Spring Web转Spring Reactive Web后Webflux控制器空响应问题求助

将Spring Web应用改造为Spring Reactive Web后，新增了返回Mono/Flux类型结果的控制器，但通过Postman调用接口时，HTTP响应码为200却没有响应体。

控制台日志如下：

022-08-23 15:00:11.315 [http-nio-8083-exec-5] [user=kashif]
[request_id=8df3ef65-e9b7-4aaf-b3ef-65e9b7eaaf31]
[org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping]
DEBUG - Mapped to
org.dummy.services.controller.TestController#hello()
2022-08-23 15:00:11.315 [http-nio-8083-exec-5] [user=kashif]
[request_id=8df3ef65-e9b7-4aaf-b3ef-65e9b7eaaf31]
[org.dummy.services.controller.TestController] INFO - POI hello
2022-08-23 15:00:11.315 [http-nio-8083-exec-5] [user=qaz] [request_id=8aaaaaaaaaaaaaf31]
[org.springframework.web.context.request.async.WebAsyncManager] DEBUG - Started async request
2022-08-23 15:00:11.315 [http-nio-8083-exec-5] [user=qaz]
[request_id=8aaaaaaaaaaaaaf31]
[org.springframework.web.context.request.async.WebAsyncManager] DEBUG - Async result set, dispatch to /poi/test/hello
2022-08-23 15:00:11.315 [http-nio-8083-exec-5] [user=qaz]
[request_id=8df3ef65-e9b7-4aaf-b3ef-65e9b7eaaf31]
[org.springframework.web.servlet.DispatcherServlet] DEBUG - Exiting but response remains open for further handling
2022-08-23 15:00:11.346 [http-nio-8083-exec-5] [user=] [request_id=]
[org.springframework.web.servlet.DispatcherServlet] DEBUG - "ASYNC" dispatch for POST "/poi/test/hello", parameters={masked}
2022-08-23 15:00:11.346 [http-nio-8083-exec-5] [user=] [request_id=]
[org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter]
DEBUG - Resume with async result ["hello"]
2022-08-23 15:00:11.346 [http-nio-8083-exec-5] [user=] [request_id=]
[org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor]
DEBUG - Using 'text/plain', given [/] and supported [text/plain, /, text/plain, /, application/json, application/+json, application/json, application/+json, application/cbor]
2022-08-23 15:00:11.346 [http-nio-8083-exec-5] [user=] [request_id=]
[org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor]
DEBUG - Writing ["hello"]
2022-08-23 15:00:11.346 [http-nio-8083-exec-5] [user=] [request_id=]
[org.springframework.web.servlet.DispatcherServlet] DEBUG - Exiting from "ASYNC" dispatch, status 200

示例控制器代码：

@RestController
@RequestMapping("test")
public class TestController {

    @RequestMapping(value = "/hello", method = RequestMethod.POST)
    public Mono<String> hello() {
        log.info("POI hello");
        return Mono.just("hello");//.map(ResponseEntity::ok);
    }
}

相关版本信息：

• Spring Boot版本：2.2.5
• Java版本：8

从日志可以看出，应用仍在使用org.springframework.web.servlet相关组件（传统Servlet栈），而非WebFlux的Reactive栈。这意味着改造时没有完全切换到WebFlux环境，导致Mono类型被当作普通异步Servlet请求处理，响应体未能正确返回。

1. 切换依赖到WebFlux #

移除传统Spring Web依赖，添加Spring WebFlux依赖：

Maven配置 #

<!-- 移除原有Spring Web依赖 -->
<!-- <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency> -->

<!-- 添加WebFlux依赖 -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-webflux</artifactId>
</dependency>

Gradle配置 #

// 移除原有Spring Web依赖
// implementation 'org.springframework.boot:spring-boot-starter-web'

// 添加WebFlux依赖
implementation 'org.springframework.boot:spring-boot-starter-webflux'

2. 优化控制器注解（可选） #

使用WebFlux推荐的简化注解，替代@RequestMapping：

@RestController
@RequestMapping("test")
public class TestController {

    @PostMapping("/hello")
    public Mono<String> hello() {
        log.info("POI hello");
        return Mono.just("hello");
    }
}

3. 清理Servlet相关配置 #

确保应用启动类没有添加@ServletComponentScan等Servlet栈专属注解，避免同时启动两种环境。

4. 检查Postman请求设置 #

• 确认请求方法为POST，路径与控制器配置一致
• 确保Headers中包含Accept: text/plain或Accept: */*（日志显示已支持该类型）
• 关闭"Send and Download"模式，使用普通Send模式发送请求

内容的提问来源于stack exchange，提问作者oOXAam