JAVA 监控并获取日志类文件变化(新增)

JAVA 监控并获取日志类文件变化(新增)

使用 JDK7+（1.7之前没有的哈！？） 工具类 java.nio.file.WatchService
写来用于监控日志文件新增内容（只能检测获取新增内容哈！？中间改一手读不出来的哈！）
要配置目录和文件哈！

源码：

import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.charset.StandardCharsets;
import java.nio.file.*;
import java.util.List;
import java.util.concurrent.atomic.AtomicLong;
import java.util.function.Consumer;

/**
 * 监控文件变化
 * @author YL
 **/
public class FileWatcher {

    public static void main(String[] args) throws IOException, InterruptedException {
        // 监控的目录
        String filePath = "C:\\project\\imony_abroad\\logs\\";
        // 要监控的文件
        String fileName = "spring.log";

        FileWatcher.watcherLog(filePath, fileName, System.out::println);
    }

    /**
     * 文件监控
     * 同步调用会阻塞
     * @param filePath
     * @param fileName
     * @param consumer
     * @throws IOException
     * @throws InterruptedException
     */
    public static void watcherLog(String filePath, String fileName, Consumer<String> consumer) throws IOException, InterruptedException {
        WatchService watchService = FileSystems.getDefault().newWatchService();

        Paths.get(filePath).register(watchService, StandardWatchEventKinds.ENTRY_CREATE,
                StandardWatchEventKinds.ENTRY_MODIFY, StandardWatchEventKinds.ENTRY_DELETE);
		// 文件读取行数
        AtomicLong lastPointer = new AtomicLong(0L);
        do {
            WatchKey key = watchService.take();
            List<WatchEvent<?>> watchEvents = key.pollEvents();
            watchEvents.stream().filter(
                    i -> StandardWatchEventKinds.ENTRY_MODIFY == i.kind()
                            && fileName.equals(((Path) i.context()).getFileName().toString())
            ).forEach(i -> {
                if (i.count() > 1) {
                    // "重复事件"
                    return;
                }

                File configFile = Paths.get(filePath + "/" + i.context()).toFile();
                StringBuilder str = new StringBuilder();
                // 读取文件
                lastPointer.set(getFileContent(configFile, lastPointer.get(), str));

                if (str.length() != 0 ) {
                    consumer.accept(str.toString());
                }
            });
            key.reset();
        } while (true);
    }

    /**
     * beginPointer > configFile 时会从头读取
     * @param configFile
     * @param beginPointer
     * @param str 内容会拼接进去
     * @return 读到了多少字节, -1 读取失败
     */
    private static long getFileContent(File configFile, long beginPointer, StringBuilder str) {
        if (beginPointer < 0) {
            beginPointer = 0;
        }
        RandomAccessFile file = null;
        boolean top = true;
        try {
            file = new RandomAccessFile(configFile, "r");
            if (beginPointer > file.length()) {
                return 0;
            }
            file.seek(beginPointer);
            String line;
            while ((line = file.readLine()) != null) {
                if (top) {
                    top = false;
                } else {
                    str.append("\n");
                }
                str.append(new String(line.getBytes(StandardCharsets.ISO_8859_1), StandardCharsets.UTF_8));
            }
            return file.getFilePointer();
        } catch (IOException e) {
            e.printStackTrace();
            return -1;
        } finally {
            if (file != null) {
                try {
                    file.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}