If Internet Explorer 8 performs a HTTP GET against some resource and receives a mime-type that it wasn’t expecting, it will ask the user to download the resource and save it. Annoyingly for JSON content this means you wont see the JSON ‘in-browser’ like in Firefox and Chrome. If you’re using Jersey, Oracle’s JAX-RS reference implementation, here’s how to make IE8 play nice.

The problem is in IE8’s default set of Accept header values. For some reason, it’ll ask for a very specific set of Microsoft types in the request;

Accept: application/x-ms-application, application/xaml+xml, application/x-ms-xbap, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, */*

When the server responds with a Content-Type of anything other than what’s in the accept list, IE will prompt the user to save the resource instead of attempting to display it. That’s fair enough as I imagine its saying “I didn’t say I could accept this so therefore, I don’t know how to display it”.

Responding to a request with the above Accept header from IE with a response including the following header

Content-Type: application/json

will prompt IE8 to save the file rather than display ‘in-browser’.

When we return a response with a JSON content type, IE won’t know how to handle it. We could send back our JSON as text/plain for all cases, but that kind of defeats the object of using Content-Type all together.

However, we can use Jersey to handle the IE case (where the request is for say application/x-ms-application) by sending back plain text but still return JSON for all other cases.

@Path("/customers")
public class Customers {

    @GET
    @Produces("application/json")
    public String getAllCustomers() {
        return allCustomersAsJson();
    }

    @GET
    @Produces("application/x-ms-application")
    public TextPlainOkResponse getAllCustomersForInternetExplorer() {
        return new TextPlainOkResponse(getAllCustomersAsJson());
    }
}

The class above will return a list of all Customers as JSON. The getAllCustomers method will be dispatched to via Jersey and send back the String with a Content-Type of application/json for all cases unless the client asks for application/x-ms-application. This is the case for IE. Now, although the same JSON string is constructed, we’ll overwrite the Content-Type masquerading as text/plain in the TextPlainOkResponse class.

public class TextPlainOkResponse extends Response {

    private final String json;

    public TextPlainOkResponse(String json) {
        this.json = json;
    }

    @Override
    public Object getEntity() {
        return json;
    }

    @Override
    public int getStatus() {
        return 200;
    }

    @Override
    public MultivaluedMap<String, Object> getMetadata() {
        return new MetadataMap<String, Object>() {{
            put("Content-Type", Arrays.<Object>asList("text/plain"));
        }};
    }
}

So for all clients asking for application/x-ms-application, they’ll actually get text/plain. In the case of Internet Explorer 8, it will display the JSON ‘in-browser’. It won’t apply any formatting though, so you may want to pretty print the response before sending it back.

If it doesn’t work for you, see what headers IE is actually sending and adapt the strategy accordingly. You can using something like ieHttpHeaders or the awesome Membrane to see what headers are going over the wire.