dubbo ExtensionDirector 源码

dubbo ExtensionDirector 代码

文件路径：/dubbo-common/src/main/java/org/apache/dubbo/common/extension/ExtensionDirector.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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.apache.dubbo.common.extension;

import org.apache.dubbo.rpc.model.ScopeModel;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 * ExtensionDirector is a scoped extension loader manager.
 *
 * <p></p>
 * <p>ExtensionDirector supports multiple levels, and the child can inherit the parent's extension instances. </p>
 * <p>The way to find and create an extension instance is similar to Java classloader.</p>
 */
public class ExtensionDirector implements ExtensionAccessor {

    private final ConcurrentMap<Class<?>, ExtensionLoader<?>> extensionLoadersMap = new ConcurrentHashMap<>(64);
    private final ConcurrentMap<Class<?>, ExtensionScope> extensionScopeMap = new ConcurrentHashMap<>(64);
    private final ExtensionDirector parent;
    private final ExtensionScope scope;
    private final List<ExtensionPostProcessor> extensionPostProcessors = new ArrayList<>();
    private final ScopeModel scopeModel;
    private final AtomicBoolean destroyed = new AtomicBoolean();

    public ExtensionDirector(ExtensionDirector parent, ExtensionScope scope, ScopeModel scopeModel) {
        this.parent = parent;
        this.scope = scope;
        this.scopeModel = scopeModel;
    }

    public void addExtensionPostProcessor(ExtensionPostProcessor processor) {
        if (!this.extensionPostProcessors.contains(processor)) {
            this.extensionPostProcessors.add(processor);
        }
    }

    public List<ExtensionPostProcessor> getExtensionPostProcessors() {
        return extensionPostProcessors;
    }

    @Override
    public ExtensionDirector getExtensionDirector() {
        return this;
    }

    @Override
    @SuppressWarnings("unchecked")
    public <T> ExtensionLoader<T> getExtensionLoader(Class<T> type) {
        checkDestroyed();
        if (type == null) {
            throw new IllegalArgumentException("Extension type == null");
        }
        if (!type.isInterface()) {
            throw new IllegalArgumentException("Extension type (" + type + ") is not an interface!");
        }
        if (!withExtensionAnnotation(type)) {
            throw new IllegalArgumentException("Extension type (" + type +
                ") is not an extension, because it is NOT annotated with @" + SPI.class.getSimpleName() + "!");
        }

        // 1. find in local cache
        ExtensionLoader<T> loader = (ExtensionLoader<T>) extensionLoadersMap.get(type);

        ExtensionScope scope = extensionScopeMap.get(type);
        if (scope == null) {
            SPI annotation = type.getAnnotation(SPI.class);
            scope = annotation.scope();
            extensionScopeMap.put(type, scope);
        }

        if (loader == null && scope == ExtensionScope.SELF) {
            // create an instance in self scope
            loader = createExtensionLoader0(type);
        }

        // 2. find in parent
        if (loader == null) {
            if (this.parent != null) {
                loader = this.parent.getExtensionLoader(type);
            }
        }

        // 3. create it
        if (loader == null) {
            loader = createExtensionLoader(type);
        }

        return loader;
    }

    private <T> ExtensionLoader<T> createExtensionLoader(Class<T> type) {
        ExtensionLoader<T> loader = null;
        if (isScopeMatched(type)) {
            // if scope is matched, just create it
            loader = createExtensionLoader0(type);
        }
        return loader;
    }

    @SuppressWarnings("unchecked")
    private <T> ExtensionLoader<T> createExtensionLoader0(Class<T> type) {
        checkDestroyed();
        ExtensionLoader<T> loader;
        extensionLoadersMap.putIfAbsent(type, new ExtensionLoader<T>(type, this, scopeModel));
        loader = (ExtensionLoader<T>) extensionLoadersMap.get(type);
        return loader;
    }

    private boolean isScopeMatched(Class<?> type) {
        final SPI defaultAnnotation = type.getAnnotation(SPI.class);
        return defaultAnnotation.scope().equals(scope);
    }

    private static boolean withExtensionAnnotation(Class<?> type) {
        return type.isAnnotationPresent(SPI.class);
    }

    public ExtensionDirector getParent() {
        return parent;
    }

    public void removeAllCachedLoader() {
    }

    public void destroy() {
        if (destroyed.compareAndSet(false, true)) {
            for (ExtensionLoader<?> extensionLoader : extensionLoadersMap.values()) {
                extensionLoader.destroy();
            }
            extensionLoadersMap.clear();
            extensionScopeMap.clear();
            extensionPostProcessors.clear();
        }
    }

    private void checkDestroyed() {
        if (destroyed.get()) {
            throw new IllegalStateException("ExtensionDirector is destroyed");
        }
    }
}

相关信息

dubbo 源码目录

相关文章

dubbo Activate 源码

dubbo Adaptive 源码

dubbo AdaptiveClassCodeGenerator 源码

dubbo DisableInject 源码

dubbo DubboInternalLoadingStrategy 源码

dubbo DubboLoadingStrategy 源码

dubbo ExtensionAccessor 源码

dubbo ExtensionAccessorAware 源码

dubbo ExtensionFactory 源码

dubbo ExtensionInjector 源码