Not able to get error object in JSON format while using #Valid and MessageSource to get display errors in Spring boot - spring

Question

I am currently learning Spring REST and I am trying to build a demo spring boot app. Incase of DTO object has validation error I want to show it as below:
{
"errors": [
{
"code": "first_error_code",
"message": "1st error message"
"field":"field_name"
}
]
}
Where the code in above JSON should display the validation message that I have given in my entity class i.e
#NotEmpty(message = "{name.not.empty}")
String name;
then code should be name.not.empty and message should be taken from messages.properties file.
Now to achieve this, I used several tutorials. Below are the classes:
Main class: (Included MessageSource and LocalValidatorFactoryBean)
#SpringBootApplication
#EnableSwagger2
public class Demo3PathvariableApplication implements WebMvcConfigurer {
#Bean
public MessageSource messageSource() {
ReloadableResourceBundleMessageSource messageSource = new ReloadableResourceBundleMessageSource();
messageSource.setBasename("classpath:messages");
messageSource.setDefaultEncoding("UTF-8");
return messageSource;
}
#Bean
public LocalValidatorFactoryBean validator(MessageSource messageSource) {
LocalValidatorFactoryBean bean = new LocalValidatorFactoryBean();
bean.setValidationMessageSource(messageSource());
return bean;
}
public static void main(String[] args) {
SpringApplication.run(Demo3PathvariableApplication.class, args);
}
/*
* To enable matrix variables, configurePathMatch() method of WebMvcConfigurer
* needs to overriden. Matrix variables are disabled by default and the
* following configuration
*
* urlPathHelper.setRemoveSemicolonContent(false);
*
* should be present in the overriden method to enable the same. see below
* method.
*/
#Override
public void configurePathMatch(PathMatchConfigurer configurer) {
UrlPathHelper urlPathHelper = new UrlPathHelper();
urlPathHelper.setRemoveSemicolonContent(false);
configurer.setUrlPathHelper(urlPathHelper);
}
#Override
public void addCorsMappings(CorsRegistry registry) {
registry.addMapping("/**").allowedMethods("GET", "POST");
}
/* For Swagger Document Generation */
#Bean
public Docket api() {
return new Docket(DocumentationType.SWAGGER_2).select()
.apis(RequestHandlerSelectors.basePackage("com.infytel.controller")).paths(PathSelectors.any()).build()
.useDefaultResponseMessages(false);
// To scan for RestControllers from this package and For disabling default
// response messages
}
}
Controller class:
#RestController
#RequestMapping("/customers")
#Api(value = "CustomerController, REST APIs that deal with Customer DTO")
public class CustomerController {
#Autowired
private CustomerService customerService;
#PostMapping(consumes = "application/json")
public ResponseEntity createCustomer(#RequestBody #Valid CustomerDTO customer, Errors errors) {
return ResponseEntity.ok(customerService.createCustomer(customer));
}
}
FieldErrorDTO.java:
public class FieldErrorDTO {
private String errorCode;
private String message;
private String field;
public FieldErrorDTO(String errorCode, String message, String field) {
this.errorCode = errorCode;
this.message = message;
this.field = field;
}
//Getter setter
ValidationErrorDTO.java:
public class ValidationErrorDTO {
private List<FieldErrorDTO> fieldErrors = new ArrayList<>();
public ValidationErrorDTO() {
super();
}
public void addFieldError(String errorCode, String message, String field) {
FieldErrorDTO error = new FieldErrorDTO(errorCode, message, field);
fieldErrors.add(error);
}
public List<FieldErrorDTO> getFieldErrors() {
return fieldErrors;
}
public void setFieldErrors(List<FieldErrorDTO> fieldErrors) {
this.fieldErrors = fieldErrors;
}
}
RestErrorHandler .java
#ControllerAdvice
public class RestErrorHandler {
#Autowired
private MessageSource messageSource;
#ResponseStatus(BAD_REQUEST)
#ResponseBody
#ExceptionHandler(MethodArgumentNotValidException.class)
public ValidationErrorDTO processValidationError(MethodArgumentNotValidException ex) {
BindingResult result = ex.getBindingResult();
List<org.springframework.validation.FieldError> fieldErrors = result.getFieldErrors();
return processFieldErrors(fieldErrors);
}
private ValidationErrorDTO processFieldErrors(List<FieldError> fieldErrors) {
ValidationErrorDTO dto = new ValidationErrorDTO();
for (FieldError fieldError : fieldErrors) {
String localizedErrorMessage = resolveLocalizedErrorMessage(fieldError);
dto.addFieldError(fieldError.getCode(), localizedErrorMessage, fieldError.getField());
}
return dto;
}
private String resolveLocalizedErrorMessage(FieldError fieldError) {
Locale currentLocale = LocaleContextHolder.getLocale();
String localizedErrorMessage = messageSource.getMessage(fieldError, currentLocale);
return localizedErrorMessage;
}
}
messages.properties
name.not.empty=Please provide a name.
email.not.valid=Please provide valid email id.
age.adult.only=Age should be more than 18.
Now with all these config, I am able to see below JSON,
{
"fieldErrors": [
{
"errorCode": "NotEmpty",
"message": "Please provide a name.",
"field": "name"
},
{
"errorCode": "Email",
"message": "Please provide valid email id.",
"field": "email"
}
]
}
How do I acheive this requirement, where instead of "errorCode": "NotEmpty", I want show
"errorCode": "name.not.empty"
From CustomerDTO class?

Answer 1

To do so you need to change you processFieldErrors:
First remove "{}" from your anotations:
#NotEmpty(message = "name.not.empty")
String name;
Second:
private ValidationErrorDTO processFieldErrors(List<FieldError> fieldErrors) {
ValidationErrorDTO dto = new ValidationErrorDTO();
for (FieldError fieldError : fieldErrors) {
String localizedErrorMessage = resolveLocalizedErrorMessage(fieldError);
dto.addFieldError(fieldError.getDefaultMessage(), localizedErrorMessage, fieldError.getField());
}
return dto;
}
And third, change your message.getMessage:
private String resolveLocalizedErrorMessage(FieldError fieldError) {
Locale currentLocale = LocaleContextHolder.getLocale();
String localizedErrorMessage = messageSource.getMessage(fieldError.getDefaultMessage(), null, currentLocale);
return localizedErrorMessage;
}
This way you would retrieve the key for the message. In your example it will be :
name.not.empty
Hope this helps