Question

Im using Spring MVC 3.1 which by default uses Jackson for JSON-Java conversions.

I need to create custom conversions for the following:

1. java.util.List (for all sorts of different types).
2. Enums to strings
3. java.util.Calendar

I have encountered a few different approaches for creating my custom converters:

1. As described here more or less, create a custom ObjectMapper:

   public class CustomObjectMapper extends ObjectMapper…

Then adding MappingJacksonHttpMessageConverter to my servlet-context and register it with my custom ObjectMapper:

Then i guess I need to have some specific implementations in my custom objectMapper (how should it look like?).

2. A second approach talks about extending FormattingConversionServiceFactoryBean and create my own converters (a class that implements org.springframework.core.convert.converter.Converter) as described here.

UPDATE 1:
Another approach I have seen is to subcalss MappingJacksonHttpMessageConverter and override getJavaType method, as described here. To do this I will have to add my custom converter to the list of converters:

<bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
<property name="messageConverters">
    <list>
        <bean class="com.yl.app.CustomMappingJacksonHttpMessageConverter">
    </list>
</property>

Which approach is the recommended one? Are these the only ones, is there a better way of doing it?

UPDATE 2:

I still don’t get it. In practice, suppose I have class A and class B.

Class A holds a list of B:

public class A {

   public List<B> list;

}

I would like to return an object of type A to my client. What should I do in my server besides adding the @ResponseBody annotation (which is not enough in this case as far as I get it)?

Answer 1

After trying it myself, non of the listed approaches is required. Jackson (as is) is capable of handling nested Collections just fine, no customization required.