使用 Spring WebFlux 路由器功能时如何获取模型属性？

Question

Spring WebFlux 提供了两个编程选项的选择：Annotated Controllers 和 Functional Endpoints。对于第一个，我们可以使用 @ModelAttribute 注释将模型属性从控制器传输到视图（例如 Thymeleaf html-template），反之亦然。然而，当谈到路由器功能时，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。考虑以下代码片段：

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

然后利用 return 类型的反应式存储库方法的优势 ReactiveCrudRepository::save returning Mono<T> using Mono::flatMap。

我还没有测试过，但应该可以。

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))

请注意，方法 Mono::then 丢弃了源中的元素，因此重定向的对象仍然是 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));
}

使用 Spring WebFlux 路由器功能时如何获取模型属性？

How to get model attributes when using Spring WebFlux router functions?

java

thymeleaf

spring-boot

project-reactor

spring-webflux