@linux1s1s 2015-09-01T16:46:35.000000Z 字数 8548 阅读 3763

Android 热更新——非侵入AOP框架

AndroidBuild

Android 客户端应用上线以后，一旦出现Bug，一般的解决思路是发修复包升级应用，这种方式不仅耗时，更重要的是用户需要频繁的升级版本，体验不好，所以优化的思路是在不发版本的情况下热更新，以期提高用户体验。

近期GitHub新出一种非侵入运行期AOP框架Dexposed，下面简单了解一下这个框架，GitHub地址。

简要说明：

该框架基于AOP思想，支持经典的AOP使用场景，可应用于日志记录，性能统计，安全控制，事务处理，异常处理等方面。
针对Android平台，Dexposed支持函数级别的在线热更新，例如对已经发布在应用市场上的宿主APK，当我们从crash统计平台上发现某个函数调用有bug，导致经常性crash，这时，可以在本地开发一个补丁APK，并发布到服务器中，宿主APK下载这个补丁APK并集成后，就可以很容易修复这个crash。
Dexposed是基于久负盛名的开源Xposed框架实现的一个Android平台上功能强大的无侵入式运行时AOP框架。Dexposed的AOP实现是完全非侵入式的，没有使用任何注解处理器，编织器或者字节码重写器。

Patch初步

首先从GitHub上拉下来代码有几个坑需要注意：

如果想直接拿过来用，你可能会失望而归，因为patchsample这个android程序就没有入口Activity，所以需要自行新建。
注意Lib包如何添加，不能直接添加在libs这个工程自建的文件中，应该放在lib文件中，并手动添加java build依赖
patchsample只是个简单的patch，如果需要增加比较复杂的patch，需要有依赖关系，为了缩小patch体积，这个依赖只能是部分依赖，所以推荐方式是将需要补丁的class文件打jar包引入依赖即可。

接下来我们看看具体的流程：

首先需要我们动态监测AOP环境

runPatchApk();

这里需要注意的是PatchMain.load()这个方法，该方法的主要用途是加载patch APK的所有类，并将实现IPatch的类添加到List中去，然后通过匹配加载的类或者类方法来实现非侵入式AOP。

public void runPatchApk() {
    if (android.os.Build.VERSION.SDK_INT == 21) {
        return;
    }
    if (!DexposedBridge.canDexposed(this)) {
        Log.d("Hotpatch", "This device doesn't support dexposed!");
        return;
    }
    File cacheDir = getExternalCacheDir();
    if (cacheDir != null) {
        String fullpath = cacheDir.getAbsolutePath() + File.separator + "PATCH_NAME.apk";
        PatchResult result = PatchMain.load(this, fullpath, null);
        if (result.isSuccess()) {
            Log.e("Hotpatch", "patch success!");
        } else {
            Log.e("Hotpatch", "patch error is " + result.getErrorInfo());
        }
    }
}

DexposedBridge.canDexposed(this)

public static synchronized boolean canDexposed(Context context) {
    return !DeviceCheck.isDeviceSupport(context)?false:loadDexposedLib(context);
}
private static boolean loadDexposedLib(Context context) {
    try {
        if(VERSION.SDK_INT != 10 && VERSION.SDK_INT != 9) {
            if(VERSION.SDK_INT > 19) {
                System.loadLibrary("dexposed_l");
            } else {
                System.loadLibrary("dexposed");
            }
        } else {
            System.loadLibrary("dexposed2.3");
        }
        return true;
    } catch (Throwable var2) {
        return false;
    }
}

Patch实例

public class Activity extends BaseSherlockSubActivity implements
    OnNewIconUIRefreshListener {
    private void showDialog() {
    final AlertDialog.Builder builder = new AlertDialog.Builder(this);
    builder.setTitle("Dexposed sample")
            .setMessage("Please clone patchsample project to generate apk, and copy it to \"/Android/data/PACKAGE_NAME/cache/PATCH_NAME.apk\"")
            .setPositiveButton("ok", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int whichButton) {
                }
            }).create().show();
    }
}

