将bean注入GraphQL的DataFetcher

Question

我在用Spring

奇怪的是：myService总是空的。有人知道原因吗？

数据提取程序

@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;
    }
}

我的服务

@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();
}




Answer 1

@Nir Levy提供的解决方案运行完美。只是为了让它在这里更具可重用性。我们可以提取一个抽象类来封装bean查找逻辑并使其子类的自动装配工作。

public abstract class SpringContextAwareDataFetcher implements DataFetcher, ApplicationContextAware {

    private static ApplicationContext applicationContext;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.applicationContext = applicationContext;
    }

    @Override
    public final Object get(DataFetchingEnvironment environment) {
        return applicationContext.getBean(this.getClass()).fetch(environment);
    }

    protected abstract Object fetch(DataFetchingEnvironment environment);
}

子类可以是这样的：

@Component
public class UserDataFetcher extends SpringContextAwareDataFetcher {

    @Autowired
    private UserService userService;

    @Override
    public String fetch(DataFetchingEnvironment environment) {
        User user = (User) environment.getSource();
        return userService.getUser(user.getId()).getName();
    }
}

Answer 2

匿名用户

尽管@Nir的方法有效（我经常在JPA事件侦听器中使用它），但DataFetcher对象是单例，因此通过静态属性注入有点麻烦。

但是，GraphQL的执行方法允许您将对象作为上下文传入，然后该上下文将在DataFetching环境DataFetcher内的对象中可用（参见下面的graphql.execute（）行）：

@Component
public class GraphQLService {

    @Autowired
    MyService myService;

    public Object getGraphQLResult() {
        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}}", myService);

        return result.getData();
    }
}

public class MyDataFetcher implements DataFetcher {

    @Override
    public Object get(DataFetchingEnvironment environment) {
        MyService myService = (MyService) environment.getContext();

        return myService.getData();
    }
}

Answer 3

由于在graph ql-java-anotation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。

我为此找到的解决方法是将其设置为Application ationContextAware，然后我可以初始化一些静态字段而不是bean。不是最好的事情，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，您仍将获得一个由graphQL初始化的数据获取程序的新实例，但spring也将对其进行初始化，因为myService是静态的，所以您将获得初始化的实例。