Java Code Examples for jdk.internal.org.objectweb.asm.ClassWriter#toByteArray()

public byte[] transform(
        ClassLoader classLoader, String className, Class<?> classBeingRedefined,
        ProtectionDomain pd, byte[] bytes) throws IllegalClassFormatException {
    // Check if this class should be instrumented.
    if (!instrClassesTarget.contains(className)) {
        return null;
    }

    boolean isRedefinition = classBeingRedefined != null;
    log("instrument class(" + className + ") " + (isRedefinition ? "redef" : "load"));

    ClassReader reader = new ClassReader(bytes);
    ClassWriter writer = new ClassWriter(
            reader, ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES);
    CallbackClassVisitor classVisitor = new CallbackClassVisitor(writer);
    reader.accept(classVisitor, 0);
    instrClassesDone.add(className);
    return writer.toByteArray();
}
 

static void verifyASM() throws Exception {
    ClassWriter cw = new ClassWriter(0);
    cw.visit(V1_8, ACC_PUBLIC, "X", null, "java/lang/Object", null);
    MethodVisitor mv = cw.visitMethod(ACC_STATIC, "foo",
            "()V", null, null);
    mv.visitMaxs(2, 1);
    mv.visitMethodInsn(INVOKESTATIC,
            "java/util/function/Function.class",
            "identity", "()Ljava/util/function/Function;", true);
    mv.visitInsn(RETURN);
    cw.visitEnd();
    byte[] carray = cw.toByteArray();
    // for debugging
    // write((new File("X.class")).toPath(), carray, CREATE, TRUNCATE_EXISTING);

    // verify using javap/classfile reader
    ClassFile cf = ClassFile.read(new ByteArrayInputStream(carray));
    int mcount = checkMethod(cf, "foo");
    if (mcount < 1) {
        throw new RuntimeException("unexpected method count, expected 1" +
                "but got " + mcount);
    }
}
 

private static byte[] loadC(boolean redefine) {
    ClassWriter cw = new ClassWriter(0);

    cw.visit(52, ACC_SUPER | ACC_PUBLIC, "C", null, "java/lang/Object", null);
    {
        MethodVisitor mv;

        mv = cw.visitMethod(ACC_PUBLIC | ACC_STATIC, "m", "()V", null, null);
        mv.visitCode();

        // First time we run we will:
        // 1) Cache resolution errors
        // 2) Redefine the class / method
        // 3) Try to read the resolution errors that were cached
        //
        // The redefined method will never run, throw error to be sure
        if (redefine) {
            createThrowRuntimeExceptionCode(mv, "The redefined method was called");
        } else {
            createMethodBody(mv);
        }
        mv.visitMaxs(3, 0);
        mv.visitEnd();
    }
    cw.visitEnd();
    return cw.toByteArray();
}
 

public static void main(String[] args) throws NoSuchMethodException,SecurityException,
        IllegalAccessException,IllegalArgumentException,InvocationTargetException{
    ClassWriter cw=new ClassWriter(ClassWriter.COMPUTE_MAXS|ClassWriter.COMPUTE_FRAMES);
    cw.visit(V1_7,ACC_PUBLIC,"Example",null,"java/lang/Object",null);
    MethodVisitor mw=cw.visitMethod(ACC_PUBLIC,"<init>","()V",null,null);
    mw.visitVarInsn(ALOAD,0);
    mw.visitMethodInsn(INVOKESPECIAL,"java/lang/Object","<init>","()V");
    mw.visitInsn(RETURN);
    mw.visitMaxs(0,0);
    mw.visitEnd();
    mw=cw.visitMethod(ACC_PUBLIC+ACC_STATIC,"main","([Ljava/lang/String;)V",null,null);
    mw.visitFieldInsn(GETSTATIC,"java/lang/System","out","Ljava/io/PrintStream;");
    mw.visitLdcInsn("Hello world!");
    mw.visitMethodInsn(INVOKEVIRTUAL,"java/io/PrintStream","println","(Ljava/lang/String;)V");
    mw.visitInsn(RETURN);
    mw.visitMaxs(0,0);
    mw.visitEnd();
    byte[] code=cw.toByteArray();
    for(int i=0;i<1;i++){
        ClassLoader loader=UnloadClass.class.getClassLoader();
        Method m=ClassLoader.class.getDeclaredMethod("defineClass", String.class, byte[].class, int.class, int.class);
        m.setAccessible(true);
        m.invoke(loader,"Example",code,0,code.length);
        m.setAccessible(false);
        System.gc();
    }

