Minimal sample to simulate https://stackoverflow.com/questions/48931256/how-to-register-converter-in-spring-data-rest-application
- Run Spring boot application
- Navigate to http://localhost:8080/browser/index.html#http://localhost:8080/profile/specifications in browser
- Add custom request headers in HAL browser
- Accept: application/schema+json
- Accept-Language: de
You should see JSON schema response with translated enum values:
{
"title": "Specification",
"properties": {
"status": {
"title": "Status",
"readOnly": false,
"type": "string",
"enum": [
"de_Draft",
"de_Active",
"de_Closed",
"de_Expired"
]
}
},
"definitions": {},
"type": "object",
"$schema": "http://json-schema.org/draft-04/schema#"
}
Imagine that these enum values are used to populated dropdown in frontend UI client in a grid. e.g. statuses in dropdown
When user selects any value, client makes REST call by following e.g. http://localhost:8080/specifications?status=de_Draft what behind the scenes uses org.springframework.data.querydsl.binding.QuerydslPredicateBuilder and this component uses org.springframework.core.convert.support.GenericConversionService.convert
Without any customization, this REST call fails because:
Caused by: java.lang.IllegalArgumentException: No enum constant net.homecredit.mer.web.evaluation.spec.Specification.Status.de_Draft
I essentially need to translate translated value de_Draft back to DRAFT enum value.
This can be accomplished with EnumTranslator, so I can add TranslationStringToSpecificationStatusEnumConverter:
@Component
public class TranslationStringToSpecificationStatusEnumConverter implements Converter<String, Specification.Status> {
private final EnumTranslator enumTranslator;
@Autowired
public TranslationStringToSpecificationStatusEnumConverter(EnumTranslator enumTranslator) {
this.enumTranslator = enumTranslator;
}
@Override
public Specification.Status convert(String source) {
return enumTranslator.fromText(Specification.Status.class, source);
}
}
and register it with:
@Configuration
public class RepositoryRestConfig extends RepositoryRestConfigurerAdapter {
private final TranslationStringToSpecificationStatusEnumConverter converter;
@Autowired
public RepositoryRestConfig(TranslationStringToSpecificationStatusEnumConverter converter) {
this.converter = converter;
}
@Override
public void configureConversionService(ConfigurableConversionService conversionService) {
conversionService.addConverter(converter);
super.configureConversionService(conversionService);
}
}
but this fails on startup with circular spring bean dependency reason
***************************
APPLICATION FAILED TO START
***************************
Description:
The dependencies of some of the beans in the application context form a cycle:
┌─────┐
| repositoryRestConfig defined in file [C:\dev\minimal-reproducible-samples\custom-converter-in-spring-data-rest\target\classes\mihalcin\customconverter\RepositoryRestConfig.class]
↑ ↓
| translationStringToSpecificationStatusEnumConverter defined in file [C:\dev\minimal-reproducible-samples\custom-converter-in-spring-data-rest\target\classes\mihalcin\customconverter\TranslationStringToSpecificationStatusEnumConverter.class]
↑ ↓
| org.springframework.data.rest.webmvc.config.RepositoryRestMvcConfiguration (field java.util.List org.springframework.data.rest.webmvc.config.RepositoryRestMvcConfiguration.configurers)
└─────┘
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