public int arity(ELContext elctx) {
if (node instanceof ELNode.LAMBDA) {
return ((ELNode.LAMBDA) node).vars.length;
}
MethodInfo info = node.getMethodInfo(getContext(elctx));
if (info != null && info.getParamTypes() != null) {
return info.getParamTypes().length;
} else {
return -1;
}
}
/**
* This method wraps a <code>MethodExpression</code> in a <code>Method</code> which can be
* statically invoked.
*
* <p>Since Method is a final class with only a non-public constructor, various reflective tricks
* have been used to create an instance of this class and make sure it calls the given method
* expression. It has been tested on the Sun/Oracle JDK versions 6 and 7, and it should work on
* OpenJDK 6 and 7 as well. Other JDKs might not work.
*
* @param context the context used for evaluation of the method expression when it's invoked
* later. NOTE, this reference is retained by the returned method.
* @param methodExpression the method expression to be wrapped
* @return a Method instance that when invoked causes the wrapped method expression to be invoked.
*/
public static Method methodExpressionToStaticMethod(
final ELContext context, final MethodExpression methodExpression) {
final MethodInfo methodInfo =
methodExpression.getMethodInfo(FacesContext.getCurrentInstance().getELContext());
try {
// Create a Method instance with the signature (return type, name,
// parameter types) corresponding
// to the method the MethodExpression references.
final Constructor<Method> methodConstructor =
Method.class.getDeclaredConstructor(
Class.class,
String.class,
Class[].class,
Class.class,
Class[].class,
int.class,
int.class,
String.class,
byte[].class,
byte[].class,
byte[].class);
methodConstructor.setAccessible(true);
final Method staticMethod =
methodConstructor.newInstance(
null,
methodInfo.getName(),
methodInfo.getParamTypes(),
methodInfo.getReturnType(),
null,
0,
0,
null,
null,
null,
null);
// The Sun/Oracle/OpenJDK Method makes use of a private delegator
// called MethodAccessor.
// Though specific to those JDKs, this is what we can use to let our
// Method instance execute something
// we want. (simply overriding the invoke method would be much
// better, but unfortunately Method is final)
final Class<?> methodAccessorClass = Class.forName("sun.reflect.MethodAccessor");
// Create a proxy for our MethodAccessor, so we don't have to
// reference the actual type at compile-time.
final Object MethodAccessor =
Proxy.newProxyInstance(
Method.class.getClassLoader(),
new Class[] {methodAccessorClass},
new InvocationHandler() {
@Override
public Object invoke(final Object proxy, final Method method, final Object[] args)
throws Throwable {
Object[] params = null;
if (args != null && args.length > 1) {
// args[0]
// should
// be
// the
// Object
// on
// which
// the
// method
// is
// to
// be
// invoked
// (null
// in
// case
// of
// static
// call)
// args[1]
// should
// be
// the
// parameters
// for
// the
// method
// invocation
// (possibly
// empty)
params = (Object[]) args[1];
} else {
params = Hacks.EMPTY_PARAMETERS;
}
return methodExpression.invoke(context, params);
}
});
final Method setMethodAccessor =
Method.class.getDeclaredMethod("setMethodAccessor", methodAccessorClass);
setMethodAccessor.setAccessible(true);
setMethodAccessor.invoke(staticMethod, MethodAccessor);
// Another private implementation detail of the Sun/Oracle/OpenJDK
// Method - unless override is set
// to true, a couple of nasty language checks are done before
// invoking the MethodAccessor
final Field override = AccessibleObject.class.getDeclaredField("override");
override.setAccessible(true);
override.set(staticMethod, true);
return staticMethod;
} catch (final Exception e) {
throw new IllegalStateException(e);
}
}