Add a method to ServiceDiscovery to set context classloader for service providers in OSGi

git-svn-id: http://svn.us.apache.org/repos/asf/tuscany@802470 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 122 insertions, 0 deletions

diff --git a/java/sca/modules/extensibility/src/main/java/org/apache/tuscany/sca/extensibility/ServiceDiscovery.java b/java/sca/modules/extensibility/src/main/java/org/apache/tuscany/sca/extensibility/ServiceDiscovery.java
index 70274752e4..e92655146c 100644
--- a/java/sca/modules/extensibility/src/main/java/org/apache/tuscany/sca/extensibility/ServiceDiscovery.java
+++ b/java/sca/modules/extensibility/src/main/java/org/apache/tuscany/sca/extensibility/ServiceDiscovery.java
@@ -20,12 +20,16 @@
 package org.apache.tuscany.sca.extensibility;
 
 import java.io.IOException;
+import java.net.URL;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Comparator;
+import java.util.Enumeration;
+import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Set;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
@@ -185,5 +189,123 @@ public final class ServiceDiscovery implements ServiceDiscoverer {
     public ClassLoader getContextClassLoader() {
         return discoverer.getContextClassLoader();
     }
+    
+    private static class ClassLoaderDelegate extends ClassLoader {
+        private final List<ClassLoader> classLoaders = new ArrayList<ClassLoader>();
+
+        /**
+         * @param parent The parent classloaders
+         * @param loaders A list of classloaders to be used to load classes or resources
+         */
+        public ClassLoaderDelegate(ClassLoader parent, Collection<ClassLoader> loaders) {
+            super(parent);
+            if (loaders != null) {
+                for (ClassLoader cl : loaders) {
+                    if (cl != null && cl != parent && !classLoaders.contains(cl)) {
+                        this.classLoaders.add(cl);
+                    }
+                }
+            }
+        }
+
+        @Override
+        protected Class<?> findClass(String className) throws ClassNotFoundException {
+            for (ClassLoader parent : classLoaders) {
+                try {
+                    return parent.loadClass(className);
+                } catch (ClassNotFoundException e) {
+                    continue;
+                }
+            }
+            throw new ClassNotFoundException(className);
+        }
+
+        @Override
+        protected URL findResource(String resName) {
+            for (ClassLoader parent : classLoaders) {
+                URL url = parent.getResource(resName);
+                if (url != null) {
+                    return url;
+                }
+            }
+            return null;
+        }
+
+        @Override
+        protected Enumeration<URL> findResources(String resName) throws IOException {
+            Set<URL> urlSet = new HashSet<URL>();
+            for (ClassLoader parent : classLoaders) {
+                Enumeration<URL> urls = parent.getResources(resName);
+                if (urls != null) {
+                    while (urls.hasMoreElements()) {
+                        urlSet.add(urls.nextElement());
+                    }
+                }
+            }
+            return Collections.enumeration(urlSet);
+        }
+    }
+
+    private ClassLoader getClassLoader(String serviceProvider) {
+        try {
+            ServiceDeclaration sd = getServiceDeclaration(serviceProvider);
+            if (sd != null) {
+                return sd.loadClass().getClassLoader();
+            }
+        } catch (Exception e) {
+            // Ignore
+        }
+        return null;
+    }
+    
+    /**
+     * Set the context classloader so that it can access the list of service providers
+     * @param parent The parent classloader
+     * @param serviceProviders A list of service provider names
+     * @return The old TCCL if a new one is set, otherwise null
+     */
+    public ClassLoader setContextClassLoader(ClassLoader parent, String... serviceProviders) {
+        List<ClassLoader> loaders = getClassLoaders(serviceProviders);
+        return setContextClassLoader(parent, loaders.toArray(new ClassLoader[loaders.size()]));
+    }
+
+    private List<ClassLoader> getClassLoaders(String... serviceProviders) {
+        List<ClassLoader> loaders = new ArrayList<ClassLoader>();
+        for (String sp : serviceProviders) {
+            ClassLoader loader = getClassLoader(sp);
+            if (loader != null) {
+                if (!loaders.contains(loader)) {
+                    loaders.add(loader);
+                }
+            }
+        }
+        return loaders;
+    }
+
+    public ClassLoader setContextClassLoader(ClassLoader parent, ClassLoader... delegates) {
+        ClassLoader tccl = Thread.currentThread().getContextClassLoader();
+        List<ClassLoader> loaders = new ArrayList<ClassLoader>();
+        for (ClassLoader loader : delegates) {
+            if (loader != null && loader != tccl && loader != parent) {
+                if (!loaders.contains(loader)) {
+                    loaders.add(loader);
+                }
+            }
+        }
+        if (!loaders.isEmpty()) {
+            ClassLoader cl = getContextClassLoader();
+            if (cl != parent) {
+                loaders.add(cl);
+            }
+            if (tccl != parent) {
+                loaders.add(tccl);
+            }
+            ClassLoader newTccl = new ClassLoaderDelegate(parent, loaders);
+            Thread.currentThread().setContextClassLoader(newTccl);
+            return tccl;
+        } else {
+            return null;
+        }
+    }
 
 }