != null) {
                interfaces.each { itName ->
                    if (itName == ext.interfaceName) {
                        //fix repeated inject init code when Multi-channel packaging
                        if (!ext.classList.contains(name)) {
                            ext.classList.add(name)
                        }
                    }
                }
            }
        }
    }
}

目标文件字节码操作

通过上面的扫描操作：获取到Arouter框架生成类的路径存放于RegisterTransform.registerList中的ScanSetting对象中，以及arouter-api初始化类 LogisticsCenter 所在的文件由 RegisterTransform.fileContainsInitClass 持有。扫描完成后，调用 RegisterCodeGenerator.insertInitCodeTo(ext) ，遍历RegisterTransform.registerList中的ScanSetting对象作为输入，对 LogisticsCenter 类所在的文件读写操作。

// 读写过程：创建临时文件optJar，从源文件jarFile中读取数据，转写到临时optJar文件中，完成后使用optJar覆盖源文件jarFile。
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))

        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)
            if (ScanSetting.GENERATE_TO_CLASS_FILE_NAME == entryName) {
                def bytes = referHackWhenInit(inputStream)
                jarOutputStream.write(bytes)
            } else {
                jarOutputStream.write(IOUtils.toByteArray(inputStream))
            }
            inputStream.close()
            jarOutputStream.closeEntry()
        }
        jarOutputStream.close()
        file.close()

        if (jarFile.exists()) {
            jarFile.delete()
        }
        optJar.renameTo(jarFile)
    }
    return jarFile
}

// 找到com/alibaba/android/arouter/core/LogisticsCenter.class，调用这个方法
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()
}

// 在LogisticsCenter.class中查找 loadRouterMap 方法
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)
        //generate code into this method
        if (name == ScanSetting.GENERATE_TO_METHOD_NAME) {
            mv = new RouteMethodVisitor(Opcodes.ASM5, mv)
        }
        return mv
    }
}

// 向 loadRouterMap 插入语句：retister(className)
// register函数在 LogisticsCenter 中定义，用于把给定的类名生成实例，注册到 Warehouse 管理器中。
class RouteMethodVisitor extends MethodVisitor {

    RouteMethodVisitor(int api, MethodVisitor mv) {
        super(api, mv)
    }

    @Override
    void visitInsn(int opcode) {
        //generate code before return
        if ((opcode >= Opcodes.IRETURN && opcode <= Opcodes.RETURN)) {
            extension.classList.each { name ->
                name = name.replaceAll("/", ".")
                mv.visitLdcInsn(name)//类名
                // generate invoke register method into LogisticsCenter.loadRouterMap()
                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)
    }
}

arouter-register与arouter-api 初始化Arouter

Arouter-register是AutoRegister的一个实现，可以参考。

Arouter-api在运行时，通过扫描类文件进行初始化操操作。
Arouter-register在编译阶段的尾声部分，扫描jar文件和.class文件找到路由注册类，在 LogisticsCenter.class#loadRouterMap() 方法中插入LogisticsCenter.class#register(className) 调用语句，使得loadRouterMap可以直接完成路由注册，节省了运行时扫描的时间。
Arouter-register工作在Arouter-api的基础上，register(className)和 loadRouterMap()都由Arouter-api库提供。

插件中使用的方法记录

JarFile

file.entries() -> Enumeration : Jar文件中打包的.class文件集合
enumeration.nextElement() -> JarEntry : Jar文件中打包的.class 文件

类访问

使用 ClassVisiter、ClassReader、ClassWriter 对.class文件的读写操作，都在这一组类中。

void scanClass(InputStream inputStream) {
    ClassReader cr = new ClassReader(inputStream)
    ClassWriter cw = new ClassWriter(cr, 0)
    ScanClassVisitor cv = new ScanClassVisitor(Opcodes.ASM5, cw)
    cr.accept(cv, ClassReader.EXPAND_FRAMES)
    inputStream.close()
}

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()
}

static class MyClassVisitor extends ClassVisitor {

    ScanClassVisitor(int api, ClassVisitor cv) {
        super(api, cv)
    }

    @Override
    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)
        //generate code into this method
        if (name == ScanSetting.GENERATE_TO_METHOD_NAME) {
            mv = new RouteMethodVisitor(Opcodes.ASM5, mv)
        }
        return mv
    }
}

方法访问

使用 MethodVisitor 对类方法进行读写，可以插入代码。

class RouteMethodVisitor extends MethodVisitor {

    RouteMethodVisitor(int api, MethodVisitor mv) {
        super(api, mv)
    }

    @Override
    void visitInsn(int opcode) {
        super.visitInsn(opcode)
    }
    @Override
    void visitMaxs(int maxStack, int maxLocals) {
        super.visitMaxs(maxStack + 4, maxLocals)
    }
}

ASM库

Arouter-register插件，是基于字节码插桩技术实现的。ASM是一个插桩框架，框架集成在 com.android.tools.build:gradle 内，下表有删减。

字节码插桩技术
ASM：字节码插桩的一个框架实现

\--- com.android.tools.build:gradle:2.1.3
     \--- com.android.tools.build:gradle-core:2.1.3
          +--- com.android.tools.build:builder:2.1.3
          |    +--- org.ow2.asm:asm:5.0.3
          |    \--- org.ow2.asm:asm-tree:5.0.3
          |         \--- org.ow2.asm:asm:5.0.3
          +--- org.ow2.asm:asm:5.0.3
          +--- org.ow2.asm:asm-commons:5.0.3
          |    \--- org.ow2.asm:asm-tree:5.0.3 (*)
          +--- net.sf.proguard:proguard-gradle:5.2.1
          |    \--- net.sf.proguard:proguard-base:5.2.1
          +--- org.jacoco:org.jacoco.core:0.7.6.201602180812
          |    \--- org.ow2.asm:asm-debug-all:5.0.4
          \--- org.antlr:antlr:3.5.2
               +--- org.antlr:antlr-runtime:3.5.2
               \--- org.antlr:ST4:4.0.8 (*)

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