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 class :

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我的配置文件。我怎样才能让它在运行时工作？

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：为包属性设置正确的值）：

<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>

Answer 2

不要忘记插件的工厂方法，否则将无法启动：

    @PluginFactory
    public static MarkerInjectorRewritePolicy createPolicy() {
        return new MarkerInjectorRewritePolicy();
    }

这是我的 github 帐户的一个工作示例：https://github.com/sercasti/Log4j-RewriteAppender/

如何在 log4j2 中创建自定义 RewritePolicy？

How to create custom RewritePolicy in log4j2?

java

configuration

logging

log4j

log4j2