Java 如何配置DropWizard来解释请求失败？

如果发送JSON时没有请求正文：

POST /stuff
Content-Type: application/json
Content-Length: 0
                       <---- Body missing!

现在，日志中只有一行：

127.0.0.1 - - [04/May/2015:13:21:25 +0000] "POST /stuff HTTP/1.1" 422 370 232 232

HTTP 422并不是一个不合理的暗示，但我必须相信这里有一个更详细的信息。类似地，如果缺少标头或路径组件与提供的格式不匹配，我希望看到类似“header\uuuuuuuuuuuu无法解析”这样的日志行

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这样的日志记录是否内置于DropWizard中？如何启用它？

在这种情况下，您需要覆盖异常映射程序。在422情况下，您需要为ConstraintViolationException实现一个异常映射器

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请参阅此答案：

默认情况下，Dropwizard/Jersey将异常映射到响应（默认异常映射器），在某些情况下，日志记录是有限的，因此不是很有用；因为简单，或者仅仅是为了迫使开发人员自己做更好的日志记录。请参阅更完整的说明：

Jersey，或者我应该说JAX-RS，公开了一种机制，允许您将抛出的异常或可丢弃的映射到REST响应，而不是未经处理并以stacktrace或错误文本的形式呈现给用户（这种机制需要您实现通用ExceptionMapper接口，然后注册它）这对于喜欢在使用API时将错误返回给客户机的RESTAPI来说是非常好的，比如返回可以在客户机上解析和处理的异常的JSON表示。“（）

通过编程，可以通过以下步骤创建自己的自定义异常映射器。代码正在考虑Dropwizard 0.9.x，以及您问题中的具体情况；然而，处理其他情况/例外情况的过程是类似的。此外，为了简单起见，省略了一些行）：

禁用默认异常映射程序：

public class CustomConstraintViolationExceptionMapper extends ConstraintViolationExceptionMapper
{
    @Override
    public Response toResponse( ConstraintViolationException exception )
    {
        Response superResponse = super.toResponse( exception );
        ValidationErrorMessage validationErrorMessage = (ValidationErrorMessage) superResponse.getEntity();
        log.error( String.format( "%s\t%s",
                              exception.getMessage(),
                              String.join( ";", validationErrorMessage.getErrors() ) ) );

        return superResponse;
    }
}

public class CustomJsonProcessingExceptionMapper extends JsonProcessingExceptionMapper
{
    @Override
    public Response toResponse( JsonProcessingException exception )
    {
         log.error( String.format( "%s", exception.getOriginalMessage() ) );
         return super.toResponse( exception );
    }
}

environment.jersey().register( new LoggingExceptionMapper<Throwable>(){} );
environment.jersey().register( new EarlyEofExceptionMapper() );

ERROR [2016-07-05 13:06:36,690] x.y.CustomConstraintViolationExceptionMapper: The request entity had the following errors:  field may not be empty
ERROR [2016-07-05 13:19:41,326] x.y.CustomJsonProcessingExceptionMapper: Unrecognized field "UnknownField" (class x.y.z.Xyz), not marked as ignorable

• 通过应用程序子类：

  AbstractServerFactory sf = (AbstractServerFactory) config.getServerFactory();
  sf.setRegisterDefaultExceptionMappers( false );
  

• 通过应用程序配置：

  server:
      registerDefaultExceptionMappers: false
  

通过添加日志记录（JSON和验证异常）创建自定义异常映射程序，以扩展原始异常映射程序：

public class CustomConstraintViolationExceptionMapper extends ConstraintViolationExceptionMapper
{
    @Override
    public Response toResponse( ConstraintViolationException exception )
    {
        Response superResponse = super.toResponse( exception );
        ValidationErrorMessage validationErrorMessage = (ValidationErrorMessage) superResponse.getEntity();
        log.error( String.format( "%s\t%s",
                              exception.getMessage(),
                              String.join( ";", validationErrorMessage.getErrors() ) ) );

        return superResponse;
    }
}

public class CustomJsonProcessingExceptionMapper extends JsonProcessingExceptionMapper
{
    @Override
    public Response toResponse( JsonProcessingException exception )
    {
         log.error( String.format( "%s", exception.getOriginalMessage() ) );
         return super.toResponse( exception );
    }
}

environment.jersey().register( new LoggingExceptionMapper<Throwable>(){} );
environment.jersey().register( new EarlyEofExceptionMapper() );

ERROR [2016-07-05 13:06:36,690] x.y.CustomConstraintViolationExceptionMapper: The request entity had the following errors:  field may not be empty
ERROR [2016-07-05 13:19:41,326] x.y.CustomJsonProcessingExceptionMapper: Unrecognized field "UnknownField" (class x.y.z.Xyz), not marked as ignorable

注册您创建的自定义异常映射程序：

environment.jersey().register( new CustomConstraintViolationExceptionMapper() );
environment.jersey().register( new CustomJsonProcessingExceptionMapper() );

不要忘记添加其他默认异常映射程序（如果需要-）：

public class CustomConstraintViolationExceptionMapper extends ConstraintViolationExceptionMapper
{
    @Override
    public Response toResponse( ConstraintViolationException exception )
    {
        Response superResponse = super.toResponse( exception );
        ValidationErrorMessage validationErrorMessage = (ValidationErrorMessage) superResponse.getEntity();
        log.error( String.format( "%s\t%s",
                              exception.getMessage(),
                              String.join( ";", validationErrorMessage.getErrors() ) ) );

        return superResponse;
    }
}

public class CustomJsonProcessingExceptionMapper extends JsonProcessingExceptionMapper
{
    @Override
    public Response toResponse( JsonProcessingException exception )
    {
         log.error( String.format( "%s", exception.getOriginalMessage() ) );
         return super.toResponse( exception );
    }
}

environment.jersey().register( new LoggingExceptionMapper<Throwable>(){} );
environment.jersey().register( new EarlyEofExceptionMapper() );

ERROR [2016-07-05 13:06:36,690] x.y.CustomConstraintViolationExceptionMapper: The request entity had the following errors:  field may not be empty
ERROR [2016-07-05 13:19:41,326] x.y.CustomJsonProcessingExceptionMapper: Unrecognized field "UnknownField" (class x.y.z.Xyz), not marked as ignorable

有关该主题的更多信息，您还可以参考以下参考资料：