我的场景：配置文件变更，不用重启程序，环境变量即可生效

但是我又不想监听整个文件夹，只想针对某个或某些文件做监听，自己抽象了个实现类

先上代码

接口

import java.io.File;

public interface DynamicConfiguration {
    void addListener(File file);

    void removeListener(File file);

    void start();

    void close();
}

import lombok.Data;
import lombok.experimental.Accessors;
import lombok.extern.slf4j.Slf4j;
import lombok.var;

import java.io.File;
import java.util.List;
import java.util.concurrent.*;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.ReentrantLock;

@Slf4j
public abstract class AbstractDynamicConfiguration implements DynamicConfiguration, Runnable{
    private static final String DEFAULT_THREAD_POOL_PREFIX_NAME = "thread-pool.prefix.workers";
    private static final int DEFAULT_THREAD_POOL_SIZE = 1;
    private static final long DEFAULT_KEEP_ALIVE_TIME = TimeUnit.MINUTES.toMillis(1);

    private final List<FileInfo> fileInfoChain;
    private final ThreadPoolExecutor workersThreadPool;
    private volatile Boolean running;

    private final ReentrantLock lock = new ReentrantLock();

    public AbstractDynamicConfiguration(String threadPoolPrefixName, int threadPoolSize, long keepAliveTime) {
        this.workersThreadPool = initWorkersThreadPool(threadPoolPrefixName, threadPoolSize, keepAliveTime);
        this.fileInfoChain = new CopyOnWriteArrayList<>();
        this.running = false;
    }

    public AbstractDynamicConfiguration() {
        this(DEFAULT_THREAD_POOL_PREFIX_NAME, DEFAULT_THREAD_POOL_SIZE, DEFAULT_KEEP_ALIVE_TIME);
    }

    @Override
    public void start() {
        this.running = true;
        this.workersThreadPool.execute(this::run);
    }

    @Override
    public void close() {
        this.running = false;
        fileInfoChain.clear();
        if (!workersThreadPool.isShutdown()) {
            workersThreadPool.shutdown();
        }
    }

    @Override
    public void addListener(File file) {
        fileInfoChain.add(new FileInfo(file));
        if(log.isInfoEnabled()) {
            log.info("Reload enabled, watching {}...", file.getPath());
        }
    }

    @Override
    public void removeListener(File file) {
        fileInfoChain.remove(new FileInfo(file));
    }

    protected ThreadPoolExecutor initWorkersThreadPool(String threadPoolPrefixName,
                                                       int threadPoolSize,
                                                       long keepAliveTime) {
        return new ThreadPoolExecutor(threadPoolSize, threadPoolSize, keepAliveTime,
                TimeUnit.MILLISECONDS, new LinkedBlockingQueue<>(), new NamedThreadFactory(threadPoolPrefixName, true));
    }

    @Override
    public void run() {
        while (this.running) {
            lock.lock();
            try {
                var iterator = fileInfoChain.iterator();
                while (iterator.hasNext()) {
                    try {
                        var fileInfo = iterator.next();
                        File newFile = new File(fileInfo.getFile().toURI());
                        if (newFile.lastModified() != fileInfo.getLastModified()) {
                            fileInfo.updateLastModified(newFile.lastModified());

                            try {
                                dynamicConfiguration(newFile);
                            }finally {
                                if(log.isDebugEnabled()) {
                                    log.debug("The gateway environment variable has been reloaded");
                                }
                            }
                        }
                    } catch (Exception e) {
                        close();
                    }
                }
            } finally {
                lock.unlock();
            }

            if(!this.running) {
                break;
            }

            try {
                Thread.sleep(10000L);
            } catch (InterruptedException var3) {
                close();
            }
        }
    }

    public abstract void dynamicConfiguration(File file);

    @Data
    @Accessors(chain = true)
    class FileInfo {
        private File file;
        private Long lastModified;

        public FileInfo(File file) {
            this.file = file;
            this.lastModified = file.lastModified();
        }

        public void updateLastModified(Long lastModified){
            this.lastModified = lastModified;
        }
    }

    class NamedThreadFactory implements ThreadFactory {
        protected final AtomicInteger mThreadNum = new AtomicInteger(1);
        protected final String mPrefix;
        protected final boolean mDaemon;
        protected final ThreadGroup mGroup;

        public NamedThreadFactory(String prefix, boolean daemon) {
            mPrefix = prefix + "-thread-";
            mDaemon = daemon;
            SecurityManager s = System.getSecurityManager();
            mGroup = (s == null) ? Thread.currentThread().getThreadGroup() : s.getThreadGroup();
        }

        @Override
        public Thread newThread(Runnable runnable) {
            String name = mPrefix + mThreadNum.getAndIncrement();
            Thread ret = new Thread(mGroup, runnable, name, 0);
            ret.setDaemon(mDaemon);
            return ret;
        }
    }
}

使用：
第一步：实现抽象类里面得dynamicConfiguration方法
第二步：添加自己需要监听得文件
第三步：启动监听程序

image.png

效果：

image.png

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