按文件同步访问文件[副本]

Question

public void logUser(long uniqueID, String event) throws IOException
{
    BufferedWriter buffWriter = new BufferedWriter(new FileWriter(uniqueID + ".log", true));
    buffWriter.write(event);
    buffWriter.close();
}

Answer 1

我相信同步整个事情的另一个选择是使用异步方法。假设所有日志条目都被添加到blockingqueue中，其他线程使用该队列。那么，就不需要同步。

示例：

public class LogAsync {
    // Some kind of abstraction for a log entry
    public static class LogEntry {
        private final String event;
        private final long uniqueId;

        public LogEntry(long uniqueId, String event) {
            this.uniqueId = uniqueId;
            this.event = event;
        }

        public String getEvent() {
            return event;
        }

        public long getUniqueId() {
            return uniqueId;
        }
    }

    // A blocking queue where the entries are stored    
    private final BlockingQueue<LogEntry> logEvents = new LinkedBlockingQueue<>();

    // Adds a log entry to the blocking queue    
    public void logUser(long uniqueID, String event) {
        logEvents.add(new LogEntry(uniqueID, event));
    }

    // Starts the thread that handles the "writing to file"
    public LogAsync start() {
        // Run in another thread
        CompletableFuture.runAsync(() -> {
                    while (true) {
                        try {
                            final LogEntry entry = logEvents.take();

                            try (BufferedWriter buffWriter = new BufferedWriter(new FileWriter(entry.getUniqueId() + ".log", true))) {
                                buffWriter.write(entry.getEvent());
                            } catch (IOException e) {
                                e.printStackTrace();
                            }
                        } catch (InterruptedException e) {
                            break;
                        }
                    }
                }
        );
        return this;
    }
}

初始化整个过程的方式可以如下所示：

final LogAsync logger = new LogAsync().start();
logger.logUser(1, "Hello");
logger.logUser(1, "there");
logger.logUser(2, "Goodbye");