@Retention(RetentionPolicy.RUNTIME) @Target(ElementType.METHOD) public @interface CostTime { } 

public class CostTimePlugin implements Plugin<Project> { @Override public void apply(Project project) { project.android.registerTransform(new CostTimeTransform()) } } 

package com.dsg.CostTImePlugin import com.android.build.api.transform.Context import com.android.build.api.transform.DirectoryInput import com.android.build.api.transform.Format import com.android.build.api.transform.JarInput import com.android.build.api.transform.QualifiedContent import com.android.build.api.transform.Transform import com.android.build.api.transform.TransformException import com.android.build.api.transform.TransformInput import com.android.build.api.transform.TransformOutputProvider import com.android.build.gradle.internal.pipeline.TransformManager import org.apache.commons.codec.digest.DigestUtils import org.apache.commons.io.FileUtils import org.objectweb.asm.ClassReader import org.objectweb.asm.ClassWriter class CostTimeTransform extends Transform { @Override String getName() { //Transform名称 return "CostTime" } @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(Context context, Collection<TransformInput> inputs, Collection<TransformInput> referencedInputs, TransformOutputProvider outputProvider, boolean isIncremental) throws IOException, TransformException, InterruptedException { //遍历输入 for (TransformInput input in inputs) { //遍历Directioy for (DirectoryInput dirInput in input.directoryInputs) { //处理需要插桩的文件 modifyClassWithPath(dirInput.file) //Copy修改之后的文件 File dest = outputProvider.getContentLocation(dirInput.name, dirInput.contentTypes, dirInput.scopes, Format.DIRECTORY) FileUtils.copyDirectory(dirInput.file, dest) } //遍历JarInput 因为我们这里只对自己的方法插桩 所以不对JarInput做处理 for (JarInput jarInput : input.jarInputs) {//jar（第三方库，module） if (jarInput.scopes.contains(QualifiedContent.Scope.SUB_PROJECTS)) {//module library //从module中获取注解信息 // readClassWithJar(jarInput) } //虽然不做处理 但是还是要记得重新拷贝回去 不然会有问题 copyFile(jarInput, outputProvider) } } } void modifyClassWithPath(File dir) { def root = dir.absolutePath dir.eachFileRecurse { File file -> def filePath = file.absolutePath //过滤非class文件 if (!filePath.endsWith(".class")) return def className = getClassName(root, filePath) //过滤系统文件 if (isSystemClass(className)) return //hook关键代码 hookClass(filePath, className) } } void hookClass(String filePath, String className) { //1.声明ClassReader ClassReader reader = new ClassReader(new FileInputStream(new File(filePath))) //2声明 ClassWriter ClassWriter writer = new ClassWriter(reader, ClassWriter.COMPUTE_MAXS) //3声明ClassVisitor CostTimeMethodAdapter adapter = new CostTimeMethodAdapter(writer) //4调用accept方法 传入classVisitor reader.accept(adapter, ClassReader.EXPAND_FRAMES) if (adapter.changed) { println className + "is changed:" + adapter.changed byte[] bytes = writer.toByteArray() FileOutputStream fos = new FileOutputStream(new File(filePath)) fos.write(bytes) } } //默认排除 static final DEFAULT_EXCLUDE = [ '^android\\..*', '^androidx\\..*', '.*\\.R$', '.*\\.R\\$.*$', '.*\\.BuildConfig$', ] //获取类名 String getClassName(String root, String classPath) { return classPath.substring(root.length() + 1, classPath.length() - 6) .replaceAll("/", ".") // unix/linux .replaceAll("\\\\", ".") //windows } boolean isSystemClass(String fileName) { for (def exclude : DEFAULT_EXCLUDE) { if (fileName.matches(exclude)) return true } return false } void copyFile(JarInput jarInput, TransformOutputProvider outputProvider) { def dest = getDestFile(jarInput, outputProvider) FileUtils.copyFile(jarInput.file, dest) } static File getDestFile(JarInput jarInput, TransformOutputProvider outputProvider) { def destName = jarInput.name // 重名名输出文件,因为可能同名,会覆盖 def hexName = DigestUtils.md5Hex(jarInput.file.absolutePath) if (destName.endsWith(".jar")) { destName = destName.substring(0, destName.length() - 4) } // 获得输出文件 File dest = outputProvider.getContentLocation(destName + "_" + hexName, jarInput.contentTypes, jarInput.scopes, Format.JAR) return dest } } 

