从Spring开机Rest服务下载文件

Question

我正在尝试从Spring boot rest服务下载一个文件。

@RequestMapping(path="/downloadFile",method=RequestMethod.GET)
    @Consumes(MediaType.APPLICATION_JSON_VALUE)
    public  ResponseEntity<InputStreamReader> downloadDocument(
                String acquistionId,
                String fileType,
                Integer expressVfId) throws IOException {
        File file2Upload = new File("C:\\Users\\admin\\Desktop\\bkp\\1.rtf");
        HttpHeaders headers = new HttpHeaders();
        headers.add("Cache-Control", "no-cache, no-store, must-revalidate");
        headers.add("Pragma", "no-cache");
        headers.add("Expires", "0");
        InputStreamReader i = new InputStreamReader(new FileInputStream(file2Upload));
        System.out.println("The length of the file is : "+file2Upload.length());

        return ResponseEntity.ok().headers(headers).contentLength(file2Upload.length())
                .contentType(MediaType.parseMediaType("application/octet-stream"))
                .body(i);
        }

当我试图从浏览器下载文件时，它会启动下载，但总是失败。该服务是否存在导致下载失败的问题？

Answer 1

我建议使用StreamingResponseBody，因为有了它，应用程序可以直接写入响应（OutputStream），而无需占用Servlet容器线程。如果你正在下载一个非常大的文件，这是一个很好的方法。

@GetMapping("download")
public StreamingResponseBody downloadFile(HttpServletResponse response, @PathVariable Long fileId) {

    FileInfo fileInfo = fileService.findFileInfo(fileId);
    response.setContentType(fileInfo.getContentType());
    response.setHeader(
        HttpHeaders.CONTENT_DISPOSITION, "attachment;filename=\"" + fileInfo.getFilename() + "\"");

    return outputStream -> {
        int bytesRead;
        byte[] buffer = new byte[BUFFER_SIZE];
        InputStream inputStream = fileInfo.getInputStream();
        while ((bytesRead = inputStream.read(buffer)) != -1) {
            outputStream.write(buffer, 0, bytesRead);
        }
    };
}

注：当使用StreamingResponseBody时，强烈建议配置Spring MVC中用于执行异步请求的TaskExecutor。TaskExecutor是一个抽象可运行程序执行的接口。

更多信息：https://medium.com/swlh/streaming-data-with-spring-boot-restful-web-service-87522511c071

Answer 2

下面的示例代码对我有用，可能会对某人有所帮助。

import org.springframework.core.io.ByteArrayResource;
import org.springframework.core.io.Resource;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

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

@RestController
@RequestMapping("/app")
public class ImageResource {

    private static final String EXTENSION = ".jpg";
    private static final String SERVER_LOCATION = "/server/images";

    @RequestMapping(path = "/download", method = RequestMethod.GET)
    public ResponseEntity<Resource> download(@RequestParam("image") String image) throws IOException {
        File file = new File(SERVER_LOCATION + File.separator + image + EXTENSION);

        HttpHeaders header = new HttpHeaders();
        header.add(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=img.jpg");
        header.add("Cache-Control", "no-cache, no-store, must-revalidate");
        header.add("Pragma", "no-cache");
        header.add("Expires", "0");

        Path path = Paths.get(file.getAbsolutePath());
        ByteArrayResource resource = new ByteArrayResource(Files.readAllBytes(path));

        return ResponseEntity.ok()
                .headers(header)
                .contentLength(file.length())
                .contentType(MediaType.parseMediaType("application/octet-stream"))
                .body(resource);
    }

}

Answer 3

选项1使用输入流资源

给定InputStream的资源实现。

只有当没有其他特定的资源实现时才应该使用

@RequestMapping(path = "/download", method = RequestMethod.GET)
public ResponseEntity<Resource> download(String param) throws IOException {

    // ...

    InputStreamResource resource = new InputStreamResource(new FileInputStream(file));

    return ResponseEntity.ok()
            .headers(headers)
            .contentLength(file.length())
            .contentType(MediaType.APPLICATION_OCTET_STREAM)
            .body(resource);
}

选项2如InputStreamResource的文档所示，使用ByteArrayResource：

@RequestMapping(path = "/download", method = RequestMethod.GET)
public ResponseEntity<Resource> download(String param) throws IOException {

    // ...

    Path path = Paths.get(file.getAbsolutePath());
    ByteArrayResource resource = new ByteArrayResource(Files.readAllBytes(path));

    return ResponseEntity.ok()
            .headers(headers)
            .contentLength(file.length())
            .contentType(MediaType.APPLICATION_OCTET_STREAM)
            .body(resource);
}