假如我们上线的代码中如上所示，在弹层中出现文案bug，那么该如何热更新。
代码修复操作在Patch工程中，添加如下代码：

public class DialogPatch implements IPatch {
    @Override
    public void handlePatch(final PatchParam arg0) throws Throwable {
        Class<?> cls = null;
        try {
            cls = arg0.context.getClassLoader().loadClass("com.android.activity.Activity");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
            return;
        }
        DexposedBridge.findAndHookMethod(cls, "showDialog", new XC_MethodReplacement() {
            @Override
            protected Object replaceHookedMethod(MethodHookParam param) throws Throwable {
                final Activity mainActivity = (Activity) param.thisObject;
                AlertDialog.Builder builder = new AlertDialog.Builder(mainActivity);
                builder.setTitle("Fanli Dexposed sample").setMessage("The dialog is shown from patch apk!").setPositiveButton("ok", new OnClickListener() {
                    public void onClick(DialogInterface dialog, int whichButton) {
                        Class<?> clsInner;
                        try {
                            clsInner = arg0.context.getClassLoader().loadClass("com.android.activity.OutObject");
                        } catch (ClassNotFoundException e) {
                            e.printStackTrace();
                            return;
                        }
                        try {
                            OutObject outObject = (OutObject) clsInner.newInstance();
                            if (outObject.callFromOutMethod()) {
                                AlertDialog.Builder builder = new AlertDialog.Builder(mainActivity);
                                builder.setTitle("Fanli Dexposed sample").setMessage("com.android.activity.OutObject is Worked!")
                                        .setPositiveButton("ok", new OnClickListener() {
                                            @Override
                                            public void onClick(DialogInterface dialog, int which) {
                                                dialog.dismiss();
                                            }
                                        }).create().show();
                            }
                        } catch (InstantiationException e) {
                            e.printStackTrace();
                        } catch (IllegalAccessException e) {
                            e.printStackTrace();
                        }
                    }
                }).create().show();
                return null;
            }
        });
    }
}

然后将这个patch APK 传到Server，在主APK中通过下载patch apk到指定目录，然后动态监测AOP环境并loadPatch即可实现热更新。
接下来如果应用到实际项目中需要完善的有以下几点：

