Tomcat从8.5.0版本开始，HTTP响应中不再发送STATUS_MSG状态码说明changelog_Tomcat_8.5.0_Coyote。
RFC7230 中的说明
根据RFC7230中关于Status Line状态行的描述RFC7230-3.1.2
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The first line of a response message is the status-line, consisting of the protocol version, a space (SP), the status code, another space, a possibly empty textual phrase describing the status code, and ending with CRLF.
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A client SHOULD ignore the reason-phrase content.
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HTTP响应中状态行的状态码说明文本是可选且应该忽略。
Tomcat 8.5.0 更新说明
Tomcat从8.5.0版本开始，HTTP响应中不再发送STATUS_MSG状态码说明changelog_Tomcat_8.5.0_Coyote。
RFC 7230 states that clients should ignore reason phrases in HTTP/1.1 response messages. Since the reason phrase is optional, Tomcat no longer sends it. As a result the system property org.apache.coyote.USE_CUSTOM_STATUS_MSG_IN_HEADER is no longer used and has been removed. (markt)