如何仅为一种方法或控制器类禁用 Jersey POJOMappingFeature

Question

我在 web.xml 中打开了 Jersey JSON POJOMappingFeature，如下所示将 POJO 转换为 JSON：

<init-param>
        <param-name>com.sun.jersey.api.json.POJOMappingFeature</param-name>
        <param-value>true</param-value>
</init-param>

我在其中一个控制器中有一个方法来处理文件上传。它获取多部分表单数据，从表单中提取文件输入字段，将其转换为 InputStream 并将文件保存到磁盘：

@POST
@Path("/upload")
@Consumes(MediaType.MULTIPART_FORM_DATA)
@Produces("application/json")
public FileMetaData uploadFiles(FormDataMultiPart formDataMultiPart) {
    return new FileUploadHandler(SERVER_FILE_UPLOAD_LOCATION).upload(formDataMultiPart);
}

public FileMetaData upload(FormDataMultiPart formDataMultiPart) {
    FormDataBodyPart formFile = formDataMultiPart.getField("files");
    ContentDisposition contentDisposition = formFile.getContentDisposition();
    return saveFile(formFile.getValueAs(InputStream.class), contentDisposition.getFileName(), formFile.getMediaType().toString());
}

这适用于所有文件格式，但当我尝试上传 JSON 文件时，formFile.getValueAs(InputStream.class) 会引发错误，抱怨无法将字符串转换为 InputStream。我认为这是因为 Jersey 自动将 JSON 文件转换为字符串对象。 那么我怎样才能防止 Jersey 只为这个方法或控制器这样做呢？我的要求是我需要将 json 文件保存为文件本身。

我已经尝试在这方面进行了很多搜索，但我最终得到的只是关于如何启用 POJOMapping 而不是选择性地禁用它的文档。任何帮助将不胜感激！

更新： 我的自定义 MessageBodyReader 如下所示：

public class JSONMessageBodyReader implements MessageBodyReader<Object> {

private static final Logger log = LoggerFactory.getLogger(JSONMessageBodyReader.class);

@Override
public boolean isReadable(Class<?> type, Type genericType,
                          Annotation[] annotations, MediaType mediaType) {
    // return true;
    return mediaType.isCompatible(MediaType.APPLICATION_JSON_TYPE)
            || mediaType.isCompatible(MediaType.APPLICATION_OCTET_STREAM_TYPE);
            || mediaType.isCompatible(MediaType.TEXT_HTML_TYPE);
}

@Override
public Object readFrom(Class<Object> type, Type genericType,
                       Annotation[] annotations, MediaType mediaType,
                       MultivaluedMap<String, String> httpHeaders, InputStream entityStream)
        throws IOException, WebApplicationException {
    if (log.isTraceEnabled()) {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        byte[] chunk = new byte[256];
        int read = -1;
        while ((read = entityStream.read(chunk)) != -1) {
            baos.write(chunk, 0, read);
        }
        chunk = baos.toByteArray();
        String entity = new String(chunk);
        log.trace("the entity: " + entity);
        return ObjectMapperFactory.getInstance().readValue(chunk, 0, chunk.length, type);
    }

    return ObjectMapperFactory.getInstance().readValue(entityStream, type);
}

}

Answer 1

我最终通过使用较低级别的 HttpServletRequest 而不是 Jersey 的 FormDataParams 处理上传的文件来解决我的要求，如下所示：

@POST
@Path("/upload")
@Consumes("multipart/form-data")
@Produces("application/json")
public FileMetaData uploadFiles(@Context ServletContext servletContext, @Context HttpServletRequest request) {
    return fileUploadHandler.upload(request, servletContext);
}


public FileMetaData upload(HttpServletRequest request, ServletContext servletContext) {
    FileMetaData fileMetaData = null;
    boolean isMultipart = ServletFileUpload.isMultipartContent(request);
    if (isMultipart) {
        LOGGER.info("About to save file on the server : {}", this.SERVER_UPLOAD_DIRECTORY);

        DiskFileItemFactory diskFileItemFactory = new DiskFileItemFactory();
        File repository = (File) servletContext.getAttribute("javax.servlet.context.tempdir");
        diskFileItemFactory.setRepository(repository);
        ServletFileUpload servletFileUpload = new ServletFileUpload(diskFileItemFactory);
        try {
            List<FileItem> files = servletFileUpload.parseRequest(request);
            Iterator<FileItem> iter = files.iterator();
            while(iter.hasNext()) {
                FileItem fileItem = iter.next();
                String fileName = fileItem.getName();
                if (fileName != null) {
                    fileName = FilenameUtils.getName(fileName);
                }
                String fileUploadDirectory = this.SERVER_UPLOAD_DIRECTORY;
                File uploadDirectory = new File(fileUploadDirectory);
                if(!uploadDirectory.exists()) {
                    uploadDirectory.mkdir();
                    LOGGER.info("creating directory {}", uploadDirectory.getAbsolutePath());
                }
                String fileUploadPath = fileUploadDirectory + File.separator + fileName;
                File fileToStore = new File(fileUploadPath);
                LOGGER.info("saved file {} on server", fileName);

                fileItem.write(fileToStore);
                long fileSize = fileToStore.length();
                String size = (fileSize > 1024) ? (fileSize/1024) + "Kb" : fileSize + "b";
                fileMetaData = new FileMetaData(fileName, size, true);
            }
        } catch (Exception e) {
            LOGGER.warn("error occurred while saving file to server : {}", e.getStackTrace());
            e.printStackTrace();
        }
    }

    else {
        LOGGER.info("No files to upload in request");
    }

    return fileMetaData;
}

这个解决方案对我来说非常有效，尽管我觉得它是对我最初问题的一种破解。如果这个解决方案也能帮助其他人，我会很高兴。 但是有人必须提供一种纯粹的 Jersey 方法来解决这个问题，而不涉及 HttpServletRequest 我很乐意尝试一下。 谢谢！