logstash 自定义正则

aav77%%(?<str>([a-zA-Z0-9])){  "str": [    [      "a"    ]  ]}+ 匹配前导字符一次或多次aav77%%(?<str>([a-zA-Z0-9]+)){  "str": [    [      "aav77"    ]  ]}下面是从官方文件中摘抄的最简单但是足够说明用法的示例：+USERNAME [a-zA-Z0-9._-]+USER %{USERNAME}aav.%%_(?<str>([a-zA-Z0-9._-]+)){  "str": [    [      "aav."    ]  ]}aavssrr_%%_(?<str>(%{USERNAME})){  "str": [    [      "aavssrr_"    ]  ]}