使用RestTemplate请求将Multipart File作为POST参数发送

import org.springframework.core.io.ByteArrayResource;
import org.springframework.http.*;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import org.springframework.web.client.RestTemplate;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

public class FileUploadExample {
    public static void main(String[] args) throws IOException {
        // 1. 创建MultiValueMap对象
        MultiValueMap<String, Object> map = new LinkedMultiValueMap<>();

        // 2. 创建Resource对象
        Path filePath = Paths.get("path/to/file");
        byte[] fileBytes = Files.readAllBytes(filePath);
        ByteArrayResource resource = new ByteArrayResource(fileBytes) {
            @Override
            public String getFilename() {
                return filePath.getFileName().toString();
            }
        };

        // 3. 将Resource对象添加到MultiValueMap中
        map.add("file", resource);

        // 4. 创建HttpHeaders对象
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.MULTIPART_FORM_DATA);

        // 5. 创建HttpEntity对象
        HttpEntity<MultiValueMap<String, Object>> requestEntity = new HttpEntity<>(map, headers);

        // 6. 发送POST请求
        RestTemplate restTemplate = new RestTemplate();
        String url = "http://example.com/upload";
        ResponseEntity<String> response = restTemplate.postForEntity(url, requestEntity, String.class);

        // 处理响应结果
        HttpStatus statusCode = response.getStatusCode();
        if (statusCode == HttpStatus.OK) {
            String responseBody = response.getBody();
            System.out.println("上传成功：" + responseBody);
        } else {
            System.out.println("上传失败：" + statusCode);
        }
    }
}