GraphQL 與 Spring Boot 的初體驗

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GraphQL 既是一種用於 API 的查詢語言也是一個滿足你數據查詢的運行時。 GraphQL 對你的 API 中的數據提供了一套易於理解的完整描述，使得客戶端能夠準確地獲得它需要的數據，而且沒有任何冗餘，也讓 API 更容易地隨著時間推移而演進，還能用於構建強大的開發者工具。

定義 Schema#

# src/main/resources/schema.graphql
schema {
  query: Query
}

type Query {
  allBooks: [Book]
  book(id: String): Book
}

type Book {
  isbn: String
  title: String
  publisher: String
  authors: [String]
  publishedDate: String
}

加載並解析上面定義的 Schema#

@Service
public class GraphQLService {

  @Value("classpath:schema.graphql")
  private Resource resource;

  @Getter
  private GraphQL graphQL;
  @Autowired
  private AllBooksDataFetcher allBooksDataFetcher;
  @Autowired
  private BookDataFetcher bookDataFetcher;

  @PostConstruct
  private void loadSchema() throws IOException {
    // 獲取本地定義的 Schema 文件
    File schemaFile = resource.getFile();
    // 解析 Schema 文件
    TypeDefinitionRegistry typeRegistry = new SchemaParser().parse(schemaFile);
    RuntimeWiring wiring = buildRuntimeWiring();
    GraphQLSchema schema = new SchemaGenerator().makeExecutableSchema(typeRegistry, wiring);
    graphQL = GraphQL.newGraphQL(schema).build();
  }

  private RuntimeWiring buildRuntimeWiring() {
    return RuntimeWiring.newRuntimeWiring()
      .type("Query", typeWiring -> typeWiring
        .dataFetcher("allBooks", allBooksDataFetcher)
        .dataFetcher("book", bookDataFetcher)
      ).build();
  }
}

提供 DataFetcher#

相當於提供 Schema 中的 Query 實現：

type Query {
  allBooks: [Book]
  book(id: String): Book
}

AllBooksDataFetcher 對應實現 allBooks: [Book]：

@Component
public class AllBooksDataFetcher implements DataFetcher<List<Book>> {

  @Autowired
  private BookRepository bookRepository;

  @Override
  public List<Book> get(DataFetchingEnvironment dataFetchingEnvironment) {
    return bookRepository.findAll();
  }
}

BookDataFetcher 對應實現 book(id: String): Book：

@Component
public class BookDataFetcher implements DataFetcher<Book> {

  @Autowired
  private BookRepository bookRepository;

  @Override
  public Book get(DataFetchingEnvironment dataFetchingEnvironment) {
    String isn = dataFetchingEnvironment.getArgument("id");
    return bookRepository.findById(isn).orElse(null);
  }
}

提供 GraphQL API#

@RestController
@RequestMapping(path = "/v1/books")
public class BookController {

  @Autowired
  private GraphQLService graphQLService;

  @PostMapping
  public ResponseEntity<Object> getAllBooks(@RequestBody String query) {
    ExecutionResult execute = graphQLService.getGraphQL().execute(query);
    return new ResponseEntity<>(execute, HttpStatus.OK);
  }
}

啟動並測試#

$ mvn install
...
[INFO] BUILD SUCCESS
...
$ mvn spring-boot:run
...
2019-08-24 19:35:11.700  INFO 14464 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2019-08-24 19:35:11.702  INFO 14464 --- [           main] i.g.y.s.graphql.GraphQLApplication       : Started GraphQLApplication in 16.808 seconds (JVM running for 25.601)

查詢部分字段

$ curl -X POST \
  http://127.0.0.1:8080/v1/books \
  -H 'Content-Type: text/plain' \
  -d '{
    allBooks {
      isbn
      title
  }
}' | jq
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   579    0   524  100    55  34933   3666 --:--:-- --:--:-- --:--:-- 38600
{
  "errors": [],
  "data": {
    "allBooks": [
      {
        "isbn": "9787111213826",
        "title": "Java 編程思想（第4版）"
      },
      ...
    ]
  },
  "extensions": null,
  "dataPresent": true
}

