diff --git a/examples/basic/data-source.ts b/examples/basic/data-source.ts
index c4a9e69..e89393c 100644
--- a/examples/basic/data-source.ts
+++ b/examples/basic/data-source.ts
@@ -1,9 +1,7 @@
-import {dataSources, Resource} from '../../src';
 import {DataSource} from '../../src/backend/data-source';
-import {BaseDataSource} from '../../src/common/data-source';
 
-export const autoIncrement = async (dataSource: BaseDataSource) => {
-	const data = await (dataSource as DataSource).getMultiple() as Record<string, string>[];
+export const autoIncrement = async (dataSource: DataSource) => {
+	const data = await dataSource.getMultiple() as Record<string, string>[];
 
 	const highestId = data.reduce<number>(
 		(highestId, d) => (Number(d.id) > highestId ? Number(d.id) : highestId),
@@ -16,5 +14,3 @@ export const autoIncrement = async (dataSource: BaseDataSource) => {
 
 	return 1;
 };
-
-export const dataSource = (resource: Resource) => new dataSources.jsonlFile.DataSource(resource, 'examples/basic');
diff --git a/examples/basic/server.ts b/examples/basic/server.ts
index 1ba6361..bcd5c59 100644
--- a/examples/basic/server.ts
+++ b/examples/basic/server.ts
@@ -1,10 +1,10 @@
 import {
-	application,
+	application, dataSources,
 	resource,
 	validation as v,
 } from '../../src';
 import {TEXT_SERIALIZER_PAIR} from './serializers';
-import {autoIncrement, dataSource} from './data-source';
+import {autoIncrement} from './data-source';
 
 const Piano = resource(v.object(
 	{
@@ -14,18 +14,18 @@ const Piano = resource(v.object(
 ))
 	.name('Piano')
 	.route('pianos')
-	.id('id', {
-		generationStrategy: autoIncrement,
-		serialize: (id) => id?.toString() ?? '0',
-		deserialize: (id) => Number.isFinite(Number(id)) ? Number(id) : 0,
-		schema: v.number(),
-	})
 	.canFetchItem()
 	.canFetchCollection()
 	.canCreate()
 	.canEmplace()
 	.canPatch()
-	.canDelete();
+	.canDelete()
+	.id('id', {
+		generationStrategy: autoIncrement,
+		serialize: (id) => id?.toString() ?? '0',
+		deserialize: (id) => Number.isFinite(Number(id)) ? Number(id) : 0,
+		schema: v.number(),
+	});
 
 const User = resource(v.object(
 	{
@@ -37,15 +37,15 @@ const User = resource(v.object(
 	},
 	v.never()
 ))
+	.name('User')
+	.route('users')
+	.fullText('bio')
 	.id('id' as const, {
 		generationStrategy: autoIncrement,
 		serialize: (id) => id?.toString() ?? '0',
 		deserialize: (id) => Number.isFinite(Number(id)) ? Number(id) : 0,
 		schema: v.number(),
-	})
-	.name('User')
-	.route('users')
-	.fullText('bio');
+	});
 
 const app = application({
 	name: 'piano-service',
@@ -55,7 +55,7 @@ const app = application({
 	.resource(User);
 
 const backend = app.createBackend({
-	dataSource,
+	dataSource: new dataSources.jsonlFile.DataSource('examples/basic'),
 });
 
 const server = backend.createHttpServer({
diff --git a/src/backend/common.ts b/src/backend/common.ts
index a54fe06..2f6d7e0 100644
--- a/src/backend/common.ts
+++ b/src/backend/common.ts
@@ -1,12 +1,12 @@
-import {ApplicationState, ContentNegotiation, Resource} from '../common';
-import {BaseDataSource} from '../common/data-source';
+import {ApplicationState, ContentNegotiation} from '../common';
+import {DataSource} from './data-source';
 
 export interface BackendState {
 	app: ApplicationState;
-	dataSource: (resource: Resource) => BaseDataSource;
+	dataSource: DataSource;
 	cn: ContentNegotiation;
 	showTotalItemCountOnGetCollection: boolean;
-	throws404OnDeletingNotFound: boolean;
+	throwsErrorOnDeletingNotFound: boolean;
 	checksSerializersOnDelete: boolean;
 	showTotalItemCountOnCreateItem: boolean;
 }
diff --git a/src/backend/core.ts b/src/backend/core.ts
index 237cafa..e7c5cea 100644
--- a/src/backend/core.ts
+++ b/src/backend/core.ts
@@ -1,25 +1,11 @@
-import * as v from 'valibot';
 import {ApplicationState, FALLBACK_CHARSET, FALLBACK_LANGUAGE, FALLBACK_MEDIA_TYPE, Resource} from '../common';
 import http from 'http';
 import {createServer, CreateServerParams} from './http/server';
 import https from 'https';
 import {BackendState} from './common';
-import {BaseDataSource} from '../common/data-source';
 import {DataSource} from './data-source';
 
-export interface BackendResource<
-	DataSourceType extends BaseDataSource = DataSource,
-	ResourceSchema extends v.BaseSchema = v.BaseSchema,
-	ResourceName extends string = string,
-	ResourceRouteName extends string = string,
-	IdAttr extends string = string,
-	IdSchema extends v.BaseSchema = v.BaseSchema
-> extends Resource<ResourceSchema, ResourceName, ResourceRouteName, IdAttr, IdSchema> {
-	newId(dataSource: DataSourceType): string | number | unknown;
-	dataSource: DataSourceType;
-}
-
-export interface BackendBuilder<T extends BaseDataSource = BaseDataSource> {
+export interface BackendBuilder<T extends DataSource = DataSource> {
 	showTotalItemCountOnGetCollection(b?: boolean): this;
 	showTotalItemCountOnCreateItem(b?: boolean): this;
 	checksSerializersOnDelete(b?: boolean): this;
@@ -30,7 +16,7 @@ export interface BackendBuilder<T extends BaseDataSource = BaseDataSource> {
 
 export interface CreateBackendParams {
 	app: ApplicationState;
-	dataSource: (resource: Resource) => BaseDataSource;
+	dataSource: DataSource;
 }
 
 export const createBackend = (params: CreateBackendParams) => {
@@ -44,7 +30,7 @@ export const createBackend = (params: CreateBackendParams) => {
 		},
 		showTotalItemCountOnGetCollection: false,
 		showTotalItemCountOnCreateItem: false,
-		throws404OnDeletingNotFound: false,
+		throwsErrorOnDeletingNotFound: false,
 		checksSerializersOnDelete: false,
 	};
 
@@ -58,7 +44,7 @@ export const createBackend = (params: CreateBackendParams) => {
 			return this;
 		},
 		throwsErrorOnDeletingNotFound(b = true) {
-			backendState.throws404OnDeletingNotFound = b;
+			backendState.throwsErrorOnDeletingNotFound = b;
 			return this;
 		},
 		checksSerializersOnDelete(b = true) {
diff --git a/src/backend/data-source.ts b/src/backend/data-source.ts
index d85f2ec..915bda4 100644
--- a/src/backend/data-source.ts
+++ b/src/backend/data-source.ts
@@ -1,13 +1,34 @@
-import {BaseDataSource} from '../common/data-source';
+import * as v from 'valibot';
+import {Resource} from '../common';
 
