Android-AndFix 热修复框架原理及源码解析

AndFix原理

AndFix的原理就是通过c++指针进行方法的替换，把有bug的方法替换成补丁文件中的方法。


注：在Native层使用指针替换的方式替换bug方法，已达到修复bug的目的。使用AndFix修复热修复的整体流程：

方法替换过程：

源码解析

解析源码从使用的方法一一解析。

在自定义Application中初始化PatchManger：

PatchManager mPatchManager = new PatchManager();

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[/code]直接实例化了一个PatchManger实例对象，接下看PatchManager类源码：

public PatchManager(Context context) {
mContext = context;
mAndFixManager = new AndFixManager(mContext);//初始化AndFixManager
mPatchDir = new File(mContext.getFilesDir(), DIR);//初始化存放patch补丁文件的文件夹
mPatchs = new ConcurrentSkipListSet<Patch>();//初始化存在Patch类的集合,此类适合大并发
mLoaders = new ConcurrentHashMap<String, ClassLoader>();//初始化存放类对应的类加载器集合
}

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[/code]然后看AndFixManager的初始化：

public AndFixManager(Context context) {
mContext = context;
mSupport = Compat.isSupport();//判断Android机型是否适支持AndFix
if (mSupport) {
mSecurityChecker = new SecurityChecker(mContext);//初始化签名判断类
mOptDir = new File(mContext.getFilesDir(), DIR);//初始化patch文件存放的文件夹
if (!mOptDir.exists() && !mOptDir.mkdirs()) {// make directory fail
mSupport = false;
Log.e(TAG, "opt dir create error.");
} else if (!mOptDir.isDirectory()) {// not directory
mOptDir.delete();//如果不是文件目录就删除
mSupport = false;
}
}
}
public static synchronized boolean isSupport() {//此处加了同步锁机制
if (isChecked)
return isSupport;

isChecked = true;
// not support alibaba's YunOs
boolean isYunOs = isYunOS();//判断系统是否是YunOs系统，YunOs系统是阿里巴巴的系统
boolean setup  =AndFix.setup();//判断是Dalvik还是Art虚拟机，来注册Native方法
boolean isSupportSDKVersion = isSupportSDKVersion();//根据sdk版本判断是否支持
if (!isYunOs && setup && isSupportSDKVersion) {//根据上面三个boolean值判断是否支持
isSupport = true;
}

if (inBlackList()) {
isSupport = false;
}
return isSupport;
}
private static boolean isSupportSDKVersion() {
if (android.os.Build.VERSION.SDK_INT >= 8
&& android.os.Build.VERSION.SDK_INT <= 23) {
return true;
}
return false;
}
public static boolean setup() {
try {
final String vmVersion = System.getProperty("java.vm.version");
boolean isArt = vmVersion != null && vmVersion.startsWith("2");
int apilevel = Build.VERSION.SDK_INT;
return setup(isArt, apilevel);
} catch (Exception e) {
Log.e(TAG, "setup", e);
return false;
}
}
//签名机制的初始化过程
public SecurityChecker(Context context) {
mContext = context;
init(mContext);
}
//主要是获取当前应用的签名及其他信息，为了判断与patch文件的签名是否一致
private void init(Context context) {
try {
PackageManager pm = context.getPackageManager();
String packageName = context.getPackageName();

PackageInfo packageInfo = pm.getPackageInfo(packageName,
PackageManager.GET_SIGNATURES);
CertificateFactory certFactory = CertificateFactory
.getInstance("X.509");
ByteArrayInputStream stream = new ByteArrayInputStream(
packageInfo.signatures[0].toByteArray());
X509Certificate cert = (X509Certificate) certFactory
.generateCertificate(stream);
mDebuggable = cert.getSubjectX500Principal().equals(DEBUG_DN);
mPublicKey = cert.getPublicKey();
} catch (NameNotFoundException e) {
Log.e(TAG, "init", e);
} catch (CertificateException e) {
Log.e(TAG, "init", e);
}
}

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[/code]接下，看一下版本的初始化：

mPatchManager.init("version")

