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Date: Fri, 30 Jan 2015 20:59:35 +0000 (UTC)
From: =?utf-8?Q?Michael_Gro=C3=9F_=28JIRA=29?= <jira@apache.org>
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Subject: [jira] [Commented] (IMAGING-159) There should be a Parameters class
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    [ https://issues.apache.org/jira/browse/IMAGING-159?page=3Dcom.atlassia=
n.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=3D142=
99220#comment-14299220 ]=20

Michael Gro=C3=9F commented on IMAGING-159:
--------------------------------------

@[~britter] Don't worry, maybe [~ebourg] is right. The builder-pattern appr=
oach requires the user to know/remember of which type a parameter value is =
to get the value. I completed a second proposal at

http://github.com/mgmechanics/commons-imaging/tree/IMAGING-159-POJO

which uses the POJO/inheritance pattern as he pointed out. I did not apply =
the new classes (org.apache.commons.imaging.ImagingParameters/~Jpeg/~Tiff) =
but I am willing to do this when my patch is accepted.

For some values I found default values, for some not. For PARAM_KEY_VERBOSE=
 I assumed Boolean.FALSE. If there are more default values, please let me k=
now. Each default value means one isXyzPresent() method less.

I avoid strictly to return null values. There are few people in Java-relate=
d projects which doesn't know what an "NPE" (NullPointerException) is, so c=
ommon is it. Lessons learned for me: If the value wasn't set when we try to=
 get it there is a RuntimeException. It should pop up during testing and we=
 will go there and fix it. You may ask via isXyzPresent() if a value was se=
t so you never get the RuntimeException. "if (xyz =3D=3D null)" would mean =
to know that null means "this parameter didn't got a value yet". "if isXyzP=
resent()" seems to be more obvious. Its merely a lesson I learned.

> There should be a Parameters class
> ----------------------------------
>
>                 Key: IMAGING-159
>                 URL: https://issues.apache.org/jira/browse/IMAGING-159
>             Project: Commons Imaging
>          Issue Type: Improvement
>          Components: imaging.*
>            Reporter: Benedikt Ritter
>             Fix For: Patch Needed
>
>
> Currently options for image I/O are defined as Maps. The leads to the pro=
blem that our code has to validate parameter types when they are used:
> {code:java}
> final Object value =3D params.get(PARAM_KEY_COMPRESSION);
> if (value !=3D null) {
>   if (!(value instanceof Number)) {
>     throw new ImageWriteException(
>       "Invalid compression parameter, must be numeric: "
>          + value);
>   }
>   compression =3D ((Number) value).intValue();
> }
> {code}
> This can be simplified if we define a Parameters class that provides addi=
tional methods like {{public int getInt(String key)}}. The implementation c=
ould then look up the value from the map through an exception if it is null=
 or not a number.


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