java - 如何在 log4j2 中创建自定义 RewritePolicy？

Question

我正在尝试在 Log4j2 中编写我自己的 RewritePolicy。 documentation指出:

RewritePolicy is an interface that allows implementations to inspect and possibly modify LogEvents before they are passed to Appender. RewritePolicy declares a single method named rewrite that must be implemented. The method is passed the LogEvent and can return the same event or create a new one.

这是我的 java 类:

public final class MarkerInjectorRewritePolicy implements RewritePolicy {

    @Override
    public LogEvent rewrite(final LogEvent event) {
        final Marker marker = event.getMarker();
        if (marker == null)
            return event;

        // If there's a Marker, add it to the ThreadContextMap so the RoutingAppender can properly routes log messages
        event.getContextMap().put("_marker", marker.getName());
        return event;
    }
}

这是我的yaml 配置 文件:

Rewrite:
  name: REWRITE_APPENDER
  AppenderRef:
    ref: ROUTING_APPENDER
  PropertiesRewritePolicy:
    Property:
      - name: foo
        value: bar

但是我不知道如何将它注入(inject)到我的配置文件中。如何让它在运行时运行？

Answer 1

您的自定义重写策略应编码为 log4j2 插件。这使您能够在 RewriteAppender 中配置自定义 RewritePolicy。

@Plugin(name = "InjectMarkerPolicy", category = "Core",
        elementType = "rewritePolicy", printObject = true)
public final class MarkerInjectorRewritePolicy implements RewritePolicy {

    @Override
    public LogEvent rewrite(final LogEvent event) {
        final Marker marker = event.getMarker();
        if (marker == null)
            return event;

        // If there's a Marker, add it to the ThreadContextMap
        // so the RoutingAppender can properly routes log messages

        // event's context map is immutable, so need to make a copy...
        Map<String, String> mdc = new HashMap<>(event.getContextMap());
        mdc.put("_marker", marker.getName());

        LogEvent result = new Log4jLogEvent(event.getLoggerName(), event.getMarker(),
            event.getLoggerFqcn(), event.getLevel(), event.getMessage(),
            event.getThrown(), mdc, event.getContextStack(),
            event.getThreadName(), event.getSource(), event.getTimeMillis());

        return result;
    }
}

示例配置(TODO:为 packages 属性设置正确的值):

<Configuration status="trace" packages="my.rewritepolicy.plugin.package">
  <Appenders>
    <Console name="STDOUT">
      <PatternLayout pattern="[%-5level] %c{1.} %m%n"/>
    </Console>
    <Rewrite name="Rewrite">
      <InjectMarkerPolicy />
      <AppenderRef ref="STDOUT"/>
    </Rewrite>
  </Appenders>
  <Loggers>
    <Root level="trace">
      <AppenderRef ref="Rewrite"/>
    </Root>
  </Loggers>
</Configuration>