google-nomulus/java/google/registry/config/RegistryConfigLoader.java
Justine Tunney 3f471a32e2 System property loader for RegistryConfig
This change allows registries to customize the values returned by
RegistryConfig methods without needing to edit Domain Registry code in a
forked repository. This is accomplished by defining a custom
RegistryConfig implementation and specifying its name as a system
property in appengine-web.xml.

This change also open-sources the production configuration values that
Google has chosen to use for these methods. TestRegistryConfig was
hitherto used for production configuration in the open source world,
which is misleading and inappropriate, considering it tunes values such
as the number of commit log buckets to 1.

Another important benefit of this change is that it helps registry_tool
work out of the box in the open source world.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=129022675
2016-08-02 19:17:19 -04:00

75 lines
3.2 KiB
Java

// Copyright 2016 The Domain Registry Authors. All Rights Reserved.
//
// 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 google.registry.config;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Modifier;
import javax.annotation.concurrent.ThreadSafe;
/**
* System property loader of {@link RegistryConfig} instance.
*
* <p>This class reflectively loads the Java class defined by the system property
* {@value #REGISTRY_CONFIG_PROPERTY} whose default value is {@value #REGISTRY_CONFIG_DEFAULT} and
* can be set in {@code appengine-web.xml}. Once the class is loaded, its constructor is called,
* passing the {@link RegistryEnvironment} as a single parameter.
*/
@ThreadSafe
public final class RegistryConfigLoader {
public static final String REGISTRY_CONFIG_PROPERTY = "com.google.domain.registry.config";
public static final String REGISTRY_CONFIG_DEFAULT =
"google.registry.config.ProductionRegistryConfigExample";
static RegistryConfig load(RegistryEnvironment environment) {
String className = System.getProperty(REGISTRY_CONFIG_PROPERTY, REGISTRY_CONFIG_DEFAULT);
Class<?> clazz;
try {
clazz = Class.forName(className);
} catch (ClassNotFoundException e) {
throw new RuntimeException(String.format(
"Failed to load '%s' as specified by system property '%s'",
className, REGISTRY_CONFIG_PROPERTY), e);
}
if (!RegistryConfig.class.isAssignableFrom(clazz)) {
throw new RuntimeException(String.format(
"%s does not implement %s",
clazz.getSimpleName(), RegistryConfig.class.getSimpleName()));
}
@SuppressWarnings("unchecked")
Class<? extends RegistryConfig> clazzy = (Class<? extends RegistryConfig>) clazz;
if (!Modifier.isPublic(clazzy.getModifiers())) {
throw new RuntimeException(String.format(
"Must be a public class: %s", clazzy.getCanonicalName()));
}
Constructor<? extends RegistryConfig> constructor;
try {
constructor = clazzy.getConstructor(RegistryEnvironment.class);
} catch (NoSuchMethodException | SecurityException e) {
throw new RuntimeException(String.format(
"Must have a public constructor(RegistryEnvironment): %s", clazzy.getCanonicalName()), e);
}
try {
return constructor.newInstance(environment);
} catch (InvocationTargetException e) {
throw new RuntimeException(
String.format("%s constructor threw an exception", clazzy.getSimpleName()), e);
} catch (InstantiationException | IllegalAccessException | IllegalArgumentException e) {
throw new RuntimeException(
String.format("Failed to instantiate: %s", clazz.getCanonicalName()), e);
}
}
}