Java MethodHandles.filterArguments方法代碼示例

import java.lang.invoke.MethodHandles; //導入方法依賴的package包/類
void testFilterArguments(int nargs, int pos) throws Throwable {
    countTest();
    MethodHandle target = varargsList(nargs);
    MethodHandle filter = varargsList(1);
    filter = filter.asType(filter.type().generic());
    Object[] argsToPass = randomArgs(nargs, Object.class);
    if (verbosity >= 3)
        System.out.println("filter "+target+" at "+pos+" with "+filter);
    MethodHandle target2 = MethodHandles.filterArguments(target, pos, filter);
    // Simulate expected effect of filter on arglist:
    Object[] filteredArgs = argsToPass.clone();
    filteredArgs[pos] = filter.invokeExact(filteredArgs[pos]);
    List<Object> expected = Arrays.asList(filteredArgs);
    Object result = target2.invokeWithArguments(argsToPass);
    if (verbosity >= 3)
        System.out.println("result: "+result);
    if (!expected.equals(result))
        System.out.println("*** fail at n/p = "+nargs+"/"+pos+": "+Arrays.asList(argsToPass)+" => "+result+" != "+expected);
    assertEquals(expected, result);
}
 

import java.lang.invoke.MethodHandles; //導入方法依賴的package包/類
private static MethodHandle convertArgToInt(final MethodHandle mh, final LinkerServices ls, final CallSiteDescriptor desc) {
    final Class<?> sourceType = desc.getMethodType().parameterType(1);
    if(TypeUtilities.isMethodInvocationConvertible(sourceType, Number.class)) {
        return mh;
    } else if(ls.canConvert(sourceType, Number.class)) {
        final MethodHandle converter = ls.getTypeConverter(sourceType, Number.class);
        return MethodHandles.filterArguments(mh, 1, converter.asType(converter.type().changeReturnType(
                mh.type().parameterType(1))));
    }
    return mh;
}
 

import java.lang.invoke.MethodHandles; //導入方法依賴的package包/類
private static MethodHandle applyConverters(final MethodHandle handle, final int pos, final List<MethodHandle> converters) {
    if(converters.isEmpty()) {
        return handle;
    }
    final MethodHandle newHandle =
            MethodHandles.filterArguments(handle, pos, converters.toArray(new MethodHandle[converters.size()]));
    converters.clear();
    return newHandle;
}
 

import java.lang.invoke.MethodHandles; //導入方法依賴的package包/類
private static MethodHandle convertArgToNumber(final MethodHandle mh, final LinkerServices ls, final CallSiteDescriptor desc) {
    final Class<?> sourceType = desc.getMethodType().parameterType(1);
    if(TypeUtilities.isMethodInvocationConvertible(sourceType, Number.class)) {
        return mh;
    } else if(ls.canConvert(sourceType, Number.class)) {
        final MethodHandle converter = ls.getTypeConverter(sourceType, Number.class);
        return MethodHandles.filterArguments(mh, 1, converter.asType(converter.type().changeReturnType(
                mh.type().parameterType(1))));
    }
    return mh;
}
 

import java.lang.invoke.MethodHandles; //導入方法依賴的package包/類
private static MethodHandle applyConverters(final MethodHandle handle, final int pos, final List<MethodHandle> converters) {
    if(converters.isEmpty()) {
        return handle;
    }
    final MethodHandle newHandle =
            MethodHandles.filterArguments(handle, pos, converters.toArray(new MethodHandle[0]));
    converters.clear();
    return newHandle;
}
 

import java.lang.invoke.MethodHandles; //導入方法依賴的package包/類
@Override
public GuardedInvocation getGuardedInvocation(final LinkRequest linkRequest, final LinkerServices linkerServices)
        throws Exception {
    final Object objSuperAdapter = linkRequest.getReceiver();
    if(!(objSuperAdapter instanceof JavaSuperAdapter)) {
        return null;
    }

    final CallSiteDescriptor descriptor = linkRequest.getCallSiteDescriptor();
    if(!CallSiteDescriptorFactory.tokenizeOperators(descriptor).contains(GET_METHOD)) {
        // We only handle getMethod
        return null;
    }

    final Object adapter = ((JavaSuperAdapter)objSuperAdapter).getAdapter();

