Enable lazy loading of ServletHost extensions

git-svn-id: http://svn.us.apache.org/repos/asf/tuscany@822343 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 150 insertions, 1 deletions

diff --git a/java/sca/modules/host-http/src/main/java/org/apache/tuscany/sca/host/http/DefaultServletHostExtensionPoint.java b/java/sca/modules/host-http/src/main/java/org/apache/tuscany/sca/host/http/DefaultServletHostExtensionPoint.java
index 5e6de0b29b..7573141656 100644
--- a/java/sca/modules/host-http/src/main/java/org/apache/tuscany/sca/host/http/DefaultServletHostExtensionPoint.java
+++ b/java/sca/modules/host-http/src/main/java/org/apache/tuscany/sca/host/http/DefaultServletHostExtensionPoint.java
@@ -19,27 +19,176 @@
 
 package org.apache.tuscany.sca.host.http;
 
+import java.io.IOException;
+import java.lang.reflect.Constructor;
+import java.net.URL;
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.List;
 
+import javax.servlet.RequestDispatcher;
+import javax.servlet.Servlet;
+
+import org.apache.tuscany.sca.core.ExtensionPointRegistry;
+import org.apache.tuscany.sca.core.LifeCycleListener;
+import org.apache.tuscany.sca.extensibility.ServiceDeclaration;
+import org.apache.tuscany.sca.extensibility.ServiceDiscovery;
+
 /**
  * Default implementation of a Servlet host extension point.
  * 
  * @version $Rev$ $Date$
  */
-public class DefaultServletHostExtensionPoint implements ServletHostExtensionPoint {
+public class DefaultServletHostExtensionPoint implements ServletHostExtensionPoint, LifeCycleListener {
 
     private List<ServletHost> servletHosts = new ArrayList<ServletHost>();
+    private boolean loaded;
+
+    private ExtensionPointRegistry registry;
+
+    public DefaultServletHostExtensionPoint(ExtensionPointRegistry registry) {
+        this.registry = registry;
+    }
 
     public void addServletHost(ServletHost servletHost) {
         servletHosts.add(servletHost);
+        if (servletHost instanceof LifeCycleListener) {
+            ((LifeCycleListener)servletHost).start();
+        }
     }
 
     public void removeServletHost(ServletHost servletHost) {
         servletHosts.remove(servletHost);
+        if (servletHost instanceof LifeCycleListener) {
+            ((LifeCycleListener)servletHost).stop();
+        }
     }
 
     public List<ServletHost> getServletHosts() {
+        loadServletHosts();
         return servletHosts;
     }
+
+    private synchronized void loadServletHosts() {
+        if (loaded)
+            return;
+
+        // Get the databinding service declarations
+        Collection<ServiceDeclaration> sds;
+        try {
+            sds = ServiceDiscovery.getInstance().getServiceDeclarations(ServletHost.class, true);
+        } catch (IOException e) {
+            throw new IllegalStateException(e);
+        }
+
+        // Load data bindings
+        for (ServiceDeclaration sd : sds) {
+            // Create a data binding wrapper and register it
+            ServletHost servletHost = new LazyServletHost(sd);
+            addServletHost(servletHost);
+        }
+
+        loaded = true;
+    }
+
+    /**
+     * A data binding facade allowing data bindings to be lazily loaded and
+     * initialized.
+     */
+    private class LazyServletHost implements ServletHost, LifeCycleListener {
+        private ServiceDeclaration sd;
+        private ServletHost host;
+
+        /**
+         * @param sd
+         */
+        public LazyServletHost(ServiceDeclaration sd) {
+            super();
+            this.sd = sd;
+        }
+
+        private synchronized ServletHost getServletHost() {
+            if (host == null) {
+                try {
+                    Class<?> cls = sd.loadClass();
+                    Constructor<?> ctor = null;
+                    try {
+                        ctor = cls.getConstructor(ExtensionPointRegistry.class);
+                        host = (ServletHost)ctor.newInstance(registry);
+                    } catch (NoSuchMethodException e) {
+                        ctor = cls.getConstructor();
+                        host = (ServletHost)ctor.newInstance();
+                    }
+                    if(host instanceof LifeCycleListener) {
+                        ((LifeCycleListener) host).start();
+                    }
+                } catch (Throwable e) {
+                    throw new IllegalStateException(e);
+                }
+            }
+            return host;
+        }
+
+        public void addServletMapping(String uri, Servlet servlet) throws ServletMappingException {
+            getServletHost().addServletMapping(uri, servlet);
+        }
+
+        public String getContextPath() {
+            return getServletHost().getContextPath();
+        }
+
+        public int getDefaultPort() {
+            return getServletHost().getDefaultPort();
+        }
+
+        public RequestDispatcher getRequestDispatcher(String uri) throws ServletMappingException {
+            return getServletHost().getRequestDispatcher(uri);
+        }
+
+        public Servlet getServletMapping(String uri) throws ServletMappingException {
+            return getServletHost().getServletMapping(uri);
+        }
+
+        public URL getURLMapping(String uri) {
+            return getServletHost().getURLMapping(uri);
+        }
+
+        public Servlet removeServletMapping(String uri) throws ServletMappingException {
+            return getServletHost().removeServletMapping(uri);
+        }
+
+        public void setAttribute(String name, Object value) {
+            getServletHost().setAttribute(name, value);
+        }
+
+        public void setContextPath(String path) {
+            getServletHost().setContextPath(path);
+        }
+
+        public void setDefaultPort(int port) {
+            getServletHost().setDefaultPort(port);
+        }
+
+        public void start() {
+        }
+
+        public void stop() {
+            if (host instanceof LifeCycleListener) {
+                ((LifeCycleListener)host).stop();
+            }
+        }
+    }
+
+    public void start() {
+    }
+
+    public void stop() {
+        for (ServletHost host : servletHosts) {
+            if (host instanceof LifeCycleListener) {
+                ((LifeCycleListener)host).stop();
+            }
+        }
+        servletHosts.clear();
+        registry = null;
+    }
 }