/**
* Copyright (C) 2008 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 com.google.inject.assistedinject;
import com.google.inject.AbstractModule;
import com.google.inject.Binder;
import com.google.inject.Binding;
import com.google.inject.ConfigurationException;
import com.google.inject.Inject;
import com.google.inject.Injector;
import com.google.inject.Key;
import com.google.inject.Module;
import com.google.inject.Provider;
import com.google.inject.ProvisionException;
import com.google.inject.TypeLiteral;
import static com.google.inject.internal.Annotations.getKey;
import com.google.inject.internal.Errors;
import com.google.inject.internal.ErrorsException;
import com.google.inject.internal.ImmutableList;
import com.google.inject.internal.ImmutableMap;
import static com.google.inject.internal.Iterables.getOnlyElement;
import com.google.inject.internal.Lists;
import static com.google.inject.internal.Preconditions.checkState;
import com.google.inject.spi.Message;
import com.google.inject.util.Providers;
import java.lang.annotation.Annotation;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.Arrays;
import java.util.List;
/**
* The newer implementation of factory provider. This implementation uses a child injector to
* create values.
*
* @author jessewilson@google.com (Jesse Wilson)
* @author dtm@google.com (Daniel Martin)
*/
final class FactoryProvider2<F> implements InvocationHandler, Provider<F> {
/** if a factory method parameter isn't annotated, it gets this annotation. */
static final Assisted DEFAULT_ANNOTATION = new Assisted() {
public String value() {
return "";
}
public Class<? extends Annotation> annotationType() {
return Assisted.class;
}
@Override public boolean equals(Object o) {
return o instanceof Assisted
&& ((Assisted) o).value().equals("");
}
@Override public int hashCode() {
return 127 * "value".hashCode() ^ "".hashCode();
}
@Override public String toString() {
return "@" + Assisted.class.getName() + "(value=)";
}
};
/** the produced type, or null if all methods return concrete types */
private final Key<?> producedType;
private final ImmutableMap<Method, Key<?>> returnTypesByMethod;
private final ImmutableMap<Method, ImmutableList<Key<?>>> paramTypes;
/** the hosting injector, or null if we haven't been initialized yet */
private Injector injector;
/** the factory interface, implemented and provided */
private final F factory;
/**
* @param factoryType a Java interface that defines one or more create methods.
* @param producedType a concrete type that is assignable to the return types of all factory
* methods.
*/
FactoryProvider2(TypeLiteral<F> factoryType, Key<?> producedType) {
this.producedType = producedType;
Errors errors = new Errors();
@SuppressWarnings("unchecked") // we imprecisely treat the class literal of T as a Class<T>
Class<F> factoryRawType = (Class) factoryType.getRawType();
try {
ImmutableMap.Builder<Method, Key<?>> returnTypesBuilder = ImmutableMap.builder();
ImmutableMap.Builder<Method, ImmutableList<Key<?>>> paramTypesBuilder
= ImmutableMap.builder();
// TODO: also grab methods from superinterfaces
for (Method method : factoryRawType.getMethods()) {
Key<?> returnType = getKey(
factoryType.getReturnType(method), method, method.getAnnotations(), errors);
returnTypesBuilder.put(method, returnType);
List<TypeLiteral<?>> params = factoryType.getParameterTypes(method);
Annotation[][] paramAnnotations = method.getParameterAnnotations();
int p = 0;
List<Key<?>> keys = Lists.newArrayList();
for (TypeLiteral<?> param : params) {
Key<?> paramKey = getKey(param, method, paramAnnotations[p++], errors);
keys.add(assistKey(method, paramKey, errors));
}
paramTypesBuilder.put(method, ImmutableList.copyOf(keys));
}
returnTypesByMethod = returnTypesBuilder.build();
paramTypes = paramTypesBuilder.build();
} catch (ErrorsException e) {
throw new ConfigurationException(e.getErrors().getMessages());
}
factory = factoryRawType.cast(Proxy.newProxyInstance(factoryRawType.getClassLoader(),
new Class[] { factoryRawType }, this));
}
public F get() {
return factory;
}
/**
* Returns a key similar to {@code key}, but with an {@literal @}Assisted binding annotation.
