* Made sure ServerBootstrap accepts only ServerChannelFactory

* Validation first, state check later

src/main/java/org/jboss/netty/bootstrap/Bootstrap.java

@@ -100,13 +100,13 @@ public class Bootstrap {
      *         if the factory is already set
      */
     public void setFactory(ChannelFactory factory) {
+        if (factory == null) {
+            throw new NullPointerException("factory");
+        }
         if (this.factory != null) {
             throw new IllegalStateException(
                     "factory can't change once set.");
         }
-        if (factory == null) {
-            throw new NullPointerException("factory");
-        }
         this.factory = factory;
     }
 

src/main/java/org/jboss/netty/bootstrap/ServerBootstrap.java

@@ -46,6 +46,7 @@ import org.jboss.netty.channel.ChannelPipelineFactory;
 import org.jboss.netty.channel.ChannelStateEvent;
 import org.jboss.netty.channel.ChildChannelStateEvent;
 import org.jboss.netty.channel.ExceptionEvent;
+import org.jboss.netty.channel.ServerChannelFactory;
 import org.jboss.netty.channel.SimpleChannelHandler;
 
 /**
@@ -166,6 +167,20 @@ public class ServerBootstrap extends Bootstrap {
         super(channelFactory);
     }
 
+    @Override
+    public void setFactory(ChannelFactory factory) {
+        if (factory == null) {
+            throw new NullPointerException("factory");
+        }
+        if (!(factory instanceof ServerChannelFactory)) {
+            throw new IllegalArgumentException(
+                    "factory must be a " +
+                    ServerChannelFactory.class.getSimpleName() + ": " +
+                    factory.getClass());
+        }
+        super.setFactory(factory);
+    }
+
     /**
      * Returns an optional {@link ChannelHandler} which intercepts an event
      * of a new bound server-side channel which accepts incoming connections.