如何使用log4j2在elastic search中记录JSON结构作为源而不是消息

<dependencies>
    <!-- log4j2 -->
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-api</artifactId>
        <version>2.x.x</version>
    </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-core</artifactId>
        <version>2.x.x</version>
    </dependency>
</dependencies>

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="warn">
    <Appenders>
        <Elasticsearch name="elasticsearch" hosts="http://localhost:9200" index="myindex" indexPattern="myindex-%d{yyyy.MM.dd}" ignoreExceptions="false">
            <Mapping type="mytype">
                <Property name="message" value="$${json:$.message}" />
            </Mapping>
        </Elasticsearch>
    </Appenders>
    <Loggers>
        <Root level="debug">
            <AppenderRef ref="elasticsearch"/>
        </Root>
    </Loggers>
</Configuration>

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

public class MyClass {
    private static final Logger logger = LogManager.getLogger(MyClass.class);

    public static void main(String[] args) {
        String json = "{\"key1\": \"value1\", \"key2\": \"value2\"}";
        logger.info(json);
    }
}