jsinterop.annotations.JsFunction Maven / Gradle / Ivy
/*
* Copyright 2015 Google Inc.
*
* 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 jsinterop.annotations;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* Marks a type containing a Single Abstract Method (SAM) as eligible for automatic conversion into
* a JavaScript function.
*
* This enables lambda expressions to be passed directly to JavaScript as callbacks.
*
* However there are some additional limitations that are imposed to make this practical and
* efficient:
*
A class may not implement more than one @JsFunction type. This restriction allows the
* compiler to construct a one-to-one mapping to the JavaScript function generated and the SAM to be
* invoked in Java and to preserve referential equality.
* A JsFunction interface cannot extend any other interfaces.
* A JsFunction interface cannot have defender methods.
* A class that implements a @JsFunction type (directly or indirectly) cannot be a @JsType.
*
* As a best practice, we recommend marking @JsFunction interfaces also with @FunctionalInterface to
* get improved checking in IDEs.
*/
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
public @interface JsFunction {
}