com.budjb.httprequests.HttpClientFactoryHolder Maven / Gradle / Ivy
/*
* Copyright 2016-2018 the original author or authors.
*
* 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 com.budjb.httprequests;
import java.util.Objects;
/**
* A holder class that is useful to contain an instance of {@link HttpClientFactory} and make it available to the rest
* of an application as a global singleton.
*
* It also serves to isolate the rest of the application from having to be aware of the specific HTTP client
* implementation, since the {@link HttpClientFactory} can be created and stored during an application's initialization,
* and classes that use this holder will no longer need to create a factory instance any time an {@link HttpClient} is
* required.
*
* This class is useful in applications that do not use Spring Framework, but for those applications that are using
* Spring Framework, a better option is to register the {@link HttpClientFactory} implementation as a bean that can be
* injected into other Spring beans. This holder effectively serves to provide global access to a factory object in
* the absence of Spring Framework bean injection.
*/
public class HttpClientFactoryHolder {
/**
* Singleton instance of the holder.
*/
private static final HttpClientFactoryHolder instance = new HttpClientFactoryHolder();
/**
* Instance of the HTTP client factory contained in the holder.
*/
private HttpClientFactory factory;
/**
* Returns the {@link HttpClientFactory} registered with the holder.
*
* An {@link IllegalStateException} will be thrown if there is no client registered.
*
* @return The {@link HttpClientFactory} registered with the holder.
*/
public static HttpClientFactory getHttpClientFactory() {
return Objects.requireNonNull(instance.factory, "no HttpClientFactory is registered with the HttpClientFactoryHolder");
}
/**
* Sets the {@link HttpClientFactory} registered with the holder.
*
* @param factory The {@link HttpClientFactory} to register with the holder.
*/
public static void setHttpClientFactory(HttpClientFactory factory) {
instance.factory = factory;
}
}