Spring Boot接口无法解析带引号boundary的MuleSoft文件上传请求

我们有一个运行已久的Spring Boot后端服务，近期新用户使用MuleSoft调用文件上传接口时持续失败，报错信息如下：

Failed to parse multipart servlet request; nested exception is java.io.IOException: org.apache.tomcat.util.http.fileupload.FileUploadException: the request was rejected because no multipart boundary was found

经排查，MuleSoft与curl/Postman请求的唯一差异在于：MuleSoft发送的Content-Type头中boundary值被双引号包裹。

MuleSoft请求头示例 #

<Header name="Content-Type">multipart/form-data; charset=UTF-8; boundary="--------------------------669816398596264398718285"</Header>

curl请求头示例 #

*  SSL certificate verify ok.
* Using HTTP2, server supports multiplexing
* Connection state changed (HTTP/2 confirmed)
* Copying HTTP/2 data in stream buffer to connection buffer after upgrade: len=0
* Using Stream ID: 1 (easy handle 0x7fd656810a00)
> POST /api/upload HTTP/2
> Host: myhost
> user-agent: curl/7.79.1
> accept: */*
> content-length: 97255
> content-type: multipart/form-data; boundary=------------------------111fd08cb4fafe1c
> 
* Connection state changed (MAX_CONCURRENT_STREAMS == 128)!
* We are completely uploaded and fine
< HTTP/2 200 
< date: Mon, 19 Dec 2022 04:56:25 GMT
< content-length: 0

Spring Controller代码 #

@RestController
class MyController {

    @PostMapping("/upload", consumes = [MediaType.MULTIPART_FORM_DATA_VALUE])
    @ResponseStatus(HttpStatus.OK)
    fun uploadDocument(@RequestPart("file") file: MultipartFile) {
        logger.info { "ContentType: ${file.contentType}" }
        logger.info { "Name: ${file.name}" }
        logger.info { "Byte: ${String(file.bytes)}" }
    }
}

可正常调用的curl命令 #

curl -v -X POST -F file=@/Users/myhomefolder/Documents/some-file.jpg https://host-name/api/upload

无法正常调用的MuleSoft脚本 #

import dw::module::Multipart 
output multipart/form-data boundary = "---WebKitFormBoundary7MA4YWxkTrZu0gW"
---
{
               parts : {
                    file : {
                        headers : {
                            "Content-Disposition" : {
                                "name": "file",
                                "filename": payload.name
                             },
                            "Content-Type" : "multipart/form-data"            
                        },
                        content : payload.byteArray
                    }
               }

}

请问Spring是否有配置可支持带双引号的boundary？或需补充哪些后端配置以适配不同HTTP客户端？

后端Spring Boot配置调整 #

1. 自定义MultipartResolver处理带引号的boundary #

Spring默认的StandardServletMultipartResolver依赖Tomcat的文件上传解析器，而Tomcat原生解析逻辑不会处理boundary值的双引号，导致无法识别分隔符。可以通过自定义MultipartResolver重写解析逻辑，自动移除boundary的引号：

import org.springframework.web.multipart.MultipartException;
import org.springframework.web.multipart.MultipartHttpServletRequest;
import org.springframework.web.multipart.commons.CommonsMultipartResolver;

import javax.servlet.http.HttpServletRequest;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class CustomMultipartResolver extends CommonsMultipartResolver {

    private static final Pattern BOUNDARY_PATTERN = Pattern.compile("boundary=\"?([^\"]+)\"?", Pattern.CASE_INSENSITIVE);

    @Override
    protected String determineEncoding(HttpServletRequest request) {
        String contentType = request.getContentType();
        if (contentType != null && contentType.contains("boundary")) {
            Matcher matcher = BOUNDARY_PATTERN.matcher(contentType);
            if (matcher.find()) {
                String cleanBoundary = matcher.group(1);
                // 重构Content-Type头，移除boundary的双引号
                String updatedContentType = contentType.replaceAll("boundary=\"?([^\"]+)\"?", "boundary=" + cleanBoundary);
                request.setAttribute("CONTENT_TYPE", updatedContentType);
            }
        }
        return super.determineEncoding(request);
    }

    @Override
    public MultipartHttpServletRequest resolveMultipart(HttpServletRequest request) throws MultipartException {
        // 先处理Content-Type头再执行解析
        determineEncoding(request);
        return super.resolveMultipart(request);
    }
}

然后在配置类中注册这个自定义解析器：

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.multipart.MultipartResolver;

@Configuration
public class MultipartConfig {

    @Bean(name = "multipartResolver")
    public MultipartResolver customMultipartResolver() {
        CustomMultipartResolver resolver = new CustomMultipartResolver();
        // 按需配置文件上传参数，比如最大文件大小
        resolver.setMaxUploadSize(10 * 1024 * 1024);
        resolver.setMaxUploadSizePerFile(5 * 1024 * 1024);
        return resolver;
    }
}

2. 升级Spring Boot及Tomcat版本 #

Tomcat 9.0.60及以上版本已经修复了带引号boundary的解析问题，对应的Spring Boot版本（如2.7.x及以上）集成了该版本的Tomcat。如果项目版本允许，直接升级Spring Boot依赖即可原生支持带引号的boundary，无需自定义代码。

前端MuleSoft端调整建议 #

如果后端暂时无法修改，也可以要求MuleSoft调整请求构造逻辑：

• 修改DataWeave脚本中的输出配置，移除boundary值的双引号：

  output multipart/form-data boundary = ---WebKitFormBoundary7MA4YWxkTrZu0gW
  

• 检查MuleSoft HTTP请求组件的配置，确保Content-Type头中的boundary没有被自动添加引号

内容的提问来源于stack exchange，提问作者xbmono