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[/code]

init方法源码：

public void init(String appVersion) {
if (!mPatchDir.exists() && !mPatchDir.mkdirs()) {// make directory fail
Log.e(TAG, "patch dir create error.");
return;
} else if (!mPatchDir.isDirectory()) {// not directory
mPatchDir.delete();
return;
}
SharedPreferences sp = mContext.getSharedPreferences(SP_NAME,
Context.MODE_PRIVATE);//存储关于patch文件的信息
//根据你传入的版本号和之前的对比，做不同的处理
String ver = sp.getString(SP_VERSION, null);
if (ver == null || !ver.equalsIgnoreCase(appVersion)) {
cleanPatch();//删除本地patch文件
sp.edit().putString(SP_VERSION, appVersion).commit();//并把传入的版本号保存
} else {
initPatchs();//初始化patch列表，把本地的patch文件加载到内存
}
}

private void cleanPatch() {
File[] files = mPatchDir.listFiles();
for (File file : files) {
mAndFixManager.removeOptFile(file);//删除所有的本地缓存patch文件
if (!FileUtil.deleteFile(file)) {
Log.e(TAG, file.getName() + " delete error.");
}
}
}
private void initPatchs() {
File[] files = mPatchDir.listFiles();
for (File file : files) {
addPatch(file);//加载Patch文件
}
}
private Patch addPatch(File file) {
Patch patch = null;
if (file.getName().endsWith(SUFFIX)) {
try {
patch = new Patch(file);//实例化Patch对象
mPatchs.add(patch);//把patch实例存储到内存的集合中,在PatchManager实例化集合
} catch (IOException e) {
Log.e(TAG, "addPatch", e);
}
}
return patch;
}

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[/code]

Patch文件的加载

public Patch(File file) throws IOException {
mFile = file;
init();
}

@SuppressWarnings("deprecation")
private void init() throws IOException {
JarFile jarFile = null;
InputStream inputStream = null;
try {
jarFile = new JarFile(mFile);//使用JarFile读取Patch文件
JarEntry entry = jarFile.getJarEntry(ENTRY_NAME);//获取META-INF/PATCH.MF文件
inputStream = jarFile.getInputStream(entry);
Manifest manifest = new Manifest(inputStream);
Attributes main = manifest.getMainAttributes();
mName = main.getValue(PATCH_NAME);//获取PATCH.MF属性Patch-Name
mTime = new Date(main.getValue(CREATED_TIME));//获取PATCH.MF属性Created-Time

mClassesMap = new HashMap<String, List<String>>();
Attributes.Name attrName;
String name;
List<String> strings;
for (Iterator<?> it = main.keySet().iterator(); it.hasNext();) {
attrName = (Attributes.Name) it.next();
name = attrName.toString();
//判断name的后缀是否是-Classes，并把name对应的值加入到集合中，对应的值就是class类名的列表
if (name.endsWith(CLASSES)) {
strings = Arrays.asList(main.getValue(attrName).split(","));
if (name.equalsIgnoreCase(PATCH_CLASSES)) {
mClassesMap.put(mName, strings);
} else {
mClassesMap.put(
name.trim().substring(0, name.length() - 8),// remove
// "-Classes"
strings);
}
}
}
} finally {
if (jarFile != null) {
jarFile.close();
}
if (inputStream != null) {
inputStream.close();
}
}

}

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[/code]

loadPatch方法源码

mPatchManager.loadPatch();

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[/code]loadPatch源码：

public void loadPatch() {
mLoaders.put("*", mContext.getClassLoader());// wildcard
Set<String> patchNames;
List<String> classes;
for (Patch patch : mPatchs) {
patchNames = patch.getPatchNames();
for (String patchName : patchNames) {
classes = patch.getClasses(patchName);//获取patch对用的class类的集合List
mAndFixManager.fix(patch.getFile(), mContext.getClassLoader(),
classes);//修复bug方法
}
}
}

