我得到以下日志输出。我想drop向导试图错误，但它使用的Jersey JAX-RS实现不知道如何格式化错误？我怎么看呢？
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我正在击中的方法签名是：
@POST
@UnitOfWork
@Path("/update")
@Consumes(MediaType.APPLICATION_JSON)
@Produces(MediaType.TEXT_PLAIN)
public String updateResults(ResultsUpdate results) {...}
你需要一个用于ErrorMessage的序列化器。如果你使用eclipse Strg + Shift + T并搜索“JsonProcessingExceptionMapper”。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：
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中默认添加的所有异常映射器。现在您可以添加您真正想要的所有异常映射器。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而不使用实体：
@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：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());
希望这可以帮助 ：-）
只需要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)
Dropwizard将在DEBUG级别记录底层错误，因此您可以在日志配置中打开它以查看原因：
io.dropwizard.jersey.jackson.JsonProcessingExceptionMapper: DEBUG
这是愚蠢的，但我点击了dropwizard从主类运行，因此你可以在ErrorMessage中放置一个断点并在Eclipse中运行它（例如）。
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
我最近遇到过这种情况，因此提交了一个（现已接受的）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