捕获 log4j 输出

我们正在使用log4j2广泛地存在于我们的系统中，并对其进行配置log4j2.xml.

现在我需要一个可以运行的新应用程序jobs，我想单独捕获时间 X 和 Y 之间产生的所有日志并将其放入数据库中。我们框架的正常日志记录应该照常发生（记录到文件或 log4j2.xml 指向的任何地方），但是从时间 X 到时间 Y。

我还希望所有日志记录都应该被捕获，最好是字符串列表或可以保存在数据库表中的内容。

我的想法是创建一个新的 Appender（捕获所有日志输出）并动态添加/删除该 Appender 以启动和停止日志记录？那行得通吗？我也可以在框架类中重新配置记录器吗？

有可能的。您需要创建一个自定义附加程序。例如。：

public class CustomAppender extends AbstractAppender {

    private List<String> list = new ArrayList<>();

    public CustomAppender(String name, Filter filter, Layout<? extends Serializable> layout) {
        super(name, filter, layout);
    }

    public CustomAppender(String name, Filter filter, Layout<? extends Serializable> layout, boolean ignoreExceptions) {
        super(name, filter, layout, ignoreExceptions);
    }

    @Override
    public void append(LogEvent event) {
        byte[] data = getLayout().toByteArray(event);
        list.add(new String(data).trim()); // optional trim
    }

    @Override
    public void stop() {
        // Write to the database
        System.out.println(list);
    }

}

每个事件都会转换为字符串，然后添加到列表中。这stop删除appender后自动执行方法。

以下代码示例了此附加程序的使用。

public static void main(String[] args) {
    // Execute some jobs
    for (int n = 0; n < 10; n++) {
        dummyJob(n);
    }
}

private static void dummyJob(int n) {
    final LoggerContext ctx = (LoggerContext) LogManager.getContext(false);
    final AbstractConfiguration config = (AbstractConfiguration) ctx.getConfiguration();

    // Create and add the appender
    CustomAppender appender = new CustomAppender("Custom", null, PatternLayout.createDefaultLayout());
    appender.start();
    config.addAppender(appender);

    // Create and add the logger
    AppenderRef[] refs = new AppenderRef[]{AppenderRef.createAppenderRef("Custom", null, null)};
    LoggerConfig loggerConfig = LoggerConfig.createLogger("false", Level.INFO, "com.company", "true", refs, null, config, null);
    loggerConfig.addAppender(appender, null, null);
    config.addLogger("com.company", loggerConfig);
    ctx.updateLoggers();

    // Run the job
    Logger logger = LogManager.getLogger("com.company");
    logger.info("Job {}", n);
    logger.info("Hello, World!");
    logger.info("This is awesome!");
    logger.info("Hope it works!");
    logger.info("Hope it helps!");

    // Remove the logger and appender
    config.removeLogger("com.company");
    config.removeAppender("Custom");
    ctx.updateLoggers();

}

后者的输出：

[Job 0, Hello, World!, This is awesome!, Hope it works!, Hope it helps!]
[Job 1, Hello, World!, This is awesome!, Hope it works!, Hope it helps!]
[Job 2, Hello, World!, This is awesome!, Hope it works!, Hope it helps!]
[Job 3, Hello, World!, This is awesome!, Hope it works!, Hope it helps!]
[Job 4, Hello, World!, This is awesome!, Hope it works!, Hope it helps!]
[Job 5, Hello, World!, This is awesome!, Hope it works!, Hope it helps!]
[Job 6, Hello, World!, This is awesome!, Hope it works!, Hope it helps!]
[Job 7, Hello, World!, This is awesome!, Hope it works!, Hope it helps!]
[Job 8, Hello, World!, This is awesome!, Hope it works!, Hope it helps!]
[Job 9, Hello, World!, This is awesome!, Hope it works!, Hope it helps!]