Customizing the exception thrown by jackson bind on GAE standard

Question

I've been searching to find a way to customise exception thrown by Jackson bind on GAE.

The problem is that when I sent a string parameter where API method expects Integer throws a Jackson's InvalidFormatException. I want to customize the message thrown by the exception but I couldn't find a way. Please help with this.

For e.g:

@Api(
name = "echo",
version = "v1",
namespace =
@ApiNamespace(
    ownerDomain = "echo.example.com",
    ownerName = "echo.example.com",
    packagePath = ""
),
issuers = {
    @ApiIssuer(
        name = "firebase",
        issuer = "https://securetoken.google.com/YOUR-PROJECT-ID",
        jwksUri =
            "https://www.googleapis.com/service_accounts/v1/metadata/x509/securetoken@system"
                + ".gserviceaccount.com"
    )
})

public class Echo {
   @ApiMethod(name = "echo")
   public Message echo(Message message, @Named("n") @Nullable Integer n) {
      return doEcho(message, n);
   }    
}

In the above code if the echo endpoint is hit with payload

then the response is

In this case is it possible to throw a custom exception or customize the message

score 0 · Answer 1 · answered Feb 16 '19 at 11:15

0

To do that you need to register DeserializationProblemHandler

ObjectMapper mapper = new ObjectMapper();
mapper.enable(SerializationFeature.INDENT_OUTPUT);
mapper.addHandler(new DeserializationProblemHandler() {
    @Override
    public Object handleWeirdStringValue(DeserializationContext ctxt, Class<?> targetType, String valueToConvert, String failureMsg) throws IOException {
        System.out.println("Handle parse problem for value = " + valueToConvert);
        throw new CanNotParseJsonException("Can not deserialise " + valueToConvert, null);
    }
});

Your exception should extend JsonMappingException in other case it will be wrapped. Example exception:

class CanNotParseJsonException extends JsonMappingException {

    public CanNotParseJsonException(String msg, Throwable problem) {
        super(null, msg, problem);
    }
}

See:

answered Feb 16 '19 at 11:15

Michał Ziober

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I got the point what you are suggesting but my application is not Spring Boot based – Chaturasan Feb 16 '19 at 20:16
You do not need to have `Spring Boot` to make it work. You just need to configure `ObjectMapper` instance and it should work. I linked to some examples where `Spring Boot` is used but it is not required. – Michał Ziober Feb 17 '19 at 00:57
Ziober,I tried using Guice to configure it still it is not working `@Provides ObjectMapper ObjectMapperProvider() { ObjectMapper mapper = new ObjectMapper(); mapper.enable(SerializationFeature.INDENT_OUTPUT); mapper.addHandler(new DeserializationProblemHandler() { @Override public Object handleWeirdStringValue(DeserializationContext ctxt, Class> targetType, String valueToConvert, String failureMsg) throws IOException { throw new JacksonBindingException("Can not deserialise " + valueToConvert, null); }}); return mapper;}` . I added this code in Guice module – Chaturasan Feb 17 '19 at 04:05
@Chaturasan, You need to be sure `Guice` uses this `ObjectMapper` which you have configured and for which created `ObjectMapperProvider` factory method. – Michał Ziober Feb 17 '19 at 15:10

Customizing the exception thrown by jackson bind on GAE standard

1 Answers1