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[/code]

fix bug

public synchronized void fix(File file, ClassLoader classLoader,
List<String> classes) {
if (!mSupport) {
return;
}
//判断patch文件的签名
if (!mSecurityChecker.verifyApk(file)) {// security check fail
return;
}

try {
File optfile = new File(mOptDir, file.getName());
boolean saveFingerprint = true;
if (optfile.exists()) {
// need to verify fingerprint when the optimize file exist,
// prevent someone attack on jailbreak device with
// Vulnerability-Parasyte.
// btw:exaggerated android Vulnerability-Parasyte
// http://secauo.com/Exaggerated-Android-Vulnerability-Parasyte.html if (mSecurityChecker.verifyOpt(optfile)) {
saveFingerprint = false;
} else if (!optfile.delete()) {
return;
}
}
//加载patch文件中的dex
final DexFile dexFile = DexFile.loadDex(file.getAbsolutePath(),
optfile.getAbsolutePath(), Context.MODE_PRIVATE);

if (saveFingerprint) {
mSecurityChecker.saveOptSig(optfile);
}

ClassLoader patchClassLoader = new ClassLoader(classLoader) {
@Override
protected Class<?> findClass(String className)
throws ClassNotFoundException {//重写ClasLoader的findClass方法
Class<?> clazz = dexFile.loadClass(className, this);
if (clazz == null
&& className.startsWith("com.alipay.euler.andfix")) {
return Class.forName(className);// annotation’s class
// not found
}
if (clazz == null) {
throw new ClassNotFoundException(className);
}
return clazz;
}
};
Enumeration<String> entrys = dexFile.entries();
Class<?> clazz = null;
while (entrys.hasMoreElements()) {
String entry = entrys.nextElement();
if (classes != null && !classes.contains(entry)) {
continue;// skip, not need fix
}
clazz = dexFile.loadClass(entry, patchClassLoader);//获取有bug的类文件
if (clazz != null) {
fixClass(clazz, classLoader);// next code
}
}
} catch (IOException e) {
Log.e(TAG, "pacth", e);
}
}
private void fixClass(Class<?> clazz, ClassLoader classLoader) {
Method[] methods = clazz.getDeclaredMethods();
MethodReplace methodReplace;
String clz;
String meth;
for (Method method : methods) {
//获取此方法的注解，因为有bug的方法在生成的patch的类中的方法都是有注解的，下面会给图进行展示
methodReplace = method.getAnnotation(MethodReplace.class);
if (methodReplace == null)
continue;
clz = methodReplace.clazz();//获取注解中clazz的值
meth = methodReplace.method();//获取注解中method的值
if (!isEmpty(clz) && !isEmpty(meth)) {
replaceMethod(classLoader, clz, meth, method);//next code
}
}
}
private void replaceMethod(ClassLoader classLoader, String clz,
String meth, Method method) {
try {
String key = clz + "@" + classLoader.toString();
Class<?> clazz = mFixedClass.get(key);//判断此类是否被fix
if (clazz == null) {// class not load
Class<?> clzz = classLoader.loadClass(clz);
// initialize target class
clazz = AndFix.initTargetClass(clzz);//初始化class
}
if (clazz != null) {// initialize class OK
mFixedClass.put(key, clazz);
Method src = clazz.getDeclaredMethod(meth,
method.getParameterTypes());//根据反射获取到有bug的类的方法(有bug的apk)
AndFix.addReplaceMethod(src, method);//src是有bug的方法，method是补丁方法
}
} catch (Exception e) {
Log.e(TAG, "replaceMethod", e);
}
}
public static void addReplaceMethod(Method src, Method dest) {
try {
replaceMethod(src, dest);//调用了native方法，next code
initFields(dest.getDeclaringClass());
} catch (Throwable e) {
Log.e(TAG, "addReplaceMethod", e);
}
}
private static native void replaceMethod(Method dest, Method src);

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[/code]由于Android4.4后才用的Art虚拟机，之前的系统都是Dalvik虚拟机，因此Natice层写了2个方法，对不同的系统做不同的处理方式。

extern void dalvik_replaceMethod(JNIEnv* env, jobject src, jobject dest);//Dalvik
extern void art_replaceMethod(JNIEnv* env, jobject src, jobject dest);//Art

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Dalvik replaceMethod的实现：

extern void __attribute__ ((visibility ("hidden"))) dalvik_replaceMethod(
JNIEnv* env, jobject src, jobject dest) {
jobject clazz = env->CallObjectMethod(dest, jClassMethod);
ClassObject* clz = (ClassObject*) dvmDecodeIndirectRef_fnPtr(
dvmThreadSelf_fnPtr(), clazz);
clz->status = CLASS_INITIALIZED;

