Externalizable classes generate wrong JSON

Hi Johann,

we should know which JSON driver you're using resp. how you've initialized the XStream.

Hey Jörg, this is the code PWR (Pico Web Remoting) uses:

	protected XStream createXStream() {
		return new XStream(makeJsonDriver(JsonWriter.DROP_ROOT_MODE));
	}

    public static HierarchicalStreamDriver makeJsonDriver(final int dropRootMode) {
        HierarchicalStreamDriver driver = new HierarchicalStreamDriver() {
...
            public HierarchicalStreamWriter createWriter(Writer out) {
                HierarchicalStreamWriter jsonWriter = new JsonWriter(out, dropRootMode);
                return new WriterWrapper(jsonWriter) {
                    public void startNode(String name) {
                        startNode(name, null);
                    }

                    @SuppressWarnings("unchecked")
					public void startNode(String name, Class clazz) {
                        ((JsonWriter) wrapped).startNode(name.replace('-', '_'), clazz);
                    }
                };
            }

Hi Johann,

what I can do is to handle Externalizable types as array, which would result in a JSON string like:

[
    "文件名 +().mp3",
    690037,
    {},
    0,
    {},
    1.0,
    {},
    {}
]

How would you go on with the root Object, i.e. would

class Foo implements Externalizable {
 double rofl = 42, copter = 42
 ...(Externalizable)...
}

by converted to

{ fields:
 [ 42, 42 ]
}

or would it be this?

[ 42, 42 ]

From what I know, objects will be converted to an JS Object literal by XStream. By converting the object to an Array, you might break certain clients.

Depends on the dropRoot mode. When you drop the root (as Pico does), you might get an array as first element, but this is nothing special for an Externalizable, this applies then for all collections and arrays.

Available in head.

Looks like I'm too late but I was going to suggest printing a message in the affected class that says that the functionality of this class has significantly changed.

Something like this:

static {
 synchronized(System.out) {
  System.out.println("The behaviour of this class has changed from version keks to blub. Please see https://jira.codehaus.org/browse/XSTR-655 on how to change your clients.")
 }
}

I'm asking because, this Monday, we ran into a problem where bug fixes in Log4j caused problems in my company's system. And I think every bug fix will break the software for somebody who's depending on the bug so I'd make it easy for everybody to spot the change.

No, there will be never messages to the console. Changes are recorded in the changes report and especially in this case no harm is done, since the old code cannot handle Externalizable types anyway.