spring - RestController 与 Spring WebFlux :Required parameter is not present

Question

我用Spring WebFlux写了一个Rest Controller Demo，不能正常运行，源码如下:

@RestController
public class Demo{
    @PostMapping(value = "test2")
    public Integer getHashCode(@RequestParam("parameters") String parameters){
        return parameters.hashCode();
    }
}

我用Postman测试了一下，返回:

{
    "timestamp": "2018-05-07T07:19:05.303+0000",
    "path": "/test2",
    "status": 400,
    "error": "Bad Request",
    "message": "Required String parameter 'parameters' is not present"
}

依赖项:

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.0.1.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
</parent>
<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    <java.version>1.8</java.version>
</properties>

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-webflux</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>io.projectreactor</groupId>
        <artifactId>reactor-test</artifactId>
        <scope>test</scope>
    </dependency>
</dependencies>

I wrote the same controller demo with Spring boot(v2.0.1.RELEASE), it can run correctly. Why can't it run correctly in Spring Webflux?

Answer 1

作为described in the reference documentation ，在请求参数方面，基于 Servlet 的应用程序 (Spring MVC) 和 Spring WebFlux 之间存在细微的行为差异。

在Spring WebFlux中，@RequestParam只会绑定(bind)查询参数。在您的情况下，您的 HTTP 请求未提供此类查询参数，并且您的方法签名未将其标记为可选。

看看您的 Postman 屏幕截图，您似乎打算将 HTTP 表单数据绑定(bind)到该参数，那么您应该看看 command objects相反。