Практическая инженерия байт-кода

Метод transform передает обработку байтового кода классу ProfileClassVisitor:

public class ProfileClassVisitor extends ClassVisitor {

    String classDotName;

    public ProfileClassVisitor(ClassVisitor cv) {
        super(Opcodes.ASM5, 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);
        this.classDotName = name.replace('/', '.');
    }

    @Override
    public MethodVisitor visitMethod(int access,
            String name,
            String desc,
            String signature,
            String[] exceptions) {    

        MethodVisitor mv = super.visitMethod(access, name, desc, signature, exceptions);
        return new ProfileMethodVisitor(mv, access, name, desc);
    }

    class ProfileMethodVisitor extends AdviceAdapter {

        String methodName = null;
        String desc = null;

        int startTimeVar = -1;

        Label timeStart = new Label();
        Label timeEnd = new Label();

        Label finallyStart = new Label();
        Label finallyEnd = new Label();

        String signature = null;

        public ProfileMethodVisitor(MethodVisitor mv, int access, String name, String desc) {
            super(Opcodes.ASM5, mv, access, name, desc);
            this.methodName = name;
            this.desc = desc;

            signature = classDotName + '.' + methodName + toParameterString(desc); 
        }

        String toParameterString(String desc) {
            Type methodType = Type.getMethodType(desc);
            StringBuilder buffer = new StringBuilder();

            buffer.append('(');

            Type argTypes[] = methodType.getArgumentTypes();
            for (int i=0; i<argTypes.length; i++) {
                buffer.append(argTypes[i].getClassName());

                if (i<argTypes.length-1)
                    buffer.append(", ");
            }

            buffer.append(')');

            return buffer.toString();
        }

        public void visitCode() {
            super.visitCode();

            visitLabel(timeStart);
            startTimeVar = newLocal(Type.LONG_TYPE);
            mv.visitMethodInsn(INVOKESTATIC, "java/lang/System", "currentTimeMillis", "()J", false);
            mv.visitVarInsn(LSTORE, startTimeVar);

            visitLabel(finallyStart);
        }

        protected void onMethodExit(int opcode) {
            if (opcode != ATHROW)  
                onFinally(opcode); 
        }

        private void onFinally(int opcode) {
            if (opcode == ATHROW)
                mv.visitInsn(Opcodes.DUP);
            else
                mv.visitInsn(Opcodes.ACONST_NULL);

            int throwableVarIndex = newLocal(Type.getType(Throwable.class));
            mv.visitVarInsn(Opcodes.ASTORE, throwableVarIndex);

            mv.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
            mv.visitLdcInsn(signature + ": ");
            mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/io/PrintStream", "print", "(Ljava/lang/String;)V", false);

            mv.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
            mv.visitMethodInsn(INVOKESTATIC, "java/lang/System", "currentTimeMillis", "()J", false);
            mv.visitVarInsn(Opcodes.LLOAD, startTimeVar);
            mv.visitInsn(Opcodes.LNEG);
            mv.visitInsn(LADD);
            mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/io/PrintStream", "print", "(J)V", false);

            mv.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
            mv.visitLdcInsn("ms");
            mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V", false);
        }

        public void visitMaxs(int stack, int locals) { 
            Label endFinally = new Label(); 
            mv.visitTryCatchBlock(finallyStart, endFinally, endFinally, null); 
            mv.visitLabel(endFinally); 
            onFinally(ATHROW); 
            mv.visitInsn(ATHROW);
            visitLabel(timeEnd);
            visitLocalVariable("_time_", Type.LONG_TYPE.getDescriptor(), null, timeStart, timeEnd, startTimeVar);

            super.visitMaxs(stack, locals); 
        }
    }
}

public class ProfileAsmTest {

    public static void main(String[] args) throws Exception {
        ProfileTest test = new ProfileTest();
        test.sleep();
    }
}

public class ProfileTest {

    static final long DEFAULT_SLEEP = 500;

    static {
        System.out.println("in static initializer");
    }

    public ProfileTest() throws InterruptedException {
        sleep(100);
    }

    public void sleep() throws InterruptedException {
        sleep(DEFAULT_SLEEP);
    }

    public void sleep(long sleep) throws InterruptedException {
        Thread.sleep(sleep);
    }
}

java -noverify -javaagent:.../discotek-agent-example-7-profile-asm/dist/agent-profile-asm.jar=.*discotek.*test.* -classpath .../discotek-agent-example-7-profile-asm/bin;.../discotek-agent-example-7-profile-asm/lib/asm-5.0.4.jar;.../discotek-agent-example-7-profile-asm/lib/asm-commons-5.0.4.jar ca.discotek.agent.example.profile.asm.test.ProfileAsmTest

