春季启动 setContentType 不起作用

Question

我正在尝试在 spring-boot (1.2.2) 上返回图像
我应该如何设置内容类型？ 以下都不对我有用（意味着响应标头根本不包含“内容类型”标头）：

    @RequestMapping(value = "/files2/{file_name:.+}", method = RequestMethod.GET)
public ResponseEntity<InputStreamResource> getFile2(final HttpServletResponse response) throws IOException {
    InputStream is = //someInputStream...
    org.apache.commons.io.IOUtils.copy(is, response.getOutputStream());
    response.setContentType("image/jpeg");
    InputStreamResource inputStreamR = new InputStreamResource(is);
    return new ResponseEntity<>(inputStreamR, HttpStatus.OK);
}

@RequestMapping(value = "/files3/{file_name:.+}", method = RequestMethod.GET)
public HttpEntity<byte[]> getFile3() throws IOException {
    InputStream is = //someInputStream...
    HttpHeaders headers = new HttpHeaders();
    headers.setContentType(MediaType.IMAGE_JPEG);
    return new HttpEntity<>(IOUtils.toByteArray(is), headers);
}

Answer 1

首先，除了@RequestMapping 之外，您还需要应用@ResponseBody 注释，除非您在类级别使用@RestController 而不仅仅是@Controller。另外，尝试@RequestMapping 的produces 元素，例如

@RequestMapping(value = "/files2/{file_name:.+}", method = RequestMethod.GET, produces = {MediaType.IMAGE_JPEG_VALUE})

这应该“缩小主映射”并确保设置了正确的内容类型。查看文档：http://docs.spring.io/spring/docs/current/spring-framework-reference/htmlsingle/#mvc-ann-requestmapping-produces

Answer 2

知道了...必须将ByteArrayHttpMessageConverter 添加到WebConfiguration 类：

@Configuration
@EnableWebMvc
@ComponentScan
public class WebConfiguration extends WebMvcConfigurerAdapter {

@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> httpMessageConverters) {
    httpMessageConverters.add(new ByteArrayHttpMessageConverter());
}
}

然后我的第二次尝试 (getFile3()) 工作正常