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FallbackHandler.java
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FallbackHandler.java
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/*
* Copyright (c) 2017 Contributors to the Eclipse Foundation
*
* See the NOTICE file(s) distributed with this work for additional
* information regarding copyright ownership.
*
* 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 org.eclipse.microprofile.faulttolerance;
/**
* The handler instance used by the container to service a fallback invocation is a non-contextual instance created
* using the CDI SPI. The instance exists to service a single invocation only. The type parameter of the handler
* instance must be assignable to the return type of the method, where the {@link Fallback} is specified. The container
* must ensure this type safety. Otherwise, {@link IllegalArgumentException} should be thrown.
* <h2>Usage</h2>
*
* <pre>
* public class MyService {
* @Inject
* OtherService otherService;
*
* @Timeout(3000)
* @Fallback(MyFallback.class)
* Long getAmount() {
* return otherService.getAmount() * 2;
* }
* }
* </pre>
*
* The fallback handler implementation is shown below. The type parameter must be assignable to {@link Long}.
*
* <pre>
* public class MyFallback implements FallbackHandler<Long> {
* Long handle(ExecutionContext context) {
* return 42;
* }
* }
* </pre>
*
* @author <a href="mailto:emijiang@uk.ibm.com">Emily Jiang</a>
* @author Ken Finnigan
*
*/
public interface FallbackHandler<T> {
/**
* Handle the previous calling failure and then call alternative methods or perform any alternative operations.
*
* @param context
* the execution context
*
* @return the result of the fallback
*/
T handle(ExecutionContext context);
}