-export interface DataSource<T = object, Q = object> extends BaseDataSource {
+type IsCreated = boolean;
+
+type TotalCount = number;
+
+type DeleteResult = unknown;
+
+export interface DataSource<Schema = object, Query = object, ID = string> {
 	initialize(): Promise<unknown>;
-	getTotalCount?(query?: Q): Promise<number>;
-	getMultiple(query?: Q): Promise<T[]>;
-	getById(id: string): Promise<T | null>;
-	getSingle?(query?: Q): Promise<T | null>;
-	create(data: T): Promise<T>;
-	delete(id: string): Promise<unknown>;
-	emplace(id: string, data: T): Promise<[T, boolean]>;
-	patch(id: string, data: Partial<T>): Promise<T | null>;
+	getTotalCount?(query?: Query): Promise<TotalCount>;
+	getMultiple(query?: Query): Promise<Schema[]>;
+	getById(id: ID): Promise<Schema | null>;
+	getSingle?(query?: Query): Promise<Schema | null>;
+	create(data: Schema): Promise<Schema>;
+	delete(id: ID): Promise<DeleteResult>;
+	emplace(id: ID, data: Schema): Promise<[Schema, IsCreated]>;
+	patch(id: ID, data: Partial<Schema>): Promise<Schema | null>;
+	prepareResource(resource: Resource): void;
+	newId(): Promise<ID>;
+}
+
+
+export interface ResourceIdConfig<IdSchema extends v.BaseSchema> {
+	generationStrategy: GenerationStrategy;
+	serialize: (id: unknown) => string;
+	deserialize: (id: string) => v.Output<IdSchema>;
+	schema: IdSchema;
+}
+
+export interface GenerationStrategy {
+	(dataSource: DataSource, ...args: unknown[]): Promise<string | number | unknown>;
 }
diff --git a/src/backend/data-sources/file-jsonl.ts b/src/backend/data-sources/file-jsonl.ts
index edc6a52..c93ae3d 100644
--- a/src/backend/data-sources/file-jsonl.ts
+++ b/src/backend/data-sources/file-jsonl.ts
@@ -1,18 +1,64 @@
 import {readFile, writeFile} from 'fs/promises';
 import {join} from 'path';
-import {DataSource as DataSourceInterface} from '../data-source';
+import {DataSource as DataSourceInterface, ResourceIdConfig} from '../data-source';
 import {Resource} from '../..';
+import * as v from 'valibot';
+
+declare module '../..' {
+
+
+	interface BaseResourceState {
+		idAttr: string;
+		idConfig: ResourceIdConfig<v.BaseSchema>
+	}
+
+	interface Resource<
+		Schema extends v.BaseSchema = v.BaseSchema,
+		CurrentName extends string = string,
+		CurrentRouteName extends string = string,
+		CurrentIdAttr extends string = string,
+		IdSchema extends v.BaseSchema = v.BaseSchema
+	> {
+		dataSource?: DataSourceInterface;
+		id<NewIdAttr extends CurrentIdAttr, TheIdSchema extends IdSchema>(
+			newIdAttr: NewIdAttr,
+			params: ResourceIdConfig<TheIdSchema>
+		): Resource<Schema, CurrentName, CurrentRouteName, NewIdAttr, TheIdSchema>;
+		fullText(fullTextAttr: string): this;
+	}
+}
 
 export class DataSource<T extends Record<string, string>> implements DataSourceInterface<T> {
-	private readonly path: string;
+	private path?: string;
+
+	private resource?: Resource;
 
 	data: T[] = [];
 
-	constructor(private readonly resource: Resource,  baseDir = '') {
-		this.path = join(baseDir, `${this.resource.state.routeName}.jsonl`);
+	constructor(private readonly baseDir = '') {
+		// noop
+	}
+
+	prepareResource<
+		Schema extends v.BaseSchema = v.BaseSchema,
+		CurrentName extends string = string,
+		CurrentRouteName extends string = string
+	>(resource: Resource<Schema, CurrentName, CurrentRouteName>) {
+		this.path = join(this.baseDir, `${resource.state.routeName}.jsonl`);
+		resource.dataSource = resource.dataSource ?? this;
+		const originalResourceId = resource.id;
+		resource.id = <NewIdAttr extends string, NewIdSchema extends v.BaseSchema>(newIdAttr: NewIdAttr, params: ResourceIdConfig<NewIdSchema>) => {
+			originalResourceId(newIdAttr, params);
+			return resource as Resource<Schema, CurrentName, CurrentRouteName, NewIdAttr, NewIdSchema>;
+		};
+		this.resource = resource;
 	}
 
 	async initialize() {
+		if (typeof this.path !== 'string') {
+			throw new Error('Resource not prepared.');
+		}
+
 		try {
 			const fileContents = await readFile(this.path, 'utf-8');
 			const lines = fileContents.split('\n');
@@ -30,9 +76,38 @@ export class DataSource<T extends Record<string, string>> implements DataSourceI
 		return [...this.data];
 	}
 
+	async newId() {
+		const idConfig = this.resource?.state.shared.get('idConfig') as ResourceIdConfig<any>;
+		if (typeof idConfig === 'undefined') {
+			throw new Error('Resource not prepared.');
+		}
+
+		const theNewId = await idConfig.generationStrategy(this);
+		return theNewId as string;
+	}
+
 	async getById(idSerialized: string) {
-		const id = this.resource.state.idConfig.deserialize(idSerialized);
-		const foundData = this.data.find((s) => s[this.resource.state.idAttr as string] === id);
+		if (typeof this.resource === 'undefined') {
+			throw new Error('Resource not prepared.');
+		}
+
+		if (typeof this.path !== 'string') {
+			throw new Error('Resource not prepared.');
+		}
+
+		const theIdAttr = this.resource.state.shared.get('idAttr');
+		if (typeof theIdAttr === 'undefined') {
+			throw new Error('Resource not prepared.');
+		}
+		const idAttr = theIdAttr as string;
+		const theIdConfigRaw = this.resource.state.shared.get('idConfig');
+		if (typeof theIdConfigRaw === 'undefined') {
+			throw new Error('Resource not prepared.');
+		}
+		const theIdConfig = theIdConfigRaw as ResourceIdConfig<any>;
+
+		const id = theIdConfig.deserialize(idSerialized);
+		const foundData = this.data.find((s) => s[idAttr] === id);
 
 		if (foundData) {
 			return {
@@ -44,12 +119,31 @@ export class DataSource<T extends Record<string, string>> implements DataSourceI
 	}
 
 	async create(data: T) {
+		if (typeof this.resource === 'undefined') {
+			throw new Error('Resource not prepared.');
+		}
+
+		if (typeof this.path !== 'string') {
+			throw new Error('Resource not prepared.');
+		}
+
+		const theIdAttr = this.resource.state.shared.get('idAttr');
+		if (typeof theIdAttr === 'undefined') {
+			throw new Error('Resource not prepared.');
+		}
+		const idAttr = theIdAttr as string;
+		const theIdConfigRaw = this.resource.state.shared.get('idConfig');
+		if (typeof theIdConfigRaw === 'undefined') {
+			throw new Error('Resource not prepared.');
+		}
+		const theIdConfig = theIdConfigRaw as ResourceIdConfig<any>;
+
 		const newData = {
 			...data
 		} as Record<string, unknown>;
 
