DelegatingMethodAccessorImpl.java

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
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 * 2 along with this work; if not, write to the Free Software Foundation,
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package jdk.internal.reflect;

import java.lang.reflect.InvocationTargetException;

/**
 * Delegates its invocation to another MethodAccessorImpl and can change its delegate at run time.
 */
/*
 * 方法访问器的代理，配合"Inflation"技术的实现。
 *
 * 该代理会包装一个被代理的方法访问器。
 * 如果开启了"Inflation"技术，则会用到当前代理类。
 *
 * 当某个方法被反射调用的次数小于某个阈值时(参考ReflectionFactory#inflationThreshold字段)，被代理的方法访问器是基于JNI的方法访问器，
 * 当某个方法被反射调用的次数超过某个阈值时，被代理的方法访问器是基于纯Java实现的方法访问器。
 */
class DelegatingMethodAccessorImpl extends MethodAccessorImpl {
    private MethodAccessorImpl delegate;    // 被代理的方法访问器
    
    DelegatingMethodAccessorImpl(MethodAccessorImpl delegate) {
        setDelegate(delegate);
    }
    
    /*
     * delegate可能的值：
     * 基于JNI的方法访问器：NativeMethodAccessorImpl
     * 基于纯Java实现的方法访问器：jdk/internal/reflect/GeneratedMethodAccessor
     *
     * delegate的切换参见"Inflation"技术的描述
     */
    public Object invoke(Object obj, Object[] args) throws IllegalArgumentException, InvocationTargetException {
        return delegate.invoke(obj, args);
    }
    
    void setDelegate(MethodAccessorImpl delegate) {
        this.delegate = delegate;
    }
}