Graphql

2021/10/31 21:16 下午

简介

Graphql 是一种类似于 REST 的一种 API 标准。
不是一种数据库技术。

总的来说就是，后端可以根据前端需要的字段返回对应的信息，不需要修改原有接口。

--- 1.前端请求字段
{
  hero {
    name
  }
}

--- 2.后端返回结果
{
  "data": {
    "hero": {
      "name": "R2-D2"
    }
  }
}


--- 1.前端请求字段
{
  hero {
    name
    # Queries can have comments!
    friends {
      name
    }
  }
}

--- 2.后端返回结果
{
  "data": {
    "hero": {
      "name": "R2-D2",
      "friends": [
        {
          "name": "Luke Skywalker"
        },
        {
          "name": "Han Solo"
        },
        {
          "name": "Leia Organa"
        }
      ]
    }
  }
}

demo

https://gitee.com/hitol/graphql-demo.git

dependencies

<dependency>
    <groupId>com.graphql-java</groupId>
    <artifactId>graphql-java</artifactId>
    <version>11.0</version>
</dependency>

<dependency>
    <groupId>com.graphql-java</groupId>
    <artifactId>graphiql-spring-boot-starter</artifactId>
    <version>3.10.0</version>
</dependency>

<dependency>
    <groupId>com.graphql-java</groupId>
    <artifactId>graphql-java-spring-boot-starter-webmvc</artifactId>
    <version>1.0</version>
</dependency>

<dependency>
    <groupId>com.google.guava</groupId>
    <artifactId>guava</artifactId>
    <version>26.0-jre</version>
</dependency>

Schema

在 resources 文件夹下新建一个 schema.graphqls 文件，其内容如下

type Query {
  bookById(id: ID): Book 
}

type Book {
  id: ID
  name: String
  pageCount: Int
  author: Author
}

type Author {
  id: ID
  firstName: String
  lastName: String
}

Graphql 加载到 Spring


@Component
public class GraphQLProvider {


    @Autowired
    GraphQLDataFetchers graphQLDataFetchers;

    private GraphQL graphQL;

    @PostConstruct
    public void init() throws IOException {
        URL url = Resources.getResource("schema.graphqls");
        String sdl = Resources.toString(url, Charsets.UTF_8);
        GraphQLSchema graphQLSchema = buildSchema(sdl);
        this.graphQL = GraphQL.newGraphQL(graphQLSchema).build();
    }

    private GraphQLSchema buildSchema(String sdl) {
        TypeDefinitionRegistry typeRegistry = new SchemaParser().parse(sdl);
        RuntimeWiring runtimeWiring = buildWiring();
        SchemaGenerator schemaGenerator = new SchemaGenerator();
        return schemaGenerator.makeExecutableSchema(typeRegistry, runtimeWiring);
    }

    private RuntimeWiring buildWiring() {
        return RuntimeWiring.newRuntimeWiring()
                .type(newTypeWiring("Query")
                        .dataFetcher("bookById", graphQLDataFetchers.getBookByIdDataFetcher()))
                .type(newTypeWiring("Book")
                        .dataFetcher("author", graphQLDataFetchers.getAuthorDataFetcher()))
                .build();
    }

    @Bean
    public GraphQL graphQL() {
        return graphQL;
    }

}

其中对于文件的解析最重要的方法就是 buildWiring

这一块其实就是后端提供的关于 graphql 的接口。

使用了一个插件，方便调试 graphiql

项目启动之后浏览器中访问，http://localhost:8080/graphiql