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From "Roman Kurmanowytsch (JIRA)" <j...@apache.org>
Subject [jira] Created: (CONFIGURATION-280) autoSave and FileChangedReloadingStrategy corrupts configuration
Date Thu, 07 Jun 2007 21:34:26 GMT
autoSave and FileChangedReloadingStrategy corrupts configuration
----------------------------------------------------------------

                 Key: CONFIGURATION-280
                 URL: https://issues.apache.org/jira/browse/CONFIGURATION-280
             Project: Commons Configuration
          Issue Type: Bug
    Affects Versions: 1.4
         Environment: Linux, Sun Java 5
            Reporter: Roman Kurmanowytsch


First of all, sorry if this is not a bug. I may have missed some information on how to make
autoSave and FileChangedReloadingStrategy work.

When a change has been detected by the FileChangedReloadingStrategy code, a clear() followed
by a load() is executed in the AbstractFileConfiguration class (around line 809 of version
1.4). The clear() method leads to a possiblySave() call which overwrites the configuration.
At the end of the clear() method, the configuration file is empty and the following load()
method loads this empty configuration. The possiblySave() call is invoked via the work-around
(according to the comment in the code) in AbstractConfiguration (line 538).

I'm using the following code:

CompositeConfiguration config = new CompositeConfiguration();
XMLConfiguration xmlconfig = new XMLConfiguration("config.xml");
FileChangedReloadingStrategy fcrs = new FileChangedReloadingStrategy();
xmlconfig.setReloadingStrategy(fcrs);
config.addConfiguration(new SystemConfiguration());
config.addConfiguration(xmlconfig);
xmlconfig.setAutoSave(true);
...wait for config changes...		


A workaround for the problem is to deactivate autoSave in the reload() method of the AbstractFileConfiguration
class. After the configuration is cleared and loaded, the original autoSave is restored. See
the diff below:

806a807,808
>                         boolean autoSaveBak = this.isAutoSave(); // save the current
state
>                         this.setAutoSave(false); // deactivate autoSave to prevent information
loss
813a816
>                               this.setAutoSave(autoSaveBak); // set autoSave to previous
value


The code fragment looks like:
--------------------------
                    if (strategy.reloadingRequired())
                    {
                        if (getLogger().isInfoEnabled())
                        {
                            getLogger().info("Reloading configuration. URL is " + getURL());
                        }
                        fireEvent(EVENT_RELOAD, null, getURL(), true);
                        setDetailEvents(false);
                        boolean autoSaveBak = this.isAutoSave(); // save the current state
                        this.setAutoSave(false); // deactivate autoSave to prevent information
loss
                        try
                        {
                            clear();
                            load();
                        }
                        finally
                        {
                                this.setAutoSave(autoSaveBak); // set autoSave to previous
value
                            setDetailEvents(true);
                        }
                        fireEvent(EVENT_RELOAD, null, getURL(), false);

                        // notify the strategy
                        strategy.reloadingPerformed();
                    }
--------------------------

I hope this is a valid fix. 

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