diff --git a/packages/hydrooj/src/lib/avatar.ts b/packages/hydrooj/src/lib/avatar.ts
index 55fd76ff1..a493a5404 100644
--- a/packages/hydrooj/src/lib/avatar.ts
+++ b/packages/hydrooj/src/lib/avatar.ts
@@ -1,5 +1,5 @@
-import { Types } from '../service/decorators';
 import { md5 } from '../utils';
+import { Types } from './validator';
 
 type AvatarProvider = (src: string, size: number) => string;
 
diff --git a/packages/hydrooj/src/lib/validator.ts b/packages/hydrooj/src/lib/validator.ts
new file mode 100644
index 000000000..1e7d79878
--- /dev/null
+++ b/packages/hydrooj/src/lib/validator.ts
@@ -0,0 +1,179 @@
+import assert from 'assert';
+import emojiRegex from 'emoji-regex';
+import { isSafeInteger } from 'lodash';
+import moment from 'moment-timezone';
+import { ObjectID } from 'mongodb';
+import saslprep from 'saslprep';
+
+type InputType = string | number | Record<string, any> | any[];
+export type Converter<T> = (value: any) => T;
+export type Validator<Loose extends boolean = true> = (value: Loose extends true ? any : InputType) => boolean;
+export type Type<T> = readonly [Converter<T>, Validator<false>?, boolean?];
+
+export interface Types {
+    // String outputs
+    Content: Type<string>;
+    Key: Type<string>;
+    /** @deprecated */
+    Name: Type<string>;
+    Username: Type<string>;
+    Password: Type<string>;
+    UidOrName: Type<string>;
+    Email: Type<string>;
+    Filename: Type<string>;
+    DomainId: Type<string>;
+    ProblemId: Type<string | number>;
+    Role: Type<string>;
+    Title: Type<string>;
+    Emoji: Type<string>;
+    String: Type<string>;
+
+    // Number outputs
+    Int: Type<number>;
+    UnsignedInt: Type<number>;
+    PositiveInt: Type<number>;
+    Float: Type<number>;
+
+    // Other
+    ObjectID: Type<ObjectID>;
+    Boolean: Type<boolean>;
+    Date: Type<string>;
+    Time: Type<string>;
+    Range: <T extends string | number>(range: Array<T> | Record<string, any>) => Type<T>;
+    /** @deprecated */
+    Array: Type<any[]>;
+    NumericArray: Type<number[]>;
+    CommaSeperatedArray: Type<string[]>;
+    Set: Type<Set<any>>;
+    Any: Type<any>;
+    ArrayOf: <T extends Type<any>>(type: T) => (T extends Type<infer R> ? Type<R[]> : never);
+    AnyOf: <T extends Type<any>>(...type: T[]) => (T extends Type<infer R> ? Type<R> : never);
+}
+
+const saslprepString = <T = string>(regex?: RegExp, cb?: (i: string) => boolean, convert?: (i: string) => T) => [
+    convert || ((v) => saslprep(v.toString().trim())),
+    (v) => {
+        try {
+            const res = saslprep(v.toString().trim());
+            if (regex && !regex.test(res)) return false;
+            if (cb && !cb(res)) return false;
+            return !!res.length;
+        } catch (e) {
+            return false;
+        }
+    },
+] as [(v) => string, (v) => boolean];
+
+export const Types: Types = {
+    Content: [(v) => v.toString().trim(), (v) => v && v.toString().trim().length < 65536],
+    Key: saslprepString(/^[a-zA-Z0-9-_]+$/),
+    /** @deprecated */
+    Name: saslprepString(/^.{1,255}$/),
+    Filename: saslprepString(/^[^\\/?#~!|*]{1,255}$/, (i) => !['con', '.', '..'].includes(i)),
+    UidOrName: saslprepString(/^(.{3,31}|[\u4e00-\u9fa5]{2}|-?[0-9]+)$/),
+    Username: saslprepString(/^(.{3,31}|[\u4e00-\u9fa5]{2})$/),
+    Password: saslprepString(/^.{6,255}$/),
