GraphQL介绍

发表于 2023-01-03 | 分类于 note

GraphQL协议

schema即协议，通俗的来讲，可以类似rest openapi schema
客户端以及服务端根据schema通信，根据其定义进行校验约束
客户端在schema范围内可以自由获取（query）或者更新（mutation）需要的字段

type Hero {
    id:ID!
    name :String
    friends:[People]
}

type Query{
    heroes:[Hero]
    heroById(id:ID):Hero
}

heroes{
name 
}


data{
heroes: [{name:"A"},{name:"B"}]
}

type Mutation{
updateHero(new:Hero!):Hero
}

updateHero{
id:1
name:"C"
}

data{
updateHero: {id:1 , name:"C"}
}

需要关注的GraphQL Java概念

DataFetcher 定义具体数据获取方式，可以是db，memory
DataLoader 用于 1对n，数据关联查询，解决 n+1 查询问题，用key做了一些cache

对应SpringBoot以及Netflix DGS 封装映射

Fetcher

@Controller @MutationMapping @QueryMapping
@DgsComponent @DgsMutation @DgsQuery

Loader

@SchemaMapping @BatchMapping
@DgsData

原生GraphQL SDK demo

DataFetcher 定义

private RuntimeWiring buildWiring(){
    return RuntimeWiring.newRuntimeWiring()
    .type(newTypeWiring("Query")
    .dataFetcher("hero",starWarsWiring.heroDataFetcher)
    .dataFetcher("human",starWarsWiring.humanDataFetcher)
    .dataFetcher("droid",starWarsWiring.droidDataFetcher)
    )
    .type(newTypeWiring("Human")
    .dataFetcher("friends",starWarsWiring.friendsDataFetcher)
    )
    .type(newTypeWiring("Droid")
    .dataFetcher("friends",starWarsWiring.friendsDataFetcher)
    )

    .type(newTypeWiring("Character")
    .typeResolver(starWarsWiring.characterTypeResolver)
    )
    .type(newTypeWiring("Episode")
    .enumValues(starWarsWiring.episodeResolver)
    )
    .build();
    }

DataFetcher & DataLoader 实现


@Component
public class StarWarsWiring {

    private final DataLoaderRegistry dataLoaderRegistry;

    public StarWarsWiring() {
        this.dataLoaderRegistry = new DataLoaderRegistry();
        dataLoaderRegistry.register("characters", newCharacterDataLoader());
    }

    @Bean
    public DataLoaderRegistry getDataLoaderRegistry() {
        return dataLoaderRegistry;
    }


    private List<Object> getCharacterDataViaBatchHTTPApi(List<String> keys) {
        return keys.stream().map(StarWarsData::getCharacterData).collect(Collectors.toList());
    }

    // a batch loader function that will be called with N or more keys for batch loading
    private BatchLoader<String, Object> characterBatchLoader = keys -> {

        //
        // we are using multi threading here.  Imagine if getCharacterDataViaBatchHTTPApi was
        // actually a HTTP call - its not here - but it could be done asynchronously as
        // a batch API call say
        //
        //
        // direct return of values
        //CompletableFuture.completedFuture(getCharacterDataViaBatchHTTPApi(keys))
        //
        // or
        //
        // async supply of values
        return CompletableFuture.supplyAsync(() -> getCharacterDataViaBatchHTTPApi(keys));
    };

    // a data loader for characters that points to the character batch loader
    private DataLoader<String, Object> newCharacterDataLoader() {
        return new DataLoader<>(characterBatchLoader);
    }

    // we define the normal StarWars data fetchers so we can point them at our data loader
    DataFetcher humanDataFetcher = environment -> {
        String id = environment.getArgument("id");
        Context ctx = environment.getContext();
        return ctx.getCharacterDataLoader().load(id);
    };


    DataFetcher droidDataFetcher = environment -> {
        String id = environment.getArgument("id");
        Context ctx = environment.getContext();
        return ctx.getCharacterDataLoader().load(id);
    };

    DataFetcher heroDataFetcher = environment -> {
        Context ctx = environment.getContext();
        return ctx.getCharacterDataLoader().load("2001"); // R2D2
    };

    DataFetcher friendsDataFetcher = environment -> {
        FilmCharacter character = environment.getSource();
        List<String> friendIds = character.getFriends();
        Context ctx = environment.getContext();
        return ctx.getCharacterDataLoader().loadMany(friendIds);
    };
}

Reference