1 files changed, 177 insertions, 0 deletions
diff --git a/sca-java-1.x/tags/java-stable-20060304/sca/common/src/main/java/org/apache/tuscany/common/discovery/util/ServiceProviderRegistry.java b/sca-java-1.x/tags/java-stable-20060304/sca/common/src/main/java/org/apache/tuscany/common/discovery/util/ServiceProviderRegistry.java
new file mode 100644
index 0000000000..65ede08a32
--- /dev/null
+++ b/sca-java-1.x/tags/java-stable-20060304/sca/common/src/main/java/org/apache/tuscany/common/discovery/util/ServiceProviderRegistry.java
@@ -0,0 +1,177 @@
+/**
+ *
+ *  Copyright 2005 The Apache Software Foundation or its licensors, as applicable.
+ *
+ *  Licensed 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.common.discovery.util;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.net.URL;
+import java.security.AccessController;
+import java.security.PrivilegedAction;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Enumeration;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.WeakHashMap;
+
+import org.apache.tuscany.common.io.util.FixedURLInputStream;
+
+//FIXME Port to 1.5 collections
+
+/**
+ * A Registry for service  providers defined using the
+ * <a href="http://java.sun.com/j2se/1.5.0/docs/guide/jar/jar.html#Service%20Provider">JAR service provider mechanism</a>.
+ *
+ */
+public class ServiceProviderRegistry {
+
+    private Map registry = Collections.synchronizedMap(new WeakHashMap());
+
+    private final static ServiceProviderRegistry instance = new ServiceProviderRegistry();
+
+    /**
+     * Constructor.
+     */
+    public ServiceProviderRegistry() {
+        super();
+    }
+
+    /**
+     * @return Returns the instance.
+     */
+    public static ServiceProviderRegistry getInstance() {
+        return instance;
+    }
+
+    /**
+     * Get the available providers of a given type.
+     *
+     * @param clazz
+     * @return
+     */
+    public List getServiceProviders(final Class clazz) {
+        List providers = (List) registry.get(clazz);
+        if (providers != null)
+            return providers;
+
+        providers = (List) AccessController.doPrivileged(new PrivilegedAction() {
+            public Object run() {
+                return loadServiceProviders(clazz);
+            }
+        });
+
+        registry.put(clazz, providers);
+        return providers;
+    }
+
+    /**
+     * Get an provider of a given type.
+     *
+     * @param clazz
+     * @return
+     */
+    public Object getServiceProvider(Class clazz) {
+        List providers = getServiceProviders(clazz);
+        if (providers.isEmpty())
+            return null;
+        else {
+            return providers.get(0);
+        }
+    }
+
+    /**
+     * Registers an provider programatically
+     *
+     * @param clazz
+     * @param provider
+     */
+    public void registerServiceProvider(Class clazz, Object provider) {
+        getServiceProviders(clazz).add(provider);
+    }
+
+    /**
+     * Load providers of the given type
+     *
+     * @param clazz
+     * @return
+     */
+    private List loadServiceProviders(Class clazz) {
+        List classNames = new ArrayList();
+
+        // First look for a system property named <SPI className>
+        String className = System.getProperty(clazz.getName());
+        if (className != null)
+            classNames.add(className);
+
+        //	 Find all the class names mentioned in all the META-INF/services/<SPI className>
+        ClassLoader loader = Thread.currentThread().getContextClassLoader();
+        try {
+            Enumeration files = loader.getResources("META-INF/services/" + clazz.getName());
+            while (files.hasMoreElements()) {
+                URL url = (URL) files.nextElement();
+                readClassNames(url, classNames);
+            }
+        } catch (IOException e) {
+        }
+
+        // Instantiate an provider for each of the named classes
+        List providers = new ArrayList();
+        Iterator i = classNames.iterator();
+        while (i.hasNext()) {
+            String name = (String) i.next();
+            try {
+                Class providerClass = Class.forName(name, true, loader);
+                providers.add(providerClass.newInstance());
+            } catch (Exception e) {
+                // Ignore ClassNotFoundException
+            }
+        }
+        return providers;
+    }
+
+    /**
+     * Read class names from the given URL.
+     * @param url
+     * @param classNames
+     * @throws IOException
+     */
+    private void readClassNames(URL url, List classNames) throws IOException {
+        InputStream is = new FixedURLInputStream(url);
+        try {
+            BufferedReader in = new BufferedReader(new InputStreamReader(is, "UTF-8"));
+            String inputLine = null;
+            while ((inputLine = in.readLine()) != null) {
+                int i = inputLine.indexOf('#');
+                if (i >= 0) {
+                    inputLine = inputLine.substring(0, i);
+                }
+                inputLine = inputLine.trim();
+                if (inputLine.length() > 0) {
+                    if (!classNames.contains(inputLine)) {
+                        classNames.add(inputLine);
+                    }
+                }
+            }
+        } finally {
+            is.close();
+		}
+	}
+
+}