+    ProblemId: saslprepString(/^[a-zA-Z0-9]+$/i, () => true, (s) => (Number.isSafeInteger(+s) ? +s : s)),
+    Email: saslprepString(/^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+(?:\.[a-zA-Z0-9-]+)+$/i),
+    DomainId: saslprepString(/^[a-zA-Z][a-zA-Z0-9_]{3,31}$/),
+    Role: saslprepString(/^[_0-9A-Za-z\u4e00-\u9fa5]{1,31}$/i),
+    Title: saslprepString(/^.{1,64}$/),
+    String: [(v) => v.toString(), null],
+
+    Int: [(v) => +v, (v) => /^[+-]?[0-9]+$/.test(v.toString().trim()) && isSafeInteger(+v)],
+    UnsignedInt: [(v) => +v, (v) => /^(-0|\+?[0-9]+)$/.test(v.toString().trim()) && isSafeInteger(+v)],
+    PositiveInt: [(v) => +v, (v) => /^\+?[1-9][0-9]*$/.test(v.toString().trim()) && isSafeInteger(+v)],
+    Float: [(v) => +v, (v) => Number.isFinite(+v)],
+
+    ObjectID: [(v) => new ObjectID(v), ObjectID.isValid],
+    Boolean: [(v) => v && !['false', 'off'].includes(v), null, true],
+    Date: [
+        (v) => {
+            const d = v.split('-');
+            assert(d.length === 3);
+            return `${d[0]}-${d[1].length === 1 ? '0' : ''}${d[1]}-${d[2].length === 1 ? '0' : ''}${d[2]}`;
+        },
+        (v) => {
+            const d = v.toString().split('-');
+            if (d.length !== 3) return false;
+            const st = `${d[0]}-${d[1].length === 1 ? '0' : ''}${d[1]}-${d[2].length === 1 ? '0' : ''}${d[2]}`;
+            return moment(st).isValid();
+        },
+    ],
+    Time: [
+        (v) => {
+            const t = v.split(':');
+            assert(t.length === 2);
+            return `${(t[0].length === 1 ? '0' : '') + t[0]}:${t[1].length === 1 ? '0' : ''}${t[1]}`;
+        },
+        (v) => {
+            const t = v.toString().split(':');
+            if (t.length !== 2) return false;
+            return moment(`2020-01-01 ${(t[0].length === 1 ? '0' : '') + t[0]}:${t[1].length === 1 ? '0' : ''}${t[1]}`).isValid();
+        },
+    ],
+    Range: (range) => [
+        (v) => {
+            if (range instanceof Array) {
+                for (const item of range) {
+                    if (typeof item === 'number' && item === +v) return +v;
+                    if (item === v) return v;
+                }
+            }
+            return v;
+        },
+        (v) => {
+            if (range instanceof Array) {
+                for (const item of range) {
+                    if (typeof item === 'string' && item === v) return true;
+                    if (typeof item === 'number' && item === +v) return true;
+                }
+            } else {
+                for (const key in range) {
+                    if (key === v) return true;
+                }
+            }
+            return false;
+        },
+    ],
+    /** @deprecated suggested to use Types.ArrayOf instead. */
+    Array: [(v) => {
+        if (v instanceof Array) return v;
+        return v ? [v] : [];
+    }, null],
+    NumericArray: [(v) => {
+        if (v instanceof Array) return v.map(Number);
+        return v.split(',').map(Number);
+    }, (v) => {
+        if (v instanceof Array) return v.map(Number).every(Number.isSafeInteger);
+        return v.toString().split(',').map(Number).every(Number.isSafeInteger);
+    }],
+    CommaSeperatedArray: [
+        (v) => v.toString().replace(/，/g, ',').split(',').map((e) => e.trim()).filter((i) => i),
+        (v) => !!v.toString(),
+    ],