}
 

public static byte[] dumpT1() {
    ClassWriter cw = new ClassWriter(0);
    MethodVisitor mv;

    cw.visit(52, ACC_PUBLIC | ACC_SUPER, "p1/T1", null, "java/lang/Object", null);
    {
        mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
        mv.visitCode();
        mv.visitVarInsn(ALOAD, 0);
        mv.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "<init>", "()V", false);
        mv.visitInsn(RETURN);
        mv.visitMaxs(1, 1);
        mv.visitEnd();
    }
    {
        mv = cw.visitMethod(ACC_PUBLIC, "m", "()I", null, null);
        mv.visitCode();
        mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
        mv.visitLdcInsn("p1/T1.m()");
        mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "print", "(Ljava/lang/String;)V", false);
        mv.visitIntInsn(BIPUSH, 3);
        mv.visitInsn(IRETURN);
        mv.visitMaxs(2, 1);
        mv.visitEnd();
    }
    cw.visitEnd();

    return cw.toByteArray();
}
 

private byte[] loadClassData(String name) throws Exception {
    ClassWriter cw = new ClassWriter(0);
    MethodVisitor mv;
    switch (name) {
        case INTERFACE_NAME:
            cw.visit(V1_8, ACC_ABSTRACT | ACC_INTERFACE | ACC_PUBLIC, INTERFACE_NAME, null, "java/lang/Object", null);
            {
                mv = cw.visitMethod(ACC_PRIVATE, "privInstance", "()I", null, null);
                mv.visitCode();
                mv.visitLdcInsn(EXPECTED);
                mv.visitInsn(IRETURN);
                mv.visitMaxs(1, 1);
                mv.visitEnd();
            }
            break;
        case CLASS_NAME:
            cw.visit(52, ACC_SUPER | ACC_PUBLIC, CLASS_NAME, null, "java/lang/Object", new String[]{INTERFACE_NAME});
            {
                mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
                mv.visitCode();
                mv.visitVarInsn(ALOAD, 0);
                mv.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "<init>", "()V");
                mv.visitInsn(RETURN);
                mv.visitMaxs(1, 1);
                mv.visitEnd();
            }
            break;
        default:
            break;
    }
    cw.visitEnd();

    return cw.toByteArray();
}
 

public byte[] asm(ClassLoader loader, String className,
        Class<?> classBeingRedefined,
        ProtectionDomain protectionDomain, byte[] classfileBuffer)
    throws IllegalClassFormatException {

    ClassWriter cw = new ClassWriter(0);
    ClassVisitor cv = new ReAddDummyFieldsClassVisitor(ASM5, cw) { };
    ClassReader cr = new ClassReader(classfileBuffer);
    cr.accept(cv, 0);
    return cw.toByteArray();
}
 

private byte[] toByteArray() {
    ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES);
    classNode.accept(cw);
    cw.visitEnd();
    byte[] result = cw.toByteArray();
    Utils.writeGeneratedASM(classNode.name, result);
    return result;
}
 

private byte[] makeBytecode() throws IOException, ClassNotFoundException {

        // Find the methods to instrument and inline

        final List<Method> instrumentationMethods = new ArrayList<>();
        for (final Method m : instrumentor.getDeclaredMethods()) {
            JIInstrumentationMethod im = m.getAnnotation(JIInstrumentationMethod.class);
            if (im != null) {
                instrumentationMethods.add(m);
            }
        }

        // We begin by inlining the target's methods into the instrumentor

        ClassNode temporary = new ClassNode();
        ClassVisitor inliner = new JIInliner(
                Opcodes.ASM5,
                temporary,
                targetName,
                instrumentorName,
                targetClassReader,
                instrumentationMethods);
        instrClassReader.accept(inliner, ClassReader.EXPAND_FRAMES);

        // Now we have the target's methods inlined into the instrumentation code (in 'temporary').
        // We now need to replace the target's method with the code in the
        // instrumentation method.

        ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES);
        JIMethodMergeAdapter ma = new JIMethodMergeAdapter(
                cw,
                temporary,
                instrumentationMethods,
                instrumentor.getAnnotationsByType(JITypeMapping.class));
        targetClassReader.accept(ma, ClassReader.EXPAND_FRAMES);

       return cw.toByteArray();
    }
 

private byte[] loadClassData(String name) throws Exception {
    ClassWriter cw = new ClassWriter(
            ClassWriter.COMPUTE_FRAMES | ClassWriter.COMPUTE_MAXS);
    if (name.equals(BOOTSTRAP_METHOD_CLASS_NAME)) {
        defineIndyBootstrapMethodClass(cw);
        return cw.toByteArray();
    }
    else if (name.equals("Exec")) {
        defineIndyCallingClass(cw);
        return cw.toByteArray();
    }
    return null;
}
 

/**
 * Returns the bytes of the modified module-info.class.
 * Once this method has been called then the Extender object should
 * be discarded.
 */
public byte[] toByteArray() throws IOException {
    ClassWriter cw
        = new ClassWriter(ClassWriter.COMPUTE_MAXS + ClassWriter.COMPUTE_FRAMES);

    AttributeAddingClassVisitor cv
        = new AttributeAddingClassVisitor(Opcodes.ASM5, cw);

    ClassReader cr = new ClassReader(in);

    if (packages != null)
        cv.addAttribute(new ModulePackagesAttribute(packages));
    if (mainClass != null)
        cv.addAttribute(new ModuleMainClassAttribute(mainClass));
    if (targetPlatform != null)
        cv.addAttribute(new ModuleTargetAttribute(targetPlatform));
    if (hashes != null)
        cv.addAttribute(new ModuleHashesAttribute(hashes));
    if (moduleResolution != null)
        cv.addAttribute(new ModuleResolutionAttribute(moduleResolution.value()));

    List<Attribute> attrs = new ArrayList<>();

    // prototypes of attributes that should be parsed
    attrs.add(new ModuleAttribute(version));
    attrs.add(new ModulePackagesAttribute());
    attrs.add(new ModuleMainClassAttribute());
    attrs.add(new ModuleTargetAttribute());
    attrs.add(new ModuleHashesAttribute());

    cr.accept(cv, attrs.toArray(new Attribute[0]), 0);

    // add any attributes that didn't replace previous attributes
    cv.finish();

    return cw.toByteArray();
}
 

private static byte[] generateStringMaker() {
    // interface StringMaker extends Maker {
    //   String make();
    // }
    ClassWriter cw = new ClassWriter(0);
    cw.visit(V1_7, ACC_INTERFACE | ACC_ABSTRACT, "StringMaker", null, "java/lang/Object", new String[]{"Maker"});
    cw.visitMethod(ACC_PUBLIC | ACC_ABSTRACT, "make",
            "()Ljava/lang/String;", null, null);
    cw.visitEnd();
    return cw.toByteArray();
}
 

/**
 * Writes the given module descriptor to a module-info.class file,
 * returning it in a byte array.
 */
private static byte[] toModuleInfo(ModuleDescriptor md, ModuleTarget target) {
    ClassWriter cw = new ClassWriter(0);
    cw.visit(Opcodes.V1_9, ACC_MODULE, "module-info", null, null, null);
    cw.visitAttribute(new ModuleAttribute(md));

    // for tests: write the ModulePackages attribute when there are packages
    // that aren't exported or open
    Stream<String> exported = md.exports().stream()
            .map(ModuleDescriptor.Exports::source);
    Stream<String> open = md.opens().stream()
            .map(ModuleDescriptor.Opens::source);
    long exportedOrOpen = Stream.concat(exported, open).distinct().count();
    if (md.packages().size() > exportedOrOpen)
        cw.visitAttribute(new ModulePackagesAttribute(md.packages()));

    // write ModuleMainClass if the module has a main class
    md.mainClass().ifPresent(mc -> cw.visitAttribute(new ModuleMainClassAttribute(mc)));

