Hi.
On Mon, 21 Dec 2015 22:44:16 -0600, Ole Ersoy wrote:
On 12/21/2015 06:44 PM, Gilles wrote:
On Mon, 21 Dec 2015 12:14:16 -0600, Ole Ersoy wrote:
Hi,
I was considering jumping into the JDKRandomGenerator exception
discussion, but I did not want to hijack it.
Not sure if any of you have had a chance to looks at this:
https://github.com/firefly-math/firefly-math-exceptions/
https://github.com/firefly-math/firefly-math-exceptions/blob/master/src/main/java/com/fireflysemantics/math/exception/MathException.java
I had a rapid look; unfortunately not in sufficient details to
grasp the major departures from the existing framework.
Could you display one or two examples comparing CM and firefly?
In addition to what I summarized below one detail that I think is
important is that the ExceptionTypes enum allows for more exact
targeting of the exception root cause. For instance right now I have
the following arithmetic exception types:
/**
* MATH ARITHMETIC EXCEPTIONS
*/
MAE("MAE"),
MAE__INTEGER_OVERFLOW("MAE__INTEGER_OVERFLOW"),
MAE__LONG_OVERFLOW("MAE__LONG_OVERFLOW"),
MAE__OVERFLOW_IN_ADDITION("MAE__OVERFLOW_IN_ADDITION"),
MAE__OVERFLOW_IN_SUBTRACTION("MAE__OVERFLOW_IN_SUBTRACTION"),
MAE__GCD_OVERFLOW_32_BITS("MAE__GCD_OVERFLOW_32_BITS"),
MAE__GCD_OVERFLOW_64_BITS("MAE__GCD_OVERFLOW_64_BITS"),
MAE__LCM_OVERFLOW_32_BITS("MAE__LCM_OVERFLOW_32_BITS"),
MAE__LCM_OVERFLOW_64_BITS("MAE__LCM_OVERFLOW_64_BITS"),
MAE__DIVISION_BY_ZERO("MAE__DIVISION_BY_ZERO"),
Side remark: The argument to the enum element is the same as the enum
element's name; is there a way to avoid the duplication (i.e. the
string
would be generated automatically)?
So by looking at the exception type we know exactly what the issue
is.
With this approach CM will always only have 1 exception. If more
types are needed then just add another line to the ExceptionTypes
Enum. The new type is used to look up the message template in the
I18N resource bundle.
It looks neat.
Thanks :)
But I did not see how localization is handled.
I did leave localization out. I think localization was a hard
requirement in earlier versions of CM, but I'm hoping that there is
some flexibility on this
There was not, since I argued many times to leave it out.
So unless you can show practically how it can work, I have my doubts
that we'll be allowed to go forward with this approach.
and that future versions can defer to a
utility that uses the ExceptionTypes Enum instance as the key to look
up the internationalized template string.
Looks good. Where is the code? ;-)
I think it satisfies everyone's requirements with:
- A single MathException (No hierarchy)
That would not satisfy everyone. :-!
- The ExceptionTypes Enum contains all the exception types
- The ExceptionTypes Enum 'key' maps to the corresponding message 1
to 1
- The ExceptionFactory (Utility) throws exceptions, if necessary,
that have always have a single unique root cause, such as NPEs
I was wondering whether the "factory" idea could indeed satisfy
everyone.
Rather than throwing the non-standard "MathException", the factory
would
generate one of the standard exceptions, constructed with the
internal
"MathException" as its cause:
I think it's good that CM throws CM specific exceptions. This way
when I write the handler I can know that the exception is CM specific
without having to unwrap it.
But if there are several CM exceptions hierarchies, the handler will
have
to check for every base type, leading to more code.
We could provide a utility:
public boolean isMathException(RuntimeException e) {
if (e instanceof MathException) {
return true;
}
final Throwable t = e.getCause();
if (t != null) {
if (e instanceof MathException) {
return true;
}
}
return false;
}
public class ExceptionFactory {
public static void throwIllegalArgumentException(MathException e)
{
throw new IllegalArgumentException(e);
}
public static void throwNullPointerException(MathException e) {
throw new NullPointerException(e);
}
// And so on...
}
So, CM code would be
public class Algo {
public void evaluate(double value) {
// Check precondition.
final double min = computeMin();
if (value < min) {
final MathException e = new
MathException(NUMBER_TOO_SMALL).put(CONSTRAINT, min).put(VALUE,
value);
ExceptionFactory.throwIllegalArgumentException(e);
}
// Precondition OK.
}
}
Another thing that I hinted to is that the the factory builds in the
precondition check in the throw method. So that the line:
if (value < min) {
can be nixed.
It seems nice to ensure that the exception raised is consistent with
the
checked condition.
Then, a factory method like
throwNotStrictlyPositiveException(Number value, String key)
should probably be renamed to
checkNotStrictlyPositiveException(Number value, String key)
Also, shouldn't the "key" argument should be optional?
Then, in an application's code:
public void appMethod() {
// ...
// Use CM.
try {
Algo a = new Algo();
a.evaluate(2);
} catch (IllegalArgumentException iae) {
final Throwable cause = iae.getCause();
if (cause instanceof MathException) {
final MathException e = (MathException) cause;
// Rethrow an application-specific exception that will make
more sense
// to my customers.
throw new InvalidDataInputException(e.get(CONSTRAINT),
e.get(VALUE));
}
}
}
This is all untested.
Did I miss something?
I think you got it all...But the handler will be shorter if the
exception is not wrapped.
But not significantly, I guess.
We could also provide
public MathException getMathException(RuntimeException e) {
if (e instanceof MathException) {
return (MathException) e;
}
final Throwable t = e.getCause();
if (t != null) {
if (e instanceof MathException) {
return (MathException) e;
}
}
return null;
}
And then define the other utility as:
public boolean isMathException(RuntimeException e) {
return getMathException(e) != null;
}
The pattern I'm used to is that libraries
wrap the exceptions of other libraries in order to offer a
standardized facade to the user. For example Spring wraps Hibernate
exceptions, since Spring is a layer on top of Hibernate and other
data
access providers.
What do they advertize? Standard exception, possibly extended, or
specific ones, possibly belonging to single hierarchy?
Gilles
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