Method* meth = (Method*) env->FromReflectedMethod(src);
Method* target = (Method*) env->FromReflectedMethod(dest);
LOGD("dalvikMethod: %s", meth->name);

meth->jniArgInfo = 0x80000000;
meth->accessFlags |= ACC_NATIVE;//把Method的属性设置成Native方法

int argsSize = dvmComputeMethodArgsSize_fnPtr(meth);
if (!dvmIsStaticMethod(meth))
argsSize++;
meth->registersSize = meth->insSize = argsSize;
meth->insns = (void*) target;

meth->nativeFunc = dalvik_dispatcher;//把方法的实现替换成native方法
}

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[/code]

Art replaceMethod的实现：

//不同的art系统版本不同处理也不同
extern void __attribute__ ((visibility ("hidden"))) art_replaceMethod(
JNIEnv* env, jobject src, jobject dest) {
if (apilevel > 22) {
replace_6_0(env, src, dest);
} else if (apilevel > 21) {
replace_5_1(env, src, dest);
} else {
replace_5_0(env, src, dest);
}
}
//以5.0为例：
void replace_5_0(JNIEnv* env, jobject src, jobject dest) {
art::mirror::ArtMethod* smeth =
(art::mirror::ArtMethod*) env->FromReflectedMethod(src);

art::mirror::ArtMethod* dmeth =
(art::mirror::ArtMethod*) env->FromReflectedMethod(dest);

dmeth->declaring_class_->class_loader_ =
smeth->declaring_class_->class_loader_; //for plugin classloader
dmeth->declaring_class_->clinit_thread_id_ =
smeth->declaring_class_->clinit_thread_id_;
dmeth->declaring_class_->status_ = (void *)((int)smeth->declaring_class_->status_-1);
//把一些参数的指针给补丁方法
smeth->declaring_class_ = dmeth->declaring_class_;
smeth->access_flags_ = dmeth->access_flags_;
smeth->frame_size_in_bytes_ = dmeth->frame_size_in_bytes_;
smeth->dex_cache_initialized_static_storage_ =
dmeth->dex_cache_initialized_static_storage_;
smeth->dex_cache_resolved_types_ = dmeth->dex_cache_resolved_types_;
smeth->dex_cache_resolved_methods_ = dmeth->dex_cache_resolved_methods_;
smeth->vmap_table_ = dmeth->vmap_table_;
smeth->core_spill_mask_ = dmeth->core_spill_mask_;
smeth->fp_spill_mask_ = dmeth->fp_spill_mask_;
smeth->mapping_table_ = dmeth->mapping_table_;
smeth->code_item_offset_ = dmeth->code_item_offset_;
smeth->entry_point_from_compiled_code_ =
dmeth->entry_point_from_compiled_code_;

smeth->entry_point_from_interpreter_ = dmeth->entry_point_from_interpreter_;
smeth->native_method_ = dmeth->native_method_;//把补丁方法替换掉
smeth->method_index_ = dmeth->method_index_;
smeth->method_dex_index_ = dmeth->method_dex_index_;

LOGD("replace_5_0: %d , %d", smeth->entry_point_from_compiled_code_,
dmeth->entry_point_from_compiled_code_);

}

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[/code]

添加Patch

mPatchManager.addPatch(path)

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[/code]源码：

public void addPatch(String path) throws IOException {
File src = new File(path);
File dest = new File(mPatchDir, src.getName());
if (!src.exists()) {
throw new FileNotFoundException(path);
}
if (dest.exists()) {
Log.d(TAG, "patch [" + path + "] has be loaded.");
return;
}
FileUtil.copyFile(src, dest);// copy to patch's directory
Patch patch = addPatch(dest);//同loadPatch中的addPatch一样的操作
if (patch != null) {
loadPatch(patch);//加载pach，同上loadPatch
}
}

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[/code]

移除Patch

mPatchManager.removeAllPatch();

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[/code]源码:

public void removeAllPatch() {
cleanPatch();//删除本地缓存的patch文件列表
SharedPreferences sp = mContext.getSharedPreferences(SP_NAME,
Context.MODE_PRIVATE);
sp.edit().clear().commit();//把关于patch的数据进行清空
}

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[/code]到此源代码就解析结束。

反编译Patch dex文件代码

patch文件中.dex文件反编译后，看到源码效果如下：



红框标注的部分，就是补丁方法。方法的注解部分写了clazz和method的值，对应着apk包中的类名和方法名称。