如何将字段添加到log4j2的JSON日志

说我有一个标准的JSON日志，如docs中的示例所示（如下）

{
    "logger":"com.foo.Bar",
    "timestamp":"1376681196470",
    "level":"INFO",
    "thread":"main",
    "message":"Message flushed with immediate flush=true"
}

现在，我想向此日志添加自定义信息，如下所示：

{
    "logger":"com.foo.Bar",
    "timestamp":"1376681196470",
    "level":"INFO",
    "thread":"main",
    "message":"Message flushed with immediate flush=true",
    "extrainformation":"Some very important stuff I need to include",
    "extrainformation2":"Some other very important stuff I need to include"
}

有没有办法做到这一点？文档似乎没有提及有关向日志对象添加属性的任何内容。我是否需要进行自定义布局或以编程方式添加字段或其他内容？

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