java - Can Jackson be configured to trim leading/trailing whitespace from all string properties?

Question

Example JSON (note that the string has trailing spaces):

{ "aNumber": 0, "aString": "string   " }

Ideally, the deserialised instance would have an aString property with a value of "string" (i.e. without trailing spaces). This seems like something that is probably supported but I can't find it (e.g. in DeserializationConfig.Feature).

We're using Spring MVC 3.x so a Spring-based solution would also be fine.

I tried configuring Spring's WebDataBinder based on a suggestion in a forum post but it does not seem to work when using a Jackson message converter:

@InitBinder
public void initBinder( WebDataBinder binder )
{
    binder.registerCustomEditor( String.class, new StringTrimmerEditor( " 
f", true ) );
}

Answer 1

Easy solution for Spring Boot users, just add that walv's SimpleModule extension to your application context:

package com.example;

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.deser.std.StdScalarDeserializer;
import com.fasterxml.jackson.databind.module.SimpleModule;
import org.springframework.stereotype.Component;

import java.io.IOException;

@Component
public class StringTrimModule extends SimpleModule {

    public StringTrimModule() {
        addDeserializer(String.class, new StdScalarDeserializer<String>(String.class) {
            @Override
            public String deserialize(JsonParser jsonParser, DeserializationContext ctx) throws IOException,
                    JsonProcessingException {
                return jsonParser.getValueAsString().trim();
            }
        });
    }
}

Another way to customize Jackson is to add beans of type com.fasterxml.jackson.databind.Module to your context. They will be registered with every bean of type ObjectMapper, providing a global mechanism for contributing custom modules when you add new features to your application.

http://docs.spring.io/spring-boot/docs/current/reference/html/howto-spring-mvc.html#howto-customize-the-jackson-objectmapper

if you are not using spring boot, you have to register the StringTrimModule yourself (you do not need to annotate it with @Component)

<bean class="org.springframework.http.converter.json.Jackson2Objec??tMapperFactoryBean">
    <property name="modulesToInstall" value="com.example.StringTrimModule"/>
</bean