Examples with PUTFIELD org.objectweb.asm.Opcodes.PUTFIELD used on opensource projects

Example 1 with PUTFIELD

use of org.objectweb.asm.Opcodes.PUTFIELD in project LanternServer by LanternPowered.

the class FieldAccessFactory method createSetter.

/**
 * Creates a setter {@link BiConsumer} for the given {@link Field}.
 *
 * @param field The field
 * @param <T> The target object type
 * @param <V> The field value type
 * @return The bi consumer
 */
public static <T, V> BiConsumer<T, V> createSetter(Field field) {
    checkNotNull(field, "field");
    field.setAccessible(true);
    boolean isFinal = Modifier.isFinal(field.getModifiers());
    // Better check is somebody changed the final modifier already
    if (!isFinal) {
        final Field[] fields = field.getDeclaringClass().getDeclaredFields();
        boolean isFound = false;
        for (Field field1 : fields) {
            // The same signature, now check if somebody tinkered with the field
            if (field.getName().equals(field1.getName()) && field.getType().equals(field1.getType())) {
                isFinal = Modifier.isFinal(field1.getModifiers());
                isFound = true;
                break;
            }
        }
        if (!isFound) {
            throw new IllegalStateException("Something funky happened with: " + field.getName());
        }
    } else {
        try {
            modifiersField.setInt(field, field.getModifiers() & ~Modifier.FINAL);
        } catch (IllegalAccessException e) {
            throw new IllegalStateException(e);
        }
    }
    // Final fields don't allow direct access, so MethodHandles will do the trick.
    if (isFinal) {
        try {
            final MethodHandle methodHandle = MethodHandleMagic.trustedLookup().in(field.getDeclaringClass()).unreflectSetter(field).asType(setterMethodType);
            return (a, b) -> {
                try {
                    methodHandle.invokeExact(a, b);
                } catch (Throwable throwable) {
                    throw new IllegalStateException(throwable);
                }
            };
        } catch (IllegalAccessException e) {
            throw new IllegalStateException(e);
        }
    }
    final ClassWriter cw = new ClassWriter(0);
    final String className = field.getName().replace('.', '/') + "$$LanternSetter$" + setterCounter.incrementAndGet();
    cw.visit(V1_8, ACC_PUBLIC + ACC_SUPER, className, "Ljava/lang/Object;Ljava/util/function/BiConsumer<Ljava/lang/Object;Ljava/lang/Object;>;", "java/lang/Object", new String[] { "java/util/function/BiConsumer" });
    // Add a empty constructor
    BytecodeUtils.visitEmptyConstructor(cw);
    // Generate the apply method
    final MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, "accept", "(Ljava/lang/Object;Ljava/lang/Object;)V", null, null);
    mv.visitCode();
    final String descriptor = Type.getDescriptor(field.getType());
    final String targetName = Type.getInternalName(field.getDeclaringClass());
    final boolean isStatic = Modifier.isStatic(field.getModifiers());
    if (!isStatic) {
        // Load the target parameter
        mv.visitVarInsn(ALOAD, 1);
        // Cast it
        mv.visitTypeInsn(CHECKCAST, targetName);
    }
    // Load the value parameter
    mv.visitVarInsn(ALOAD, 2);
    // Unbox the values in case they are primitives, otherwise cast
    GeneratorUtils.visitUnboxingMethod(mv, Type.getType(field.getType()));
    // Put the value into the field
    if (isStatic) {
        mv.visitFieldInsn(PUTSTATIC, targetName, field.getName(), descriptor);
    } else {
        mv.visitFieldInsn(PUTFIELD, targetName, field.getName(), descriptor);
    }
    // Return
    mv.visitInsn(RETURN);
    mv.visitMaxs(2, 3);
    mv.visitEnd();
    // Finish class generation
    cw.visitEnd();
    // Define the class and create a function instance
    final MethodHandles.Lookup lookup = MethodHandleMagic.trustedLookup().in(field.getDeclaringClass());
    final Class<?> functionClass = MethodHandleMagic.defineNestmateClass(lookup, cw.toByteArray());
    try {
        return (BiConsumer<T, V>) functionClass.newInstance();
    } catch (Exception e) {
        throw new IllegalStateException("Something went wrong!", e);
    }
}