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/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch licenses this file to you 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 org.elasticsearch.common.util;
import org.elasticsearch.common.inject.Binder;
import org.elasticsearch.common.inject.multibindings.MapBinder;
import org.elasticsearch.common.inject.multibindings.Multibinder;
import org.elasticsearch.common.settings.Settings;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
/**
* This class defines an official elasticsearch extension point. It registers
* all extensions by a single name and ensures that extensions are not registered
* more than once.
*/
public abstract class ExtensionPoint {
protected final String name;
protected final Class<?>[] singletons;
/**
* Creates a new extension point
*
* @param name the human readable underscore case name of the extension point. This is used in error messages etc.
* @param singletons a list of singletons to bind with this extension point - these are bound in {@link #bind(Binder)}
*/
public ExtensionPoint(String name, Class<?>... singletons) {
this.name = name;
this.singletons = singletons;
}
/**
* Binds the extension as well as the singletons to the given guice binder.
*
* @param binder the binder to use
*/
public final void bind(Binder binder) {
for (Class<?> c : singletons) {
binder.bind(c).asEagerSingleton();
}
bindExtensions(binder);
}
/**
* Subclasses can bind their type, map or set extensions here.
*/
protected abstract void bindExtensions(Binder binder);
/**
* A map based extension point which allows to register keyed implementations ie. parsers or some kind of strategies.
*/
public static class ClassMap<T> extends ExtensionPoint {
protected final Class<T> extensionClass;
private final Map<String, Class<? extends T>> extensions = new HashMap<>();
private final Set<String> reservedKeys;
/**
* Creates a new {@link ClassMap}
*
* @param name the human readable underscore case name of the extension poing. This is used in error messages etc.
* @param extensionClass the base class that should be extended
* @param singletons a list of singletons to bind with this extension point - these are bound in {@link #bind(Binder)}
* @param reservedKeys a set of reserved keys by internal implementations
*/
public ClassMap(String name, Class<T> extensionClass, Set<String> reservedKeys, Class<?>... singletons) {
super(name, singletons);
this.extensionClass = extensionClass;
this.reservedKeys = reservedKeys;
}
/**
* Returns the extension for the given key or <code>null</code>
*/
public Class<? extends T> getExtension(String type) {
return extensions.get(type);
}
/**
* Registers an extension class for a given key. This method will thr
*
* @param key the extensions key
* @param extension the extension
* @throws IllegalArgumentException iff the key is already registered or if the key is a reserved key for an internal implementation
*/
public final void registerExtension(String key, Class<? extends T> extension) {
if (extensions.containsKey(key) || reservedKeys.contains(key)) {
throw new IllegalArgumentException("Can't register the same [" + this.name + "] more than once for [" + key + "]");
}
extensions.put(key, extension);
}
@Override
protected final void bindExtensions(Binder binder) {
MapBinder<String, T> parserMapBinder = MapBinder.newMapBinder(binder, String.class, extensionClass);
for (Map.Entry<String, Class<? extends T>> clazz : extensions.entrySet()) {
parserMapBinder.addBinding(clazz.getKey()).to(clazz.getValue());
}
}
}
/**
* A Type extension point which basically allows to registerd keyed extensions like {@link ClassMap}
* but doesn't instantiate and bind all the registered key value pairs but instead replace a singleton based on a given setting via {@link #bindType(Binder, Settings, String, String)}
* Note: {@link #bind(Binder)} is not supported by this class
*/
public static final class SelectedType<T> extends ClassMap<T> {
public SelectedType(String name, Class<T> extensionClass) {
super(name, extensionClass, Collections.emptySet());
}
/**
* Binds the extension class to the class that is registered for the give configured for the settings key in
* the settings object.
*
* @param binder the binder to use
* @param settings the settings to look up the key to find the implementation to bind
* @param settingsKey the key to use with the settings
* @param defaultValue the default value if the settings do not contain the key, or null if there is no default
* @return the actual bound type key
*/
public String bindType(Binder binder, Settings settings, String settingsKey, String defaultValue) {
final String type = settings.get(settingsKey, defaultValue);
if (type == null) {
throw new IllegalArgumentException("Missing setting [" + settingsKey + "]");
}
final Class<? extends T> instance = getExtension(type);
if (instance == null) {
throw new IllegalArgumentException("Unknown [" + this.name + "] type [" + type + "]");
}
if (extensionClass == instance) {
binder.bind(extensionClass).asEagerSingleton();
} else {
binder.bind(extensionClass).to(instance).asEagerSingleton();
}
return type;
}
}
/**
* A set based extension point which allows to register extended classes that might be used to chain additional functionality etc.
*/
public final static class ClassSet<T> extends ExtensionPoint {
protected final Class<T> extensionClass;
private final Set<Class<? extends T>> extensions = new HashSet<>();
/**
* Creates a new {@link ClassSet}
*
* @param name the human readable underscore case name of the extension poing. This is used in error messages etc.
* @param extensionClass the base class that should be extended
* @param singletons a list of singletons to bind with this extension point - these are bound in {@link #bind(Binder)}
*/
public ClassSet(String name, Class<T> extensionClass, Class<?>... singletons) {
super(name, singletons);
this.extensionClass = extensionClass;
}
/**
* Registers a new extension
*
* @param extension the extension to register
* @throws IllegalArgumentException iff the class is already registered
*/
public final void registerExtension(Class<? extends T> extension) {
if (extensions.contains(extension)) {
throw new IllegalArgumentException("Can't register the same [" + this.name + "] more than once for [" + extension.getName() + "]");
}
extensions.add(extension);
}
@Override
protected final void bindExtensions(Binder binder) {
Multibinder<T> allocationMultibinder = Multibinder.newSetBinder(binder, extensionClass);
for (Class<? extends T> clazz : extensions) {
binder.bind(clazz).asEagerSingleton();
allocationMultibinder.addBinding().to(clazz);
}
}
}
/**
* A an instance of a map, mapping one instance value to another. Both key and value are instances, not classes
* like with other extension points.
*/
public final static class InstanceMap<K, V> extends ExtensionPoint {
private final Map<K, V> map = new HashMap<>();
private final Class<K> keyType;
private final Class<V> valueType;
/**
* Creates a new {@link ClassSet}
*
* @param name the human readable underscore case name of the extension point. This is used in error messages.
* @param singletons a list of singletons to bind with this extension point - these are bound in {@link #bind(Binder)}
*/
public InstanceMap(String name, Class<K> keyType, Class<V> valueType, Class<?>... singletons) {
super(name, singletons);
this.keyType = keyType;
this.valueType = valueType;
}
/**
* Registers a mapping from {@code key} to {@code value}
*
* @throws IllegalArgumentException iff the key is already registered
*/
public final void registerExtension(K key, V value) {
V old = map.put(key, value);
if (old != null) {
throw new IllegalArgumentException("Cannot register [" + this.name + "] with key [" + key + "] to [" + value + "], already registered to [" + old + "]");
}
}
@Override
protected void bindExtensions(Binder binder) {
MapBinder<K, V> mapBinder = MapBinder.newMapBinder(binder, keyType, valueType);
for (Map.Entry<K, V> entry : map.entrySet()) {
mapBinder.addBinding(entry.getKey()).toInstance(entry.getValue());
}
}
}
}
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