1 files changed, 253 insertions, 0 deletions
diff --git a/sca-java-2.x/tags/2.0.1-RC1/modules/extensibility/src/main/java/org/apache/tuscany/sca/extensibility/ClassLoaderContext.java b/sca-java-2.x/tags/2.0.1-RC1/modules/extensibility/src/main/java/org/apache/tuscany/sca/extensibility/ClassLoaderContext.java
new file mode 100644
index 0000000000..598c897402
--- /dev/null
+++ b/sca-java-2.x/tags/2.0.1-RC1/modules/extensibility/src/main/java/org/apache/tuscany/sca/extensibility/ClassLoaderContext.java
@@ -0,0 +1,253 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.tuscany.sca.extensibility;
+
+import java.io.IOException;
+import java.net.URL;
+import java.security.PrivilegedAction;
+import java.security.PrivilegedActionException;
+import java.security.PrivilegedExceptionAction;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Enumeration;
+import java.util.List;
+
+import org.apache.tuscany.sca.extensibility.impl.ClassLoaderDelegate;
+
+/**
+ * A utility that controls context class loaders
+ * @tuscany.spi.extension.asclient
+ */
+public class ClassLoaderContext {
+    private ClassLoader classLoader;
+
+    /**
+     * Create a context with the parent classloader and a list of service types that can be discovered
+     * by the {@link ServiceDiscovery}
+     * @param parent
+     * @param discovery
+     * @param serviceTypes
+     */
+    public ClassLoaderContext(ClassLoader parent, ServiceDiscovery discovery, Class<?>... serviceTypes) {
+        this(parent, getClassLoaders(discovery, serviceTypes));
+    }
+
+    private ClassLoaderContext(ClassLoader parent, List<ClassLoader> delegates) {
+        List<ClassLoader> loaders = new ArrayList<ClassLoader>(delegates);
+        loaders.remove(parent);
+        if (delegates.isEmpty()) {
+            classLoader = parent;
+        } else {
+            classLoader = new ClassLoaderDelegate(parent, loaders);
+        }
+    }
+
+    /**
+     * Create a context that is visible to the parent classloader as well as the list of classloaders
+     * @param parent
+     * @param delegates
+     */
+    public ClassLoaderContext(ClassLoader parent, ClassLoader... delegates) {
+        this(parent, Arrays.asList(delegates));
+    }
+
+    /**
+     * Create a context with the parent classloader and a list of service types that can be discovered
+     * by the {@link ServiceDiscovery}
+     * @param parent
+     * @param discovery
+     * @param serviceTypes
+     */
+    public ClassLoaderContext(ClassLoader parent, ServiceDiscovery discovery, String... serviceTypes) {
+        this(parent, getClassLoaders(discovery, serviceTypes));
+    }
+
+    public <T> T doPrivileged(PrivilegedAction<T> action) {
+        ClassLoader tccl = Thread.currentThread().getContextClassLoader();
+        if (tccl != classLoader) {
+            Thread.currentThread().setContextClassLoader(classLoader);
+        }
+        try {
+            return action.run();
+        } finally {
+            if (tccl != classLoader) {
+                Thread.currentThread().setContextClassLoader(tccl);
+            }
+        }
+    }
+
+    public <T> T doPrivileged(PrivilegedExceptionAction<T> action) throws PrivilegedActionException {
+        ClassLoader tccl = Thread.currentThread().getContextClassLoader();
+        if (tccl != classLoader) {
+            Thread.currentThread().setContextClassLoader(classLoader);
+        }
+        try {
+            return action.run();
+        } catch (Exception e) {
+            throw new PrivilegedActionException(e);
+        } finally {
+            if (tccl != classLoader) {
+                Thread.currentThread().setContextClassLoader(tccl);
+            }
+        }
+    }
+
+    /**
+     * Set the thread context classloader (TCCL) to a classloader that delegates to a collection
+     * of classloaders
+     * @param parent The parent classloader
+     * @param delegates A list of classloaders to try
+     * @return The existing TCCL
+     */
+    public static ClassLoader setContextClassLoader(ClassLoader parent, ClassLoader... delegates) {
+        ClassLoaderContext context = new ClassLoaderContext(parent, delegates);
+        return context.setContextClassLoader();
+    }
+
+    /**
+     * Set the context classloader so that it can access the list of service providers
+     * @param parent The parent classloader
+     * @param serviceNames A list of service provider names
+     * @return The old TCCL if a new one is set, otherwise null
+     */
