我正在使用Spring&我的项目中的graphql-java(graphql-java-annotation).
为了检索数据部分,我使用DataFetcher从服务(从数据库)获取数据.

奇怪的是：myService始终为null.谁知道原因？

DataFetcher

@Component
public class MyDataFetcher implements DataFetcher {

    // get data from database
    @Autowired
    private MyService myService;

    @Override
    public Object get(DataFetchingEnvironment environment) {
        return myService.getData();
    }
}

架构

@Component
@GraphQLName("Query")
public class MyGraphSchema {

    @GraphQLField
    @GraphQLDataFetcher(MyDataFetcher.class)
    public Data getData() {
        return null;
    }
}

为MyService

@Service
public class MyService {

    @Autowired
    private MyRepository myRepo;

    @Transactional(readOnly = true)
    public Data getData() {
        return myRepo.getData();
    }
}

主要测试

@Bean
public String testGraphql(){
    GraphQLObjectType object = GraphQLAnnotations.object(MyGraphSchema.class);
    GraphQLSchema schema = newSchema().query(object).build();
    GraphQL graphql = new GraphQL(schema);

    ExecutionResult result = graphql.execute("{getData {id name desc}}");;
    Map<String, Object> v = (Map<String, Object>) result.getData();
    System.out.println(v);
    return v.toString();
}

最佳答案:

由于在graphql-java-annotation中数据获取器是由注释定义的,它是由框架构造的(使用反射来获取构造函数),因此它不能是bean.

我发现的解决方法是将其设置为ApplicationContextAware,然后我可以初始化一些静态字段而不是bean.不是最好的东西,但它有效：

@Component
public class MyDataFetcher implements DataFetcher, ApplicationContextAware {

    private static MyService myService;
    private static ApplicationContext context;

    @Override
    public Object get(DataFetchingEnvironment environment) {
        return myService.getData();
    }

    @override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansExcepion {
        context = applicationContext;
        myService = context.getBean(MyService.class);
    }
}

基本上你仍然会得到一个由graphQL初始化的数据提取器的新实例,但是spring会初始化它,并且由于myService是静态的,你将得到初始化的.