使用Spring和反应器的API组合物(BFF)

Question

假设我有两个微服务，我想在使用WebFlux的Spring REST控制器中实现BFF（前端的后端）模式。

来自2个远程服务的域对象是：

public class Comment {
    private Long id;
    private String text;
    private Long authorId;
    private Long editorId;
}

public class Person {
    private Long id;
    private String firstName;
    private String lastName;
}

并且API编写器必须返回以下类型的对象：

public class ComposedComment {
    private String text;
    private String authorFullName;
    private String editorFullName;
}

为了简洁起见，我编写了一个控制器，它将所有服务模拟在一个。

@RestController
@RequestMapping("/api")
public class Controller {

    private static final List<Comment> ALL_COMMENTS = Arrays.asList(//
            new Comment(1L, "Bla bla", 1L, null), //
            new Comment(2L, "lorem ipsum", 2L, 3L), //
            new Comment(3L, "a comment", 2L, 1L));
    private static final Map<Long, Person> PERSONS;

    static {
        PERSONS = new HashMap<>();
        PERSONS.put(1L, new Person(1L, "John", "Smith"));
        PERSONS.put(2L, new Person(2L, "Paul", "Black"));
        PERSONS.put(3L, new Person(3L, "Maggie", "Green"));
    }

    private WebClient clientCommentService = WebClient.create("http://localhost:8080/api");
    private WebClient clientPersonService = WebClient.create("http://localhost:8080/api");

    @GetMapping("/composed/comments")
    public Flux<ComposedComment> getComposedComments() {
     //This is the tricky part
    }

    private String extractFullName(Map<Long, Person> map, Long personId) {
        Person person = map.get(personId);
        return person == null ? null : person.getFirstName() + " " + person.getLastName();
    }

    @GetMapping("/comments")
    public ResponseEntity<List<Comment>> getAllComments() {
        return new ResponseEntity<List<Comment>>(ALL_COMMENTS, HttpStatus.OK);
    }

    @GetMapping("/persons/{personIds}")
    public ResponseEntity<List<Person>> getPersonsByIdIn(@PathVariable("personIds") Set<Long> personIds) {
        List<Person> persons = personIds.stream().map(id -> PERSONS.get(id)).filter(person -> person != null)
                .collect(Collectors.toList());
        return new ResponseEntity<List<Person>>(persons, HttpStatus.OK);
    }
}

我的问题是我刚刚开始与反应堆，我不是真的确定我在做什么…这是我的composer方法的当前版本：

@GetMapping("/composed/comments")
public Flux<ComposedComment> getComposedComments() {
    Flux<Comment> commentFlux = clientCommentService.get().uri("/comments").retrieve().bodyToFlux(Comment.class);
    Set<Long> personIds = commentFlux.toStream().map(comment -> Arrays.asList(comment.getAuthorId(), comment.getEditorId())).flatMap(Collection::stream).filter(Objects::nonNull).collect(Collectors.toSet());
    Map<Long, Person> personsById = clientPersonService.get().uri("/persons/{ids}", personIds.stream().map(Object::toString).collect(Collectors.joining(","))).retrieve().bodyToFlux(Person.class).collectMap(Person::getId).block();
    return commentFlux.map(
            comment -> new ComposedComment(
                    comment.getText(),
                    extractFullName(personsById, comment.getAuthorId()),
                    extractFullName(personsById, comment.getEditorId()))
    );
}

它可以工作，但是我知道我应该用map、flatMap和zip进行几个转换，而不是调用block（）和toStream（）...你能帮我正确地重写这个方法吗？：）

Answer 1

您正在控制器中返回null。将其替换为返回反应流。

return commentFlux.flatMap(comment -> ....)
....

您的控制器签名返回

Flux<ComposedComment>

所以确保在最后一次返回中，您必须使用flatMap或map将它们转换为ComposedComment。您可以将其视为一个promise链，在该链中您可以在实现中执行许多flatMap、map，以转换为最终的数据集。