/*
* Copyright 2010 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.jstestdriver.requesthandlers;
import com.google.common.base.Preconditions;
import com.google.common.collect.Maps;
import com.google.inject.Guice;
import com.google.inject.Key;
import com.google.inject.OutOfScopeException;
import com.google.inject.Provider;
import com.google.inject.Scope;
import java.util.Map;
/**
* The {@link Guice} {@link Scope} associated with HTTP requests. Maintains a
* {@link Map} of {@link Key}s to {@link Object}s that exist within the scope
* of the HTTP request.
*
* @author rdionne@google.com (Robert Dionne)
*/
class RequestScope implements Scope {
private final ThreadLocal<Map<Key<?>, Object>> values =
new ThreadLocal<Map<Key<?>, Object>>();
/**
* Enter the {@link RequestScope}.
*/
public void enter() {
Preconditions.checkState(values.get() == null, "Scope already entered.");
values.set(Maps.<Key<?>, Object>newHashMap());
}
/**
* Exit the {@link RequestScope}.
*/
public void exit() {
Preconditions.checkState(values.get() != null, "Scope not entered.");
values.remove();
}
/**
* Seed the {@link RequestScope} with an object of type T.
*
* @param key a {@link Key} that represents T
* @param value the object of type T
* @param <T> the type of {@code value}
*/
public <T> void seed(Key<T> key, T value) {
Map<Key<?>, Object> scopedObjects = getScopedObjectMap(key);
// TODO(rdionne): replace error message
Preconditions.checkState(!scopedObjects.containsKey(key), "Error");
scopedObjects.put(key, value);
}
/**
* Seed the {@link RequestScope} with an object of type T
*
* @param clazz {@code value}'s class
* @param value the object of type T
* @param <T> the type of {@code value}
*/
public <T> void seed(Class<T> clazz, T value) {
seed(Key.get(clazz), value);
}
public <T> Provider<T> scope(final Key<T> tKey, final Provider<T> tProvider) {
return new Provider<T>() {
public T get() {
Map<Key<?>, Object> scopedObjects = getScopedObjectMap(tKey);
@SuppressWarnings("unchecked")
T current = (T) scopedObjects.get(tKey);
if (current == null && !scopedObjects.containsKey(tKey)) {
current = tProvider.get();
scopedObjects.put(tKey, current);
}
return current;
}
};
}
private <T> Map<Key<?>, Object> getScopedObjectMap(Key<T> key) {
Map<Key<?>, Object> scopedObjects = values.get();
if (scopedObjects == null) {
throw new OutOfScopeException(new StringBuilder("Cannot access ")
.append(key)
.append(" outside of a scoping block.")
.toString());
}
return scopedObjects;
}
}