-		if (this.resource.state.idAttr in newData) {
-			newData[this.resource.state.idAttr] = this.resource.state.idConfig.deserialize(newData[this.resource.state.idAttr] as string);
+		if (idAttr in newData) {
+			newData[idAttr] = theIdConfig.deserialize(newData[idAttr] as string);
 		}
 
 		const newCollection = [
@@ -63,10 +157,29 @@ export class DataSource<T extends Record<string, string>> implements DataSourceI
 	}
 
 	async delete(idSerialized: string) {
+		if (typeof this.resource === 'undefined') {
+			throw new Error('Resource not prepared.');
+		}
+
+		if (typeof this.path !== 'string') {
+			throw new Error('Resource not prepared.');
+		}
+
+		const theIdAttr = this.resource.state.shared.get('idAttr');
+		if (typeof theIdAttr === 'undefined') {
+			throw new Error('Resource not prepared.');
+		}
+		const idAttr = theIdAttr as string;
+		const theIdConfigRaw = this.resource.state.shared.get('idConfig');
+		if (typeof theIdConfigRaw === 'undefined') {
+			throw new Error('Resource not prepared.');
+		}
+		const theIdConfig = theIdConfigRaw as ResourceIdConfig<any>;
+
 		const oldDataLength = this.data.length;
 
-		const id = this.resource.state.idConfig.deserialize(idSerialized);
-		const newData = this.data.filter((s) => !(s[this.resource.state.idAttr] === id));
+		const id = theIdConfig.deserialize(idSerialized);
+		const newData = this.data.filter((s) => !(s[idAttr] === id));
 
 		await writeFile(this.path, newData.map((d) => JSON.stringify(d)).join('\n'));
 
@@ -74,17 +187,36 @@ export class DataSource<T extends Record<string, string>> implements DataSourceI
 	}
 
 	async emplace(idSerialized: string, dataWithId: T) {
+		if (typeof this.resource === 'undefined') {
+			throw new Error('Resource not prepared.');
+		}
+
+		if (typeof this.path !== 'string') {
+			throw new Error('Resource not prepared.');
+		}
+
+		const theIdAttr = this.resource.state.shared.get('idAttr');
+		if (typeof theIdAttr === 'undefined') {
+			throw new Error('Resource not prepared.');
+		}
+		const idAttr = theIdAttr as string;
+		const theIdConfigRaw = this.resource.state.shared.get('idConfig');
+		if (typeof theIdConfigRaw === 'undefined') {
+			throw new Error('Resource not prepared.');
+		}
+		const theIdConfig = theIdConfigRaw as ResourceIdConfig<any>;
+
 		const existing = await this.getById(idSerialized);
-		const id = this.resource.state.idConfig.deserialize(idSerialized);
-		const { [this.resource.state.idAttr]: idFromResource, ...data } = dataWithId;
+		const id = theIdConfig.deserialize(idSerialized);
+		const { [idAttr]: idFromResource, ...data } = dataWithId;
 		const dataToEmplace = {
 			...data,
-			[this.resource.state.idAttr]: id,
+			[idAttr]: id,
 		} as T;
 
 		if (existing) {
 			const newData = this.data.map((d) => {
-				if (d[this.resource.state.idAttr] === id) {
+				if (d[idAttr] === id) {
 					return dataToEmplace;
 				}
 
@@ -101,6 +233,25 @@ export class DataSource<T extends Record<string, string>> implements DataSourceI
 	}
 
 	async patch(idSerialized: string, data: Partial<T>) {
+		if (typeof this.resource === 'undefined') {
+			throw new Error('Resource not prepared.');
+		}
+
+		if (typeof this.path !== 'string') {
+			throw new Error('Resource not prepared.');
+		}
+
+		const theIdAttr = this.resource.state.shared.get('idAttr');
+		if (typeof theIdAttr === 'undefined') {
+			throw new Error('Resource not prepared.');
+		}
+		const idAttr = theIdAttr as string;
+		const theIdConfigRaw = this.resource.state.shared.get('idConfig');
+		if (typeof theIdConfigRaw === 'undefined') {
+			throw new Error('Resource not prepared.');
+		}
+		const theIdConfig = theIdConfigRaw as ResourceIdConfig<any>;
+
 		const existing = await this.getById(idSerialized);
 		if (!existing) {
 			return null;
@@ -111,9 +262,9 @@ export class DataSource<T extends Record<string, string>> implements DataSourceI
 			...data,
 		}
 
-		const id = this.resource.state.idConfig.deserialize(idSerialized);
+		const id = theIdConfig.deserialize(idSerialized);
 		const newData = this.data.map((d) => {
-			if (d[this.resource.state.idAttr as string] === id) {
+			if (d[idAttr] === id) {
 				return newItem;
 			}
 
diff --git a/src/backend/http/decorators/backend/resource.ts b/src/backend/http/decorators/backend/resource.ts
index b91f551..05b4f3b 100644
--- a/src/backend/http/decorators/backend/resource.ts
+++ b/src/backend/http/decorators/backend/resource.ts
@@ -1,7 +1,5 @@
 import {RequestDecorator} from '../../../common';
-import {DataSource} from '../../../data-source';
 import {Resource} from '../../../../common';
-import {BackendResource} from '../../../core';
 
 declare module '../../../common' {
 	interface RequestContext {
@@ -11,14 +9,16 @@ declare module '../../../common' {
 }
 
 export const decorateRequestWithResource: RequestDecorator = (req) => {
-	const [, resourceRouteName, resourceId = ''] = req.url?.split('/') ?? [];
+	const [, resourceRouteName, resourceId] = req.url?.split('/') ?? [];
 	const resource = Array.from(req.backend.app.resources)
-		.find((r) => r.state.routeName === resourceRouteName) as BackendResource | undefined;
+		.find((r) => r.state.routeName === resourceRouteName) as Resource | undefined;
 
 	if (typeof resource !== 'undefined') {
+		req.backend.dataSource.prepareResource(resource);
 		req.resource = resource;
-		req.resource.dataSource = req.backend.dataSource(req.resource) as DataSource;
-		req.resourceId = resourceId;
+		if (resourceId?.trim().length > 0) {
+			req.resourceId = resourceId;
+		}
 	}
 
 	return req;
diff --git a/src/backend/http/handlers.ts b/src/backend/http/handlers.ts
index faf0cff..8a64d53 100644
--- a/src/backend/http/handlers.ts
+++ b/src/backend/http/handlers.ts
@@ -2,7 +2,6 @@ import { constants } from 'http2';
 import * as v from 'valibot';
 import {HttpMiddlewareError, PlainResponse, Middleware} from './server';
 import {LinkMap} from './utils';
-import {BackendResource} from '../core';
 
 export const handleGetRoot: Middleware = (req) => {
 	const { backend, basePath } = req;
@@ -41,12 +40,19 @@ export const handleGetRoot: Middleware = (req) => {
 };
 
 export const handleGetCollection: Middleware = async (req) => {
-	const { query, resource: resourceRaw, backend } = req;
+	const { query, resource, backend } = req;
 
