使用 Rest 模板发送文件时，MultipartFile 为空

Question

嗨，我有 2 个独立的应用程序。

第一个正在发送 post 请求：我正在尝试将文件发送到第二个应用程序

public static String httpPostMultipartFile(String url, File file) throws IOException{
    RestTemplate restTemplate = new RestTemplate();
    MultiValueMap<String, Object> parameters = new LinkedMultiValueMap<String, Object>();
    parameters.add("file", file); // load file into parameter
    HttpHeaders headers1 = new HttpHeaders();
    headers1.setContentType(MediaType.MULTIPART_FORM_DATA);
    String result = restTemplate.exchange(
            url,
            HttpMethod.POST,
            new HttpEntity<MultiValueMap<String, Object>>(parameters, headers1),
            String.class
        ).getBody();
    return result;

这是收到 post 请求的第二个应用程序

@RequestMapping(value = "/fileupload/save", method = RequestMethod.POST, produces = "text/plain")
@ResponseBody
public String save(@RequestParam(value = "file", required = false) MultipartFile file, @RequestParam(required = false) Boolean suggestTranspose, @RequestParam(value = "transformers", required = false) String transformersString, @RequestParam(required = false) Integer brandId) throws Exception {
.....
}

但在我的第二个应用程序中，MultipartFile 在其余调用中实际上是空的

我找到了这个 link 对我没有帮助 link 1

link 2

Answer 1

您的 httpPostMultipartFile 方法应该如下所示。您需要使用 new FileSystemResource(file.getPath()).

添加文件

public static String httpPostMultipartFile(String url, File file) throws IOException{
   RestTemplate restTemplate = new RestTemplate();
        MultiValueMap<String, Object> multipartMap = new LinkedMultiValueMap<String, Object>();     
        multipartMap.add("file", new FileSystemResource(file.getPath()));
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.MULTIPART_FORM_DATA);
        HttpEntity<Object> request = new HttpEntity<Object>(multipartMap, headers);         
        String result = restTemplate.exchange(
                url,
                HttpMethod.POST,
                request,
                String.class
            ).getBody();

        return result;
}

Answer 2

这是一个示例（由我测试），说明如何使用 RestTemplate 调用包含文件作为 @RequestParam 的 Web 服务：

import java.io.File;
import java.io.IOException;

import org.springframework.core.io.FileSystemResource;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.MediaType;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.web.client.RestTemplate;

public class Application {
    public static void main(String[] args) throws IOException {
        LinkedMultiValueMap<String, Object> map = new LinkedMultiValueMap<>();
        FileSystemResource value = new FileSystemResource(new File("src/myFile.txt"));
        map.add("file", value);
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.MULTIPART_FORM_DATA);
        HttpEntity<LinkedMultiValueMap<String, Object>> requestEntity = new HttpEntity<>(map, headers);
        RestTemplate restTemplate = new RestTemplate();
        restTemplate.exchange("http://localhost/api/ws/myws", HttpMethod.POST, requestEntity, String.class);
    }
}

使用 Rest 模板发送文件时，MultipartFile 为空

MultipartFile is null when sending a file with Rest template

java

spring

multipartform-data

spring-mvc

resttemplate