> On Apr 21, 2016, at 9:44 PM, Xuelei Fan <xuelei....@oracle.com> wrote:
>
>>> public MyCertStore extends CertStoreSpi {
>>>
>>> public MyCertStore() {
>>> // whatever
>>> // ;-) Don't ask me why this construct is necessary.
>>> }
>>>
>>> public MyCertStore(XXX params) {
>>> // throws NoSuchMethodException
>>> // ;-) Don't ask me why throw this exception.
>>> }
>>> }
>>>
>>> newInstanceUtil(MyCertStore, ...)
>>>
>>> The MyCertStore() would get called, unexpectly. Am I missing something?
>>
>> Probably not, unless you call getInstance(arg, null). I am not sure this
>> null will trigger some other exception along the way.
>>
>> OK, I admit there is a side effect here: If you design
>> getInstance(alg,params) but params is always null, then you can only
>> implement a constructor with no params.
>>
>> This is stupid and useless, but not really harmful.
>>
> Can you explain more here?
The code change looks like this
private static Object newInstanceUtil(final Class<?> clazz,
final Class<?> ctrParamClz, final Object ctorParamObj)
throws Exception {
if (ctrParamClz == null) {
Constructor<?> con = clazz.getConstructor();
return con.newInstance();
} else {
- Constructor<?> con = clazz.getConstructor(ctrParamClz);
- return con.newInstance(ctorParamObj);
+ try {
+ Constructor<?> con = clazz.getConstructor(ctrParamClz);
+ return con.newInstance(ctorParamObj);
+ } catch (NoSuchMethodException nsme) {
+ if (ctorParamObj == null) {
+ try {
+ Constructor<?> con = clazz.getConstructor();
+ return con.newInstance();
+ } catch (NoSuchMethodException nsme2) {
+ nsme.addSuppressed(nsme2);
+ throw nsme;
+ }
+ } else {
+ throw nsme;
+ }
+ }
}
}
So in order for the arg-less constructor to be called, you will need
1. ctrParamClz != null, i.e. there is a getInstance(arg,params) API.
2. ctorParamObj == null, i.e. someone calls it with getInstance(arg) or
getInstance(arg,null).
3. nsme caught, i.e. the implementation has not provided a constructor with args
This matches the "otherwise" part of what I described in the @implSpec of
SecureRandomSpi, which I don't suggest new implementation doing it, and is not
what all non-SecureRandom implementations are doing now (they always have a
constructor with args).
>>> public MyCertStore(XXX params) {
>>> // throws NoSuchMethodException
>>> // ;-) Don't ask me why throw this exception.
>>> }
When this constructor throws a NoSuchMethodException, calling con.newInstance()
will throw an InvocationTargetException, the NoSuchMethodException should only
be caught if clazz.getConstructor(ctrParamClz) fails.
