进样豆成DataFetcher GraphQL

Question

的，我在我的项目中使用春 & graphql的Java（graphql-java的注释）。 对于检索数据部分，我使用DataFetcher从服务（从数据库）获取数据。

奇怪的是：myService总是null。任何人都知道原因？

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(); 
} 

Answer 1

由于graphql-java的注释数据提取器是由注释中定义的，它由框架构造（使用反射来得到的构造），从而它不能是豆。

我找到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，但它的工作原理：

@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); 
    } 
} 

基本上你还是会获得通过graphQL初始化的数据提取器的新实例，也是春天将进行初始化，并且由于myService是静态的，你会得到初始化的一个。

Answer 2

@Nir Levy提供的解决方案非常完美。只是为了让它在这里更加可重用。我们可以提取一个封装了bean查找逻辑的抽象类，并为其子类自动布线。

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); 
} 

而子类可以是这样的：

@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 3

虽然@尼尔方法工作（我经常用它JPA事件监听器内），该DataFetcher对象是单身，通过静态属性，以便注入是一个小黑客。

然而，GraphQL的execute方法可以让你在传递一个对象作为背景，然后将在您的DataFetchingEnvironment对象的DataFetcher的（见graphql.execute（）线以下）内：

@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(); 
    } 
}