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/*
* 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.beans.support;
import org.apache.dubbo.common.beans.factory.ScopeBeanFactory;
import org.apache.dubbo.common.extension.ExtensionLoader;
import org.apache.dubbo.rpc.model.ApplicationModel;
import org.apache.dubbo.rpc.model.FrameworkModel;
import org.apache.dubbo.rpc.model.ModuleModel;
import org.apache.dubbo.rpc.model.ScopeModel;
import org.apache.dubbo.rpc.model.ScopeModelAccessor;
import java.lang.reflect.Constructor;
import java.util.ArrayList;
import java.util.List;
/**
* Interface to create instance for specify type, using both in {@link ExtensionLoader} and {@link ScopeBeanFactory}.
*/
public class InstantiationStrategy {
private final ScopeModelAccessor scopeModelAccessor;
public InstantiationStrategy() {
this(null);
}
public InstantiationStrategy(ScopeModelAccessor scopeModelAccessor) {
this.scopeModelAccessor = scopeModelAccessor;
}
@SuppressWarnings("unchecked")
public T instantiate(Class type) throws ReflectiveOperationException {
// should not use default constructor directly, maybe also has another constructor matched scope model arguments
// 1. try to get default constructor
Constructor defaultConstructor = null;
try {
defaultConstructor = type.getConstructor();
} catch (NoSuchMethodException e) {
// ignore no default constructor
}
// 2. use matched constructor if found
List> matchedConstructors = new ArrayList<>();
Constructor[] declaredConstructors = type.getConstructors();
for (Constructor constructor : declaredConstructors) {
if (isMatched(constructor)) {
matchedConstructors.add(constructor);
}
}
// remove default constructor from matchedConstructors
if (defaultConstructor != null) {
matchedConstructors.remove(defaultConstructor);
}
// match order:
// 1. the only matched constructor with parameters
// 2. default constructor if absent
Constructor targetConstructor;
if (matchedConstructors.size() > 1) {
throw new IllegalArgumentException("Expect only one but found " +
matchedConstructors.size() + " matched constructors for type: " + type.getName() +
", matched constructors: " + matchedConstructors);
} else if (matchedConstructors.size() == 1) {
targetConstructor = matchedConstructors.get(0);
} else if (defaultConstructor != null) {
targetConstructor = defaultConstructor;
} else {
throw new IllegalArgumentException("None matched constructor was found for type: " + type.getName());
}
// create instance with arguments
Class[] parameterTypes = targetConstructor.getParameterTypes();
Object[] args = new Object[parameterTypes.length];
for (int i = 0; i < parameterTypes.length; i++) {
args[i] = getArgumentValueForType(parameterTypes[i]);
}
return (T) targetConstructor.newInstance(args);
}
private boolean isMatched(Constructor constructor) {
for (Class parameterType : constructor.getParameterTypes()) {
if (!isSupportedConstructorParameterType(parameterType)) {
return false;
}
}
return true;
}
private boolean isSupportedConstructorParameterType(Class parameterType) {
return ScopeModel.class.isAssignableFrom(parameterType);
}
private Object getArgumentValueForType(Class parameterType) {
// get scope mode value
if (scopeModelAccessor != null) {
if (parameterType == ScopeModel.class) {
return scopeModelAccessor.getScopeModel();
} else if (parameterType == FrameworkModel.class) {
return scopeModelAccessor.getFrameworkModel();
} else if (parameterType == ApplicationModel.class) {
return scopeModelAccessor.getApplicationModel();
} else if (parameterType == ModuleModel.class) {
return scopeModelAccessor.getModuleModel();
}
}
return null;
}
}