    // write ModuleTarget if there is a target platform
    if (target != null) {
        cw.visitAttribute(new ModuleTargetAttribute(target.targetPlatform()));
    }

    cw.visitEnd();
    return cw.toByteArray();
}
 

private static byte[] generateStringMaker() {
    // interface StringMaker extends Maker {
    //   String make();
    // }
    ClassWriter cw = new ClassWriter(0);
    cw.visit(V1_7, ACC_INTERFACE | ACC_ABSTRACT, "StringMaker", null, "java/lang/Object", new String[]{"Maker"});
    cw.visitMethod(ACC_PUBLIC | ACC_ABSTRACT, "make",
            "()Ljava/lang/String;", null, null);
    cw.visitEnd();
    return cw.toByteArray();
}
 

public static byte[] dumpT1() {
    ClassWriter cw = new ClassWriter(0);
    MethodVisitor mv;

    cw.visit(52, ACC_PUBLIC | ACC_SUPER, "p1/T1", null, "java/lang/Object", null);
    {
        mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
        mv.visitCode();
        mv.visitVarInsn(ALOAD, 0);
        mv.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "<init>", "()V", false);
        mv.visitInsn(RETURN);
        mv.visitMaxs(1, 1);
        mv.visitEnd();
    }
    {
        mv = cw.visitMethod(ACC_PUBLIC, "m", "()I", null, null);
        mv.visitCode();
        mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
        mv.visitLdcInsn("p1/T1.m()");
        mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "print", "(Ljava/lang/String;)V", false);
        mv.visitIntInsn(BIPUSH, 3);
        mv.visitInsn(IRETURN);
        mv.visitMaxs(2, 1);
        mv.visitEnd();
    }
    cw.visitEnd();

    return cw.toByteArray();
}
 

static byte[] generateBytes(Class<?> clz, byte[] oldBytes) throws IOException {
    InputStream in = new ByteArrayInputStream(oldBytes);
    ClassReader cr = new ClassReader(in);
    ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS);
    ConstructorTracerWriter ctw = new ConstructorTracerWriter(cw, clz);
    cr.accept(ctw, 0);
    return cw.toByteArray();
}
 

private static byte[] generateCodeBytesForLFs(String className,
        String[] names, LambdaForm[] forms) {

    ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS + ClassWriter.COMPUTE_FRAMES);
    cw.visit(Opcodes.V1_8, Opcodes.ACC_PRIVATE + Opcodes.ACC_FINAL + Opcodes.ACC_SUPER,
            className, null, InvokerBytecodeGenerator.INVOKER_SUPER_NAME, null);
    cw.visitSource(className.substring(className.lastIndexOf('/') + 1), null);

    for (int i = 0; i < forms.length; i++) {
        addMethod(className, names[i], forms[i],
                forms[i].methodType(), cw);
    }
    return cw.toByteArray();
}
 

/**
 * Returns the bytes for a class with name d_name (presumably "D" in some
 * package), extending some class with name sub_what, implementing p.I,
 * and defining two methods m() and m(11args) with access method_acc.
 *
 * @param d_name      Name of class that is defined
 * @param sub_what    Name of class that it extends
 * @param method_acc  Accessibility of method(s) m in defined class.
 * @return
 * @throws Exception
 */
public static byte[] bytesForSomeDsubSomethingSomeAccess
        (String d_name, String sub_what, int method_acc)
        throws Exception {

    ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES
            | ClassWriter.COMPUTE_MAXS);
    MethodVisitor mv;
    String[] interfaces = {"p/I"};

    cw.visit(V1_8, ACC_PUBLIC + ACC_SUPER, d_name, null, sub_what, interfaces);
    {
        mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
        mv.visitCode();
        mv.visitVarInsn(ALOAD, 0);
        mv.visitMethodInsn(INVOKESPECIAL, sub_what, "<init>", "()V");
        mv.visitInsn(RETURN);
        mv.visitMaxs(0, 0);
        mv.visitEnd();
    }
    // int m() {return 3;}
    {
        mv = cw.visitMethod(method_acc, "m", "()I", null, null);
        mv.visitCode();
        mv.visitLdcInsn(new Integer(3));
        mv.visitInsn(IRETURN);
        mv.visitMaxs(0, 0);
        mv.visitEnd();
    }
    // int m(11args) {return 3;}
    {
        mv = cw.visitMethod(method_acc, "m", "(BCSIJ"
                + "Ljava/lang/Object;"
                + "Ljava/lang/Object;"
                + "Ljava/lang/Object;"
                + "Ljava/lang/Object;"
                + "Ljava/lang/Object;"
                + "Ljava/lang/Object;"
                + ")I", null, null);
        mv.visitCode();
        mv.visitLdcInsn(new Integer(3));
        mv.visitInsn(IRETURN);
        mv.visitMaxs(0, 0);
        mv.visitEnd();
    }
    cw.visitEnd();
    return cw.toByteArray();
}
 

