Gadle插件实现代码插桩与构件时依赖

目标

在安卓开发中，传统的SDK集成方式，需要将原始的文件添加到项目中、或者在项目的构建文件(build.gradle)中明确添加对应的依赖，然后在适当的地方调取初始化等方法。这些方式至少需要修改构建文件、在项目原始java代码中编写调用等。但是，对于某些SDK而言，本身只需要进行一次初始化操作，这时候，有没有一种方式，让SDK自己来调用初始化方法，并且以最简洁的方式让用户去集成呢？
目前市面上其实已经有很多的SDK采用了类似这种方式，对原始项目的侵入非常少。而且基本思路都是从gradle插件出发。只需要一行apply plugin代码，就可以达到目的。
为了实现无侵入式的SDK集成，我们可以利用aop的方式实现在构件时动态修改安卓字节码，同时支持第三方库的构件时依赖。

字节码注入

入口

想要不修改原始的java代码，并且实现SDK的代码的集成，实现初始化init方法的调用，就不得不在编译或者打包的过程中干预原始代码的编译结果。安卓APK文件的编译过程。从宏观上是：
.java -->.class -->.dex -->.apk
可以看到除我们可以修改.class、.dex文件生成过程来实现代码的注入。本文主要研究如何修改字节码文件.class
。

工具

目前主流的字节码注入工具主要是asm以及javassist,从使用者的反馈中可以看到asm的运行效率会比javassist高很多，但是asm的编码难度比较高。在进一步研究了asm之后，发现协助asm字节码生成工具AS插件ASMified，可以快速的生成ASM字节码代码。

特点

asm主要采用了访问者模式进行字节码文件的扫描，包括注释、成员变量、方法、内部类等。工具会提供加载类文件各种属性时的入口回调

grdle插件

插件开发有多种方式，可以查阅gradle官网api说明得知。本文选择了作为独立插件的开发方式，在本地搭建了maven的nexus服务，方便测试开发，当然也可以直接使用本地的.m2仓库

引入的插件

apply plugin: 'maven'
apply plugin: 'groovy'

一个是groovy语法插件、一个是仓库插件

必须的依赖

implementation gradleApi()
implementation 'com.android.tools.build:gradle:3.5.0'

需要添加gradle的依赖，而且在实际开发过程中发现，gradle:3.5.0里面自依赖了asm框架，所以就不需要再次去添加asm的依赖了。这也方便了开发者排除重复依赖的问题

目录结构

aop-plugin(插件名称)
----src
	----main
		----groovy
			----包名
				----.groovy文件(插件逻辑)
		----java
			----包名
				----.java文件(asm逻辑)
		----resources
			----META-INF
				----gradle-plugins
					----aop-plugin.properties
----build.gradle

其中groovy目录是插件代码的目录，文件以.groovy结尾。java目录是asm注入代码的目录。resoures目录是固定结构。需要注意的是在aop-pligin.properties文件中必须指明插件实现类：

implementation-class=com.lotty520.plugin.AopPlugin

插件实现

构建

构建脚本build.gradle定义了构建的插件依赖，决定了构建插件的groovy属性

apply plugin: 'maven'
apply plugin: 'groovy'

compileGroovy {
    sourceCompatibility = 1.7
    targetCompatibility = 1.7
    options.encoding = "UTF-8"
}

dependencies {
    implementation gradleApi()
    implementation 'com.android.tools.build:gradle:3.5.0'
}

repositories {
    jcenter()
}

uploadArchives {
    repositories {
        mavenDeployer {
            pom.groupId = 'com.lotty520.plugin'
            pom.artifactId = 'aop-plugin'
            pom.version = '1.50-SNAPSHOT'
            repository(url: 'http://localhost:8081/repository/maven-snapshots/')        }
    }
}

plugin

gradle插件api的顶级接口，自定义插件时，需要实现该接口，该接口只有一个apply方法

public interface Plugin<T> {
	void apply(T var1);
}

插件开始加载时的入口，我们可以在这里进行构建环境数据的获取或者修改

Trasform

安卓系统5.0新增的api。主要用来控制java->class转换操作的中间处理。主要api有

public abstract String getName();

public abstract Set<ContentType> getInputTypes();
    
public abstract Set<? super Scope> getScopes();

public abstract boolean isIncremental();

public void transform(TransformInvocation transformInvocation) throws TransformException, InterruptedException, IOException {
        this.transform(transformInvocation.getContext(), transformInvocation.getInputs(), transformInvocation.getReferencedInputs(), transformInvocation.getOutputProvider(), transformInvocation.isIncremental());
    }

