Question

我获得了以下日志输出。我想drop向导试图错误，但它使用的Jersey JAX-RS实现并不知道如何格式化错误？我怎么看？

ERROR [2014-10-01 08:08:55,875] com.sun.jersey.spi.container.ContainerResponse: A message body writer for Java class io.dropwizard.jersey.errors.ErrorMessage, and Java type class io.dropwizard.jersey.errors.ErrorMessage, and MIME media type text/plain was not found.
The registered message body writers compatible with the MIME media type are:
*/* ->
  com.sun.jersey.core.impl.provider.entity.FormProvider
  com.sun.jersey.core.impl.provider.entity.StringProvider
  com.sun.jersey.core.impl.provider.entity.ByteArrayProvider
  com.sun.jersey.core.impl.provider.entity.FileProvider
  com.sun.jersey.core.impl.provider.entity.InputStreamProvider
  com.sun.jersey.core.impl.provider.entity.DataSourceProvider
  com.sun.jersey.core.impl.provider.entity.XMLJAXBElementProvider$General
  com.sun.jersey.core.impl.provider.entity.ReaderProvider
  com.sun.jersey.core.impl.provider.entity.DocumentProvider
  com.sun.jersey.core.impl.provider.entity.StreamingOutputProvider
  com.sun.jersey.core.impl.provider.entity.SourceProvider$SourceWriter
  com.sun.jersey.server.impl.template.ViewableMessageBodyWriter
  com.sun.jersey.core.impl.provider.entity.XMLRootElementProvider$General
  com.sun.jersey.core.impl.provider.entity.XMLListElementProvider$General
  com.fasterxml.jackson.jaxrs.json.JacksonJsonProvider
text/plain ->
  com.sun.jersey.core.impl.provider.entity.StringProvider
  com.sun.jersey.core.impl.provider.entity.ReaderProvider

FWIW方法签名我打的是：

@POST
@UnitOfWork
@Path("/update")
@Consumes(MediaType.APPLICATION_JSON)
@Produces(MediaType.TEXT_PLAIN)
public String updateResults(ResultsUpdate results) {...}

Answer 1

您需要一个用于ErrorMessage的序列化器。如果你使用eclipse Strg + Shift + T并搜索＆＃34; JsonProcessingExceptionMapper＆＃34;。此异常映射器希望使用实体ErrorMessage构建响应，但您没有此映射器。

您有两种选择：

删除此异常映射器并添加自定义异常映射器没有实体
您创建了一个邮件正文撰稿人。

选项1：在run（）中添加此方法：

private void removeDefaultExceptionMappers(boolean deleteDefault,Environment environment)
{
    if(deleteDefault){
        ResourceConfig jrConfig = environment.jersey().getResourceConfig();
        Set<Object> dwSingletons = jrConfig.getSingletons();
        List<Object> singletonsToRemove = new ArrayList<Object>();

        for (Object singletons : dwSingletons) {
            if (singletons instanceof ExceptionMapper && !singletons.getClass().getName().contains("DropwizardResourceConfig")) {
                singletonsToRemove.add(singletons);
            }
        }

        for (Object singletons : singletonsToRemove) {
            LOG.info("Deleting this ExceptionMapper: " + singletons.getClass().getName());
            jrConfig.getSingletons().remove(singletons);
        }
    }
}

这将删除DW中默认添加的所有exeption映射器。现在您可以添加您真正想要的所有exeption映射器。就我而言：

    environment.jersey().register(new ConstraintViolationExceptionMapper());
    environment.jersey().register(new CustomJsonProcessingExceptionMapper());
    environment.jersey().register(new EarlyEofExceptionMapper());

现在编写自己的自定义CustomJsonProcessingExceptionMapper，不带实体：

@Provider
public class CustomJsonProcessingExceptionMapper implements ExceptionMapper<JsonProcessingException> {

    private static final Logger LOG = LoggerFactory.getLogger(CustomJsonProcessingExceptionMapper.class);

    @Override
    public Response toResponse(JsonProcessingException exception) {
        /*
         * If the error is in the JSON generation, it's a server error.
         */
        if (exception instanceof JsonGenerationException) {
            LOG.warn("Error generating JSON", exception);
            return Response.serverError().build();
        }

        final String message = exception.getOriginalMessage();

        /*
         * If we can't deserialize the JSON because someone forgot a no-arg constructor, it's a
         * server error and we should inform the developer.
         */
        if (message.startsWith("No suitable constructor found")) {
            LOG.error("Unable to deserialize the specific type", exception);
            return Response.serverError().build();
        }

        /*
         * Otherwise, it's those pesky users.
         */
        LOG.debug("Unable to process JSON (those pesky users...)", exception);
        return Response.status(Response.Status.BAD_REQUEST)
                       .build();
    }

}

选项2：您为ErrorMessage创建序列化程序/消息正文编写器。为此，试试这个：

@Provider
@Produces(MediaType.TEXT_PLAIN)
public class ErrorMessageBodyWriter implements MessageBodyWriter<ErrorMessage> {

    private static final Logger LOG = LoggerFactory.getLogger(ErrorMessageBodyWriter.class);

    @Override
    public boolean isWriteable(
        Class<?> type,
        Type genericType,
        Annotation[] annotations,
        MediaType mediaType)
    {
        return ValidationErrorMessage.class.isAssignableFrom(type);
    }

    @Override
    public long getSize(
        ErrorMessage t,
        Class<?> type,
        Type genericType,
        Annotation[] annotations,
        MediaType mediaType)
    {
        return -1;
    }

    @Override
    public void writeTo(
        ErrorMessage t,
        Class<?> type,
        Type genericType,
        Annotation[] annotations,
        MediaType mediaType,
        MultivaluedMap<String, Object> httpHeaders,
        OutputStream entityStream) throws IOException, WebApplicationException
    {       
        String message = t.getMessage();        
        entityStream.write(message.getBytes(Charsets.UTF_8));
        LOG.info(message);
    }

}

添加你的run（）：

// Serializer
environment.jersey().register(new ErrorMessageBodyWriter());

希望这会有所帮助： - ）

Answer 2

只需为您的资源指定这些标头，以便dropwizard了解用于响应的错误消息构建器：

@Consumes(MediaType.APPLICATION_JSON)
@Produces(MediaType.APPLICATION_JSON)

Answer 3

Dropwizard会在DEBUG级别记录底层错误，因此您可以在日志配置中启用它以查看原因：

io.dropwizard.jersey.jackson.JsonProcessingExceptionMapper: DEBUG

Answer 4

这很愚蠢，但是我点击了一个dropwizard从一个主类运行，所以你可以在ErrorMessage中放一个断点并在Eclipse中运行它。

顺便提一下，这种情况下的潜在错误是：

Can not deserialize instance of java.util.ArrayList out of START_OBJECT token

Answer 5

我最近几次打了这个，所以提交了一个（现在接受的）pull请求来记录警告而不是调试的基础错误。

https://github.com/dropwizard/dropwizard/commit/ebdfcb47a030730233cf0984aadae155ec138ff3

来自泽西岛的Dropwizard错误消息

5 个答案: