JAX-RS Jersey how to customize error handling

Question

I m learning JAX-RS  aka  JSR-311  using Jersey  I ve successfuly created a Root Resource and am playing around with parameters    Path   hello   public class HelloWorldResource         GET      Produces  text html       public String get           QueryParam  name   String name           QueryParam  birthDate   Date birthDate                 Return a greeting with the name and age           This works great  and handles any format in the current locale which is understood by the Date String  constructor  like YYYY mm dd and mm dd YYYY   But if I supply a value which is invalid or not understood  I get a 404 response   For example   GET  hello name Mark amp birthDate X  404 Not Found   How can I customize this behavior  Maybe a different response code  probably  400 Bad Request    What about logging an error  Maybe add a description of the problem   bad date format   in a custom header to aid troubleshooting  Or return a whole Error response with details  along with a 5xx status code

User · Answer

One obvious solution  take in a String  convert to Date yourself  That way you can define format you want  catch exceptions and either re-throw or customize error being sent  For parsing  SimpleDateFormat should work fine   I am sure there are ways to hook handlers for data types too  but perhaps little bit of simple code is all you need in this case

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Approach 1  By extending WebApplicationException class  Create new exception by extending WebApplicationException  public class RestException extends WebApplicationException             private static final long serialVersionUID   1L            public RestException String message  Status status             super Response status status  entity message  type MediaType TEXT PLAIN  build                    Now throw  RestException  whenever required   public static Employee getEmployee int id              Employee emp   employees get id             if  emp    null                     throw new RestException  Employee with id     id     not exist   Status NOT FOUND                       return emp      You can see complete application at this link   Approach 2  Implement ExceptionMapper  Following mapper handles exception of type  DataNotFoundException    Provider public class DataNotFoundExceptionMapper implements         ExceptionMapper lt DataNotFoundException gt          Override     public Response toResponse DataNotFoundException ex            ErrorMessage model   new ErrorMessage ex getErrorCode                    ex getMessage             return Response status Status NOT FOUND  entity model  build               You can see complete application at this link

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You could also write a reusable class for QueryParam-annotated variables  public class DateParam     private SimpleDateFormat format   new SimpleDateFormat  yyyy-MM-dd       private Calendar date     public DateParam String in  throws WebApplicationException       try         date   Calendar getInstance          date setTime format parse in              catch  ParseException exception          throw new WebApplicationException 400               public Calendar getDate         return date        public String format         return format format value getTime             then use it like this   private  QueryParam  from   DateParam startDateParam  private  QueryParam  to   DateParam endDateParam         startDateParam getDate      Although the error handling is trivial in this case  throwing a 400 response   using this class allows you to factor-out parameter handling in general which might include logging etc

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Just as an extension to  Steven Lavine answer in case you want to open the browser login window  I found it hard to properly return the Response  MDN HTTP Authentication  from the Filter in case that the user wasn t authenticated yet  This helped me to build the Response to force browser login  note the additional modification of the headers  This will set the status code to 401 and set the header that causes the browser to open the username password dialog      The extended Exception class public class NotLoggedInException extends WebApplicationException     public NotLoggedInException String message        super Response status Response Status UNAUTHORIZED         entity message         type MediaType TEXT PLAIN         header  WWW-Authenticate    Basic realm SecuredApp   build                Usage in the Filter if headers get  Authorization      null    throw new NotLoggedInException  Not logged in

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I was facing the same issue   I wanted to catch all the errors at a central place and transform them   Following is the code for how I handled it   Create the following class which implements ExceptionMapper and add  Provider annotation on this class  This will handle all the exceptions   Override toResponse method and return the Response object populated with customised data     ExceptionMapperProvider java        exception thrown by restful endpoints will be caught and transformed here    so that client gets a proper error message      Provider public class ExceptionMapperProvider implements ExceptionMapper lt Throwable gt        private final ErrorTransformer errorTransformer   new ErrorTransformer         public ExceptionMapperProvider                  Override     public Response toResponse Throwable throwable              transforming the error using the custom logic of ErrorTransformer          final ServiceError errorResponse   errorTransformer getErrorResponse throwable           final ResponseBuilder responseBuilder   Response status errorResponse getStatus              if  errorResponse getBody   isPresent                  responseBuilder type MediaType APPLICATION JSON TYPE               responseBuilder entity errorResponse getBody   get                        for  Map Entry lt String  String gt  header   errorResponse getHeaders   entrySet                  responseBuilder header header getKey    header getValue                        return responseBuilder build                ErrorTransformer java        Error transformation logic     public class ErrorTransformer       public ServiceError getErrorResponse Throwable throwable            ServiceError serviceError   new ServiceError              add you logic here         serviceError setStatus getStatus throwable            serviceError setBody getBody throwable            serviceError setHeaders getHeaders throwable               private String getStatus Throwable throwable              your logic           private Optional lt String gt  getBody Throwable throwable              your logic           private Map lt String  String gt  getHeaders Throwable throwable              your logic            ServiceError java        error data holder     public class ServiceError       private int status      private Map lt String  String gt  headers      private Optional lt String gt  body        setters and getters