其中isIncremental是标记是否开启增量。getInputTypes()用来标记检测的文件类型，主要是class文件和资源文件。getScopes()用来检测文件目录范围。transform是核心的方法，主要用来实现文件的遍历和字节码注入。

代码实现

检测jar和目录的方式实现可以参照以下代码：改代码对扫描的目录和jarz中的class文件进行注入操作。利用了ASM的ClassVisitor、ClassReader、ClassWritor等实现字节码文件的读取、注入、回写等操作。

package com.lotty520.plugin

import com.android.build.api.transform.*
import com.android.build.gradle.AppExtension
import com.android.build.gradle.AppPlugin
import com.android.build.gradle.LibraryPlugin
import com.android.build.gradle.internal.pipeline.TransformManager
import org.apache.commons.io.FileUtils
import org.apache.commons.io.IOUtils
import org.gradle.api.Plugin
import org.gradle.api.Project
import org.objectweb.asm.ClassReader
import org.objectweb.asm.ClassVisitor
import org.objectweb.asm.ClassWriter

import java.util.jar.JarEntry
import java.util.jar.JarFile
import java.util.jar.JarOutputStream
import java.util.zip.ZipEntry

import static org.objectweb.asm.ClassReader.EXPAND_FRAMES

class AopPlugin extends Transform implements Plugin<Project> {

    @Override
    void apply(Project project) {
        println("==================")
        println("      Gradle插件1.50         ")
        println("==================")
        if (!project.android) {
            throw new IllegalStateException('Must apply \'com.android.application\' or \'com.android.library\' first!')
        }
        def isApp = project.plugins.withType(AppPlugin)
        def isLib = project.plugins.withType(LibraryPlugin)
        if (isApp) {
            println("build is app.")
        } else {
            println("build is lib.")
        }
        if (!isApp && !isLib) {
            throw new IllegalStateException("'android' or 'android-library' plugin required.")
        }
        def list = project.getConfigurations().toList().iterator()
        while (list.hasNext()) {
            def config = list.next().getName()
            if ("implementation".equals(config)) {
                println("----Configuration----" + config)
                project.getDependencies().add(config, "com.squareup.retrofit2:retrofit:2.5.0")
            }
        }
        project.extensions.getByType(AppExtension).registerTransform(this)

    }

    @Override
    String getName() {
        return "AopPlugin"
    }

    @Override
    Set<QualifiedContent.ContentType> getInputTypes() {
        return TransformManager.CONTENT_CLASS
    }

    @Override
    Set<? super QualifiedContent.Scope> getScopes() {
        return TransformManager.SCOPE_FULL_PROJECT
    }

    @Override
    boolean isIncremental() {
        return false
    }

    @Override
    void transform(TransformInvocation transformInvocation) throws TransformException, InterruptedException, IOException {
        println("==================")
        println("       transform begin.        ")
        println("==================")
        Collection<TransformInput> inputs = transformInvocation.inputs
        TransformOutputProvider outputProvider = transformInvocation.outputProvider
        //删除之前的输出
        if (outputProvider != null)
            outputProvider.deleteAll()
        //遍历inputs
        inputs.each { TransformInput input ->
            //遍历directoryInputs
            input.directoryInputs.each { DirectoryInput directoryInput ->
                handleDirectoryInput(directoryInput, outputProvider)
            }

            //遍历jarInputs
            input.jarInputs.each { JarInput jarInput ->
                handleJarInputs(jarInput, outputProvider)
            }
        }
    }

