restTemplate 文件下载

你可以使用 Spring Framework 中的 RestTemplate 来实现文件下载功能。下面是一个简单的示例：

import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.util.FileCopyUtils;
import org.springframework.web.client.RequestCallback;
import org.springframework.web.client.ResponseExtractor;
import org.springframework.web.client.RestTemplate;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;

public class FileDownloader {

    public static void downloadFile(String url, String savePath) throws IOException {
        RestTemplate restTemplate = new RestTemplate();

        RequestCallback requestCallback = request -> request.getHeaders()
                .setAccept(MediaType.APPLICATION_OCTET_STREAM);

        ResponseExtractor<ResponseEntity<byte[]>> responseExtractor = restTemplate.responseEntityExtractor(byte[].class);

        ResponseEntity<byte[]> responseEntity = restTemplate.execute(url, HttpMethod.GET, requestCallback, responseExtractor);
        if (responseEntity.getStatusCode().is2xxSuccessful()) {
            HttpHeaders headers = responseEntity.getHeaders();
            String fileName = getFileNameFromHeaders(headers);
            if (fileName != null) {
                savePath = savePath + File.separator + fileName;
            }

            byte[] fileData = responseEntity.getBody();
            if (fileData != null) {
                try (FileOutputStream fos = new FileOutputStream(savePath)) {
                    fos.write(fileData);
                    fos.flush();
                }
            }
        }
    }

    private static String getFileNameFromHeaders(HttpHeaders headers) {
        String[] contentDispositionHeader = headers.getFirst(HttpHeaders.CONTENT_DISPOSITION).split(";");
        for (String name : contentDispositionHeader) {
            if ((name.trim().startsWith("filename"))) {
                String[] tmp = name.split("=");
                return tmp[1].trim().replaceAll("\"", "");
            }
        }
        return null;
    }
}

你可以使用 `downloadFile` 方法来下载文件。传入文件的 URL 和保存路径即可。例如：

String url = "http://example.com/files/myfile.pdf";
String savePath = "/path/to/save/file";
FileDownloader.downloadFile(url, savePath);

这将会将指定 URL 的文件下载到指定的保存路径中。确保在使用前添加相应的依赖，如 Spring Web 客户端依赖：

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

希望对你有所帮助！如果有任何疑问，请随时提问。