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QueryParam documentation says        The type T of the annotated parameter  field or property must   either        1  Be a primitive type   2  Have a constructor that accepts a single   String argument   3  Have a static method named valueOf or fromString   that accepts a single String argument  see  for example    Integer valueOf String     4  Have a registered implementation of   javax ws rs ext ParamConverterProvider JAX-RS extension SPI that   returns a javax ws rs ext ParamConverter instance capable of a  from   string  conversion for the type    5  Be List  Set or   SortedSet  where T satisfies 2  3 or 4 above  The resulting   collection is read-only       If you want to control what response goes to user when query parameter in String form can t be converted to your type T  you can throw WebApplicationException  Dropwizard comes with following  Param classes you can use for your needs   BooleanParam  DateTimeParam  IntParam  LongParam  LocalDateParam  NonEmptyStringParam  UUIDParam  See https   github com dropwizard dropwizard tree master dropwizard-jersey src main java io dropwizard jersey params  If you need Joda DateTime  just use Dropwizard DateTimeParam    If the above list does not suit your needs  define your own by extending AbstractParam  Override parse method  If you need control over error response body  override error method   Good article from Coda Hale on this is at http   codahale com what-makes-jersey-interesting-parameter-classes   import io dropwizard jersey params AbstractParam   import java util Date   import javax ws rs core Response  import javax ws rs core Response Status   public class DateParam extends AbstractParam lt Date gt         public DateParam String input            super input               Override     protected Date parse String input  throws Exception           return new Date input               Override     protected Response error String input  Exception e               customize response body if you like here by specifying entity         return Response status Status BAD REQUEST  build              Date String arg  constructor is deprecated  I would use Java 8 date classes if you are on Java 8  Otherwise joda date time is recommended

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Jersey throws an com sun jersey api ParamException when it fails to unmarshall the parameters so one solution is to create an ExceptionMapper that handles these types of exceptions    Provider public class ParamExceptionMapper implements ExceptionMapper lt ParamException gt         Override     public Response toResponse ParamException exception            return Response status Status BAD REQUEST  entity exception getParameterName       incorrect type   build

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There are several approaches to customize the error handling behavior with JAX-RS   Here are three of the easier ways   The first approach is to create an Exception class that extends WebApplicationException   Example   public class NotAuthorizedException extends WebApplicationException        public NotAuthorizedException String message             super Response status Response Status UNAUTHORIZED                entity message  type MediaType TEXT PLAIN  build                And to throw this newly create Exception you simply    Path  accounts  accountId         public Item getItem  PathParam  accountId   String accountId              An unauthorized user tries to enter        throw new NotAuthorizedException  You Don t Have Permission        Notice  you don t need to declare the exception in a throws clause because WebApplicationException is a runtime Exception   This will return a 401 response to the client   The second and easier approach is to simply construct an instance of the  WebApplicationException directly in your code   This approach works as long as you don t have to implement your own application Exceptions     Example    Path  accounts  accountId     public Item getItem  PathParam  accountId   String accountId          An unauthorized user tries to enter    throw new WebApplicationException Response Status UNAUTHORIZED       This code too returns a 401 to the client   Of course  this is just a simple example   You can make the Exception much more complex if necessary  and you can generate what ever http response code you need to     One other approach is to wrap an existing Exception  perhaps an ObjectNotFoundException with an small wrapper class that implements the ExceptionMapper interface annotated with a  Provider annotation   This tells the JAX-RS runtime  that if the wrapped Exception is raised  return the response code defined in the ExceptionMapper

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Provider public class BadURIExceptionMapper implements ExceptionMapper lt NotFoundException gt     public Response toResponse NotFoundException exception        return Response status Response Status NOT FOUND       entity new ErrorResponse exception getClass   toString                    exception getMessage           build          Create above class  This will handle 404  NotFoundException  and here in toResponse method you can give your custom response  Similarly there are ParamException etc  which you would need to map to provide customized responses

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This is the correct behavior actually  Jersey will try to find a handler for your input and will try to construct an object from the provided input  In this case it will try to create a new Date object with the value X provided to the constructor  Since this is an invalid date  by convention Jersey will return 404    What you can do is rewrite and put birth date as a String  then try to parse and if you don t get what you want  you re free to throw any exception you want by any of the exception mapping mechanisms  there are several

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I too like StaxMan would probably implement that QueryParam as a String  then handle the conversion  rethrowing as necessary   If the locale specific behavior is the desired and expected behavior  you would use the following to return the 400 BAD REQUEST error   throw new WebApplicationException Response Status BAD REQUEST    See the JavaDoc for javax ws rs core Response Status for more options

[java] JAX-RS / Jersey how to customize error handling?

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