+    Set: [(v) => {
+        if (v instanceof Array) return new Set(v);
+        return v ? new Set([v]) : new Set();
+    }, null],
+    Emoji: [
+        (v: string) => v.matchAll(emojiRegex()).next().value[0],
+        (v) => emojiRegex().test(v.toString()),
+    ],
+    Any: [(v) => v, null],
+    ArrayOf: (type) => [
+        (v) => {
+            const arr = v instanceof Array ? v : [v];
+            return arr.map((i) => type[0](i));
+        },
+        (v) => {
+            if (!type[1]) return true;
+            const arr = v instanceof Array ? v : [v];
+            return arr.every((i) => type[1](i));
+        },
+    ] as any,
+    AnyOf: (...types) => [
+        (v) => types.find((type) => type[1](v))[0](v),
+        (v) => types.some((type) => type[1](v)),
+    ] as any,
+};
diff --git a/packages/hydrooj/src/plugin-api.ts b/packages/hydrooj/src/plugin-api.ts
index 7ce689563..cefc15f8f 100644
--- a/packages/hydrooj/src/plugin-api.ts
+++ b/packages/hydrooj/src/plugin-api.ts
@@ -41,6 +41,7 @@ export { buildContent } from './lib/content';
 export { default as avatar } from './lib/avatar';
 export { default as rank } from './lib/rank';
 export { default as paginate } from './lib/paginate';
+export * from './lib/validator';
 export * from './service/decorators';
 export {
     Handler, ConnectionHandler, captureAllRoutes,
diff --git a/packages/hydrooj/src/service/decorators.ts b/packages/hydrooj/src/service/decorators.ts
index 69f9791ea..4ad2c283a 100644
--- a/packages/hydrooj/src/service/decorators.ts
+++ b/packages/hydrooj/src/service/decorators.ts
@@ -1,17 +1,9 @@
-import assert from 'assert';
-import emojiRegex from 'emoji-regex';
-import { isSafeInteger } from 'lodash';
-import moment from 'moment-timezone';
-import { ObjectID } from 'mongodb';
-import saslprep from 'saslprep';
 import { Time } from '@hydrooj/utils';
 import { ValidationError } from '../error';
+import { Converter, Type, Validator } from '../lib/validator';
 import type { Handler } from './server';
 
 type MethodDecorator = (target: any, name: string, obj: any) => any;
-type InputType = string | number | Record<string, any> | any[];
-type Converter<T> = (value: any) => T;
-type Validator<Loose extends boolean = true> = (value: Loose extends true ? any : InputType) => boolean;
 export interface ParamOption<T> {
     name: string,
     source: 'all' | 'get' | 'post' | 'route',
@@ -20,176 +12,6 @@ export interface ParamOption<T> {
     validate?: Validator,
 }
 
-type Type<T> = readonly [Converter<T>, Validator<false>?, boolean?];
-
-export interface Types {
-    // String outputs
-    Content: Type<string>;
-    Key: Type<string>;
-    /** @deprecated */
-    Name: Type<string>;
-    Username: Type<string>;
-    Password: Type<string>;
-    UidOrName: Type<string>;
-    Email: Type<string>;
-    Filename: Type<string>;
-    DomainId: Type<string>;
-    ProblemId: Type<string | number>;
-    Role: Type<string>;
-    Title: Type<string>;
-    Emoji: Type<string>;
-    String: Type<string>;
-
-    // Number outputs
-    Int: Type<number>;
-    UnsignedInt: Type<number>;
-    PositiveInt: Type<number>;
-    Float: Type<number>;
-
-    // Other
-    ObjectID: Type<ObjectID>;
-    Boolean: Type<boolean>;
-    Date: Type<string>;
-    Time: Type<string>;
-    Range: <T extends string | number>(range: Array<T> | Record<string, any>) => Type<T>;
