resttemplate 上传文件

使用 RestTemplate 上传文件的步骤如下：

1. 创建一个 MultiValueMap 对象并添加文件内容

MultiValueMap<String, Object> body = new LinkedMultiValueMap<>();
body.add("file", new FileSystemResource(new File(filePath)));

2. 创建一个 HttpHeaders 对象并设置 Content-Type 为 multipart/form-data

HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.MULTIPART_FORM_DATA);

3. 创建一个 HttpEntity 对象并将 MultiValueMap 和 HttpHeaders 对象添加到其中

HttpEntity<MultiValueMap<String, Object>> requestEntity = new HttpEntity<>(body, headers);

4. 使用 RestTemplate 的 postForObject 方法上传文件

String url = "http://example.com/upload";
String response = restTemplate.postForObject(url, requestEntity, String.class);

完整的示例代码如下：

RestTemplate restTemplate = new RestTemplate();
String filePath = "/path/to/file";

// Create the request body with the file content
MultiValueMap<String, Object> body = new LinkedMultiValueMap<>();
body.add("file", new FileSystemResource(new File(filePath)));

// Set the Content-Type header to multipart/form-data
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.MULTIPART_FORM_DATA);

// Create the HttpEntity with the request body and headers
HttpEntity<MultiValueMap<String, Object>> requestEntity = new HttpEntity<>(body, headers);

// Upload the file using RestTemplate
String url = "http://example.com/upload";
String response = restTemplate.postForObject(url, requestEntity, String.class);