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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 commented on IMAGING-159:
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@[~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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