-    /** @deprecated */
-    Array: Type<any[]>;
-    NumericArray: Type<number[]>;
-    CommaSeperatedArray: Type<string[]>;
-    Set: Type<Set<any>>;
-    Any: Type<any>;
-    ArrayOf: <T extends Type<any>>(type: T) => (T extends Type<infer R> ? Type<R[]> : never);
-    AnyOf: <T extends Type<any>>(...type: T[]) => (T extends Type<infer R> ? Type<R> : never);
-}
-
-const saslprepString = <T = string>(regex?: RegExp, cb?: (i: string) => boolean, convert?: (i: string) => T) => [
-    convert || ((v) => saslprep(v.toString().trim())),
-    (v) => {
-        try {
-            const res = saslprep(v.toString().trim());
-            if (regex && !regex.test(res)) return false;
-            if (cb && !cb(res)) return false;
-            return !!res.length;
-        } catch (e) {
-            return false;
-        }
-    },
-] as [(v) => string, (v) => boolean];
-
-export const Types: Types = {
-    Content: [(v) => v.toString().trim(), (v) => v && v.toString().trim().length < 65536],
-    Key: saslprepString(/^[a-zA-Z0-9-_]+$/),
-    /** @deprecated */
-    Name: saslprepString(/^.{1,255}$/),
-    Filename: saslprepString(/^[^\\/?#~!|*]{1,255}$/, (i) => !['con', '.', '..'].includes(i)),
-    UidOrName: saslprepString(/^(.{3,31}|[\u4e00-\u9fa5]{2}|-?[0-9]+)$/),
-    Username: saslprepString(/^(.{3,31}|[\u4e00-\u9fa5]{2})$/),
-    Password: saslprepString(/^.{6,255}$/),
-    ProblemId: saslprepString(/^[a-zA-Z0-9]+$/i, () => true, (s) => (Number.isSafeInteger(+s) ? +s : s)),
-    Email: saslprepString(/^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+(?:\.[a-zA-Z0-9-]+)+$/i),
-    DomainId: saslprepString(/^[a-zA-Z][a-zA-Z0-9_]{3,31}$/),
-    Role: saslprepString(/^[_0-9A-Za-z\u4e00-\u9fa5]{1,31}$/i),
-    Title: saslprepString(/^.{1,64}$/),
-    String: [(v) => v.toString(), null],
-
-    Int: [(v) => +v, (v) => /^[+-]?[0-9]+$/.test(v.toString().trim()) && isSafeInteger(+v)],
-    UnsignedInt: [(v) => +v, (v) => /^(-0|\+?[0-9]+)$/.test(v.toString().trim()) && isSafeInteger(+v)],
-    PositiveInt: [(v) => +v, (v) => /^\+?[1-9][0-9]*$/.test(v.toString().trim()) && isSafeInteger(+v)],
-    Float: [(v) => +v, (v) => Number.isFinite(+v)],
-
-    ObjectID: [(v) => new ObjectID(v), ObjectID.isValid],
-    Boolean: [(v) => v && !['false', 'off'].includes(v), null, true],
-    Date: [
-        (v) => {
-            const d = v.split('-');
-            assert(d.length === 3);
-            return `${d[0]}-${d[1].length === 1 ? '0' : ''}${d[1]}-${d[2].length === 1 ? '0' : ''}${d[2]}`;
-        },
-        (v) => {
-            const d = v.toString().split('-');
-            if (d.length !== 3) return false;
-            const st = `${d[0]}-${d[1].length === 1 ? '0' : ''}${d[1]}-${d[2].length === 1 ? '0' : ''}${d[2]}`;
-            return moment(st).isValid();
-        },
-    ],
-    Time: [
-        (v) => {
-            const t = v.split(':');
-            assert(t.length === 2);
-            return `${(t[0].length === 1 ? '0' : '') + t[0]}:${t[1].length === 1 ? '0' : ''}${t[1]}`;
-        },
-        (v) => {
-            const t = v.toString().split(':');
-            if (t.length !== 2) return false;
-            return moment(`2020-01-01 ${(t[0].length === 1 ? '0' : '') + t[0]}:${t[1].length === 1 ? '0' : ''}${t[1]}`).isValid();
-        },
-    ],
-    Range: (range) => [
-        (v) => {
