回程中的CyclicBufferAppender

Question

在logback中有一个名为CyclicBufferAppender的appender，似乎没有它的示例。它是做什么的？它如何在rollingFileAppender的上下文中工作？它是与RollingFileAppender一起工作还是独立工作？它类似于Asyncappender吗？任何以编程方式编写的示例都是受欢迎的。

Answer 1

让我分享一个例子，说明我如何使用它让我的Spring Boot web应用程序在UI中显示自己的日志消息。

我有一个CyclicBufferAppender子类，InmemoryAppender，其唯一目的是让Spring将其作为bean进行管理。（受@neemepraks回答的启发。）

@Component
public class InMemoryAppender extends CyclicBufferAppender<ILoggingEvent> implements SmartLifecycle {
    @Override
    public boolean isRunning() {
        return isStarted();
    }
}

我在启动过程中添加该组件（这意味着它将错过Spring Boot启动日志消息，如链接的答案所示，但我对此没有意见）：

public static void main(String[] args) {
    ConfigurableApplicationContext context = SpringApplication.run(WebApplication.class, args);

    LoggerContext loggerContext = (LoggerContext)LoggerFactory.getILoggerFactory();
    Logger rootLogger = loggerContext.getLogger(Logger.ROOT_LOGGER_NAME);
    rootLogger.addAppender(context.getBean(InMemoryAppender.class));
}

@Controller
@RequestMapping(path = "/logs")
public class LogController {
    public LogController(InMemoryAppender appender) {
        this.appender = appender;
    }

    private final InMemoryAppender appender;

    @GetMapping
    public String index(Model model) throws Exception {
        ILoggingEvent[] events = new ILoggingEvent[appender.getLength()];
        for (int i = 0; i < appender.getLength(); i++) {
            events[i] = appender.get(i);
        }
        model.addAttribute("logs", events);
        return "logs/index";
    }
}

<h1>Logs</h1>

<table style="border-collapse: separate; border-spacing: 2px;">
    <thead>
        <tr>
            <th scope="col">Timestamp</th>
            <th scope="col">Level</th>
            <th scope="col">Message</th>
        </tr>
    </thead>
    <tbody>
        <tr th:each="log: ${logs}" th:object="${log}">
            <td th:text="*{#dates.format(timeStamp, 'yyyy-MM-dd HH:mm:ss.SSS')}" style="white-space: nowrap;">[timestamp]</td>
            <td th:text="*{level}">[level]</td>
            <td th:text="*{message}">[message]</td>
        </tr>
    </tbody>
</table>