-	if (typeof resourceRaw === 'undefined') {
-		throw new Error('No resource');
+	if (typeof resource === 'undefined') {
+		throw new HttpMiddlewareError('resourceNotFound', {
+			statusCode: constants.HTTP_STATUS_NOT_FOUND,
+		});
+	}
+
+	if (typeof resource.dataSource === 'undefined') {
+		throw new HttpMiddlewareError('unableToInitializeResourceDataSource', {
+			statusCode: constants.HTTP_STATUS_INTERNAL_SERVER_ERROR,
+		});
 	}
-	const resource = resourceRaw as BackendResource;
 
 	let data: v.Output<typeof resource.schema>[];
 	let totalItemCount: number | undefined;
@@ -80,12 +86,19 @@ export const handleGetCollection: Middleware = async (req) => {
 };
 
 export const handleGetItem: Middleware = async (req) => {
-	const { resource: resourceRaw, resourceId } = req;
+	const { resource, resourceId } = req;
 
-	if (typeof resourceRaw === 'undefined') {
-		throw new Error('No resource');
+	if (typeof resource === 'undefined') {
+		throw new HttpMiddlewareError('resourceNotFound', {
+			statusCode: constants.HTTP_STATUS_NOT_FOUND,
+		});
+	}
+
+	if (typeof resource.dataSource === 'undefined') {
+		throw new HttpMiddlewareError('unableToInitializeResourceDataSource', {
+			statusCode: constants.HTTP_STATUS_INTERNAL_SERVER_ERROR,
+		});
 	}
-	const resource = resourceRaw as BackendResource;
 
 	if (typeof resourceId === 'undefined') {
 		throw new HttpMiddlewareError(
@@ -135,12 +148,19 @@ export const handleGetItem: Middleware = async (req) => {
 };
 
 export const handleDeleteItem: Middleware = async (req) => {
-	const { resource: resourceRaw, resourceId, backend } = req;
+	const { resource, resourceId, backend } = req;
 
-	if (typeof resourceRaw === 'undefined') {
-		throw new Error('No resource');
+	if (typeof resource === 'undefined') {
+		throw new HttpMiddlewareError('resourceNotFound', {
+			statusCode: constants.HTTP_STATUS_NOT_FOUND,
+		});
+	}
+
+	if (typeof resource.dataSource === 'undefined') {
+		throw new HttpMiddlewareError('unableToInitializeResourceDataSource', {
+			statusCode: constants.HTTP_STATUS_INTERNAL_SERVER_ERROR,
+		});
 	}
-	const resource = resourceRaw as BackendResource;
 
 	if (typeof resourceId === 'undefined') {
 		throw new HttpMiddlewareError(
@@ -161,7 +181,7 @@ export const handleDeleteItem: Middleware = async (req) => {
 		});
 	}
 
-	if (!existing && backend!.throws404OnDeletingNotFound) {
+	if (!existing && backend!.throwsErrorOnDeletingNotFound) {
 		throw new HttpMiddlewareError('deleteNonExistingResource', {
 			statusCode: constants.HTTP_STATUS_NOT_FOUND
 		});
@@ -185,12 +205,19 @@ export const handleDeleteItem: Middleware = async (req) => {
 };
 
 export const handlePatchItem: Middleware = async (req) => {
-	const { resource: resourceRaw, resourceId, body } = req;
+	const { resource, resourceId, body } = req;
 
-	if (typeof resourceRaw === 'undefined') {
-		throw new Error('No resource');
+	if (typeof resource === 'undefined') {
+		throw new HttpMiddlewareError('resourceNotFound', {
+			statusCode: constants.HTTP_STATUS_NOT_FOUND,
+		});
+	}
+
+	if (typeof resource.dataSource === 'undefined') {
+		throw new HttpMiddlewareError('unableToInitializeResourceDataSource', {
+			statusCode: constants.HTTP_STATUS_INTERNAL_SERVER_ERROR,
+		});
 	}
-	const resource = resourceRaw as BackendResource;
 
 	if (typeof resourceId === 'undefined') {
 		throw new HttpMiddlewareError(
@@ -232,24 +259,37 @@ export const handlePatchItem: Middleware = async (req) => {
 		statusMessage: 'resourcePatched',
 		body: newObject,
 	});
-
-	// TODO finish the rest of the handlers!!!
 };
 
 export const handleCreateItem: Middleware = async (req) => {
-	const { resource: resourceRaw, body, backend, basePath } = req;
+	const { resource, body, backend, basePath } = req;
+
+	if (typeof resource === 'undefined') {
+		throw new HttpMiddlewareError('resourceNotFound', {
+			statusCode: constants.HTTP_STATUS_NOT_FOUND,
+		});
+	}
 
-	if (typeof resourceRaw === 'undefined') {
-		throw new Error('No resource');
+	if (typeof resource.dataSource === 'undefined') {
+		throw new HttpMiddlewareError('unableToInitializeResourceDataSource', {
+			statusCode: constants.HTTP_STATUS_INTERNAL_SERVER_ERROR,
+		});
+	}
+
+	const idAttrRaw = resource.state.shared.get('idAttr');
+	if (typeof idAttrRaw === 'undefined') {
+		throw new HttpMiddlewareError('unableToInitializeResourceDataSource', {
+			statusCode: constants.HTTP_STATUS_INTERNAL_SERVER_ERROR,
+		});
 	}
-	const resource = resourceRaw as BackendResource;
+	const idAttr = idAttrRaw as string;
 
 	let newId;
 	let params: v.Output<typeof resource.schema>;
 	try {
-		newId = await resource.newId(resource.dataSource);
+		newId = await resource.dataSource.newId();
 		params = { ...body as Record<string, unknown> };
-		params[resource.state.idAttr] = newId;
+		params[idAttr] = newId;
 	} catch (cause) {
 		throw new HttpMiddlewareError('unableToGenerateIdFromResourceDataSource', {
 			cause,
@@ -296,18 +336,33 @@ export const handleCreateItem: Middleware = async (req) => {
 }
 
 export const handleEmplaceItem: Middleware =  async (req) => {
-	const { resource: resourceRaw, resourceId, basePath, body, backend } = req;
+	const { resource, resourceId, basePath, body, backend } = req;
+
+	if (typeof resource === 'undefined') {
+		throw new HttpMiddlewareError('resourceNotFound', {
+			statusCode: constants.HTTP_STATUS_NOT_FOUND,
+		});
+	}
 
