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From "Mike Lucas (JIRA)" <>
Subject [jira] [Commented] (CONFIGURATION-532) FileChangedReloadingStrategy should support reloading of rolled-back (older timestamp) files
Date Wed, 01 May 2013 17:34:21 GMT


Mike Lucas commented on CONFIGURATION-532:

In case anyone is interested, here is my subclass that overrides isChanged(), useful until
you can use 2.0:

public class FileChangedReloadingStrategy extends org.apache.commons.configuration.reloading.FileChangedReloadingStrategy

   * Overrides the superclass method to do a not-equal-to comparison on the file timestamp,
rather than
   * greater-than. This ensures that virtually any* change to the config file will result
in a reload, subject
   * to the refreshDelay of course.
   * <p/>
   * * It is possible to make a change to the content and then set the timestamp to the exact
same as it was
   * before, which won't result in a reload. But that would just be weird and very unlikely.
   * @see org.apache.commons.configuration.reloading.FileChangedReloadingStrategy#hasChanged()
  protected boolean hasChanged() {
        File file = getFile();
        if (file == null || !file.exists())
            return false;

        return file.lastModified() != lastModified;

> FileChangedReloadingStrategy should support reloading of rolled-back (older timestamp)
> --------------------------------------------------------------------------------------------
>                 Key: CONFIGURATION-532
>                 URL:
>             Project: Commons Configuration
>          Issue Type: Improvement
>          Components: File reloading
>    Affects Versions: 1.9
>            Reporter: Mike Lucas
>             Fix For: 2.0
>   Original Estimate: 48h
>  Remaining Estimate: 48h
> Currently the {{FileChangedReloadingStrategy}} only reloads when the timestamp of the
file on the filesystem is _newer_ than the timestamp it had when it was last loaded.
> This may not be the expected behaviour when, for example, an administrator makes a backup
copy of the original configuration file before making changes. If the administrator wants
to roll back to the original configuration, he may expect that copying/renaming the backup
back to the original name, would cause the original configuration to take effect again.
> Another example where the current behaviour is problematic is when using a Deploy System
(like we do at my company). We expect to be able to roll-back to a previous configuration
by simply redeploying the Config artifact, but because the timestamps reflect when the Config
artifact was _built_ (not when it was deployed), this roll-back will not work.
> The current behaviour could be kept as the default, simply adding {{setReloadOnRollback()}}
or similarly named method to change the behaviour to reload when the timestamp is either older
or newer (i.e. not equal to) the {{lastModified}} variable. Another option would to be to
create subclass {{FileChangedOrRolledBackReloadingStrategy}} that overrides the {{hasChanged()}}
> In either option the actual change is to use {{!=}} instead of {{>}} in the {{hasChanged}}
method's comparison:
> {code}
> return file.lastModified() > lastModified;
> {code}

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