org.arquillian.spacelift.ImplementationLoader Maven / Gradle / Ivy
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* Copyright 2010, Red Hat Middleware LLC, and individual contributors
* by the @authors tag. See the copyright.txt in the distribution for a
* full listing of individual contributors.
*
* 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.arquillian.spacelift;
/**
* Utility capable of loading interface implementations available on classpath indirectly.
*
* @author ALR
*/
public final class ImplementationLoader {
private static final String CLASS_NAME_SERVICELOADER = "org.arquillian.spacelift.loader.ServiceLoader";
private static final String CLASS_NAME_SPISERVICELOADER = "org.arquillian.spacelift.loader.SpiServiceLoader";
private static final String CLASS_NAME_SERVICEREGISTRY = "org.arquillian.spacelift.loader.ServiceRegistry";
private static final String METHOD_NAME_ONLY_ONE = "onlyOne";
private static final String METHOD_NAME_REGISTER = "register";
/**
* Internal constructor; not to be called
*/
private ImplementationLoader() {
throw new UnsupportedOperationException("No instances permitted");
}
/**
* Creates a new instance of the specified type using the {@link Thread} Context
* {@link ClassLoader}. Will consult a configuration file visible to the {@link Thread} Context {@link ClassLoader}
* named
* "META-INF/services/$fullyQualfiedClassName" which should contain a fully qualified name of the implementation.
*
* The implementation class name must have a no-arg constructor.
*
* @param interfaceClass
* interface to find implementation for
*
* @return Implementation of interface class
*
* @throws IllegalArgumentException
* if {@code interfaceClass} is null
*/
static INTERFACE implementationOf(
final Class interfaceClass) throws IllegalArgumentException {
return implementationOf(interfaceClass, SecurityActions.getThreadContextClassLoader());
}
/**
* Creates a new instance of the specified user view type using the specified {@link ClassLoader}.
* Will consult a configuration file visible to the specified {@link ClassLoader} named
* "META-INF/services/$fullyQualfiedClassName" which should contain a fully qualified name of the implementation.
*
* The implementation class name must have a no-arg constructor.
*/
static INTERFACE implementationOf(
final Class factoryClass, final ClassLoader cl) {
assert factoryClass != null : "user view class must be specified";
assert cl != null : "ClassLoader must be specified";
// get SPI service loader
final Object spiServiceLoader = new Invokable(cl, CLASS_NAME_SPISERVICELOADER)
.invokeConstructor(new Class[] {ClassLoader.class}, new Object[] {cl});
// return service loader implementation
final Object serviceLoader = new Invokable(cl, CLASS_NAME_SPISERVICELOADER).invokeMethod(METHOD_NAME_ONLY_ONE,
new Class[] {Class.class, Class.class}, spiServiceLoader,
new Object[] {Invokable.loadClass(cl, CLASS_NAME_SPISERVICELOADER), spiServiceLoader.getClass()});
// get registry
final Object serviceRegistry = new Invokable(cl, CLASS_NAME_SERVICEREGISTRY).invokeConstructor(
new Class[] {Invokable.loadClass(cl, CLASS_NAME_SERVICELOADER)},
new Object[] {serviceLoader});
// register itself
new Invokable(cl, serviceRegistry.getClass()).invokeMethod(METHOD_NAME_REGISTER,
new Class[] {serviceRegistry.getClass()}, null, new Object[] {serviceRegistry});
Object userViewObject = new Invokable(cl, serviceRegistry.getClass()).invokeMethod(METHOD_NAME_ONLY_ONE,
new Class[] {Class.class}, serviceRegistry, new Object[] {factoryClass});
return factoryClass.cast(userViewObject);
}
}