gwtproject / gwt-event

GWT Events

A future-proof port of the com.google.web.bindery.event.Event GWT module, with no dependency on gwt-user (besides the Java Runtime Emulation), to prepare for GWT 3 / J2Cl.

Also features a port of com.google.gwt.event.logical.LogicalEvent, and compatibility layers, in the form of a partial port of com.google.gwt.event.Event as well as a bridge between this new library and the gwt-user modules.

All modules can be used on client-side, server-side, or Android.

Migrating from com.google.web.bindery.event.Event

1. Add the dependency to your build.

   For Maven:

   <dependency>
     <groupId>org.gwtproject.event</groupId>
     <artifactId>gwt-event</artifactId>
     <version>${gwtEventVersion}</version>
   </dependency>

   For Gradle:

   implementation("org.gwtproject.event:gwt-event:${gwtEventVersion}")

2. Update your GWT module to use

   <inherits name="org.gwtproject.event.Event" />

   (either change from com.google.web.bindery.event.Event, or add it if you inherited it transitively from another GWT module)

3. Change your imports in your Java source files:

   import org.gwtproject.event.shared.Event;
   import org.gwtproject.event.shared.EventBus;
   import org.gwtproject.event.shared.HandlerRegistration;

Use the compatibility bridge

The org.gwtproject.event.compat.EventCompat module provides a CompatEventBus class that wraps an org.gwtproject.event.EventBus as a com.google.gwt.event.shared.EventBus. This can be especially useful to start migrating to org.gwtproject.event.Event without being blocked by libraries still using com.google.web.bindery.event.Event or com.google.gwt.event.Event.

1. Add the dependency to your build.

   For Maven:

   <dependency>
     <groupId>org.gwtproject.event</groupId>
     <artifactId>gwt-event-compat</artifactId>
     <version>${gwtEventVersion}</version>
   </dependency>

   For Gradle:

   implementation("org.gwtproject.event:gwt-event-compat:${gwtEventVersion}")

2. Update your GWT module to use

   <inherits name="org.gwtproject.event.compat.EventCompat" />

3. Wrap an EventBus within a CompatEventBus whenever you need it; a CompatEventBus is very lightweight, create as many as you need.

While this is mostly equivalent to having two separate event buses, given that events aren't compatible with each others, the fact CompatEventBus can wrap any org.gwtproject.event.shared.EventBus means that, for instance, you only need one CountingEventBus, and a ResettableEventBus's removeHandler will remove all handlers added to either the wrapped bus or the CompatEventBus (and supports any other use-case where you have a specific EventBus).

Internally, CompatEventBus records a mapping between the com.google.web.bindery.event.shared.Event.Types and (internal) org.gwtproject.event.shared.Event.Types. This mapping is shared by all CompatEventBus instances, meaning that you can wrap your EventBuses as close as where you need it, and two CompatEventBuses wrapping the same EventBus will happily dispatch events to each other (through the shared bus they wrap).

Migrating from com.google.gwt.event.logical.LogicalEvent

1. Add the dependency to your build.

   For Maven:

   <dependency>
     <groupId>org.gwtproject.event</groupId>
     <artifactId>gwt-logical-event</artifactId>
     <version>${gwtEventVersion}</version>
   </dependency>

   For Gradle:

   implementation("org.gwtproject.event:gwt-logical-event:${gwtEventVersion}")

2. Update your GWT module to use

   <inherits name="org.gwtproject.event.logical.LogicalEvent" />

   (either change from com.google.gwt.event.logical.LogicalEvent, or add it if you inherited it transitively from another GWT module)

3. Change your imports in your Java source files from com.google.gwt.event.logical.* to org.gwtproject.event.logical.*

Migrating from com.google.gwt.event.Event

You should first migrate to com.google.web.bindery.event.Event then follow the steps above. However, GwtEvent and EventHandler are provided to make the migration easier (i.e. so you can first migrate away from gwt-user and then refactor your code from GwtEvent to Event).

1. Add the dependency to your build.

   For Maven:

   <dependency>
     <groupId>org.gwtproject.event</groupId>
     <artifactId>gwt-event-legacy</artifactId>
     <version>${gwtEventVersion}</version>
   </dependency>

   For Gradle:

   implementation("org.gwtproject.event:gwt-event-legacy:${gwtEventVersion}")

2. Update your GWT module to use

   <inherits name="org.gwtproject.event.legacy.EventLegacy" />

   (either change from com.google.gwt.event.Event, or add it if you inherited it transitively from another GWT module)

3. Change your imports in your Java source files:

   import org.gwtproject.event.legacy.shared.EventHandler;
   import org.gwtproject.event.legacy.shared.GwtEvent;