动态监测AOP环境（android server主动监测 patch包）
动态加载Patch文件（更新pathc以后第一时间加载patch）

Patch测试：

基于以上实现方案测试的环境包括：
Dalvik 4.0-4.4均已经通过
目前 ART 5.0 以及以上版本尚未通过。（待更新Native包和Jar包）

目前补丁机制有如下问题：

静态变量无法做补丁，因为静态变量初始化在补丁初始化之前

涉及到动态链接库的调用无法做补丁

补丁模块应用在Application初始化的时候，无法在app运行时热替换，只能等下次启动或切后台后启动

补丁方式是以Context类作为切入点替换，补丁中所有相关类的替换需要带上Context类

Application类无法替换

新补丁机制对比：

静态变量可以做补丁，但是final型变量无法做补丁。

涉及到动态链接库的调用可以引入Jar，然后在做相应的补丁操作。

可以在运行时做热更新，时间精度自己控制。

Context取Application Context，不需要其他Context。

Application类可以通过替换其中的方法完成类的替换。

附录Patch

PatchMain

public class PatchMain {
    private static final ReadWriteSet<PatchCallback> loadedPatchCallbacks = new ReadWriteSet<PatchCallback>();
    /**
     * Load a runnable patch apk.
     *
     * @param context the application or activity context.
     * @param apkPath the path of patch apk file.
     * @param contentMap the object maps that will be used by patch classes.
     * @return PatchResult include if success or error detail.
     */
    public static PatchResult load(Context context, String apkPath, HashMap<String, Object> contentMap) {
        if (!new File(apkPath).exists()) {
            return new PatchResult(false, PatchResult.FILE_NOT_FOUND, "FILE not found on " + apkPath);
        }
        PatchResult result = loadAllCallbacks(context, apkPath, context.getClassLoader());
        if (!result.isSuccess()) {
            return result;
        }
        if (loadedPatchCallbacks.getSize() == 0) {
            return new PatchResult(false, PatchResult.NO_PATCH_CLASS_HANDLE, "No patch class to be handle");
        }
        PatchParam lpparam = new PatchParam(loadedPatchCallbacks);
        lpparam.context = context;
        lpparam.contentMap = contentMap;
        return PatchCallback.callAll(lpparam);
    }
    private static PatchResult loadAllCallbacks(Context context, String apkPath, ClassLoader cl) {
        try {
            // String dexPath = new File(context.getFilesDir(), apkPath.).getAbsolutePath();
            File dexoptFile = new File(apkPath + "odex");
            if (dexoptFile.exists()) {
                dexoptFile.delete();
            }
            ClassLoader mcl = null;
            try {
                mcl = new DexClassLoader(apkPath, context.getFilesDir().getAbsolutePath(), null, cl);
            } catch (Throwable e) {
                return new PatchResult(false, PatchResult.FOUND_PATCH_CLASS_EXCEPTION, "Find patch class exception ", e);
            }
            DexFile dexFile = DexFile.loadDex(apkPath, context.getFilesDir().getAbsolutePath() + File.separator + "patch.odex", 0);
            Enumeration<String> entrys = dexFile.entries();
            // clean old callback
            synchronized (loadedPatchCallbacks) {
                loadedPatchCallbacks.clear();
            }
            while (entrys.hasMoreElements()) {
                String entry = entrys.nextElement();
                Class<?> entryClass = null;
                try {
                    entryClass = mcl.loadClass(entry);
                } catch (ClassNotFoundException e) {
                    e.printStackTrace();
                    break;
                }catch (IllegalAccessError e) {
                    e.printStackTrace();
                    break;
                }
                if (isImplementInterface(entryClass, IPatch.class)) {
                    Object moduleInstance = entryClass.newInstance();
                    hookLoadPatch(new PatchCallback((IPatch) moduleInstance));
                }
            }
        } catch (Exception e) {
            return new PatchResult(false, PatchResult.FOUND_PATCH_CLASS_EXCEPTION, "Find patch class exception ", e);
        }
        return new PatchResult(true, PatchResult.NO_ERROR, "");
    }
    private static boolean isImplementInterface(Class<?> entry, Class<?> interClass) {
        Class<?>[] interfaces = entry.getInterfaces();
        if (interfaces == null) {
            return false;
        }
        for (int i = 0; i < interfaces.length; i++) {
            if (interfaces[i].equals(interClass)) {
                return true;
            }
        }
        return false;
    }
    /**
     * Get notified when a patch is loaded. This is especially useful to hook some patch-specific methods.
     */
    private static void hookLoadPatch(PatchCallback callback) {
        synchronized (loadedPatchCallbacks) {
            loadedPatchCallbacks.add(callback);
        }
    }
}

PatchCallback

class PatchCallback {
    private final IPatch instance;
    protected PatchCallback(IPatch instance) {
        this.instance = instance;
    }
    protected static final PatchResult callAll(PatchParam param) {
        boolean isAllFailed = true;
        for (int i = 0; i < param.callbacks.length; i++) {
            try {
                ((PatchCallback) param.callbacks[i]).call(param);
                isAllFailed = false;
            } catch (Throwable t) {
                t.printStackTrace();
            }
        }
        if (isAllFailed) {
            return new PatchResult(true, PatchResult.ALL_PATCH_FAILED, "All patch classes excute failed");
        } else {
            return new PatchResult(true, PatchResult.NO_ERROR, "");
        }
    }
    protected void call(PatchParam param) throws Throwable {
        if (param instanceof PatchParam)
            handlePatch((PatchParam) param);
    }
    protected void handlePatch(PatchParam lpparam) throws Throwable {
        instance.handlePatch(lpparam);
    }
}

IPatch

public interface IPatch {
    void handlePatch(PatchParam lpparam) throws Throwable;
}

DexposedBridge

public static Unhook findAndHookMethod(Class<?> clazz, String methodName, Object... parameterTypesAndCallback) {
    if(parameterTypesAndCallback.length != 0 && parameterTypesAndCallback[parameterTypesAndCallback.length - 1] instanceof XC_MethodHook) {
        XC_MethodHook callback = (XC_MethodHook)parameterTypesAndCallback[parameterTypesAndCallback.length - 1];
        Method m = XposedHelpers.findMethodExact(clazz, methodName, parameterTypesAndCallback);
        Unhook unhook = hookMethod(m, callback);
        if(!(callback instanceof XC_MethodKeepHook) && !(callback instanceof XC_MethodKeepReplacement)) {
            ArrayList var6 = allUnhookCallbacks;
            synchronized(allUnhookCallbacks) {
                allUnhookCallbacks.add(unhook);
            }
        }
        return unhook;
    } else {
        throw new IllegalArgumentException("no callback defined");
    }
}