-	if (typeof resourceRaw === 'undefined') {
-		throw new Error('No resource');
+	if (typeof resource.dataSource === 'undefined') {
+		throw new HttpMiddlewareError('unableToInitializeResourceDataSource', {
+			statusCode: constants.HTTP_STATUS_INTERNAL_SERVER_ERROR,
+		});
+	}
+
+	const idAttrRaw = resource.state.shared.get('idAttr');
+	if (typeof idAttrRaw === 'undefined') {
+		throw new HttpMiddlewareError('unableToInitializeResourceDataSource', {
+			statusCode: constants.HTTP_STATUS_INTERNAL_SERVER_ERROR,
+		});
 	}
-	const resource = resourceRaw as BackendResource;
+	const idAttr = idAttrRaw as string;
 
 	let newObject: v.Output<typeof resource.schema>;
 	let isCreated: boolean;
 	try {
 		const params = { ...body as Record<string, unknown> };
-		params[resource.state.idAttr] = resource.state.idConfig.deserialize(params[resource.state.idAttr] as string);
+		params[idAttr] = resourceId;
 		[newObject, isCreated] = await resource.dataSource.emplace(resourceId!, params);
 	} catch (cause) {
 		throw new HttpMiddlewareError('unableToEmplaceResource', {
diff --git a/src/backend/http/server.ts b/src/backend/http/server.ts
index 01b0763..a7b5ed0 100644
--- a/src/backend/http/server.ts
+++ b/src/backend/http/server.ts
@@ -13,9 +13,6 @@ import {
 	handleGetRoot,
 	handlePatchItem,
 } from './handlers';
-import {
-	BackendResource,
-} from '../core';
 import {getBody} from './utils';
 import {decorateRequestWithBackend} from './decorators/backend';
 import {decorateRequestWithMethod} from './decorators/method';
@@ -94,14 +91,18 @@ export interface Middleware<Req extends RequestContext = RequestContext> {
 	(req: Req): undefined | Response | Promise<undefined | Response>;
 }
 
-const getAllowedMiddlewares = <T extends v.BaseSchema>(resource?: Resource<T>, mainResourceId = '') => {
+const getAllowedMiddlewares = <T extends v.BaseSchema>(resource?: Resource<T>, mainResourceId?: string) => {
 	const middlewares = [] as [string, Middleware, v.BaseSchema?][];
 
 	if (typeof resource === 'undefined') {
 		return middlewares;
 	}
 
-	if (mainResourceId === '') {
+	if (typeof resource.dataSource === 'undefined') {
+		return middlewares;
+	}
+
+	if (typeof mainResourceId !== 'string') {
 		if (resource.state.canFetchCollection) {
 			middlewares.push(['GET', handleGetCollection]);
 		}
@@ -116,14 +117,16 @@ const getAllowedMiddlewares = <T extends v.BaseSchema>(resource?: Resource<T>, m
 	}
 	if (resource.state.canEmplace) {
 		const schema = resource.schema.type === 'object' ? resource.schema as unknown as v.ObjectSchema<any> : resource.schema;
+		const idAttr = resource.state.shared.get('idAttr') as string;
+		const idConfig = resource.state.shared.get('idConfig') as any;
 		const putSchema = (
 			schema.type === 'object'
 				? v.merge([
 					schema as v.ObjectSchema<any>,
 					v.object({
-						[resource.state.idAttr]: v.transform(
+						[idAttr]: v.transform(
 							v.any(),
-							input => resource.state.idConfig.serialize(input),
+							input => idConfig!.serialize(input),
 							v.literal(mainResourceId)
 						)
 					})
@@ -178,13 +181,18 @@ export const createServer = (backendState: BackendState, serverParams = {} as Cr
 
 		if (typeof req.resource === 'undefined') {
 			throw new HttpMiddlewareError('resourceNotFound', {
-				statusCode: constants.HTTP_STATUS_NOT_FOUND
+				statusCode: constants.HTTP_STATUS_NOT_FOUND,
+			});
+		}
+
+		if (typeof req.resource.dataSource === 'undefined') {
+			throw new HttpMiddlewareError('unableToInitializeResourceDataSource', {
+				statusCode: constants.HTTP_STATUS_INTERNAL_SERVER_ERROR,
 			});
 		}
 
-		const resource = req.resource as BackendResource;
 		try {
-			await resource.dataSource.initialize();
+			await req.resource.dataSource.initialize();
 		} catch (cause) {
 			throw new HttpMiddlewareError(
 				'unableToInitializeResourceDataSource',
@@ -211,8 +219,6 @@ export const createServer = (backendState: BackendState, serverParams = {} as Cr
 					}
 
 					if (schema) {
-						const availableSerializers = Array.from(req.backend.app.mediaTypes.values());
-						const availableCharsets = Array.from(req.backend.app.charsets.values());
 						const contentTypeHeader = req.headers['content-type'] ?? 'application/octet-stream';
 						const fragments = contentTypeHeader.split(';');
 						const mediaType = fragments[0];
@@ -227,9 +233,22 @@ export const createServer = (backendState: BackendState, serverParams = {} as Cr
 								? charsetRaw.slice(1, -1).trim()
 								: charsetRaw.trim()
 						)
-						const deserializerPair = availableSerializers.find((l) => l.name === mediaType);
-						const encodingPair = availableCharsets.find((l) => l.name === charset);
-						(req as unknown as Record<string, unknown>).body = await getBody(req, schema, encodingPair, deserializerPair);
+						const theBodyBuffer = await getBody(req);
+						const encodingPair = req.backend.app.charsets.get(charset);
+						if (typeof encodingPair === 'undefined') {
+							throw new HttpMiddlewareError('unableToDecodeResource', {
+								statusCode: constants.HTTP_STATUS_UNSUPPORTED_MEDIA_TYPE,
+							});
+						}
+						const deserializerPair = req.backend.app.mediaTypes.get(mediaType);
+						if (typeof deserializerPair === 'undefined') {
+							throw new HttpMiddlewareError('unableToDeserializeResource', {
+								statusCode: constants.HTTP_STATUS_UNSUPPORTED_MEDIA_TYPE,
+							});
+						}
+						const theBodyStr = encodingPair.decode(theBodyBuffer);
+						const theBody = deserializerPair.deserialize(theBodyStr);
+						req.body = await v.parseAsync(schema, theBody, { abortEarly: false, abortPipeEarly: false });
 					}
 
 					const result = await middleware(req);
@@ -284,7 +303,7 @@ export const createServer = (backendState: BackendState, serverParams = {} as Cr
 
