Spring-boot: MultipartBodyBuilder needs dependency to work after upgrading to spring boot 2.0.0.RELEASE from 2.0.0.M7

[khe817]

In Spring Boot 2.0.0.RELEASE, to use org.springframework.http.client.MultipartBodyBuilder in my project, I now have to add a dependency for org.reactivestreams:

<dependency>
    <groupId>org.reactivestreams</groupId>
    <artifactId>reactive-streams</artifactId>
    <version>1.0.2</version>
</depende

This was not an issue in Spring Boot 2.0.0.M7.

Not sure if this is an issue.

[bclozel]

In which context are you using that class - could you share a code snippet?
It's usually being used with WebClient, from spring-webflux which depends on reactor-core. Isn't your application depending using spring-webflux?

[khe817]

I wrote this function that uses it:

/**
 * Map a form object's properties to POST parameters for {@link RestTemplate} requests.
 * This only maps properties that have {@link @Getter} methods.
 */
public MultipartBodyBuilder mapPostParams(Object formObject) throws Exception {
    MultipartBodyBuilder postParamsBuilder = new MultipartBodyBuilder();
    PropertyDescriptor[] objDescriptors = BeanUtils.getPropertyDescriptors(formObject.getClass());
    for (PropertyDescriptor objDescriptor : objDescriptors) {
        String propertyName = objDescriptor.getName();
        Method readMethod = objDescriptor.getReadMethod();
        if (readMethod != null) {
            Object propertyValue = readMethod.invoke(formObject);
            postParamsBuilder.part(propertyName, propertyValue == null ? "" : propertyValue);
        }
    }
    return postParamsBuilder;
}

The code failed at line postParamsBuilder.part(propertyName, propertyValue == null ? "" : propertyValue); when I tried to call MultipartBodyBuilder.part() method with error Java.lang.NoClassDefFoundError.

When I looked into the MultipartBodyBuilder.part() method I could see that it used org.reactivestreams.Publisher class from org.reactivestreams package. When I added the package to pom.xml, it works.

My application 's depending does not use spring-webflux, just the normal spring-boot-starter-web.

Before I upgraded to Spring Boot 2.0.0.RELEASE, I did not have to add org.reactivestreams package to my dependencies in pom.xml.

[bclozel]

Thanks for the information.

You should not use this type with Spring MVC & RestTemplate, but rather use MultipartFile (for files) and MultiValueMap<String, Object> to collect the parts and set it as the request body.
You can check the Spring Framework reference documentation.

You can also take a look at the uploading files getting started guide and its integration tests for a concrete example on that.

If you've got other questions on this subject, please use StackOverflow - the Spring Boot team and the community are actively monitoring Spring tags there.

[khe817]

Thank you for your feedback!

I have changed my code to what you suggested and everything works as expected.

I am sorry for the hassle!

[sidian123]

我碰到了同样的问题，spring mvc的环境下，spring boot 2.1.5，我用FileSystemResource来获取文件并上传。代码很简单，如下所示：

    @Test
    public void test2() throws FileNotFoundException, URISyntaxException {
        MultipartBodyBuilder builder=new MultipartBodyBuilder();
        builder.part("file",new FileSystemResource("C:\\Users\\Administrator\\Pictures\\王通.jpg"));

        Status status=new RestTemplate().postForObject("http://localhost:8080/image/upload",builder.build(),Status.class);
        System.out.println(status);
    }

必须加上楼主的依赖才能正常运行。。。

[uqix]

Thanks for the information.

You should not use this type with Spring MVC & RestTemplate, but rather use MultipartFile (for files) and MultiValueMap<String, Object> to collect the parts and set it as the request body.
You can check the Spring Framework reference documentation.

You can also take a look at the uploading files getting started guide and its integration tests for a concrete example on that.

If you've got other questions on this subject, please use StackOverflow - the Spring Boot team and the community are actively monitoring Spring tags there.

But it is quite misleading that the MultipartBodyBuilder usage is still in the RestTemplate doc

[bclozel]

Sorry @uqix and @khe817 - judging from its Javadoc, I thought that the MultipartBodyBuilder should only be used with WebClient. I've opened spring-projects/spring-framework#23295 against the Spring Framework project to fix that.