Custom AnnotationFormatterFactory doesn't work

Manuel Polacek :

I'm trying to get my Formatter for my model running. The model contains an annotation like the following code. I have multiple Formatter i don't get running yet, but can't figure out the issue.

public class Customer {
    @Trim
    private String firstName;
    //some other properties, getter and setter
}

The annotation is correctly set, as far as i know:

@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD, ElementType.FIELD, ElementType.PARAMETER, ElementType.ANNOTATION_TYPE})
public @interface Trim {
    boolean squashMultipleSpaces() default true;
}

And the AnnotationFormatterFactory

public class TrimAnnotationFormatterFactory implements AnnotationFormatterFactory<Trim> {
    public TrimAnnotationFormatterFactory() {
    }

    public Set<Class<?>> getFieldTypes() {
        return Collections.singleton(String.class);
    }

    public Printer<String> getPrinter(Trim annotation, Class<?> fieldType) {
        return new TrimAnnotationFormatterFactory.TrimFormatter(annotation.squashMultipleSpaces());
    }

    public Parser<String> getParser(Trim annotation, Class<?> fieldType) {
        return new TrimAnnotationFormatterFactory.TrimFormatter(annotation.squashMultipleSpaces());
    }

    private static class TrimFormatter implements Formatter<String> {
        private final boolean squashMultipleSpaces;

        TrimFormatter(boolean squashMultipleSpaces) {
            this.squashMultipleSpaces = squashMultipleSpaces;
        }

        public String parse(String text, Locale locale) {
            return this.process(text);
        }

        public String print(String object, Locale locale) {
            return this.process(object);
        }

        private String process(String text) {
            if (text == null) {
                return null;
            } else {
                return this.squashMultipleSpaces ? text.trim().replaceAll("\\s+", " ") : text.trim();
            }
        }
    }
}

I added my custom AnnotationFormatterFactory to the FormatterRegistry. When I'm dbuggign it, i can see that it is added to the FormatterRegistry successfully.

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {

    @Override
    public void addFormatters(FormatterRegistry registry) {
        registry.addFormatterForFieldAnnotation(new TrimAnnotationFormatterFactory());
    }
}

And the controller looks like:

@Controller
public class CustomerController {

    @PostMapping(value = "/customer")
    @ResponseBody
    public Customer saveCustomer(@RequestBody Customer customer) {
        return customer;
    }
}

if my input looks like this

"       Christian     Walter"

in the controller the model is still the same. I was expecting

"Christian Walter"

in my model.

Why doesn't my formatter work? Or do i have to use PropertyEditor and if so, how could i use it with annotations?

UPDATE: The formatter is successfully registered, but isn't called. And added the controller.

Thanks for your help.

bubbles :

From your last update, i understand that you're using json to deserialize your object. In this case you have to (in my opinion) write your own deserializer, as :

public class WhiteSpaceTrimmerDeserializer extends JsonDeserializer<String> {
    @Override
    public String deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException {
        JsonNode node = jp.getCodec().readTree(jp);
        return node.asText().replaceAll("\\s+", " ").trim();
    }
}

And use it like :

import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
public class Customer {

    private String firstName;


    public String getFirstName() {
        return firstName;
    }

    @JsonDeserialize(using = WhiteSpaceTrimmerDeserializer.class)
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
}

So " Christian Walter" will produce "Christian Walter".

There's another ways to configure this deserializer, you can look at : Can Jackson be configured to trim leading/trailing whitespace from all string properties?

But why Formatter is not working ? The only explanation i have is that @RequestBody/@ResponseBody are not handled by the WebMvcConfigurer.