/*
* Copyright (C) 2007 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 org.elasticsearch.common.inject.assistedinject;
import org.elasticsearch.common.inject.ConfigurationException;
import org.elasticsearch.common.inject.Inject;
import org.elasticsearch.common.inject.Injector;
import org.elasticsearch.common.inject.Key;
import org.elasticsearch.common.inject.Provider;
import org.elasticsearch.common.inject.TypeLiteral;
import org.elasticsearch.common.inject.internal.Errors;
import org.elasticsearch.common.inject.spi.Dependency;
import org.elasticsearch.common.inject.spi.HasDependencies;
import org.elasticsearch.common.inject.spi.Message;
import java.lang.annotation.Annotation;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import static java.util.Collections.emptyMap;
import static java.util.Collections.singleton;
import static java.util.Collections.unmodifiableSet;
/**
* Provides a factory that combines the caller's arguments with injector-supplied values to
* construct objects.
* <h3>Defining a factory</h3>
* Create an interface whose methods return the constructed type, or any of its supertypes. The
* method's parameters are the arguments required to build the constructed type.
* <pre>public interface PaymentFactory {
* Payment create(Date startDate, Money amount);
* }</pre>
* You can name your factory methods whatever you like, such as <i>create</i>, <i>createPayment</i>
* or <i>newPayment</i>.
* <h3>Creating a type that accepts factory parameters</h3>
* {@code constructedType} is a concrete class with an {@literal @}{@link Inject}-annotated
* constructor. In addition to injector-supplied parameters, the constructor should have
* parameters that match each of the factory method's parameters. Each factory-supplied parameter
* requires an {@literal @}{@link Assisted} annotation. This serves to document that the parameter
* is not bound by your application's modules.
* <pre>public class RealPayment implements Payment {
* {@literal @}Inject
* public RealPayment(
* CreditService creditService,
* AuthService authService,
* <strong>{@literal @}Assisted Date startDate</strong>,
* <strong>{@literal @}Assisted Money amount</strong>) {
* ...
* }
* }</pre>
* Any parameter that permits a null value should also be annotated {@code @Nullable}.
* <h3>Configuring factories</h3>
* In your {@link org.elasticsearch.common.inject.Module module}, bind the factory interface to the returned
* factory:
* <pre>bind(PaymentFactory.class).toProvider(
* FactoryProvider.newFactory(PaymentFactory.class, RealPayment.class));</pre>
* As a side-effect of this binding, Guice will inject the factory to initialize it for use. The
* factory cannot be used until the injector has been initialized.
* <h3>Using the factory</h3>
* Inject your factory into your application classes. When you use the factory, your arguments
* will be combined with values from the injector to construct an instance.
* <pre>public class PaymentAction {
* {@literal @}Inject private PaymentFactory paymentFactory;
* public void doPayment(Money amount) {
* Payment payment = paymentFactory.create(new Date(), amount);
* payment.apply();
* }
* }</pre>
* <h3>Making parameter types distinct</h3>
* The types of the factory method's parameters must be distinct. To use multiple parameters of
* the same type, use a named {@literal @}{@link Assisted} annotation to disambiguate the
* parameters. The names must be applied to the factory method's parameters:
* <pre>public interface PaymentFactory {
* Payment create(
* <strong>{@literal @}Assisted("startDate")</strong> Date startDate,
* <strong>{@literal @}Assisted("dueDate")</strong> Date dueDate,
* Money amount);
* } </pre>
* ...and to the concrete type's constructor parameters:
* <pre>public class RealPayment implements Payment {
* {@literal @}Inject
* public RealPayment(
* CreditService creditService,
* AuthService authService,
* <strong>{@literal @}Assisted("startDate")</strong> Date startDate,
* <strong>{@literal @}Assisted("dueDate")</strong> Date dueDate,
* <strong>{@literal @}Assisted</strong> Money amount) {
* ...
* }
* }</pre>
* <h3>Values are created by Guice</h3>
* Returned factories use child injectors to create values. The values are eligible for method
* interception. In addition, {@literal @}{@literal Inject} members will be injected before they are
* returned.
* <h3>Backwards compatibility using {@literal @}AssistedInject</h3>
* Instead of the {@literal @}Inject annotation, you may annotate the constructed classes with
* {@literal @}{@link AssistedInject}. This triggers a limited backwards-compatibility mode.
