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https://issues.apache.org/jira/browse/BEANUTILS-450?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Oliver Heger updated BEANUTILS-450:
-----------------------------------
Assignee: (was: Oliver Heger)
> BeanUtilsBean.getInstance() pseudo-singleton causes problems with Java 7
> parallelized class loader
> --------------------------------------------------------------------------------------------------
>
> Key: BEANUTILS-450
> URL: https://issues.apache.org/jira/browse/BEANUTILS-450
> Project: Commons BeanUtils
> Issue Type: Bug
> Components: Bean / Property Utils, ConvertUtils & Converters
> Affects Versions: 1.7.0
> Environment: Java 7u25+, Windows 7 32-bit desktop environments
> Reporter: Matthew Hall
> Priority: Blocker
>
> From an email I sent to the BeanUtils users mailing list:
> We recently tracked a bug in our software that started showing up with Java 7
> back to an incompatibility between BeanUtilsBean.getInstance()
> pseudo-singleton instance model, Java 7’s parallelized class loader, and the
> fact that we were registering Converters with ConvertUtils inside of a static
> class-level block. As far as I’m able to tell, this wasn’t a problem in
> previous versions of Java because the class loader was not parallelized,
> meaning that the class loader that handled the registration of our converters
> was the same class loader that was in use when ConvertUtilsBean.getInstance()
> was invoked. Now, with Java 7, it seems that there is no guarantee that the
> class loader that executes the static block containing the Converter
> registration is the same one in use when ConvertUtilsBean.getInstance() is
> invoked, meaning that our custom Converters are not necessarily available
> everywhere they used to be.
> I’m writing to the list today to ask three things about this situation:
> 1. First off, is this the correct explanation for the reason that it seems
> we’re not guaranteed to have our custom Converters loaded in Java 7.
> 2. In order to ensure that a different class loader thread is not in use
> when the Converters are registered with ConvertUtils, we’ve moved this
> registration from a static class-level block into a user interface setup
> method that is executed before the Converters are used.
> 3. Given that Java 7 introduced parallelized class loading in the base
> ClassLoader and that BeanUtilsBean builds instances on a per-classloader
> basis, should this issue be raised to the BeanUtils developers?
> Below you’ll find some pseudocode that illustrates our situation:
> {code}
> public class UtilitiesClass {
> ...
> static {
> registerConverters();
> }
> public static void registerConverters() {
> ConvertUtils.register(new OurCustomColorConverter(),
> java.awt.Color.class);
> }
> ...
> }
> public class MainGUIClass {
> ...
> public static void main(String[] args) {
> MainGUIClass mainGui = new MainGUIClass();
> mainGui.setup();
> mainGui.show();
> }
> public void setup() {
> UIManager.setLookAndFeel(new LookAndFeelClass());
> }
> public void show() {
> ((OurLookAndFeelClass) UIManager.getLookAndFeel()).getColor();
> }
> ...
> }
> public class LookAndFeelClass extends LookAndFeel {
> ...
> public java.awt.Color getColor(String colorString) {
> return (java.awt.Color) ConvertUtils.convert("someValidColorString",
> java.awt.Color.class);
> }
> ...
> }
> {code}
> In the above example, the cast of the results of ConvertUtils.convert to
> Color in LookAndFeelClass.getColor(String) sometimes results in a runtime
> exception with the message “java.lang.String cannot be cast to
> java.awt.Color.”. This appears to be due to the fact that
> ConvertUtils.convert() fails over to the built-in String.class Converter if
> it cannot find a Converter for the specified class. In production
> environments, it was completely unpredictable as to when this would happen
> and what would make the problem go away.
> The fix we implemented was to move the registration of
> OurCustomColorConverter() from the static block inside of UtilitiesClass to
> the first line of MainGUIClass.setup(), before the LookAndFeel is loaded.
> Will this fix be sufficient, or does it still suffer from the thread issue,
> if that is indeed the root cause of the problem?
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