Spring MVC - bind enum array - spring-mvc

Question

If I post in the format weather=sunny, Spring MVC happily converts this to an Weather enum instance using the enum with name=sunny.
However if I post weather=sunny&weather=windy, then Spring is not able to convert it into an instance of Weather[]. The error I get is:
Failed to convert property value of type 'java.lang.String[]' to required type 'com.blah.Weather[]' for property 'weather'
How can I achieve this?

Answer 1

You can use Converters to perform the custom conversion. For your example, you would need to do something like:
public class WeatherConverter implements Converter<String[], Weather[]> {
#Override
public Weather[] convert(String[] source) {
if(source == null || source.length == 0) {
return new Weather[0];
}
Weather[] weathers = new Weather[source.length];
int i = 0;
for(String name : source) {
weathers[i++] = Weather.valueOf(name);
}
return weathers;
}
}
You can use Converters anywhere you might want type-conversions. Now, what you need to do is register it:
<bean id="conversionService" class="org.springframework.context.support.ConversionServiceFactoryBean">
<property name="converters">
<list>
<bean class="package.path.WeatherConverter"/>
</list>
</property>
</bean>
And it is done.
You can see more details in the Spring Reference.
You could also look into PropertyEditors, with #InitBinder, and, probably, #ControllerAdvice if you want. However, Converters are much easier to use (IMO).