* <p>Instead of matching factory method arguments to constructor parameters using their names, the
* <strong>parameters are matched by their order</strong>. The first factory method argument is
* used for the first {@literal @}Assisted constructor parameter, etc.. Annotation names have no
* effect.
* <p>Returned values are <strong>not created by Guice</strong>. These types are not eligible for
* method interception. They do receive post-construction member injection.
*
* @param <F> The factory interface
* @author jmourits@google.com (Jerome Mourits)
* @author jessewilson@google.com (Jesse Wilson)
* @author dtm@google.com (Daniel Martin)
*/
public class FactoryProvider<F> implements Provider<F>, HasDependencies {
/*
* This class implements the old @AssistedInject implementation that manually matches constructors
* to factory methods.
*/
private Injector injector;
private final TypeLiteral<F> factoryType;
private final Map<Method, AssistedConstructor<?>> factoryMethodToConstructor;
private FactoryProvider(TypeLiteral<F> factoryType,
Map<Method, AssistedConstructor<?>> factoryMethodToConstructor) {
this.factoryType = factoryType;
this.factoryMethodToConstructor = factoryMethodToConstructor;
checkDeclaredExceptionsMatch();
}
private void checkDeclaredExceptionsMatch() {
for (Map.Entry<Method, AssistedConstructor<?>> entry : factoryMethodToConstructor.entrySet()) {
for (Class<?> constructorException : entry.getValue().getDeclaredExceptions()) {
if (!isConstructorExceptionCompatibleWithFactoryExeception(
constructorException, entry.getKey().getExceptionTypes())) {
throw newConfigurationException("Constructor %s declares an exception, but no compatible "
+ "exception is thrown by the factory method %s", entry.getValue(), entry.getKey());
}
}
}
}
private boolean isConstructorExceptionCompatibleWithFactoryExeception(
Class<?> constructorException, Class<?>[] factoryExceptions) {
for (Class<?> factoryException : factoryExceptions) {
if (factoryException.isAssignableFrom(constructorException)) {
return true;
}
}
return false;
}
@Override
public Set<Dependency<?>> getDependencies() {
Set<Dependency<?>> dependencies = new HashSet<>();
for (AssistedConstructor<?> constructor : factoryMethodToConstructor.values()) {
for (Parameter parameter : constructor.getAllParameters()) {
if (!parameter.isProvidedByFactory()) {
dependencies.add(Dependency.get(parameter.getPrimaryBindingKey()));
}
}
}
return unmodifiableSet(dependencies);
}
@Override
public F get() {
InvocationHandler invocationHandler = new InvocationHandler() {
@Override
public Object invoke(Object proxy, Method method, Object[] creationArgs) throws Throwable {
// pass methods from Object.class to the proxy
if (method.getDeclaringClass().equals(Object.class)) {
return method.invoke(this, creationArgs);
}
AssistedConstructor<?> constructor = factoryMethodToConstructor.get(method);
Object[] constructorArgs = gatherArgsForConstructor(constructor, creationArgs);
Object objectToReturn = constructor.newInstance(constructorArgs);
injector.injectMembers(objectToReturn);
return objectToReturn;
}
public Object[] gatherArgsForConstructor(
AssistedConstructor<?> constructor,
Object[] factoryArgs) {
int numParams = constructor.getAllParameters().size();
int argPosition = 0;
Object[] result = new Object[numParams];
for (int i = 0; i < numParams; i++) {
Parameter parameter = constructor.getAllParameters().get(i);
if (parameter.isProvidedByFactory()) {
result[i] = factoryArgs[argPosition];
argPosition++;
} else {
result[i] = parameter.getValue(injector);
}
}
return result;
}
};
@SuppressWarnings("unchecked") // we imprecisely treat the class literal of T as a Class<T>
Class<F> factoryRawType = (Class) factoryType.getRawType();
return factoryRawType.cast(Proxy.newProxyInstance(factoryRawType.getClassLoader(),
new Class[]{factoryRawType}, invocationHandler));
}
private static ConfigurationException newConfigurationException(String format, Object... args) {
return new ConfigurationException(singleton(new Message(Errors.format(format, args))));
}
}