Json <-> Java serialization that works with GWT [closed]

Answer 1

OK, I deleted my previous answer because it turned out to be exactly what you didn't want.

I don't know how well it works with GWT, but we use the json-lib library to serialize objects in a normal Java project where I work.

It can create a JSONObject directly from a JavaBean, then use the resulting JSONObject's toString() method to get the actual JSON string back.

Likewise, it can also turn JSON back into a JavaBean.

Answer 2

In Google Web Toolkit Applications, pages 510 to 522, the author, Ryan Dewsbury, shows how to use GWT code generation to do serialization to and from XML and JSON documents.

You can download the code here; you want the chapter 10 code bundles, and then you want to look in the src/com/gwtapps/serialization package. I did not see a license for this code, but have emailed the author to see what he says. I'll update this if he replies.

Issues with this solution:

• You have to add a marker interface on all your objects that you want serialized (he uses java.io.Serializable but I imagine you could use others--if you are using hibernate for your backend, your pojos might already be tagged like this).
• The code only supports string properties; it could be extended.
• The code is only written for 1.4 and 1.5.

So, this is not an out of the box solution, but a great starting point for someone to build a JSON serializer that fits with GWT. Combine that with a JSON serializer on the server side, like json-lib and you're good to go.

I also found this project (again, some marker interface is required).

Answer 3

json.org/java seems to be included with GWT these days:

gwt-servlet-deps.jar\org\json\

Or, this project seems to be comprehensive: http://code.google.com/p/piriti/

Answer 4

Check this:

GWT Professional JSON Serializer: http://code.google.com/p/gwtprojsonserializer/

!Works with GWT 2.0+!

Answer 5

Not sure if Jackson would work for you. I don't know if there's GWT-specific you are looking for; if not it should work.

But its serialization/deserialization works quite well, like:

// read json, create object
ObjectMapper mapper = new ObjectMapper();
MyBean bean = mapper.readValue(jsonAsString, MyBean.class);

// and write out
StringWriter sw = new StringWriter();
mapper.writeValue(sw, user);
String jsonOut = sw.toString();

You do need accessors (getX() to serialize, setX() to deserialize; can annotate methods with other names), but that's about it.

Answer 6

It seems that I found the right answer to my question

I figured out that bean to json and json to bean conversion in GWT isn't a trivial task. Known libraries would not work because GWT would require their full source code and this source code must use only Java classes that are amoung emulated by GWT. Also, you cannot use reflection in GWT. Very tough requirements!

I found the only existing solution named gwt-jsonizer. It uses a custom Generator class and requires a satellite interface for each "jsonable" bean. Unfortunately, it does not work without patching on the latest version of GWT and has not been updated for a long time.

So, I personally decided that it is cheaper and faster to make my beans khow how to convert themselves to and from json. Like this:

public class SmartBean {
    private String name;

    public String getName() { return name; }
    public void setName(String value) { name = value;  }

    public JSONObject toJson() {
        JSONObject result = new JSONObject();
        result.put("name", new JSONString(this.name));
        return result;
    }
    public void fromJson(JSONObject value) {
        this.name = value.get("name").isString().stringValue();
    }

}

JSONxxxx are GWT built-in classes that provide low-level json support.