UsernamePolicy

Info

Utility class enforcing username format validation: Unicode letters, digits, underscores, dots, and hyphens within 2-32 characters.

Overview

A stateless policy class (private constructor, static methods) that validates usernames at registration and profile update time. Supports international characters via Unicode letter matching.

Constants

Constant	Value	Description
MIN_LENGTH	2	Minimum username length (by code point)
MAX_LENGTH	32	Maximum username length (by code point)

Validation Rules

Rule	Error Message
Must not be null or blank	"用户名不能为空"
Length must be 2-32 code points	"用户名长度需为 2-32 位"
Only [\p{L}\p{N}_.\-] allowed	"用户名仅允许中英文、数字、下划线、点或短横线"

Methods

Method	Return	Description
validate(username)	String | null	Returns error message if invalid, null if valid

Charset Pattern

^[\p{L}\p{N}_.\-]+$

• \p{L} -- any Unicode letter (Chinese, English, etc.)
• \p{N} -- any Unicode digit
• _ -- underscore
• . -- dot
• - -- hyphen