-            if (range instanceof Array) {
-                for (const item of range) {
-                    if (typeof item === 'number' && item === +v) return +v;
-                    if (item === v) return v;
-                }
-            }
-            return v;
-        },
-        (v) => {
-            if (range instanceof Array) {
-                for (const item of range) {
-                    if (typeof item === 'string' && item === v) return true;
-                    if (typeof item === 'number' && item === +v) return true;
-                }
-            } else {
-                for (const key in range) {
-                    if (key === v) return true;
-                }
-            }
-            return false;
-        },
-    ],
-    /** @deprecated suggested to use Types.ArrayOf instead. */
-    Array: [(v) => {
-        if (v instanceof Array) return v;
-        return v ? [v] : [];
-    }, null],
-    NumericArray: [(v) => {
-        if (v instanceof Array) return v.map(Number);
-        return v.split(',').map(Number);
-    }, (v) => {
-        if (v instanceof Array) return v.map(Number).every(Number.isSafeInteger);
-        return v.toString().split(',').map(Number).every(Number.isSafeInteger);
-    }],
-    CommaSeperatedArray: [
-        (v) => v.toString().replace(/，/g, ',').split(',').map((e) => e.trim()).filter((i) => i),
-        (v) => !!v.toString(),
-    ],
-    Set: [(v) => {
-        if (v instanceof Array) return new Set(v);
-        return v ? new Set([v]) : new Set();
-    }, null],
-    Emoji: [
-        (v: string) => v.matchAll(emojiRegex()).next().value[0],
-        (v) => emojiRegex().test(v.toString()),
-    ],
-    Any: [(v) => v, null],
-    ArrayOf: (type) => [
-        (v) => {
-            const arr = v instanceof Array ? v : [v];
-            return arr.map((i) => type[0](i));
-        },
-        (v) => {
-            if (!type[1]) return true;
-            const arr = v instanceof Array ? v : [v];
-            return arr.every((i) => type[1](i));
-        },
-    ] as any,
-    AnyOf: (...types) => [
-        (v) => types.find((type) => type[1](v))[0](v),
-        (v) => types.some((type) => type[1](v)),
-    ] as any,
-};
-
 function _buildParam(name: string, source: 'get' | 'post' | 'all' | 'route', ...args: Array<Type<any> | boolean | Validator | Converter<any>>) {
     let cursor = 0;
     const v: ParamOption<any> = { name, source };
diff --git a/packages/hydrooj/src/service/server.ts b/packages/hydrooj/src/service/server.ts
index fec3d59a2..21f3cd122 100644
--- a/packages/hydrooj/src/service/server.ts
+++ b/packages/hydrooj/src/service/server.ts
@@ -17,6 +17,7 @@ import {
     UserFacingError,
 } from '../error';
 import { DomainDoc } from '../interface';
+import { Types } from '../lib/validator';
 import { Logger } from '../logger';
 import { PERM, PRIV } from '../model/builtin';
 import * as opcount from '../model/opcount';
@@ -35,6 +36,7 @@ import { Router } from './router';
 import { encodeRFC5987ValueChars } from './storage';
 
 export * from './decorators';
+export * from '../lib/validator';
 
 export interface HydroRequest {
     method: string;
@@ -556,6 +558,7 @@ ${ctx.response.status} ${endTime - startTime}ms ${ctx.response.length}`);
 
 global.Hydro.service.server = {
     ...decorators,
+    Types,
     app,
     httpServer,
     wsServer,