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如何实现集成的Jar包动态更新，实现不需要更新Jar打包APK发布，就能解决线上的问题修复。

一、介绍

Android在API中给出可动态加载的有：DexClassLoader 和 PathClassLoader

DexClassLoader：可从SD卡中加载jar、apk和dex.

PathClassLoader：只能加载已经安装搭配Android系统中的apk文件。

这两个都是集成dalvik.system.BaseDexClassClassLoader,

当类加载请求，首先委派给父类去完成加载，父类加载不了，则自己再去完成加载，我们可以利用这个机制反过来，自定义TestClassLoader去加载本地Jar里接口Impl实现类(修复问题的class)，如果加载不了，再请求到父类即(PathClassLoader)去加载工程里的Jar接口Impl实现类。

二、实现步骤

1、首先我们在Jar中定义好接口及实现类Impl,

public interface IJarFix {

void print();

}

public class IJarFixImpl implements IJarFix {

@Override

public void print() {

Log.e("umbrella1","print version 1.0");

}

}

2、自定义TestClassLoader：

import dalvik.system.BaseDexClassLoader;

public class TestClassLoader extends BaseDexClassLoader {

private Map mExcludes = new ConcurrentHashMap<>();

public TestClassLoader(String dexPath, File optimizedDirectory, String librarySearchPath, ClassLoader parent) {

super(dexPath, optimizedDirectory, librarySearchPath, parent);

}

public void setExcludedClasses(String[] classNames) {

mExcludes.clear();

if (classNames != null && classNames.length > 0) {

for (String name : classNames) {

// ConcurrentHashMap doesn't allow null key or value

if (name != null) {

mExcludes.put(name, name);

}

}

}

}

@Override

public Class> loadClass(String name) throws ClassNotFoundException {

Class> c = findLoadedClass(name);

if(c == null){

if (!mExcludes.containsKey(name)) {//这边目的是不要去加载接口IJarFix(这个是PatchClassLoader加载)

try {

c = findClass(name);

} catch (Exception e) {

// Not found within the module, continue on

}

}

}

if(c == null)

c = getParent().loadClass(name);//父classloader

return c;

}

}

TestClassLoader加载本地JAR

package cn.umbrella.mylibrary;

public class Modul {

public static final String TEMP_DEX_FILE_NAME ="IJarHotDex.jar";

//------加载是jar包(包含classes.dex)----//

public static ClassLoader createTestClassLoader(Context cxt){

ClassLoader parentLoader = cxt.getClassLoader();

File file = new File(cxt.getDir("dex",Context.MODE_PRIVATE),TEMP_DEX_FILE_NAME);

File copyFile = getTempDexFile(cxt);

FileUtil.copy(copyFile,file);

File dexLib= cxt.getDir("outdex", Context.MODE_PRIVATE);

FileUtil.ensureDir(dexLib,false);`

TestClassLoader testClassLoader = new TestClassLoader(file.getPath(),dexLib,null,parentLoader);

return testClassLoader;

}

public static File getTempDexFile(Context cxt) {

try {

String tempDexPath = FileUtil.getExternalStoragePath(cxt);

String tempDexFilePath = tempDexPath + TEMP_DEX_FILE_NAME;

Log.e("yuguohe", "tempDexFilePath:" + tempDexFilePath);

File tempDexFileDir = new File(tempDexPath);//存放在SD卡上的临时dex文件的所在目录

if (!tempDexFileDir.exists() || !tempDexFileDir.isDirectory()) {

if (!tempDexFileDir.mkdirs()) {

return null;

}

}

File tempDexFile = new File(tempDexFilePath);//存放在SD卡上的临时dex文件

if (!tempDexFile.exists()) {

if (!tempDexFile.createNewFile()) {

return null;

}

}

return tempDexFile;

}catch (Exception e){

e.printStackTrace();

}

return null;

}

}

生产JAR

task makeJar(type: Copy) {

//删除存在的

delete 'build/libs'

//设置拷贝的文件

from('build/intermediates/bundles/default/')

//打进jar包后的文件目录

into('build/libs/')

//将classes.jar放入build/libs/目录下

//include ,exclude参数来设置过滤

//(我们只关心classes.jar这个文件)

include('classes.jar')

//重命名

rename ('classes.jar', 'IJarHotDex_o.jar')

