Wsrtjtyk

I have implemented the following plugin to create custom Json layout for log4j logs. I am not sure how I can implement the context lookup in the Plugin. For example, the application puts certain keys in MDC and with the below configuration in log4j.xml, it must be written in logs.

<KeyValuePair key="customerId" value="$${customerId}" />. 

Plugin

@Plugin(name = "CustomJsonLayout", category = "Core", elementType = "layout", printObject = true)

public class CustomJsonLayout extends AbstractStringLayout {

private final ObjectMapper objectMapper;



CustomJsonLayout(Charset charset) {

    super(charset);

    SimpleModule module = new SimpleModule();

    module.addSerializer(LogEvent.class, new LogEventSerializer());

    module.addSerializer(ReadOnlyStringMap.class, new ContextDataSerializer() {

    });

    objectMapper = new ObjectMapper();

    objectMapper.registerModule(module);

    objectMapper.setSerializationInclusion(JsonInclude.Include.NON_EMPTY);

}



@Override

public String toSerializable(LogEvent logEvent) {

    try {

        return objectMapper.writeValueAsString(logEvent);

    } catch (JsonProcessingException e) {

        throw new IllegalStateException(e);

    }

}



private static class LogEventSerializer extends StdSerializer<LogEvent> {

    LogEventSerializer() {

        super(LogEvent.class);

    }



    @Override

    public void serialize(LogEvent value, JsonGenerator gen, SerializerProvider provider) throws IOException {

        String pattern = "yyyy-MM-dd HH:mm:ss.SSS";

        SimpleDateFormat simpleDateFormat = new SimpleDateFormat(pattern);

        String date = simpleDateFormat.format(new Date(value.getTimeMillis()));



        gen.writeStartObject();

        gen.writeStringField("timestamp", date);

        gen.writeStringField("component", MicroService.getAppName());

        gen.writeStringField("severity", value.getLevel().name());

        gen.writeObjectField("msg", value.getMessage().getFormattedMessage());

        gen.writeEndObject();

        gen.writeRaw("n");

    }

}



@PluginBuilderFactory

public static <B extends Builder<B>> B newBuilder() {

    return new Builder<B>().asBuilder();

}



public static class Builder<B extends Builder<B>> extends org.apache.logging.log4j.core.layout.AbstractStringLayout.Builder<B> implements org.apache.logging.log4j.core.util.Builder<CustomJsonLayout> {

    Builder() {

        this.setCharset(StandardCharsets.UTF_8);

    }



    public CustomJsonLayout build() {

        return new CustomJsonLayout(this.getCharset());

    }

}

}