com.google.gerrit.httpd.rpc.Handler Maven / Gradle / Ivy
// Copyright (C) 2009 The Android Open Source Project
//
// 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.gerrit.httpd.rpc;
import com.google.gerrit.common.errors.NoSuchEntityException;
import com.google.gerrit.server.project.NoSuchChangeException;
import com.google.gerrit.server.project.NoSuchProjectException;
import com.google.gerrit.server.project.NoSuchRefException;
import com.google.gwtjsonrpc.common.AsyncCallback;
import com.google.gwtjsonrpc.common.VoidResult;
import com.google.gwtorm.server.OrmException;
import java.util.concurrent.Callable;
/**
* Base class for RPC service implementations.
*
* Typically an RPC service implementation will extend this class and use Guice injection to
* manage its state. For example:
*
*
* class Foo extends Handler<Result> {
* interface Factory {
* Foo create(... args ...);
* }
* @Inject
* Foo(state, @Assisted args) { ... }
* Result get() throws Exception { ... }
* }
*
*
* @param type of result for {@link AsyncCallback#onSuccess(Object)} if the operation completed
* successfully.
*/
public abstract class Handler implements Callable {
public static Handler wrap(Callable r) {
return new Handler() {
@Override
public T call() throws Exception {
return r.call();
}
};
}
/**
* Run the operation and pass the result to the callback.
*
* @param callback callback to receive the result of {@link #call()}.
*/
public final void to(AsyncCallback callback) {
try {
final T r = call();
if (r != null) {
callback.onSuccess(r);
}
} catch (NoSuchProjectException | NoSuchChangeException | NoSuchRefException e) {
callback.onFailure(new NoSuchEntityException());
} catch (OrmException e) {
if (e.getCause() instanceof NoSuchEntityException) {
callback.onFailure(e.getCause());
} else {
callback.onFailure(e);
}
} catch (Exception e) {
callback.onFailure(e);
}
}
/**
* Compute the operation result.
*
* @return the result of the operation. Return {@link VoidResult#INSTANCE} if there is no
* meaningful return value for the operation.
* @throws Exception the operation failed. The caller will log the exception and the stack trace,
* if it is worth logging on the server side.
*/
@Override
public abstract T call() throws Exception;
}