GraphQL Directive（指令）是GraphQL中的一種特殊類(lèi)型，它允許開(kāi)發(fā)者在GraphQL schema中添加元數(shù)據(jù)，以控制查詢和解析操作的行為

Directive的詳細(xì)說(shuō)明及使用可見(jiàn)GraphQL（五）指令[Directive]詳解

本文將介紹通過(guò)自定義Directive實(shí)現(xiàn)的GraphQL登錄態(tài)校驗(yàn)，步驟依次為：

1. Schema中定義directive
2. 實(shí)現(xiàn)DgsReactiveCustomContextBuilderWithRequest接口，構(gòu)建請(qǐng)求內(nèi)全局使用的上下文對(duì)象
3. 實(shí)現(xiàn)SchemaDirectiveWiring，對(duì)Field進(jìn)行攔截校驗(yàn)
4. Directive注入

Schema Directive定義

"必須要登錄"
directive @needLogin on FIELD_DEFINITIONtype Employee {"雇員名稱"employees(month: Date : [String] @needLogin
}

LoginContextBuilder

實(shí)現(xiàn)DgsReactiveCustomContextBuilderWithRequest接口，可以使用當(dāng)前的請(qǐng)求信息，例如 HTTP 請(qǐng)求頭、請(qǐng)求參數(shù)等構(gòu)建自定義的上下文對(duì)象

在查詢執(zhí)行過(guò)程中，GraphQL 會(huì)將該上下文對(duì)象傳遞給所有的數(shù)據(jù)解析器（DataFetcher），使得數(shù)據(jù)解析器能夠訪問(wèn)和修改上下文對(duì)象中的數(shù)據(jù)

使用DgsReactiveCustomContextBuilderWithRequest接口可以實(shí)現(xiàn)許多有用的功能，例如：

• 存儲(chǔ)用戶身份驗(yàn)證信息，以便在數(shù)據(jù)解析器中進(jìn)行鑒權(quán)
• 將請(qǐng)求相關(guān)的信息（例如請(qǐng)求參數(shù)、請(qǐng)求頭等）傳遞給數(shù)據(jù)解析器，以便數(shù)據(jù)解析器根據(jù)這些信息返回正確的數(shù)據(jù)
• 存儲(chǔ)請(qǐng)求相關(guān)的上下文信息，例如請(qǐng)求開(kāi)始時(shí)間、請(qǐng)求結(jié)束時(shí)間等，以便進(jìn)行性能分析和監(jiān)控

@Component
public class LoginContextBuilder implements DgsReactiveCustomContextBuilderWithRequest<YyContext> {private static final Logger LOGGER = LoggerFactory.getLogger(LoginContextBuilder.class);@Autowiredprivate ReactiveLoginService reactiveLoginService;@Autowiredprivate HttpHeaderAuthorization httpHeaderAuthorization;@NotNull@Overridepublic Mono<LoginContext> build(@Nullable Map<String, ?> map, @Nullable HttpHeaders httpHeaders, @Nullable ServerRequest serverRequest) {boolean interiorAuth = httpHeaderAuthorization.auth(serverRequest);if(interiorAuth){LoginContext loginContext = new LoginContext(true, IpUtil.getClientIpAddress(serverRequest)).setInteriorAuth(true);LOGGER.info("interior request loginContext:{}",loginContext);return Mono.just(loginContext);}else{return reactiveLoginService.getUid(serverRequest).doOnSuccess(user-> LOGGER.info("login user:{}",user)).onErrorResume(e-> Mono.just(LoginUser.NOT_LOGIN_USER)).map(user -> new LoginContext(user, IpUtil.getClientIpAddress(serverRequest)));}}
}

ReactiveLoginService

subscribeOn(Schedulers.boundedElastic())將該Mono訂閱到一個(gè)boundedElastic調(diào)度器的線程中，這樣Mono中的操作就會(huì)在該線程上執(zhí)行，而不會(huì)阻塞當(dāng)前的線程

Schedulers.boundedElastic()調(diào)度器是一個(gè)彈性線程池，它根據(jù)需要?jiǎng)討B(tài)地創(chuàng)建和銷(xiāo)毀線程，以適應(yīng)不同的負(fù)載情況

public class ReactiveLoginService {private LoginService loginService;public ReactiveLoginService(LoginService loginService){this.loginService = loginService;}/*** 登錄校驗(yàn)* @param httpServerRequest* @return*/public Mono<LoginUser> getUid(ServerRequest httpServerRequest){return Mono.fromCallable(()->{long uid = loginService.login(new WebFluxHttpServletRequest(httpServerRequest),null);return uid > 0 ? new LoginUser(uid) : LoginUser.NOT_LOGIN_USER;}).subscribeOn(Schedulers.boundedElastic());}public void close(){loginService.close();}
}

Directive 實(shí)現(xiàn)

@Component
public class NeedLoginDirective implements SchemaDirectiveWiring {private static final Logger LOGGER = LoggerFactory.getLogger(NeedLoginDirective.class);public static final String NEED_LOGIN_DIRECTIVE = "needLogin";public NeedLoginDirective() {}@Overridepublic GraphQLFieldDefinition onField(SchemaDirectiveWiringEnvironment<GraphQLFieldDefinition> environment) {GraphQLFieldDefinition field = environment.getElement();GraphQLFieldsContainer parentType = environment.getFieldsContainer();// 原始DataFetcher，無(wú)需修改參數(shù)值時(shí)，最后需返回原始DataFetcher的值DataFetcher originalDataFetcher = environment.getCodeRegistry().getDataFetcher(parentType, field);if (field.getDirective(NEED_LOGIN_DIRECTIVE) == null) {return field;}LOGGER.info("onField field:{} needLogin.", field);DataFetcher needLoginDataFetcher = dfe -> {LoginContext loginContext = DgsContext.getCustomContext(dfe);if (loginContext.getLoginUser().hasLogin()) {return originalDataFetcher.get(dfe);} else {LOGGER.info("not login return null");throw new NeedLoginRuntimeException();}};environment.getCodeRegistry().dataFetcher(parentType, field, needLoginDataFetcher);return field;}
}

Directive 注入

GraphQLSchemaConfiguration

@Configuration
public class GraphQLSchemaConfiguration {@DgsComponentpublic class SecuredDirectiveRegistration {private NeedLoginDirective needLoginDirective;public SecuredDirectiveRegistration(NeedLoginDirective needLoginDirective) {this.needLoginDirective = needLoginDirective;}@DgsRuntimeWiringpublic RuntimeWiring.Builder addSecuredDirective(RuntimeWiring.Builder builder) {return builder.directive(NeedLoginDirective.NEED_LOGIN_DIRECTIVE,needLoginDirective);}}
}

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參考資料：

1. GraphQL（五）指令[Directive]詳解
2. Derectives 原理