$ curl -X POST \
  http://127.0.0.1:8080/v1/books \
  -H 'Content-Type: text/plain' \
  -d '{
    book(id: "9787121362132") {
      title
  }
}' | jq
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   210    0   159  100    51   1691    542 --:--:-- --:--:-- --:--:--  2234
{
  "errors": [],
  "data": {
    "book": {
      "title": "高可用可伸縮微服務架構：基於 Dubbo、Spring Cloud 和 Service Mesh"
    }
  },
  "extensions": null,
  "dataPresent": true
}

查詢全部字段

$ curl -X POST \
  http://127.0.0.1:8080/v1/books \
  -H 'Content-Type: text/plain' \
  -d '{
    allBooks {
      isbn
      title
      authors
      publisher
      publishedDate
  }
}' | jq
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  1139    0  1044  100    95    750     68  0:00:01  0:00:01 --:--:--   818
{
  "errors": [],
  "data": {
    "allBooks": [
      {
        "isbn": "9787111213826",
        "title": "Java 編程思想（第4版）",
        "authors": [
          "Bruce Eckel"
        ],
        "publisher": "機械工業出版社",
        "publishedDate": "2007-06-01"
      },
      ...
    ]
  },
  "extensions": null,
  "dataPresent": true
}

$ curl -X POST \
  http://127.0.0.1:8080/v1/books \
  -H 'Content-Type: text/plain' \
  -d '{
    book(id: "9787121362132") {
      title
      authors
      publisher
      publishedDate
  }
}' | jq
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   421    0   320  100   101   312k    98k --:--:-- --:--:-- --:--:--  411k
{
  "errors": [],
  "data": {
    "book": {
      "title": "高可用可伸縮微服務架構：基於 Dubbo、Spring Cloud 和 Service Mesh",
      "authors": [
        "程超",
        "梁桂釗",
        "秦金衛",
        "方志斌",
        "張逸",
        "杜琪",
        "殷琦",
        "肖冠宇"
      ],
      "publisher": "電子工業出版社",
      "publishedDate": "2019-05-01"
    }
  },
  "extensions": null,
  "dataPresent": true
}

查詢多個數據

$ curl -X POST \
  http://127.0.0.1:8080/v1/books \
  -H 'Content-Type: text/plain' \
  -d '{
    allBooks {
      isbn
      title
    }
    book(id: "9787121362132") {
      title
      authors
      publisher
      publishedDate
  }
}' | jq
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   930    0   785  100   145   3866    714 --:--:-- --:--:-- --:--:--  4581
{
  "errors": [],
  "data": {
    "allBooks": [
      {
        "isbn": "9787111213826",
        "title": "Java 編程思想（第4版）"
      },
      {
        "isbn": "9787111421900",
        "title": "深入理解 Java 虛擬機：JVM 高級特性與最佳實踐（第2版）"
      },
      {
        "isbn": "9787115221704",
        "title": "重構 改善既有代碼的設計（第2版）"
      },
      {
        "isbn": "9787121362132",
        "title": "高可用可伸縮微服務架構：基於 Dubbo、Spring Cloud 和 Service Mesh"
      },
      {
        "isbn": "9787302392644",
        "title": "人月神話（40周年中文紀念版）"
      }
    ],
    "book": {
      "title": "高可用可伸縮微服務架構：基於 Dubbo、Spring Cloud 和 Service Mesh",
      "authors": [
        "程超",
        "梁桂釗",
        "秦金衛",
        "方志斌",
        "張逸",
        "杜琪",
        "殷琦",
        "肖冠宇"
      ],
      "publisher": "電子工業出版社",
      "publishedDate": "2019-05-01"
    }
  },
  "extensions": null,
  "dataPresent": true
}

綜上可見，API 不變只改動了查詢的內容，就會自動響應不同的結果。

Aben Blog