 	const handleRequest = async (reqRaw: RequestContext, res: http.ServerResponse<RequestContext>) => {
 		const req = await decorateRequest(reqRaw);
-		const middlewares = getAllowedMiddlewares(req.resource, req.resourceId ?? '');
+		const middlewares = getAllowedMiddlewares(req.resource, req.resourceId);
 		const processRequestFn = processRequest(middlewares);
 		let middlewareState: Response;
 		try {
diff --git a/src/backend/http/utils.ts b/src/backend/http/utils.ts
index 09c3a49..bf57b6d 100644
--- a/src/backend/http/utils.ts
+++ b/src/backend/http/utils.ts
@@ -1,30 +1,19 @@
 import {IncomingMessage} from 'http';
-import {MediaType, Charset} from '../../common';
-import {BaseSchema, parseAsync} from 'valibot';
 
 export const getBody = (
 	req: IncomingMessage,
-	schema: BaseSchema,
-	encodingPair?: Charset,
-	deserializer?: MediaType,
-) => new Promise((resolve, reject) => {
+) => new Promise<Buffer>((resolve, reject) => {
 	let body = Buffer.from('');
 	req.on('data', (chunk) => {
 		body = Buffer.concat([body, chunk]);
 	});
 	req.on('end', async () => {
-		const bodyStr = encodingPair?.decode(body) ?? body.toString();
-		try {
-			const bodyDeserialized = await parseAsync(
-				schema,
-				deserializer?.deserialize(bodyStr) ?? body,
-				{abortEarly: false},
-			);
-			resolve(bodyDeserialized);
-		} catch (err) {
-			reject(err);
-		}
+		resolve(body);
 	});
+
+	req.on('error', (err) => {
+		reject(err);
+	})
 });
 
 interface LinkMapEntry {
diff --git a/src/common/app.ts b/src/common/app.ts
index 8f51fb0..bc012c1 100644
--- a/src/common/app.ts
+++ b/src/common/app.ts
@@ -24,7 +24,11 @@ export interface ApplicationBuilder {
 	mediaType(mediaType: MediaType): this;
 	language(language: Language): this;
 	charset(charset: Charset): this;
-	resource<T extends v.BaseSchema>(resRaw: Resource<T>): this;
+	resource<
+		Schema extends v.BaseSchema,
+		CurrentItemName extends string = string,
+		CurrentRouteName extends string = string
+	>(resRaw: Resource<Schema, CurrentItemName, CurrentRouteName>): this;
 	createBackend(params: Omit<CreateBackendParams, 'app'>): BackendBuilder;
 	createClient(params: Omit<CreateClientParams, 'app'>): ClientBuilder;
 }
diff --git a/src/common/language.ts b/src/common/language.ts
index d1c1a1b..4292a09 100644
--- a/src/common/language.ts
+++ b/src/common/language.ts
@@ -22,6 +22,8 @@ export const LANGUAGE_DEFAULT_STATUS_MESSAGE_KEYS = [
 	'unableToSerializeResponse',
 	'unableToEncodeResponse',
 	'unableToDeleteResource',
+	'unableToDeserializeResource',
+	'unableToDecodeResource',
 	'resourceDeleted',
 	'unableToDeserializeRequest',
 	'patchNonExistingResource',
@@ -64,6 +66,8 @@ export const FALLBACK_LANGUAGE = {
 		unableToDeleteResource: 'Unable To Delete $RESOURCE',
 		languageNotAcceptable: 'Language Not Acceptable',
 		encodingNotAcceptable: 'Encoding Not Acceptable',
+		unableToDeserializeResource: 'Unable To Deserialize $RESOURCE',
+		unableToDecodeResource: 'Unable To Decode $RESOURCE',
 		mediaTypeNotAcceptable: 'Media Type Not Acceptable',
 		methodNotAllowed: 'Method Not Allowed',
 		urlNotFound: 'URL Not Found',
diff --git a/src/common/resource.ts b/src/common/resource.ts
index 2ab6a34..8bcc13f 100644
--- a/src/common/resource.ts
+++ b/src/common/resource.ts
@@ -1,24 +1,12 @@
 import * as v from 'valibot';
-import {BaseDataSource, GenerationStrategy} from './data-source';
-
-export interface ResourceIdConfig<IdSchema extends v.BaseSchema, DataSource extends BaseDataSource = BaseDataSource> {
-	generationStrategy: GenerationStrategy<DataSource>;
-	serialize: (id: unknown) => string;
-	deserialize: (id: string) => v.Output<IdSchema>;
-	schema: IdSchema;
-}
 
 export interface ResourceState<
 	ItemName extends string = string,
-	RouteName extends string = string,
-	IdAttr extends string = string,
-	IdSchema extends v.BaseSchema = v.BaseSchema
+	RouteName extends string = string
 > {
-	idAttr: IdAttr;
+	shared: Map<string, unknown>;
 	itemName: ItemName;
 	routeName: RouteName;
-	idConfig: ResourceIdConfig<IdSchema>;
-	fullTextAttrs: Set<string>;
 	canCreate: boolean;
 	canFetchCollection: boolean;
 	canFetchItem: boolean;
@@ -30,20 +18,12 @@ export interface ResourceState<
 export interface Resource<
 	Schema extends v.BaseSchema = v.BaseSchema,
 	CurrentName extends string = string,
-	CurrentRouteName extends string = string,
-	CurrentIdAttr extends string = string,
-	IdSchema extends v.BaseSchema = v.BaseSchema
+	CurrentRouteName extends string = string
 > {
-	dataSource?: unknown;
 	schema: Schema;
-	state: ResourceState<CurrentName, CurrentRouteName, CurrentIdAttr, IdSchema>;
-	id<NewIdAttr extends CurrentIdAttr, TheIdSchema extends v.BaseSchema>(
-		newIdAttr: NewIdAttr,
-		params: ResourceIdConfig<TheIdSchema>
-	): Resource<Schema, CurrentName, CurrentRouteName, NewIdAttr, TheIdSchema>;
-	fullText(fullTextAttr: string): this;
-	name<NewName extends CurrentName>(n: NewName): Resource<Schema, NewName, CurrentRouteName, CurrentIdAttr, IdSchema>;
-	route<NewRouteName extends CurrentRouteName>(n: NewRouteName): Resource<Schema, CurrentName, NewRouteName, CurrentIdAttr, IdSchema>;
+	state: ResourceState<CurrentName, CurrentRouteName>;
+	name<NewName extends CurrentName>(n: NewName): Resource<Schema, NewName, CurrentRouteName>;
+	route<NewRouteName extends CurrentRouteName>(n: NewRouteName): Resource<Schema, CurrentName, NewRouteName>;
 	canFetchCollection(b?: boolean): this;
 	canFetchItem(b?: boolean): this;
 	canCreate(b?: boolean): this;
@@ -55,25 +35,23 @@ export interface Resource<
 export const resource = <
 	Schema extends v.BaseSchema,
 	CurrentName extends string = string,
-	CurrentRouteName extends string = string,
-	CurrentIdAttr extends string = string,
-	IdSchema extends v.BaseSchema = v.BaseSchema
->(schema: Schema): Resource<Schema, CurrentName, CurrentRouteName, CurrentIdAttr, IdSchema> => {
+	CurrentRouteName extends string = string
+>(schema: Schema): Resource<Schema, CurrentName, CurrentRouteName> => {
 	const resourceState = {
-		fullTextAttrs: new Set<string>(),
+		shared: new Map(),
 		canCreate: false,
 		canFetchCollection: false,
 		canFetchItem: false,
 		canPatch: false,
 		canEmplace: false,
 		canDelete: false,
-	} as ResourceState<CurrentName, CurrentRouteName, CurrentIdAttr, IdSchema>;
+	} as ResourceState<CurrentName, CurrentRouteName>;
 