    /**
     * 处理文件目录下的class文件
     */
    private static void handleDirectoryInput(DirectoryInput directoryInput, TransformOutputProvider outputProvider) {
        //是否是目录
        if (directoryInput.file.isDirectory()) {
            //列出目录所有文件（包含子文件夹，子文件夹内文件）
            directoryInput.file.eachFileRecurse { File file ->
                def name = file.name
                if (name.contains("View")) {
                    println("目录文件::::" + name)
                }
                if (checkClassFile(name)) {
                    ClassReader classReader = new ClassReader(file.bytes)
                    ClassWriter classWriter = new ClassWriter(classReader, ClassWriter.COMPUTE_MAXS)
                    ClassVisitor cv = new ClassVisitorImpl(classWriter)
                    classReader.accept(cv, EXPAND_FRAMES)
                    byte[] code = classWriter.toByteArray()
                    FileOutputStream fos = new FileOutputStream(
                            file.parentFile.absolutePath + File.separator + name)
                    //覆写
                    fos.write(code)
                    fos.close()
                }
            }
        }
        //替换输出
        def dest = outputProvider.getContentLocation(directoryInput.name,
                directoryInput.contentTypes, directoryInput.scopes,
                Format.DIRECTORY)
        FileUtils.copyDirectory(directoryInput.file, dest)
    }

    /**
     * 处理Jar中的class文件
     */
    private static void handleJarInputs(JarInput jarInput, TransformOutputProvider outputProvider) {
        if (jarInput.file.getAbsolutePath().endsWith(".jar")) {
            println("JAR文件::::" + jarInput.file.getAbsolutePath())
            // 创建新的jar文件
            File tmpFile = new File(jarInput.file.getParent() + File.separator + "classes_temp.jar")
            //避免上次的缓存被重复插入
            if (tmpFile.exists()) {
                tmpFile.delete()
            }
            JarOutputStream jarOutputStream = new JarOutputStream(new FileOutputStream(tmpFile))
            //用于保存
            JarFile originJar = new JarFile(jarInput.file)
            Enumeration enumeration = originJar.entries()
            while (enumeration.hasMoreElements()) {
                JarEntry nextEntry = (JarEntry) enumeration.nextElement()
                //名称
                String entryName = nextEntry.getName()
                //创建zipEntry对象
                ZipEntry zipEntry = new ZipEntry(entryName)
                //获取当前entry的输入流
                InputStream inputStream = originJar.getInputStream(nextEntry)
                //将当前entry添加到临时文件中
                jarOutputStream.putNextEntry(zipEntry)
                //插桩class
                if (checkClassFile(entryName)) {
                    //class文件处理
                    if (entryName.contains("View")) {
                        println("class文件::::" + entryName)
                    }
                    ClassReader classReader = new ClassReader(IOUtils.toByteArray(inputStream))
                    ClassWriter classWriter = new ClassWriter(classReader, ClassWriter.COMPUTE_MAXS)
                    ClassVisitor cv = new ClassVisitorImpl(classWriter)
                    //原始的CR接收CW的访问，开始重排字节码
                    classReader.accept(cv, EXPAND_FRAMES)
                    //回写
                    byte[] code = classWriter.toByteArray()
                    jarOutputStream.write(code)

                } else {
                    // 直接拷贝，不插桩
                    jarOutputStream.write(IOUtils.toByteArray(inputStream))
                }
                jarOutputStream.closeEntry()
            }
            //结束
            jarOutputStream.close()
            originJar.close()
            //重命名输出文件,因为可能同名,会覆盖
            def jarName = jarInput.name
            if (jarName.endsWith(".jar")) {
                jarName = jarName.substring(0, jarName.length() - 4)
            }
            def fileName = "aop-plugin" + jarName
            //替换输出
            def dest = outputProvider.getContentLocation(fileName, jarInput.contentTypes, jarInput.scopes, Format.JAR)
            FileUtils.copyFile(tmpFile, dest)
            tmpFile.delete()
        }
    }

    /**
     * 检查class文件是否需要处理,只处理需要的class文件
     * @param fileName 文件名
     * @return 是否需要处理
     */
    private static boolean checkClassFile(String name) {
        return (name.endsWith(".class") && !name.startsWith("R\$")
                && !"R.class".equals(name) && !"BuildConfig.class".equals(name) && !"AsmByteCode.class".equals(name))
    }
}