in static initializer
ca.discotek.agent.example.profile.asm.test.ProfileTest.<clinit>(): 0ms
ca.discotek.agent.example.profile.asm.test.ProfileTest.sleep(long): 100ms
ca.discotek.agent.example.profile.asm.test.ProfileTest.<init>(): 100ms
ca.discotek.agent.example.profile.asm.test.ProfileTest.sleep(long): 501ms
ca.discotek.agent.example.profile.asm.test.ProfileTest.sleep(): 501ms
ca.discotek.agent.example.profile.asm.test.ProfileAsmTest.main(java.lang.String[]): 607ms

public class Recorder {

    public static void record(String methodSignature, long start, long end) {
        StringBuilder buffer = new StringBuilder();
        buffer.append(methodSignature);
        buffer.append(": ");
        buffer.append(end - start);
        buffer.append("ms");
        System.out.println(buffer);
    }
}

        private void onFinally(int opcode) {
            if (opcode == ATHROW)
                mv.visitInsn(Opcodes.DUP);
            else
                mv.visitInsn(Opcodes.ACONST_NULL);

            mv.visitLdcInsn(signature);
            mv.visitVarInsn(Opcodes.LLOAD, startTimeVar);
            mv.visitMethodInsn(INVOKESTATIC, "java/lang/System", "currentTimeMillis", "()J", false);
            mv.visitMethodInsn(Opcodes.INVOKESTATIC, Recorder.class.getName().replace('.', '/'), "record", "(Ljava/lang/String;JJ)V", false);
        }

    <target name="jar" depends="compile">

        <jar destfile="${build}/${boot-classpath-jar}" update="true" >
            <fileset dir="${classes}">
                <include name="ca/discotek/agent/example/profileclasspath/Recorder.class"/>
            </fileset>
        </jar>

        <jar destfile="${dist}/${agent-jar}" update="true" >
            <manifest>
                <attribute name="Premain-Class" value="${agent-class-name}"/>
                <attribute name="Agent-Class" value="${agent-class-name}"/>
                <attribute name="Can-Redefine-Classes" value="true"/>
                <attribute name="Can-Retransform-Classes" value="true"/>
            </manifest>

            <fileset dir="${classes}">
                <include name="ca/discotek/agent/example/profileclasspath/asm/*.class"/>
                <include name="ca/discotek/example/rebundled/**/*.class"/>
            </fileset>

            <fileset dir="${build}">
                <include name="${boot-classpath-jar}"/>
            </fileset>

        </jar>

        <jar destfile="${dist}/${test-jar}" update="true" >
            <fileset dir="${test-classes}">
                <include name="ca/discotek/agent/example/profileclasspath/**/*.class"/>
            </fileset>
        </jar>

    </target>

    public static void initialize(String agentArgs, Instrumentation inst, boolean isPremain) {
        MyAgent.instrumentation = inst;

        try {
            URL url = MyAgent.class.getProtectionDomain().getCodeSource().getLocation();
            File file = new File(url.getFile());
            JarFile agentJar = new JarFile(file);
            ZipEntry entry = agentJar.getEntry("profile-classpath-boot-classpath.jar");
            InputStream is = agentJar.getInputStream(entry);

            File tmpDir = new File(System.getProperty("java.io.tmpdir"));
            File bootClassPathFile = new File(tmpDir, entry.getName());
            FileOutputStream fos = new FileOutputStream(bootClassPathFile);

            int length;
            byte bytes[] = new byte[10 * 1024];
            while ( (length = is.read(bytes)) > 0)
                fos.write(bytes, 0, length);

            fos.close();
            is.close();

            JarFile jar = new JarFile(bootClassPathFile);
            inst.appendToBootstrapClassLoaderSearch(jar);

            inst.addTransformer(new MyAgent(Pattern.compile(agentArgs)), true);
        } 
        catch (Exception e) {
            System.err.println("Unexpected error occured while installing agent. See following stack trace. Aborting.");
            e.printStackTrace();
        }
    }

java -noverify -javaagent:.../discotek-agent-example-8-profile-classpath-asm/dist/agent-profile-classpath-asm.jar=.*discotek.*test.* -classpath .../discotek-agent-example-8-profile-classpath-asm/dist/profile-classpath-test.jar ca.discotek.agent.example.profileclasspath.asm.test.ProfileClasspathAsmTest