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/*
 * Copyright (c) 2008-2025 The Aspectran Project
 *
 * 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 com.aspectran.utils.thread;

import com.aspectran.utils.annotation.jsr305.NonNull;
import com.aspectran.utils.annotation.jsr305.Nullable;

import java.util.concurrent.Callable;

/**
 * Created: 2024-12-30
 */
public abstract class ThreadContextHelper {

    /**
     * Override the thread context ClassLoader with the environment's bean ClassLoader
     * if necessary, i.e. if the bean ClassLoader is not equivalent to the thread
     * context ClassLoader already.
     * @param classLoader the actual ClassLoader to use for the thread context
     * @return the original thread context ClassLoader, or {@code null} if not overridden
     */
    @Nullable
    public static ClassLoader overrideClassLoader(@Nullable ClassLoader classLoader) {
        if (classLoader != null) {
            Thread currentThread = Thread.currentThread();
            ClassLoader contextClassLoader = currentThread.getContextClassLoader();
            if (!classLoader.equals(contextClassLoader)) {
                currentThread.setContextClassLoader(classLoader);
                return contextClassLoader;
            }
        }
        return null;
    }

    public static void restoreClassLoader(@Nullable ClassLoader classLoader) {
        if (classLoader != null) {
            Thread.currentThread().setContextClassLoader(classLoader);
        }
    }

    public static void run(ClassLoader classLoader, @NonNull Runnable runnable) {
        ClassLoader old = overrideClassLoader(classLoader);
        try {
            runnable.run();
        } finally {
            restoreClassLoader(old);
        }
    }

    public static  void runThrowable(ClassLoader classLoader, @NonNull ThrowingRunnable runnable) throws T {
        ClassLoader old = overrideClassLoader(classLoader);
        try {
            runnable.run();
        } finally {
            restoreClassLoader(old);
        }
    }

    public static  V call(ClassLoader classLoader, @NonNull Callable callable) throws Exception {
        ClassLoader old = overrideClassLoader(classLoader);
        try {
            return callable.call();
        } finally {
            restoreClassLoader(old);
        }
    }

}