 	return {
-		get state(): ResourceState<CurrentName, CurrentRouteName, CurrentIdAttr, IdSchema> {
+		get state(): ResourceState<CurrentName, CurrentRouteName> {
 			return Object.freeze({
 				...resourceState
-			}) as unknown as ResourceState<CurrentName, CurrentRouteName, CurrentIdAttr, IdSchema>;
+			}) as unknown as ResourceState<CurrentName, CurrentRouteName>;
 		},
 		canFetchCollection(b = true) {
 			resourceState.canFetchCollection = b;
@@ -99,42 +77,24 @@ export const resource = <
 			resourceState.canDelete = b;
 			return this;
 		},
-		id<NewIdAttr extends CurrentIdAttr, NewIdSchema extends IdSchema>(newIdAttr: NewIdAttr, params: ResourceIdConfig<NewIdSchema>) {
-			resourceState.idAttr = newIdAttr;
-			resourceState.idConfig = params;
-			return this as Resource<Schema, CurrentName, CurrentRouteName, NewIdAttr, NewIdSchema>;
-		},
-		newId(dataSource: BaseDataSource) {
-			return resourceState?.idConfig?.generationStrategy?.(dataSource);
+		id(idName, config) {
+			resourceState.shared.set('idAttr', idName);
+			resourceState.shared.set('idConfig', config);
+			return this;
 		},
-		fullText(fullTextAttr: string) {
-			if (
-				schema.type === 'object'
-				&& (
-					schema as unknown as v.ObjectSchema<
-						Record<string, v.BaseSchema>,
-						undefined,
-						Record<string, string>
-					>
-				)
-					.entries[fullTextAttr]?.type === 'string'
-			) {
-				resourceState.fullTextAttrs?.add(fullTextAttr);
-				return this;
-			}
-
-			throw new Error(`Could not set attribute ${fullTextAttr} as fulltext.`);
+		fullText(attrName) {
+			const fullTextAttrs = (resourceState.shared.get('fullText') ?? new Set()) as Set<string>;
+			fullTextAttrs.add(attrName);
+			resourceState.shared.set('fullText', fullTextAttrs);
+			return this;
 		},
 		name<NewName extends CurrentName>(n: NewName) {
 			resourceState.itemName = n;
-			return this as Resource<Schema, NewName, CurrentRouteName, CurrentIdAttr, IdSchema>;
+			return this as Resource<Schema, NewName, CurrentRouteName>;
 		},
 		route<NewRouteName extends CurrentRouteName>(n: NewRouteName) {
 			resourceState.routeName = n;
-			return this as Resource<Schema, CurrentName, NewRouteName, CurrentIdAttr, IdSchema>;
-		},
-		get idAttr() {
-			return resourceState.idAttr;
+			return this as Resource<Schema, CurrentName, NewRouteName>;
 		},
 		get itemName() {
 			return resourceState.itemName;
@@ -145,9 +105,7 @@ export const resource = <
 		get schema() {
 			return schema;
 		},
-	} as Resource<Schema, CurrentName, CurrentRouteName, CurrentIdAttr, IdSchema>;
+	} as Resource<Schema, CurrentName, CurrentRouteName>;
 };
 
 export type ResourceType<R extends Resource> = v.Output<R['schema']>;
-
-export type ResourceTypeWithId<R extends Resource> = ResourceType<R> & Record<R['state']['idAttr'], v.Output<R['state']['idConfig']['schema']>>;
diff --git a/test/e2e/default.test.ts b/test/e2e/default.test.ts
index 1bee371..beb670d 100644
--- a/test/e2e/default.test.ts
+++ b/test/e2e/default.test.ts
@@ -25,9 +25,11 @@ import { dataSources } from '../../src/backend';
 import { application, resource, validation as v, Resource } from '../../src';
 
 const PORT = 3000;
-const HOST = 'localhost';
-const ACCEPT_CHARSET = 'utf-8';
+const HOST = '127.0.0.1';
 const ACCEPT = 'application/json';
+const ACCEPT_LANGUAGE = 'en';
+const CONTENT_TYPE_CHARSET = 'utf-8';
+const CONTENT_TYPE = ACCEPT;
 
 const autoIncrement = async (dataSource: DataSource) => {
 	const data = await dataSource.getMultiple() as Record<string, string>[];
@@ -74,7 +76,7 @@ describe('yasumi', () => {
 			.name('Piano' as const)
 			.route('pianos' as const)
 			.id('id' as const, {
-				generationStrategy: autoIncrement as any,
+				generationStrategy: autoIncrement,
 				serialize: (id) => id?.toString() ?? '0',
 				deserialize: (id) => Number.isFinite(Number(id)) ? Number(id) : 0,
 				schema: v.number(),
@@ -90,7 +92,7 @@ describe('yasumi', () => {
 
 		const backend = app
 			.createBackend({
-				dataSource: (resource) => new dataSources.jsonlFile.DataSource(resource, baseDir),
+				dataSource: new dataSources.jsonlFile.DataSource(baseDir),
 			})
 			.throwsErrorOnDeletingNotFound();
 
@@ -146,8 +148,8 @@ describe('yasumi', () => {
 						path: '/api/pianos',
 						method: 'GET',
 						headers: {
-							'Accept': `${ACCEPT}; charset="${ACCEPT_CHARSET}"`,
-							'Accept-Language': 'en',
+							'Accept': ACCEPT,
+							'Accept-Language': ACCEPT_LANGUAGE,
 						},
 					},
 					(res) => {
@@ -165,7 +167,7 @@ describe('yasumi', () => {
 						});
 
 						res.on('close', () => {
-							const resBufferJson = resBuffer.toString(ACCEPT_CHARSET);
+							const resBufferJson = resBuffer.toString(CONTENT_TYPE_CHARSET);
 							const resData = JSON.parse(resBufferJson);
 							expect(resData).toEqual([]);
 							resolve();
@@ -190,8 +192,8 @@ describe('yasumi', () => {
 						path: '/api/pianos',
 						method: 'HEAD',
 						headers: {
-							'Accept': `${ACCEPT}; charset="${ACCEPT_CHARSET}"`,
-							'Accept-Language': 'en',
+							'Accept': ACCEPT,
+							'Accept-Language': ACCEPT_LANGUAGE,
 						},
 					},
 					(res) => {
@@ -247,7 +249,8 @@ describe('yasumi', () => {
 						path: '/api/pianos/1',
 						method: 'GET',
 						headers: {
-							'Accept': `${ACCEPT}; charset="${ACCEPT_CHARSET}"`,
+							'Accept': ACCEPT,
+							'Accept-Language': ACCEPT_LANGUAGE,
 						},
 					},
 					(res) => {
@@ -264,7 +267,7 @@ describe('yasumi', () => {
 						});
 