}

然后在D:\android-sdk\build-tools\23.0.1\目录下使用命令 dx --dex --output=IJarHotDex_o.jar IJarHotDex.jar，IJarHotDex.jar我们所需要的二进制jar包(包含class.dex)，放在后台下载下来或SD卡上。

3、实现动态加载

try {

JarInfFactory infFactory = JarInfFactory.getInstance();

infFactory.init(MainActivity.this);

cn.umbrella.mylibrary.IJarFix jarFix = infFactory.getIHotFix();

Log.e("umbrella1", "jarFix=" + jarFix + " &classLoader=" + jarFix.getClass().getClassLoader());

jarFix.print();

} catch (Exception e) {

e.printStackTrace();

}

JarInfFactory接口抽象工厂类：

package cn.umbrella.mylibrary;

import android.content.Context;

import android.util.Log;

public class JarInfFactory {

private static JarInfFactory mInstance = null;

private IJarFix mIJarFix;

private Context mContext;

ModulManager mModulManager;

public static synchronized JarInfFactory getInstance() {

if (mInstance == null) {

mInstance = new JarInfFactory();

}

return mInstance;

}

public void setExcludedClasses(){

String ex[] = new String[] {

"cn.umbrealla.mylibrary.IJarFix",

};

if(mModulManager != null)

mModulManager.setExcludedClasses("ssp", ex);

}

public IJarFix getIHotFix(){

if(mIJarFix == null){

mIJarFix =mModulManager.getModuleInterface("ssp",IJarFix.class,null,null,null);

}

return mIJarFix;

}

public void setInvalide(){

if(mIJarFix != null){

mIJarFix = null;

}

String ex[] = new String[] {

"cn.umbrealla.mylibrary.IJarFix",//接口

};

mModulManager.setExcludedClasses("ssp", ex);

mModulManager.addClassLoaderModuleName("ssp");

getIHotFix();

}

}

package cn.umbrella.mylibrary;

public class ModulManager {

private ArrayListmClassLoaderList = new ArrayList<>();

private Context mContext;

public void addClassLoaderList(ClassLoader loader){

mClassLoaderList.clear();

mClassLoaderList.add(loader);

}

public ModulManager(Context cxt){

mContext = cxt;

}

public T getModuleInterface(String moduleName,Class interfaceType,

String staticMethod,

Class>[] paramTypes, Object[] paramObjs){

Context cxt = mContext;

ClassLoader c1 = null;

c1 = getClassLoaderCache();

if(c1 == null) {

c1 = ModulManager.class.getClassLoader();

}

try {

return Util.newInstance(c1, interfaceType.getName() + "Impl", null, null);

} catch (Exception e) {

e.printStackTrace();

}

return null;

}

public void addClassLoaderModuleName(String moduleName){

Context cxt = mContext;

ClassLoader loader = Modul.createTestClassLoader(cxt);

updateExcludedClasses(loader,getExcludedClasses(moduleName));

addClassLoaderList(loader);

}

public ClassLoader getClassLoaderCache(){

if(mClassLoaderList!=null && mClassLoaderList.size() > 0)

return mClassLoaderList.get(0);

return null;

}

public void updateExcludedClasses(ClassLoader cl, String[] classNames) {

if (cl instanceof TestClassLoader) {

((TestClassLoader) cl).setExcludedClasses(classNames);

}

}

}

反射工具类：

package cn.umbrella.mylibrary;

import java.lang.reflect.Constructor;

import java.lang.reflect.InvocationHandler;

import java.lang.reflect.Method;

import java.lang.reflect.Proxy;

/**

* Created by yuguohe on 2018-8-3.

*/

public class Util {

public static T newInstance(ClassLoader classLoader,String className,Class>[] paramTypes, Object[] paramObjs){

T clT = null;

try {

Class> c = classLoader.loadClass(className);

Constructor constructor = c.getConstructor(paramTypes);

clT = (T)constructor.newInstance(paramObjs);

if(clT == null)

clT = (T)c.newInstance();

} catch (Exception e) {

e.printStackTrace();

}

return clT;

}

}

实现本地JAR方法替代工程集成的JAR的方法：

JarInfFactory infFactory = JarInfFactory.getInstance();

infFactory.setInvalide();

IJarFix o = infFactory.getIHotFix();

Log.e("umbrella1", "jarFix=" + o + " &classLoader=" + o.getClass().getClassLoader());

o.print();

Log.e("umbrella1", "o=" + o);

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