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From Michael Groß (JIRA) <j...@apache.org>
Subject [jira] [Comment Edited] (IMAGING-159) There should be a Parameters class
Date Fri, 30 Jan 2015 21:55:34 GMT

    [ https://issues.apache.org/jira/browse/IMAGING-159?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14299220#comment-14299220
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Michael Groß edited comment on IMAGING-159 at 1/30/15 9:55 PM:
---------------------------------------------------------------

@[~britter] Don't worry, maybe [~ebourg] is right. The builder-pattern approach 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 know. Each default value means one isXyzPresent()
method less.

I prevented getters from return null. You may ask via isXyzPresent() if a value was set so
you never get the RuntimeException. "if (xyz == null)" would mean to know that null means
"this parameter didn't got a value yet". "if isXyzPresent()" seems to be more obvious.


was (Author: mgmechanics):
@[~britter] Don't worry, maybe [~ebourg] is right. The builder-pattern approach 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 know. Each default value means one isXyzPresent()
method less.

I avoid strictly to return null values. There are few people in Java-related projects which
doesn't know what an "NPE" (NullPointerException) is, so common 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 set so you never get the RuntimeException. "if (xyz == null)" would mean to know that
null means "this parameter didn't got a value yet". "if isXyzPresent()" 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 problem that our
code has to validate parameter types when they are used:
> {code:java}
> final Object value = params.get(PARAM_KEY_COMPRESSION);
> if (value != null) {
>   if (!(value instanceof Number)) {
>     throw new ImageWriteException(
>       "Invalid compression parameter, must be numeric: "
>          + value);
>   }
>   compression = ((Number) value).intValue();
> }
> {code}
> This can be simplified if we define a Parameters class that provides additional methods
like {{public int getInt(String key)}}. The implementation could then look up the value from
the map through an exception if it is null or not a number.



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