 						res.on('close', () => {
-							const resBufferJson = resBuffer.toString(ACCEPT_CHARSET);
+							const resBufferJson = resBuffer.toString(CONTENT_TYPE_CHARSET);
 							const resData = JSON.parse(resBufferJson);
 							expect(resData).toEqual(data);
 							resolve();
@@ -290,7 +293,8 @@ describe('yasumi', () => {
 						path: '/api/pianos/1',
 						method: 'HEAD',
 						headers: {
-							'Accept': `${ACCEPT}; charset="${ACCEPT_CHARSET}"`,
+							'Accept': ACCEPT,
+							'Accept-Language': ACCEPT_LANGUAGE,
 						},
 					},
 					(res) => {
@@ -320,7 +324,8 @@ describe('yasumi', () => {
 						path: '/api/pianos/2',
 						method: 'GET',
 						headers: {
-							'Accept': `${ACCEPT}; charset="${ACCEPT_CHARSET}"`,
+							'Accept': ACCEPT,
+							'Accept-Language': ACCEPT_LANGUAGE,
 						},
 					},
 					(res) => {
@@ -351,7 +356,8 @@ describe('yasumi', () => {
 						path: '/api/pianos/2',
 						method: 'HEAD',
 						headers: {
-							'Accept': `${ACCEPT}; charset="${ACCEPT_CHARSET}"`,
+							'Accept': ACCEPT,
+							'Accept-Language': ACCEPT_LANGUAGE,
 						},
 					},
 					(res) => {
@@ -406,8 +412,9 @@ describe('yasumi', () => {
 						path: '/api/pianos',
 						method: 'POST',
 						headers: {
-							'Accept': `${ACCEPT}; charset="${ACCEPT_CHARSET}"`,
-							'Content-Type': ACCEPT,
+							'Accept': ACCEPT,
+							'Accept-Language': ACCEPT_LANGUAGE,
+							'Content-Type': `${CONTENT_TYPE}; charset="${CONTENT_TYPE_CHARSET}"`,
 						},
 					},
 					(res) => {
@@ -424,7 +431,7 @@ describe('yasumi', () => {
 						});
 
 						res.on('close', () => {
-							const resBufferJson = resBuffer.toString(ACCEPT_CHARSET);
+							const resBufferJson = resBuffer.toString(CONTENT_TYPE_CHARSET);
 							const resData = JSON.parse(resBufferJson);
 							expect(resData).toEqual({
 								...newData,
@@ -478,8 +485,9 @@ describe('yasumi', () => {
 						path: `/api/pianos/${data.id}`,
 						method: 'PATCH',
 						headers: {
-							'Accept': `${ACCEPT}; charset="${ACCEPT_CHARSET}"`,
-							'Content-Type': ACCEPT,
+							'Accept': ACCEPT,
+							'Accept-Language': ACCEPT_LANGUAGE,
+							'Content-Type': `${CONTENT_TYPE}; charset="${CONTENT_TYPE_CHARSET}"`,
 						},
 					},
 					(res) => {
@@ -496,7 +504,7 @@ describe('yasumi', () => {
 						});
 
 						res.on('close', () => {
-							const resBufferJson = resBuffer.toString(ACCEPT_CHARSET);
+							const resBufferJson = resBuffer.toString(CONTENT_TYPE_CHARSET);
 							const resData = JSON.parse(resBufferJson);
 							expect(resData).toEqual({
 								...data,
@@ -525,8 +533,9 @@ describe('yasumi', () => {
 						path: '/api/pianos/2',
 						method: 'PATCH',
 						headers: {
-							'Accept': `${ACCEPT}; charset="${ACCEPT_CHARSET}"`,
-							'Content-Type': ACCEPT,
+							'Accept': ACCEPT,
+							'Accept-Language': ACCEPT_LANGUAGE,
+							'Content-Type': `${CONTENT_TYPE}; charset="${CONTENT_TYPE_CHARSET}"`,
 						},
 					},
 					(res) => {
@@ -582,8 +591,9 @@ describe('yasumi', () => {
 						path: `/api/pianos/${newData.id}`,
 						method: 'PUT',
 						headers: {
-							'Accept': `${ACCEPT}; charset="${ACCEPT_CHARSET}"`,
-							'Content-Type': ACCEPT,
+							'Accept': ACCEPT,
+							'Accept-Language': ACCEPT_LANGUAGE,
+							'Content-Type': `${CONTENT_TYPE}; charset="${CONTENT_TYPE_CHARSET}"`,
 						},
 					},
 					(res) => {
@@ -600,7 +610,7 @@ describe('yasumi', () => {
 						});
 
 						res.on('close', () => {
-							const resBufferJson = resBuffer.toString(ACCEPT_CHARSET);
+							const resBufferJson = resBuffer.toString(CONTENT_TYPE_CHARSET);
 							const resData = JSON.parse(resBufferJson);
 							expect(resData).toEqual(newData);
 							resolve();
@@ -628,8 +638,9 @@ describe('yasumi', () => {
 						path: `/api/pianos/${id}`,
 						method: 'PUT',
 						headers: {
-							'Accept': `${ACCEPT}; charset="${ACCEPT_CHARSET}"`,
-							'Content-Type': ACCEPT,
+							'Accept': ACCEPT,
+							'Accept-Language': ACCEPT_LANGUAGE,
+							'Content-Type': `${CONTENT_TYPE}; charset="${CONTENT_TYPE_CHARSET}"`,
 						},
 					},
 					(res) => {
@@ -646,7 +657,7 @@ describe('yasumi', () => {
 						});
 
 						res.on('close', () => {
-							const resBufferJson = resBuffer.toString(ACCEPT_CHARSET);
+							const resBufferJson = resBuffer.toString(CONTENT_TYPE_CHARSET);
 							const resData = JSON.parse(resBufferJson);
 							expect(resData).toEqual({
 								...newData,
@@ -698,7 +709,8 @@ describe('yasumi', () => {
 						path: `/api/pianos/${data.id}`,
 						method: 'DELETE',
 						headers: {
-							'Accept': `${ACCEPT}; charset="${ACCEPT_CHARSET}"`,
+							'Accept': ACCEPT,
+							'Accept-Language': ACCEPT_LANGUAGE,
 						},
 					},
 					(res) => {
@@ -728,7 +740,8 @@ describe('yasumi', () => {
 						path: '/api/pianos/2',
 						method: 'DELETE',
 						headers: {
-							'Accept': `${ACCEPT}; charset="${ACCEPT_CHARSET}"`,
+							'Accept': ACCEPT,
+							'Accept-Language': ACCEPT_LANGUAGE,
 						},
 					},
 					(res) => {