注入部分代码实现

ClassVisitor

对类的访问，可以用来决定哪些类需要被注入、添加类属性、添加实例方法、类方法等。具体可以参考ASM官方文档，查看调用方式。以下代码是在MainActivy中添加了成员变量cls(String)、begin(long)、end(long)。ClassVisitor会在扫描字节码文件时，严格的按照调用顺序，调用相应的visit(仅调用一次)、visitMethod(多次)、visitEnd(一次)。当然还有访问注解、访问属性等visitXXX方法。这里不列举。

package com.lotty520.plugin;

import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.FieldVisitor;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;

public class ClassVisitorImpl extends ClassVisitor {

    private static final String INJEXT_CLS = "MainActivity";
    private static final String INJEXT_METHOD = "printEnter";

    private static final String CLS_VIEW = "printEnter";
    private static final String METHOD_VIEW = "performClick";


    private String currentCls;

    public ClassVisitorImpl(ClassVisitor cv) {
        super(Opcodes.ASM5, cv);
    }

    public ClassVisitorImpl(int api) {
        super(api);
    }

    public ClassVisitorImpl(int api, ClassVisitor cv) {
        super(api, cv);
    }

    @Override
    public void visit(int version, int access, String name, String signature, String superName, String[] interfaces) {
        super.visit(version, access, name, signature, superName, interfaces);
        currentCls = name;
    }

    @Override
    public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {
        MethodVisitor mv = cv.visitMethod(access, name, desc, signature, exceptions);
        if (INJEXT_METHOD.equals(name)) {
            return new AdviceAdapterImpl(Opcodes.ASM5, mv, access, name, desc);
        }
        return mv;
    }

    @Override
    public void visitEnd() {
        if (currentCls != null && currentCls.contains(INJEXT_CLS)) {
            FieldVisitor clsname = cv.visitField(Opcodes.ACC_PRIVATE, "clsname", "Ljava/lang/String;", null, null);
            if (clsname != null) {
                clsname.visitEnd();
            }
            FieldVisitor begin = cv.visitField(Opcodes.ACC_PRIVATE, "begin", "J", null, null);
            if (begin != null) {
                begin.visitEnd();
            }
            FieldVisitor end = cv.visitField(Opcodes.ACC_PRIVATE, "end", "J", null, null);
            if (end != null) {
                end.visitEnd();
            }

        }
        cv.visitEnd();
    }
}

MethodVisitor

对方法的访问，实现字节码注入的核心实现。可以实现在调用对应方法之前、之后进行字节码注入，从而实现对应的需求。针对上面注入的成员变量，在方法调用前后，我们打印一下这些成员变量的值。主要实现功能为：

public void enter() {
        clsname = getClass().getPackage().getName();
        begin = System.currentTimeMillis();
    }

public void exit() {
        end = System.currentTimeMillis();
        Log.e("wh", "cls::" + clsname + "-->method cost:::" + (end - begin));
    }

为了将java转换成asm字节码,需要借助ASM ByteCode Outline插件来进行打码转换，转换后，我们的实现逻辑为：

package com.lotty520.plugin;

import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.commons.AdviceAdapter;

public class AdviceAdapterImpl extends AdviceAdapter {

    private static final String OWNER = "com/xapplication/MainActivity";

    protected AdviceAdapterImpl(int api, MethodVisitor mv, int access, String name, String desc) {
        super(api, mv, access, name, desc);
    }

    @Override
    protected void onMethodEnter() {
        mv.visitLdcInsn("wh");
        mv.visitTypeInsn(NEW, "java/lang/StringBuilder");
        mv.visitInsn(DUP);
        mv.visitMethodInsn(INVOKESPECIAL, "java/lang/StringBuilder", "<init>", "()V", false);
        mv.visitLdcInsn("method::enter");
        mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(Ljava/lang/String;)Ljava/lang/StringBuilder;", false);
        mv.visitMethodInsn(INVOKESTATIC, "java/lang/System", "currentTimeMillis", "()J", false);
        mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(J)Ljava/lang/StringBuilder;", false);
        mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "toString", "()Ljava/lang/String;", false);
        mv.visitMethodInsn(INVOKESTATIC, "android/util/Log", "e", "(Ljava/lang/String;Ljava/lang/String;)I", false);
        mv.visitInsn(POP);

