Tweaks to Extension API based on review (#6690)

5 files changed, 45 insertions, 10 deletions

diff --git a/src/com/vaadin/terminal/AbstractExtension.java b/src/com/vaadin/terminal/AbstractExtension.java
index 353db85a18..0809d8ee99 100644
--- a/src/com/vaadin/terminal/AbstractExtension.java
+++ b/src/com/vaadin/terminal/AbstractExtension.java
@@ -8,23 +8,30 @@ import com.vaadin.terminal.gwt.server.ClientConnector;
 
 public abstract class AbstractExtension extends AbstractClientConnector
         implements Extension {
+    private boolean previouslyAttached = false;
 
     protected Class<? extends ClientConnector> getAcceptedParentType() {
         return ClientConnector.class;
     }
 
-    protected void attachTo(AbstractClientConnector parent) {
-        parent.addExtension(this);
+    protected void extend(AbstractClientConnector target) {
+        target.addExtension(this);
     }
 
     @Override
     public void setParent(ClientConnector parent) {
+        if (previouslyAttached && parent != null) {
+            throw new IllegalStateException(
+                    "An extension can not be set to extend a new target after getting detached from the previous.");
+        }
+
         Class<? extends ClientConnector> acceptedParentType = getAcceptedParentType();
         if (parent == null || acceptedParentType.isInstance(parent)) {
             super.setParent(parent);
+            previouslyAttached = true;
         } else {
             throw new IllegalArgumentException(getClass().getName()
-                    + " can only be attached to parents of type "
+                    + " can only be attached to targets of type "
                     + acceptedParentType.getName() + " but attach to "
                     + parent.getClass().getName() + " was attempted.");
         }
diff --git a/src/com/vaadin/terminal/gwt/client/extensions/AbstractExtensionConnector.java b/src/com/vaadin/terminal/gwt/client/extensions/AbstractExtensionConnector.java
new file mode 100644
index 0000000000..bcefcf05cb
--- /dev/null
+++ b/src/com/vaadin/terminal/gwt/client/extensions/AbstractExtensionConnector.java
@@ -0,0 +1,27 @@
+/* 
+@VaadinApache2LicenseForJavaFiles@
+ */
+
+package com.vaadin.terminal.gwt.client.extensions;
+
+import com.vaadin.terminal.gwt.client.ServerConnector;
+import com.vaadin.terminal.gwt.client.ui.AbstractConnector;
+
+public abstract class AbstractExtensionConnector extends AbstractConnector {
+    @Override
+    public void setParent(ServerConnector parent) {
+        ServerConnector oldParent = getParent();
+        if (oldParent != null && oldParent != parent) {
+            throw new IllegalStateException(
+                    "An extension can not be moved from one parent to another.");
+        }
+
+        super.setParent(parent);
+
+        extend(parent);
+    }
+
+    protected void extend(ServerConnector target) {
+        // Default does nothing
+    }
+}
diff --git a/src/com/vaadin/terminal/gwt/client/extensions/javascriptmanager/JavascriptManagerConnector.java b/src/com/vaadin/terminal/gwt/client/extensions/javascriptmanager/JavascriptManagerConnector.java
index 979a6d22c4..a74cd762de 100644
--- a/src/com/vaadin/terminal/gwt/client/extensions/javascriptmanager/JavascriptManagerConnector.java
+++ b/src/com/vaadin/terminal/gwt/client/extensions/javascriptmanager/JavascriptManagerConnector.java
@@ -12,12 +12,12 @@ import com.google.gwt.core.client.JsArray;
 import com.google.gwt.json.client.JSONArray;
 import com.vaadin.terminal.gwt.client.communication.MethodInvocation;
 import com.vaadin.terminal.gwt.client.communication.StateChangeEvent;
-import com.vaadin.terminal.gwt.client.ui.AbstractConnector;
+import com.vaadin.terminal.gwt.client.extensions.AbstractExtensionConnector;
 import com.vaadin.terminal.gwt.client.ui.Connect;
 import com.vaadin.ui.JavascriptManager;
 
 @Connect(JavascriptManager.class)
-public class JavascriptManagerConnector extends AbstractConnector {
+public class JavascriptManagerConnector extends AbstractExtensionConnector {
     private Set<String> currentNames = new HashSet<String>();
 
     @Override
diff --git a/src/com/vaadin/terminal/gwt/server/ClientConnector.java b/src/com/vaadin/terminal/gwt/server/ClientConnector.java
index 359e112738..860627a352 100644
--- a/src/com/vaadin/terminal/gwt/server/ClientConnector.java
+++ b/src/com/vaadin/terminal/gwt/server/ClientConnector.java
@@ -3,7 +3,7 @@
  */
 package com.vaadin.terminal.gwt.server;
 
-import java.util.Iterator;
+import java.util.Collection;
 import java.util.List;
 
 import com.vaadin.terminal.AbstractClientConnector;
@@ -137,7 +137,7 @@ public interface ClientConnector extends Connector, RpcTarget {
      */
     public void detach();
 
-    public Iterator<Extension> getExtensionIterator();
+    public Collection<Extension> getExtensions();
 
     public void removeExtension(Extension extension);
 }
diff --git a/src/com/vaadin/terminal/gwt/server/DragAndDropService.java b/src/com/vaadin/terminal/gwt/server/DragAndDropService.java
index 68fb87a986..819be7e671 100644
--- a/src/com/vaadin/terminal/gwt/server/DragAndDropService.java
+++ b/src/com/vaadin/terminal/gwt/server/DragAndDropService.java
@@ -4,7 +4,8 @@
 package com.vaadin.terminal.gwt.server;
 
 import java.io.PrintWriter;
-import java.util.Iterator;
+import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.logging.Logger;
@@ -275,9 +276,9 @@ public class DragAndDropService implements VariableOwner, ClientConnector {
 
     }
 
-    public Iterator<Extension> getExtensionIterator() {
+    public Collection<Extension> getExtensions() {
         // TODO Auto-generated method stub
-        return null;
+        return Collections.emptySet();
     }
 
     public void removeExtension(Extension extension) {