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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<String, String> 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 ArrayList<ClassLoader>mClassLoaderList = new ArrayList<>();
private Context mContext;
public void addClassLoaderList(ClassLoader loader){
mClassLoaderList.clear();
mClassLoaderList.add(loader);
}
public ModulManager(Context cxt){
mContext = cxt;
}
public <T> T getModuleInterface(String moduleName,Class<T> 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> 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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