        mv.visitVarInsn(ALOAD, 0);
        mv.visitVarInsn(ALOAD, 0);
        mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Object", "getClass", "()Ljava/lang/Class;", false);
        mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Class", "getPackage", "()Ljava/lang/Package;", false);
        mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Package", "getName", "()Ljava/lang/String;", false);
        mv.visitFieldInsn(PUTFIELD, OWNER, "clsname", "Ljava/lang/String;");

        mv.visitVarInsn(ALOAD, 0);
        mv.visitMethodInsn(INVOKESTATIC, "java/lang/System", "currentTimeMillis", "()J", false);
        mv.visitFieldInsn(PUTFIELD, OWNER, "begin", "J");
    }

    @Override
    protected void onMethodExit(int opcode) {
        mv.visitVarInsn(ALOAD, 0);
        mv.visitMethodInsn(INVOKESTATIC, "java/lang/System", "currentTimeMillis", "()J", false);
        mv.visitFieldInsn(PUTFIELD, OWNER, "end", "J");

        mv.visitLdcInsn("wh");
        mv.visitTypeInsn(NEW, "java/lang/StringBuilder");
        mv.visitInsn(DUP);
        mv.visitMethodInsn(INVOKESPECIAL, "java/lang/StringBuilder", "<init>", "()V", false);
        mv.visitLdcInsn("pkg::");
        mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(Ljava/lang/String;)Ljava/lang/StringBuilder;", false);
        mv.visitVarInsn(ALOAD, 0);
        mv.visitFieldInsn(GETFIELD, OWNER, "clsname", "Ljava/lang/String;");
        mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(Ljava/lang/String;)Ljava/lang/StringBuilder;", false);
        mv.visitLdcInsn("-->method cost:::");
        mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(Ljava/lang/String;)Ljava/lang/StringBuilder;", false);
        mv.visitVarInsn(ALOAD, 0);
        mv.visitFieldInsn(GETFIELD, OWNER, "end", "J");
        mv.visitVarInsn(ALOAD, 0);
        mv.visitFieldInsn(GETFIELD, OWNER, "begin", "J");
        mv.visitInsn(LSUB);
        mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(J)Ljava/lang/StringBuilder;", false);
        mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "toString", "()Ljava/lang/String;", false);
        mv.visitMethodInsn(INVOKESTATIC, "android/util/Log", "e", "(Ljava/lang/String;Ljava/lang/String;)I", false);
        mv.visitInsn(POP);

        mv.visitLdcInsn("wh");
        mv.visitTypeInsn(NEW, "java/lang/StringBuilder");
        mv.visitInsn(DUP);
        mv.visitMethodInsn(INVOKESPECIAL, "java/lang/StringBuilder", "<init>", "()V", false);
        mv.visitLdcInsn("method::exit");
        mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(Ljava/lang/String;)Ljava/lang/StringBuilder;", false);
        mv.visitMethodInsn(INVOKESTATIC, "java/lang/System", "currentTimeMillis", "()J", false);
        mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(J)Ljava/lang/StringBuilder;", false);
        mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "toString", "()Ljava/lang/String;", false);
        mv.visitMethodInsn(INVOKESTATIC, "android/util/Log", "e", "(Ljava/lang/String;Ljava/lang/String;)I", false);
        mv.visitInsn(POP);
    }
}

打包集成

打包插件

直接运行aop:uploadArchives就可以编译插件并上传到maven仓库中

集成插件

在项目的根目录的build.gradle中添加插件依赖版本

// Top-level build file where you can add configuration options common to all sub-projects/modules.
buildscript {
    repositories {
        google()
        jcenter()
        maven {
            url = 'http://localhost:8081/repository/maven-snapshots/'
        }
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.5.0'
        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
        classpath "cn.tongdun.plugin:aop-plugin:1.49-SNAPSHOT"

    }
}
allprojects {
    repositories {
        google()
        jcenter()
        maven {
            url = 'http://localhost:8081/repository/maven-snapshots/'
        }
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

在项目的主module的build.gradle中引入插件
apply plugin: 'aop-plugin'
到此，就可以运行APP查看结果了。