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// Copyright (C) 2018 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.server.plugincontext;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.collect.Iterators;
import com.google.gerrit.extensions.registration.DynamicSet;
import com.google.gerrit.extensions.registration.Extension;
import com.google.gerrit.server.plugincontext.PluginContext.ExtensionImplConsumer;
import com.google.gerrit.server.plugincontext.PluginContext.PluginMetrics;
import com.google.inject.Inject;
import java.util.Iterator;
import java.util.SortedSet;
/**
* Context to invoke extensions from a {@link DynamicSet}.
*
* <p>When a plugin extension is invoked a logging tag with the plugin name is set. This way any
* errors that are triggered by the plugin extension (even if they happen in Gerrit code which is
* called by the plugin extension) can be easily attributed to the plugin.
*
* <p>Example if all exceptions should be caught and logged:
*
* <pre>
* fooPluginSetContext.runEach(foo -> foo.doFoo());
* </pre>
*
* <p>Example if all exceptions, but one, should be caught and logged:
*
* <pre>
* try {
* fooPluginSetContext.runEach(foo -> foo.doFoo(), MyException.class);
* } catch (MyException e) {
* // handle the exception
* }
* </pre>
*
* <p>Example if return values should be handled:
*
* <pre>
* for (PluginSetEntryContext<Foo> c : fooPluginSetContext) {
* if (c.call(foo -> foo.handles(x))) {
* c.run(foo -> foo.doFoo());
* }
* }
* </pre>
*
* <p>Example if return values and a single exception should be handled:
*
* <pre>
* try {
* for (PluginSetEntryContext<Foo> c : fooPluginSetContext) {
* if (c.call(foo -> foo.handles(x), MyException.class)) {
* c.run(foo -> foo.doFoo(), MyException.class);
* }
* }
* } catch (MyException e) {
* // handle the exception
* }
* </pre>
*
* <p>Example if several exceptions should be handled:
*
* <pre>
* for (Extension<Foo> fooExtension : fooDynamicSet.entries()) {
* try (TraceContext traceContext = PluginContext.newTrace(fooExtension)) {
* fooExtension.get().doFoo();
* } catch (MyException1 | MyException2 | MyException3 e) {
* // handle the exception
* }
* }
* </pre>
*/
public class PluginSetContext<T> implements Iterable<PluginSetEntryContext<T>> {
private final DynamicSet<T> dynamicSet;
private final PluginMetrics pluginMetrics;
@VisibleForTesting
@Inject
public PluginSetContext(DynamicSet<T> dynamicSet, PluginMetrics pluginMetrics) {
this.dynamicSet = dynamicSet;
this.pluginMetrics = pluginMetrics;
}
/**
* Iterator that provides contexts for invoking the extensions in this set.
*
* <p>This is useful if:
*
* <ul>
* <li>invoking of each extension returns a result that should be handled
* <li>a sequence of invocations should be done on each extension
* </ul>
*/
@Override
public Iterator<PluginSetEntryContext<T>> iterator() {
return Iterators.transform(
dynamicSet.entries().iterator(), e -> new PluginSetEntryContext<>(e, pluginMetrics));
}
/**
* Checks if no implementations for this extension point have been registered.
*
* @return {@code true} if no implementations for this extension point have been registered,
* otherwise {@code false}
*/
public boolean isEmpty() {
return !dynamicSet.iterator().hasNext();
}
/**
* Returns a sorted list of the plugins that have registered implementations for this extension
* point.
*
* @return sorted list of the plugins that have registered implementations for this extension
* point
*/
public SortedSet<String> plugins() {
return dynamicSet.plugins();
}
/**
* Invokes each extension in the set. All exceptions from the plugin extensions are caught and
* logged.
*
* <p>The consumer gets the extension implementation provided that should be invoked.
*
* <p>All extension in the set are invoked, even if invoking some of the extensions failed.
*
* @param extensionImplConsumer consumer that invokes the extension
*/
public void runEach(ExtensionImplConsumer<T> extensionImplConsumer) {
dynamicSet
.entries()
.forEach(p -> PluginContext.runLogExceptions(pluginMetrics, p, extensionImplConsumer));
}
/**
* Invokes each extension in the set. All exceptions from the plugin extensions except exceptions
* of the specified type are caught and logged.
*
* <p>The consumer gets the extension implementation provided that should be invoked.
*
* <p>All extension in the set are invoked, even if invoking some of the extensions failed.
*
* @param extensionImplConsumer consumer that invokes the extension
* @param exceptionClass type of the exceptions that should be thrown
* @throws X expected exception from the plugin extension
*/
public <X extends Exception> void runEach(
ExtensionImplConsumer<T> extensionImplConsumer, Class<X> exceptionClass) throws X {
for (Extension<T> extension : dynamicSet.entries()) {
PluginContext.runLogExceptions(
pluginMetrics, extension, extensionImplConsumer, exceptionClass);
}
}
}
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