ivy settings classpath always creates new classloader when used with subant

[Derek Baum]

Hi,

I have a custom Ivy resolver that keeps a static cache because it is 
time-consuming to initialise.

However, this cache doesn't work in a multi-project build, because the 
ivysettings/classpath command is creating a new URLClassLoader for each 
subant iteration, so all static class fields are reset.

<ivysettings>

 <classpath file="${ivy.settings.dir}/sigil-ivy-plugin.jar" />

 <typedef name="sigil" classname="org.cauldron.bld.ivy.SigilResolver" />

 ...

</ivysettings>


I'm building multiple projects, using ivy:buildlist and subant, as in 
the Ivy multi-project example.

Each iteration of subant, causes IvySettings to reload.
IvySettings.classloader is thus null and so a new URLClassLoader is created.

I temporarily worked around this by loading my plugin at the same time 
as Ivy (i.e. not using settings/classpath), but I'd really like the 
setting/classpath method to work too.

One possible solution would be to add a "loaderRef" attribute to 
settings/classpath, similar to the Ant taskdef/typedef tasks, to make it 
use the same ClassLoader.

Alternatively, IvySettings could simply be changed to only create a new 
URLClassLoader if the list of URLs  has changed. I attach a simple patch 
to IvySettings.java that does this and seems to work OK.

If this is valid and useful, let me know and I'll raise it in Jira.

Thanks,

Derek













Index: src/java/org/apache/ivy/core/settings/IvySettings.java
===================================================================
--- src/java/org/apache/ivy/core/settings/IvySettings.java      (revision 
705243)
+++ src/java/org/apache/ivy/core/settings/IvySettings.java      (working copy)
@@ -644,13 +644,19 @@
         }
     }
 
+    private static Map loaderCache =  new HashMap();
+        
     private ClassLoader getClassLoader() {
         if (classloader == null) {
             if (classpathURLs.isEmpty()) {
                 classloader = Ivy.class.getClassLoader();
             } else {
-                classloader = new URLClassLoader((URL[]) classpathURLs
+                classloader = (ClassLoader) loaderCache.get(classpathURLs);
+                if (classloader == null) {
+                    classloader = new URLClassLoader((URL[]) classpathURLs
                         .toArray(new URL[classpathURLs.size()]), 
Ivy.class.getClassLoader());
+                    loaderCache.put(classpathURLs, classloader);
+                }
             }
         }
         return classloader;

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