    // Replace argument (javaSuperAdapter, ...) => (adapter, ...) when delegating to BeansLinker
    final Object[] args = linkRequest.getArguments();
    args[0] = adapter;

    // Use R(T0, ...) => R(adapter.class, ...) call site type when delegating to BeansLinker.
    final MethodType type = descriptor.getMethodType();
    final Class<?> adapterClass = adapter.getClass();
    final boolean hasFixedName = descriptor.getNameTokenCount() > 2;
    final String opName = hasFixedName ? (DYN_GET_METHOD_FIXED + descriptor.getNameToken(
            CallSiteDescriptor.NAME_OPERAND)) : DYN_GET_METHOD;

    final CallSiteDescriptor newDescriptor = NashornCallSiteDescriptor.get(descriptor.getLookup(), opName,
            type.changeParameterType(0, adapterClass), 0);

    // Delegate to BeansLinker
    final GuardedInvocation guardedInv = NashornBeansLinker.getGuardedInvocation(
            BeansLinker.getLinkerForClass(adapterClass), linkRequest.replaceArguments(newDescriptor, args),
            linkerServices);

    final MethodHandle guard = IS_ADAPTER_OF_CLASS.bindTo(adapterClass);
    if(guardedInv == null) {
        // Short circuit the lookup here for non-existent methods by linking an empty getter. If we just returned
        // null instead, BeansLinker would find final methods on the JavaSuperAdapter instead: getClass() and
        // wait().
        return new GuardedInvocation(MethodHandles.dropArguments(EMPTY_GETTER, 1,type.parameterList().subList(1,
                type.parameterCount())), guard).asType(descriptor);
    }

    final MethodHandle invocation = guardedInv.getInvocation();
    final MethodType invType = invocation.type();
    // For invocation typed R(T0, ...) create a dynamic method binder of type Object(R, T0)
    final MethodHandle typedBinder = BIND_DYNAMIC_METHOD.asType(MethodType.methodType(Object.class,
            invType.returnType(), invType.parameterType(0)));
    // For invocation typed R(T0, T1, ...) create a dynamic method binder of type Object(R, T0, T1, ...)
    final MethodHandle droppingBinder = MethodHandles.dropArguments(typedBinder, 2,
            invType.parameterList().subList(1, invType.parameterCount()));
    // Finally, fold the invocation into the binder to produce a method handle that will bind every returned
    // DynamicMethod object from dyn:getMethod calls to the actual receiver
    // Object(R(T0, T1, ...), T0, T1, ...)
    final MethodHandle bindingInvocation = MethodHandles.foldArguments(droppingBinder, invocation);

    final MethodHandle typedGetAdapter = asFilterType(GET_ADAPTER, 0, invType, type);
    final MethodHandle adaptedInvocation;
    if(hasFixedName) {
        adaptedInvocation = MethodHandles.filterArguments(bindingInvocation, 0, typedGetAdapter);
    } else {
        // Add a filter that'll prepend "super$" to each name passed to the variable-name "dyn:getMethod".
        final MethodHandle typedAddPrefix = asFilterType(ADD_PREFIX_TO_METHOD_NAME, 1, invType, type);
        adaptedInvocation = MethodHandles.filterArguments(bindingInvocation, 0, typedGetAdapter, typedAddPrefix);
    }

    return guardedInv.replaceMethods(adaptedInvocation, guard).asType(descriptor);
}
 

import java.lang.invoke.MethodHandles; //導入方法依賴的package包/類
@Override
public MethodHandle filterArguments(final MethodHandle target, final int pos, final MethodHandle... filters) {
    final MethodHandle mh = MethodHandles.filterArguments(target, pos, filters);
    return debug(mh, "filterArguments", target, pos, filters);
}
 

