jersey JAXB JSON single-element array

[ido.ran]

Hi,
I'm using GlassFish V2 with jersey 1.0 and JAXB.
I have RESTful Web Service which expose several resources.
I'm using container-item pattern.

My problem is that when the container converter has only one element to return, JAXB format the array as property and not as array.

I was expecting to see this output:
{"@uri":"http://localhost:8080/AuroraService-war/resources/objectTypes","objectType":[{"@uri":"http://localhost:8080/AuroraService-war/resources/objectTypes/61b72060-96d6-40bf-a57c-a49a4ea2a8a8/","id":"61b72060-96d6-40bf-a57c-a49a4ea2a8a8","name":"AnItem"}]}

but I'm getting this output insted:
{"@uri":"http://localhost:8080/AuroraService-war/resources/objectTypes","objectType":{"@uri":"http://localhost:8080/AuroraService-war/resources/objectTypes/61b72060-96d6-40bf-a57c-a49a4ea2a8a8/","id":"61b72060-96d6-40bf-a57c-a49a4ea2a8a8","name":"AnItem"}}

I've bold the important parts. Notice that in the first output the item is surrounded with array brackets and in the second it is not.

What annotation should I use to make JAXB understand it should be format as array?

Thank you,
Ido.

[ido.ran]

Thank you.

[roshanjk]

I faced a similar issue recently - the solution might be useful to someone, although this is a year old post.

Consider this example:
class UserWrapperPojo {
List<User> users;
// The usual getter-setters.
}

class UserPojo {
String name;
// More properties and the getter-setters.
}

Now, if the wrapper contained multiple user objects, the response was:
{"users": [ {name="John", age="21"}, {name="Jane", age="18"}] }

However, if the wrapper contained a single user object, the response was:
{"users": {name="John", age="21"} }

That was throwing my client-side parsing for a toss. The solution here is to create a "JaxbContextResolver" and add the approprite @XmlElement annotations to the Pojos.

In the ContextResolver we explicitly declare the elements which should be treated as an array.

@Component
@Provider
public class JaxbContextResolver implements ContextResolver<JAXBContext> {

private JAXBContext context;
private Class[] types = { UserPojo.class, UserWrapperPojo.class };

public JaxbContextResolver() throws Exception {
this.context = new JSONJAXBContext(JSONConfiguration.mapped().arrays("users").build(), types);
}

public JAXBContext getContext(Class<?> objectType) {
return context;
}
}

Finally add the @XmlRootElement annotation to every Pojo. Likewise the getUsers() method in the UseWrapperPojo was annotated as:

@XmlElement
public List<User> getUsers() {
...
}

This resulted in the expected response:
{"users": [{name="John", age="21"}] }

---
Roshan Kulkarni
http://www.roshankulkarni.info

[roshanjk]

An elaborate example can be found here:
http://blogs.sun.com/enterprisetechtips/entry/configuring_json_for_restful_web

---
Roshan Kulkarni
http://www.roshankulkarni.info

[pansonm]

Thanks for posting this workaround, but this is BUG and should be fixed. Can someone on the jersey team fix this? I cannot think of any situation where you would want to return a list in some cases and an object in others. The "feature" is terrible.

Jackson handles this case properly -- my solution was to change my return type to a string and use Jackson to generate the json -- not very happy with it, but it works.