我们会通过ClassReader读取字节码 然后通过ClassVisitor进行字节码的修改 然后再通过ClassWriter生成我们修改之后的字节码 大致的思路就是这样 接下来看一下源码 

package com.dsg.CostTImePlugin; import org.objectweb.asm.*; import org.objectweb.asm.commons.LocalVariablesSorter; import static org.objectweb.asm.Opcodes.*; /** * @author DSG * @Project ASMCostTime * @date 2020/6/22 * @describe */ public class CostTimeClassAdapter extends ClassVisitor { public boolean changed; //是否修改过 private String owner; private boolean isInterface; public CostTimeClassAdapter(ClassVisitor visitor) { super(ASM4, visitor); } public CostTimeClassAdapter(int api, ClassVisitor classVisitor) { super(api, classVisitor); } @Override public void visit(int version, int access, String name, String signature, String superName, String[] interfaces) { cv.visit(version, access, name, signature, superName, interfaces); owner = name; isInterface = (access & ACC_INTERFACE) != 0; } @Override public MethodVisitor visitMethod(int access, String name, String descriptor, String signature, String[] exceptions) { MethodVisitor mv = super.visitMethod(access, name, descriptor, signature, exceptions); if (!isInterface && mv != null && !name.equals("<init>")) { //将MethodVisitor交由CostTimeMethodAdapter代理 mv = new CostTimeMethodAdapter(access, name, descriptor, mv); } return mv; } //继承自LocalVariablesSorter 有序遍历素有方法 class CostTimeMethodAdapter extends LocalVariablesSorter { private String name; private boolean isAnnotationed; private int time; public CostTimeMethodAdapter(int access, String name, String descriptor, MethodVisitor methodVisitor) { super(ASM4, access, descriptor, methodVisitor); this.name = name; } /** * 遍历代码的开始 */ @Override public void visitCode() { super.visitCode(); if (isAnnotationed) { mv.visitMethodInsn(INVOKESTATIC, "java/lang/System", "currentTimeMillis", "()J", false); time = newLocal(Type.LONG_TYPE); mv.visitVarInsn(LSTORE, time); } } @Override public void visitFieldInsn(int opcode, String owner, String name, String descriptor) { super.visitFieldInsn(opcode, owner, name, descriptor); } @Override public void visitIntInsn(int opcode, int operand) { super.visitIntInsn(opcode, operand); } /** * 遍历操作码 判断是否是return语句 如果是return 就插入我们的代码 * * @param opcode 操作码 */ @Override public void visitInsn(int opcode) { if ((opcode >= IRETURN && opcode <= RETURN) || opcode == ATHROW) { if (isAnnotationed) { //这里的代码都可以由ASM插件生成 //Label可以生成局部变量 Label l1 = new Label(); mv.visitLabel(l1); mv.visitMethodInsn(INVOKESTATIC, "java/lang/System", "currentTimeMillis", "()J", false); mv.visitVarInsn(LLOAD, time); mv.visitInsn(LSUB); mv.visitVarInsn(LSTORE, 3); Label l2 = new Label(); mv.visitLabel(l2); mv.visitLdcInsn(owner); mv.visitTypeInsn(NEW, "java/lang/StringBuilder"); mv.visitInsn(DUP); mv.visitMethodInsn(INVOKESPECIAL, "java/lang/StringBuilder", "<init>", "()V", false); mv.visitLdcInsn("func " + name + " cost Time:"); mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(Ljava/lang/String;)Ljava/lang/StringBuilder;", false); mv.visitVarInsn(LLOAD, 3); 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); } } super.visitInsn(opcode); } /** * @param descriptor 最先执行 判断是否存在注解 如果存在 就进行插桩 * @param visible * @return */ @Override public AnnotationVisitor visitAnnotation(String descriptor, boolean visible) { isAnnotationed = ("Lcom/dsg/annotations/CostTime;".equals(descriptor)); if (!changed && isAnnotationed) { changed = true; } return super.visitAnnotation(descriptor, visible); } @Override public void visitMaxs(int maxStack, int maxLocals) { super.visitMaxs(maxStack, maxLocals); } @Override public void visitEnd() { super.visitEnd(); } } }