/**
 * Returns the bytes for a class with name d_name (presumably "D" in some
 * package), extending some class with name sub_what, implementing p.I,
 * and defining two methods m() and m(11args) with access method_acc.
 *
 * @param d_name      Name of class that is defined
 * @param sub_what    Name of class that it extends
 * @param method_acc  Accessibility of method(s) m in defined class.
 * @return
 * @throws Exception
 */
public static byte[] bytesForSomeDsubSomethingSomeAccess
        (String d_name, String sub_what, int method_acc)
        throws Exception {

    ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES
            | ClassWriter.COMPUTE_MAXS);
    MethodVisitor mv;
    String[] interfaces = {"p/I"};

    cw.visit(V1_8, ACC_PUBLIC + ACC_SUPER, d_name, null, sub_what, interfaces);
    {
        mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
        mv.visitCode();
        mv.visitVarInsn(ALOAD, 0);
        mv.visitMethodInsn(INVOKESPECIAL, sub_what, "<init>", "()V");
        mv.visitInsn(RETURN);
        mv.visitMaxs(0, 0);
        mv.visitEnd();
    }
    // int m() {return 3;}
    {
        mv = cw.visitMethod(method_acc, "m", "()I", null, null);
        mv.visitCode();
        mv.visitLdcInsn(new Integer(3));
        mv.visitInsn(IRETURN);
        mv.visitMaxs(0, 0);
        mv.visitEnd();
    }
    // int m(11args) {return 3;}
    {
        mv = cw.visitMethod(method_acc, "m", "(BCSIJ"
                + "Ljava/lang/Object;"
                + "Ljava/lang/Object;"
                + "Ljava/lang/Object;"
                + "Ljava/lang/Object;"
                + "Ljava/lang/Object;"
                + "Ljava/lang/Object;"
                + ")I", null, null);
        mv.visitCode();
        mv.visitLdcInsn(new Integer(3));
        mv.visitInsn(IRETURN);
        mv.visitMaxs(0, 0);
        mv.visitEnd();
    }
    cw.visitEnd();
    return cw.toByteArray();
}
 

/**
 * Returns the bytes for a class with name d_name (presumably "D" in some
 * package), extending some class with name sub_what, implementing p.I,
 * and defining two methods m() and m(11args) with access method_acc.
 *
 * @param d_name      Name of class that is defined
 * @param sub_what    Name of class that it extends
 * @param method_acc  Accessibility of method(s) m in defined class.
 * @return
 * @throws Exception
 */
public static byte[] bytesForSomeDsubSomethingSomeAccess
        (String d_name, String sub_what, int method_acc)
        throws Exception {

    ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES
            | ClassWriter.COMPUTE_MAXS);
    MethodVisitor mv;
    String[] interfaces = {"p/I"};

    cw.visit(V1_8, ACC_PUBLIC + ACC_SUPER, d_name, null, sub_what, interfaces);
    {
        mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
        mv.visitCode();
        mv.visitVarInsn(ALOAD, 0);
        mv.visitMethodInsn(INVOKESPECIAL, sub_what, "<init>", "()V");
        mv.visitInsn(RETURN);
        mv.visitMaxs(0, 0);
        mv.visitEnd();
    }
    // int m() {return 3;}
    {
        mv = cw.visitMethod(method_acc, "m", "()I", null, null);
        mv.visitCode();
        mv.visitLdcInsn(new Integer(3));
        mv.visitInsn(IRETURN);
        mv.visitMaxs(0, 0);
        mv.visitEnd();
    }
    // int m(11args) {return 3;}
    {
        mv = cw.visitMethod(method_acc, "m", "(BCSIJ"
                + "Ljava/lang/Object;"
                + "Ljava/lang/Object;"
                + "Ljava/lang/Object;"
                + "Ljava/lang/Object;"
                + "Ljava/lang/Object;"
                + "Ljava/lang/Object;"
                + ")I", null, null);
        mv.visitCode();
        mv.visitLdcInsn(new Integer(3));
        mv.visitInsn(IRETURN);
        mv.visitMaxs(0, 0);
        mv.visitEnd();
    }
    cw.visitEnd();
    return cw.toByteArray();
}