import java.lang.invoke.MethodHandles; //導入方法依賴的package包/類
private GuardedInvocationComponent getUnnamedPropertyGetter(final ComponentLinkRequest req) throws Exception {
    // Since we can't know what kind of a getter we'll get back on different invocations, we'll just
    // conservatively presume Object. Note we can't just coerce to a narrower call site type as the linking
    // runtime might not allow coercing at that call site.
    final CallSiteDescriptor callSiteDescriptor = req.getDescriptor();
    final MethodType type = callSiteDescriptor.getMethodType().changeReturnType(Object.class);
    // Must have exactly two arguments: receiver and name
    assertParameterCount(callSiteDescriptor, 2);

    // What's below is basically:
    //   foldArguments(guardWithTest(isNotNull, invoke(get_handle), null|nextComponent.invocation), get_getter_handle)
    // only with a bunch of method signature adjustments. Basically, retrieve method getter
    // AnnotatedDynamicMethod; if it is non-null, invoke its "handle" field, otherwise either return null,
    // or delegate to next component's invocation.

    final LinkerServices linkerServices = req.linkerServices;
    final MethodHandle typedGetter = linkerServices.asType(getPropertyGetterHandle, type.changeReturnType(
            AnnotatedDynamicMethod.class));
    final MethodHandle callSiteBoundMethodGetter = MethodHandles.insertArguments(
            GET_ANNOTATED_METHOD, 1, callSiteDescriptor, linkerServices);
    final MethodHandle callSiteBoundInvoker = MethodHandles.filterArguments(GETTER_INVOKER, 0,
            callSiteBoundMethodGetter);
    // Object(AnnotatedDynamicMethod, Object)->Object(AnnotatedDynamicMethod, T0)
    final MethodHandle invokeHandleTyped = linkerServices.asType(callSiteBoundInvoker,
            MethodType.methodType(type.returnType(), AnnotatedDynamicMethod.class, type.parameterType(0)));
    // Since it's in the target of a fold, drop the unnecessary second argument
    // Object(AnnotatedDynamicMethod, T0)->Object(AnnotatedDynamicMethod, T0, T1)
    final MethodHandle invokeHandleFolded = MethodHandles.dropArguments(invokeHandleTyped, 2,
            type.parameterType(1));
    final GuardedInvocationComponent nextComponent = getNextComponent(req);

    final MethodHandle fallbackFolded;
    if(nextComponent == null) {
        // Object(AnnotatedDynamicMethod)->Object(AnnotatedDynamicMethod, T0, T1); returns constant null
        fallbackFolded = MethodHandles.dropArguments(CONSTANT_NULL_DROP_ANNOTATED_METHOD, 1,
                type.parameterList()).asType(type.insertParameterTypes(0, AnnotatedDynamicMethod.class));
    } else {
        // Object(T0, T1)->Object(AnnotatedDynamicMethod, T0, T1); adapts the next component's invocation to
        // drop the extra argument resulting from fold and to change its return type to Object.
        final MethodHandle nextInvocation = nextComponent.getGuardedInvocation().getInvocation();
        final MethodType nextType = nextInvocation.type();
        fallbackFolded = MethodHandles.dropArguments(nextInvocation.asType(
                nextType.changeReturnType(Object.class)), 0, AnnotatedDynamicMethod.class);
    }

    // fold(Object(AnnotatedDynamicMethod, T0, T1), AnnotatedDynamicMethod(T0, T1))
    final MethodHandle compositeGetter = MethodHandles.foldArguments(MethodHandles.guardWithTest(
                IS_ANNOTATED_METHOD_NOT_NULL, invokeHandleFolded, fallbackFolded), typedGetter);
    if(nextComponent == null) {
        return getClassGuardedInvocationComponent(compositeGetter, type);
    }
    return nextComponent.compose(compositeGetter, getClassGuard(type), clazz, ValidationType.EXACT_CLASS);
}