使用 Spring WebFlux 路由器功能时如何获取模型属性？

Question

Spring WebFlux 提供两种编程选项可供选择：带注释的控制器和功能端点。对于第一个，我们可以使用@ModelAttribute 注解将模型属性从控制器传递到视图（例如 Thymeleaf html-template），反之亦然。但是，当涉及到路由器功能时，到目前为止，我只是想出了如何将模型属性附加到ServerResponse，但找不到将它们取回的方法。考虑以下代码 sn-p：

@Configuration
public class StudentsRouterFunctions {

    // inject repository
    private final StudentsCrudRepository repo;

    public StudentsRouterFunctions(StudentsCrudRepository repo) {
        this.repo = repo;
    }

    @Bean
    RouterFunction<?> routs() {
        return RouterFunctions.route()
                .GET("/students", this::showStudents)
                .POST("/students", this::saveStudent)
                .build();
    }

    // #1: GET-handler
    private Mono<ServerResponse> showStudents(ServerRequest request) {

        // set model attributes
        Map<String, Object> model = new HashMap<>();
        Mono<Student> studentsList = repo.findAll().collectList();
        Mono<Student> newStudent = Mono.just(new Student());
        model.put("students", studentsList);
        model.put("studentForm", newStudent);

        // render the view
        return ServerResponse.ok()
                .contentType(MediaType.TEXT_HTML)
                .render("students-template", model);
    }

    // #2: POST-handler
    private Mono<ServerResponse> saveStudent(ServerRequest request) {

        // and here I somehow need to get my new student object 
        // back from the view via "studentForm" model attribute

        // Student newStudent = request.getModel().get("studentForm"); 
        // !!! however, ServerRequest.getModel() method doesn't exist

        return repo.save(newStudent)
                .then(ServerResponse.status(HttpStatus.PERMANENT_REDIRECT)
                        .render("redirect:/students", new Object()));
    }

Answer 1

没有ServerRequest::getModel 方法，但ServerRequest::bodyToMono(Class) 可以将模型所在的主体提取到Mono<T>。

然后利用响应式存储库方法ReactiveCrudRepository::save的返回类型的优势，使用Mono::flatMap返回Mono<T>。

我还没有测试过，但它应该可以工作。

private Mono<ServerResponse> saveStudent(ServerRequest request) {
    return request.bodyToMono(Student.class)               // Mono<Student> (a new one)
                  .flatMap(repo::save)                     // Mono<Student> (a saved one)
                  .then(ServerResponse                     // redirect sequence
                      .status(HttpStatus.PERMANENT_REDIRECT)
                      .render("redirect:/students", new Object()));
}

// .flatMap(repo::save) is the same as .flatMap(newStudent -> repo.save(newStudent))

注意Mono::then 方法会丢弃源中的元素，因此重定向的对象仍为new Object()，因此您想使用Mono::map。

private Mono<ServerResponse> saveStudent(ServerRequest request) {
    return request.bodyToMono(Student.class)               // Mono<Student> (a new one)
                  .flatMap(repo::save)                     // Mono<Student> (a saved one)
                  .map(savedStudent -> ServerResponse      // redirect sequence
                      .status(HttpStatus.PERMANENT_REDIRECT)
                      .render("redirect:/students", savedStudent));
}