+    public static ClassLoader setContextClassLoader(ClassLoader parent,
+                                                    ServiceDiscovery discovery,
+                                                    String... serviceNames) {
+        ClassLoaderContext context = new ClassLoaderContext(parent, discovery, serviceNames);
+        return context.setContextClassLoader();
+    }
+
+    /**
+     * Set the context classloader so that it can access the list of service providers
+     * @param parent The parent classloader
+     * @param serviceNames A list of service provider names
+     * @return The old TCCL if a new one is set, otherwise null
+     */
+    public static ClassLoader setContextClassLoader(ClassLoader parent,
+                                                    ServiceDiscovery discovery,
+                                                    Class<?>... serviceTypes) {
+        ClassLoaderContext context = new ClassLoaderContext(parent, discovery, serviceTypes);
+        return context.setContextClassLoader();
+    }
+
+    public ClassLoader setContextClassLoader() {
+        ClassLoader tccl = Thread.currentThread().getContextClassLoader();
+        if (tccl != classLoader) {
+            Thread.currentThread().setContextClassLoader(classLoader);
+            return tccl;
+        } else {
+            return null;
+        }
+    }
+
+    private static ClassLoader getClassLoader(ServiceDiscovery discovery, String serviceProvider) {
+        try {
+            ServiceDeclaration sd = discovery.getServiceDeclaration(serviceProvider);
+            if (sd != null) {
+                try {
+                    if (sd.loadClass() != null) {
+                        return sd.loadClass().getClassLoader();
+                    } else {
+                        return new ClassLoaderImpl(sd);
+                    }
+                } catch (ClassNotFoundException e) {
+                    return new ClassLoaderImpl(sd);
+                }
+            }
+        } catch (Exception e) {
+            // Ignore
+        }
+        return null;
+    }
+
+    private static List<ClassLoader> getClassLoaders(ServiceDiscovery discovery, String... serviceNames) {
+        List<ClassLoader> loaders = new ArrayList<ClassLoader>();
+        for (String sp : serviceNames) {
+            ClassLoader loader = getClassLoader(discovery, sp);
+            if (loader != null) {
+                if (!loaders.contains(loader)) {
+                    loaders.add(loader);
+                }
+            }
+        }
+        ClassLoader tccl = discovery.getContextClassLoader();
+        if (!loaders.contains(tccl)) {
+            loaders.add(tccl);
+        }
+        return loaders;
+    }
+
+    private static ClassLoader getClassLoader(ServiceDiscovery discovery, Class<?> serviceType) {
+        try {
+            ServiceDeclaration sd = discovery.getServiceDeclaration(serviceType);
+            if (sd != null) {
+                return sd.loadClass().getClassLoader();
+            }
+        } catch (Exception e) {
+            // Ignore
+        }
+        return null;
+    }
+
+    private static List<ClassLoader> getClassLoaders(ServiceDiscovery discovery, Class<?>... serviceTypes) {
+        List<ClassLoader> loaders = new ArrayList<ClassLoader>();
+        for (Class<?> serviceType : serviceTypes) {
+            ClassLoader classLoader = getClassLoader(discovery, serviceType);
+            if (classLoader != null && !loaders.contains(classLoader)) {
+                loaders.add(classLoader);
+            }
+        }
+        ClassLoader tccl = discovery.getContextClassLoader();
+        if (!loaders.contains(tccl)) {
+            loaders.add(tccl);
+        }
+        return loaders;
+    }
+
+    public ClassLoader getClassLoader() {
+        return classLoader;
+    }
+
+    private static class ClassLoaderImpl extends ClassLoader {
+        private final ServiceDeclaration sd;
+
+        public ClassLoaderImpl(ServiceDeclaration sd) {
+            super();
+            this.sd = sd;
+        }
+
+        @Override
+        protected Class<?> findClass(String name) throws ClassNotFoundException {
+            return sd.loadClass(name);
+        }
+
+        @Override
+        protected URL findResource(String name) {
+            return sd.getResource(name);
+        }
+
+        @Override
+        protected Enumeration<URL> findResources(String name) throws IOException {
+            return sd.getResources(name);
+        }
+
+    }
+
+}