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

/**
 * Exercise Class::getModule on VM anonymous classes
 */
@Test(dataProvider = "hostclasses")
public void testGetModuleOnVMAnonymousClass(Class<?> hostClass, String ignore) {

    // choose a class name in the same package as the host class
    String prefix = hostClass.getPackageName();
    if (prefix.length() > 0)
        prefix = prefix.replace('.', '/') + "/";
    String className = prefix + "Anon";

    // create the class
    String superName = "java/lang/Object";
    ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS
                                     + ClassWriter.COMPUTE_FRAMES);
    cw.visit(V1_8, ACC_PUBLIC + ACC_FINAL + ACC_SUPER,
             className, null, superName, null);
    byte[] classBytes = cw.toByteArray();
    int cpPoolSize = constantPoolSize(classBytes);
    Class<?> anonClass
        = U.defineAnonymousClass(hostClass, classBytes, new Object[cpPoolSize]);

    assertTrue(anonClass.getModule() == hostClass.getModule());
}
 

static byte[] getClassFile(String suffix) {
    ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES | ClassWriter.COMPUTE_MAXS);
    MethodVisitor mv;
    cw.visit(52, ACC_PUBLIC | ACC_SUPER, CLASS_NAME + suffix, null, "java/lang/Object", null);
    {
        mv = cw.visitMethod(ACC_PUBLIC | ACC_STATIC, METHOD_NAME, TYPE.toMethodDescriptorString(), null, null);
        mv.visitCode();
        Handle bsm = new Handle(H_INVOKESTATIC,
                CallSiteDepContextTest.class.getName().replace(".", "/"),
                "bootstrap",
                bsmMH.type().toMethodDescriptorString());
        mv.visitInvokeDynamicInsn("methodName", TYPE.toMethodDescriptorString(), bsm);
        mv.visitInsn(IRETURN);
        mv.visitMaxs(0, 0);
        mv.visitEnd();
    }
    cw.visitEnd();
    return cw.toByteArray();
}
 

public static void writeClassFile() throws Exception {
    ClassWriter cw = new ClassWriter(0);
    MethodVisitor mv;

    cw.visit(99, ACC_PUBLIC + ACC_SUPER, "ClassFile", 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();
    cw.visitEnd();

    try (FileOutputStream fos = new FileOutputStream(new File("ClassFile.class"))) {
         fos.write(cw.toByteArray());
    }
}
 

/**
 * The bytes for D, a NOT abstract class extending abstract class C without
 * supplying an implementation for abstract method m. There is a default
 * method in the interface I, but it should lose to the abstract class.
 *
 * @return
 * @throws Exception
 */
public static byte[] bytesForD() throws Exception {

    ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES
            | ClassWriter.COMPUTE_MAXS);
    MethodVisitor mv;

    cw.visit(V1_8, ACC_PUBLIC + ACC_SUPER, "p/D", null, "p/C", null);

    {
        mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
        mv.visitCode();
        mv.visitVarInsn(ALOAD, 0);
        mv.visitMethodInsn(INVOKESPECIAL, "p/C", "<init>", "()V");
        mv.visitInsn(RETURN);
        mv.visitMaxs(0, 0);
        mv.visitEnd();
    }
    cw.visitEnd();

    return cw.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 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();
}
 

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

private byte[] loadClassData(String name) throws Exception {
  ClassWriter cw = new ClassWriter(0);
  MethodVisitor mv;

  if (name.equals("C")) {
    cw.visit(52, ACC_SUPER | ACC_PUBLIC, "C", null, "java/lang/Object", null);
    {
      mv = cw.visitMethod(ACC_PRIVATE | ACC_STATIC, "m", "()V", null, null);
      mv.visitCode();
      mv.visitInsn(RETURN);
      mv.visitMaxs(0, 1);
      mv.visitEnd();
    }
    cw.visitEnd();
    return cw.toByteArray();
  } else if (name.equals("Exec")) {
    cw.visit(52, ACC_SUPER | ACC_PUBLIC, "Exec", null, "java/lang/Object", null);
    {
      mv = cw.visitMethod(ACC_PUBLIC | ACC_STATIC, "invokeRef", "()V", null, null);
      mv.visitCode();
      Handle h = new Handle(H_INVOKESTATIC, "C", "m", "()V");
      mv.visitInvokeDynamicInsn("C", "()V", h);
      mv.visitInsn(RETURN);
      mv.visitMaxs(0, 0);
      mv.visitEnd();
    }
    cw.visitEnd();
    return cw.toByteArray();
  }
  return null;
}
 

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

public static void writeClassFile(int cfv) throws Exception {
    ClassWriter cw = new ClassWriter(0);
    MethodVisitor mv;

    cw.visit(cfv, ACC_PUBLIC + ACC_SUPER, "ClassFile", 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 + ACC_STATIC, "main", "([Ljava/lang/String;)V", null, null);
    mv.visitCode();
    mv.visitInsn(ICONST_1);
    mv.visitInsn(ICONST_2);
    mv.visitMultiANewArrayInsn("[I", 2);
    mv.visitVarInsn(ASTORE, 1);
    mv.visitInsn(RETURN);
    mv.visitMaxs(2, 2);
    mv.visitEnd();

    cw.visitEnd();

    try (FileOutputStream fos = new FileOutputStream(new File("ClassFile.class"))) {
         fos.write(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();
}
 

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 writeClassFile(int cfv) throws Exception {
    ClassWriter cw = new ClassWriter(0);
    MethodVisitor mv;

    cw.visit(cfv, ACC_PUBLIC + ACC_SUPER, "ClassFile", 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 + ACC_STATIC, "main", "([Ljava/lang/String;)V", null, null);
    mv.visitCode();
    mv.visitInsn(ICONST_1);
    mv.visitInsn(ICONST_2);
    mv.visitMultiANewArrayInsn("[I", 2);
    mv.visitVarInsn(ASTORE, 1);
    mv.visitInsn(RETURN);
    mv.visitMaxs(2, 2);
    mv.visitEnd();

    cw.visitEnd();

    try (FileOutputStream fos = new FileOutputStream(new File("ClassFile.class"))) {
         fos.write(cw.toByteArray());
    }
}
 

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

}
 

private static byte[] generateTestClass() {
    ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES);

    cw.visit(TestOSRWithNonEmptyStack.CLASS_FILE_VERSION, ACC_PUBLIC,
            TestOSRWithNonEmptyStack.CLASS_NAME, null, "java/lang/Object",
            null);

    TestOSRWithNonEmptyStack.generateConstructor(cw);
    TestOSRWithNonEmptyStack.generateTestMethod(cw);

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

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

/**
 * Base constructor for building a Class or Interface
 * @param name Name of Class/Interface, including package name
 * @param extending Name of extending Class if any
 * @param access Access for Class/Interface
 * @param classFileVersion Class file version
 * @param interfaces Interface implemented
 */
public ClassConstruct(String name,
                      String extending,
                      int access,
                      int classFileVersion,
                      int index,
                      String... interfaces) {
    this.name = name;
    isInterface = (access & Opcodes.ACC_INTERFACE) == Opcodes.ACC_INTERFACE;
    cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES);
    cw.visit(classFileVersion, access, name, null, extending, interfaces == null ?  new String[] { } : interfaces);
    this.index = index;
}
 

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