如何 return 响应实体可以是两种不同类型的 Mono<ResponseEntity>

Question

我是 Spring Webflux / Reactor Core 的新手，我正在尝试执行以下功能：

调用userservice.LoginWebApp()
如果用户 returned，return 类型为 "User" 的 ResponseEntity。如果为空，Return 类型为 "String"

以下代码给出类型错误，因为 .defaultIfEmpty() 需要用户类型的 ResponseEntity。您能否就实现此功能的正确运算符/方法提出建议。

@PostMapping("api/user/login/webApp")
public Mono<ResponseEntity> login(@RequestBody Credentials credentials, ServerWebExchange serverWebExchange) {
     return userService.loginWebApp(credentials, serverWebExchange)
             .map(user -> ResponseEntity.status(HttpStatus.OK).body(user))
             .defaultIfEmpty(ResponseEntity.status(HttpStatus.UNAUTHORIZED).body("Invalid username or password"));
}

Answer 1

我会做以下事情：

为响应建立基础class
```
abstract class Response {
}
```

为每种响应（如 UserResponse、ErrorResponse、NotFoundResponse 等）创建单独的 classes，并从基础 Response class

class UserResponse extends Response {
    private String login;
    private String password;

    public UserResponse(String login, String password) {
        this.login = login;
        this.password = password;
    }

    @JsonGetter("login")
    public String getLogin() {
        return login;
    }

    @JsonSetter("login")
    public void setLogin(String login) {
        this.login = login;
    }

    @JsonGetter("password")
    public String getPassword() {
        return password;
    }

    @JsonSetter("password")
    public void setPassword(String password) {
        this.password = password;
    }
}

class ErrorResponse extends Response {
    private String errorMessage;

    public ErrorResponse(String errorMessage) {
        this.errorMessage = errorMessage;
    }

    @JsonGetter("error_message")
    public String getErrorMessage() {
        return errorMessage;
    }

    @JsonSetter("error_message")
    public void setErrorMessage(String errorMessage) {
        this.errorMessage = errorMessage;
    }
}

明确设置return值的类型Mono<ResponseEntity<Response>> 就是这样。

@GetMapping("/test/{login}")
public Mono<ResponseEntity<Response>> test(@PathVariable(value = "login") String login) {
    return loginWebApp(login)
            .map(userResponse -> ResponseEntity.status(HttpStatus.OK).body(userResponse))
            .defaultIfEmpty(ResponseEntity.status(HttpStatus.UNAUTHORIZED).body(new ErrorResponse("bad login")));
}

现在让我们尝试登录错误：

成功登录：

可以找到完整代码here

Answer 2

您可以使用 cast 运算符从泛型中向下转换，我相信 WebFlux 仍然能够编组 User 和 String:

@PostMapping("api/user/login/webApp")
public Mono<ResponseEntity> login(@RequestBody Credentials credentials, ServerWebExchange serverWebExchange) {
     return userService.loginWebApp(credentials, serverWebExchange)
             .map(user -> ResponseEntity.status(HttpStatus.OK).body(user))
             .cast(ResponseEntity.class)
             .defaultIfEmpty(ResponseEntity.status(HttpStatus.UNAUTHORIZED).body("Invalid username or password"));
}

如何 return 响应实体可以是两种不同类型的 Mono<ResponseEntity>

How to return a Mono<ResponseEntity> where the response entity can be of two different types

functional-programming

reactive-programming

project-reactor

spring-webflux