GraphQL架构

Schema设计

GraphQL通过强类型Schema定义API契约，支持查询、变更和订阅。

type Query {
  user(id: ID!): User
  users(filter: UserFilter, first: Int, after: String): UserConnection!
}

type Mutation {
  createUser(input: CreateUserInput!): User!
  updateUser(id: ID!, input: UpdateUserInput!): User!
}

type Subscription {
  userCreated: User!
}

type User {
  id: ID!
  name: String!
  email: String!
  posts: [Post!]!
  createdAt: DateTime!
}

input CreateUserInput {
  name: String!
  email: String!
}

scalar DateTime

N+1问题解决

通过DataLoader批量加载关联数据，解决N+1查询问题。

@Component
public class UserDataLoader {

    @Autowired
    private UserRepository userRepository;

    @BatchLoader
    public Map<Long, User> loadUsersByIds(List<Long> ids) {
        List<User> users = userRepository.findAllById(ids);
        return users.stream()
            .collect(Collectors.toMap(User::getId, Function.identity()));
    }
}

@Component
public class PostDataFetcher implements DataFetcher<List<Post>> {

    @Autowired
    private PostRepository postRepository;

    @Override
    public List<Post> get(DataFetchingEnvironment env) {
        User user = env.getSource();
        return postRepository.findByUserId(user.getId());
    }
}

Apollo Federation

多服务通过Apollo Federation组合成统一的GraphQL网关。

@Configuration
public class FederatedGraphQLConfig {

    @Bean
    public ApolloFederationSchemaGeneratorwiring schemaGeneratorWiring() {
        return ApolloFederationSchemaGeneratorwiring.newWiring()
            .type("Post", wiring -> wiring.resolveReference("author",
                (env) -> {
                    Author author = env.getArgument("__typename");
                    return authorService.findById(author.getId());
                }))
            .build();
    }
}

# Apollo Gateway配置
supergraph:
  listen: 0.0.0.0:4000
  introspection: true
subgraphs:
  users:
    routing_url: http://user-service:4001/graphql
    schema:
      subgraph_url: http://user-service:4001/graphql
  posts:
    routing_url: http://post-service:4002/graphql
    schema:
      subgraph_url: http://post-service:4002/graphql

性能优化

通过查询复杂度分析、深度限制和缓存提升GraphQL性能。

@Component
public class QueryComplexityInstrumentation extends SimpleInstrumentation {

    private final int maxComplexity;

    @Override
    public InstrumentationContext<ExecutionResult> beginExecuteOperation(
            InstrumentationExecutionParameters params) {
        Document document = params.getDocument();
        int complexity = calculateComplexity(document);
        if (complexity > maxComplexity) {
            throw new GraphQLException("Query too complex: " + complexity);
        }
        return super.beginExecuteOperation(params);
    }
}