使用 Java 将 byte[] 转换为 File 对象并上传到外部服务器的方法(最新推荐)

<dependencies>
    <!-- Spring Web 依赖，用于处理 HTTP 请求 -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <!-- Spring Boot RestTemplate 依赖 -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
</dependencies>

import org.springframework.web.client.RestTemplate;
import org.springframework.http.ResponseEntity;
public byte[] getImageBytes(String imageUrl) {
    RestTemplate restTemplate = new RestTemplate();
    return restTemplate.getForObject(imageUrl, byte[].class);
}

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
public File createTempFileFromBytes(byte[] imageBytes, String fileName) throws IOException {
    // 创建临时文件，确保文件名具有唯一性
    File tempFile = File.createTempFile(fileName, ".jpg");
    // 将字节数据写入文件
    try (FileOutputStream fos = new FileOutputStream(tempFile)) {
        fos.write(imageBytes);
    }
    return tempFile;
}

import org.springframework.http.MediaType;
import org.springframework.http.HttpEntity;
import org.springframework.web.client.RestTemplate;
import org.springframework.http.ResponseEntity;
import org.springframework.web.client.RestClientException;
import java.util.HashMap;
import java.util.Map;
public String uploadFile(File file, String uploadUrl) {
    RestTemplate restTemplate = new RestTemplate();
    // 设置文件上传请求的头信息和参数
    Map<String, Object> fileMap = new HashMap<>();
    fileMap.put("file", file);
    HttpEntity<Map<String, Object>> requestEntity = new HttpEntity<>(fileMap);
    try {
        // 发送请求，获取响应
        ResponseEntity<String> responseEntity = restTemplate.postForEntity(uploadUrl, requestEntity, String.class);
        return responseEntity.getBody();  // 返回上传结果
    } catch (RestClientException e) {
        e.printStackTrace();
        return "File upload failed";
    }
}

import org.springframework.web.bind.annotation.*;
import org.springframework.http.ResponseEntity;
import org.springframework.http.io.InputStreamResource;
import org.springframework.beans.factory.annotation.Autowired;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
@RestController
public class FileController {
    @Autowired
    private RestTemplate restTemplate;
    private String imageUrl = "http://example.com/api/file/getFileInputStreamById/";
    @PostMapping("/syncUser")
    public ResponseEntity<InputStreamResource> syncUser(@RequestParam("photoId") String photoId) {
        // 从 URL 获取图片字节数据
        byte[] imageBytes = restTemplate.getForObject(imageUrl + photoId, byte[].class);
        // 将字节数组转换为文件
        File photoFile;
        try {
            photoFile = createTempFileFromBytes(imageBytes, "photo_" + photoId);
        } catch (IOException e) {
            e.printStackTrace();
            return ResponseEntity.status(500).build();
        }
        // 上传文件到目标服务器
        String fileUrl = uploadFile(photoFile, "http://example.com/upload");
        // 返回文件 URL（假设文件上传成功）
        return ResponseEntity.ok();
    }
    private File createTempFileFromBytes(byte[] imageBytes, String fileName) throws IOException {
        File tempFile = File.createTempFile(fileName, ".jpg");
        try (FileOutputStream fos = new FileOutputStream(tempFile)) {
            fos.write(imageBytes);
        }
        return tempFile;
    }
    private String uploadFile(File file, String uploadUrl) {
        RestTemplate restTemplate = new RestTemplate();
        Map<String, Object> fileMap = new HashMap<>();
        fileMap.put("file", file);
        HttpEntity<Map<String, Object>> requestEntity = new HttpEntity<>(fileMap);
        ResponseEntity<String> responseEntity = restTemplate.postForEntity(uploadUrl, requestEntity, String.class);
        return responseEntity.getBody();
    }
}