* This fails if another binding annotation is clobbered in the process. If the key already has
* the {@literal @}Assisted annotation, it is returned as-is to preserve any String value.
*/
private <T> Key<T> assistKey(Method method, Key<T> key, Errors errors) throws ErrorsException {
if (key.getAnnotationType() == null) {
return Key.get(key.getTypeLiteral(), DEFAULT_ANNOTATION);
} else if (key.getAnnotationType() == Assisted.class) {
return key;
} else {
errors.withSource(method).addMessage(
"Only @Assisted is allowed for factory parameters, but found @%s",
key.getAnnotationType());
throw errors.toException();
}
}
/**
* At injector-creation time, we initialize the invocation handler. At this time we make sure
* all factory methods will be able to build the target types.
*/
@Inject
void initialize(Injector injector) {
if (this.injector != null) {
throw new ConfigurationException(ImmutableList.of(new Message(FactoryProvider2.class,
"Factories.create() factories may only be used in one Injector!")));
}
this.injector = injector;
for (Method method : returnTypesByMethod.keySet()) {
Object[] args = new Object[method.getParameterTypes().length];
Arrays.fill(args, "dummy object for validating Factories");
getBindingFromNewInjector(method, args); // throws if the binding isn't properly configured
}
}
/**
* Creates a child injector that binds the args, and returns the binding for the method's result.
*/
public Binding<?> getBindingFromNewInjector(final Method method, final Object[] args) {
checkState(injector != null,
"Factories.create() factories cannot be used until they're initialized by Guice.");
final Key<?> returnType = returnTypesByMethod.get(method);
Module assistedModule = new AbstractModule() {
@SuppressWarnings("unchecked") // raw keys are necessary for the args array and return value
protected void configure() {
Binder binder = binder().withSource(method);
int p = 0;
for (Key<?> paramKey : paramTypes.get(method)) {
// Wrap in a Provider to cover null, and to prevent Guice from injecting the parameter
binder.bind((Key) paramKey).toProvider(Providers.of(args[p++]));
}
if (producedType != null && !returnType.equals(producedType)) {
binder.bind(returnType).to((Key) producedType);
} else {
binder.bind(returnType);
}
}
};
Injector forCreate = injector.createChildInjector(assistedModule);
return forCreate.getBinding(returnType);
}
/**
* When a factory method is invoked, we create a child injector that binds all parameters, then
* use that to get an instance of the return type.
*/
public Object invoke(Object proxy, final Method method, final Object[] args) throws Throwable {
if (method.getDeclaringClass() == Object.class) {
return method.invoke(this, args);
}
Provider<?> provider = getBindingFromNewInjector(method, args).getProvider();
try {
return provider.get();
} catch (ProvisionException e) {
// if this is an exception declared by the factory method, throw it as-is
if (e.getErrorMessages().size() == 1) {
Message onlyError = getOnlyElement(e.getErrorMessages());
Throwable cause = onlyError.getCause();
if (cause != null && canRethrow(method, cause)) {
throw cause;
}
}
throw e;
}
}
@Override public String toString() {
return factory.getClass().getInterfaces()[0].getName()
+ " for " + producedType.getTypeLiteral();
}
@Override public boolean equals(Object o) {
return o == this || o == factory;
}
/** Returns true if {@code thrown} can be thrown by {@code invoked} without wrapping. */
static boolean canRethrow(Method invoked, Throwable thrown) {
if (thrown instanceof Error || thrown instanceof RuntimeException) {
return true;
}
for (Class<?> declared : invoked.getExceptionTypes()) {
if (declared.isInstance(thrown)) {
return true;
}
}
return false;
}
}