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

Answer 1

Take a look at GWT's Overlay Types. I think this is by far the easiest way to work with JSON in GWT. Here's a modified code example from the linked article:

public class Customer extends JavaScriptObject {
    public final native String getFirstName() /*-{ 
        return this.first_name;
    }-*/;
    public final native void setFirstName(String value) /*-{
        this.first_name = value;
    }-*/;
    public final native String getLastName() /*-{
        return this.last_name;
    }-*/;
    public final native void setLastName(String value) /*-{
        this.last_name = value;
    }-*/;
}

Once you have the overlay type defined, it's easy to create a JavaScript object from JSON and access its properties in Java:

public static final native Customer buildCustomer(String json) /*-{
    return eval('(' + json + ')');
}-*/;

If you want the JSON representation of the object again, you can wrap the overlay type in a JSONObject:

Customer customer = buildCustomer("{'Bart', 'Simpson'}");
customer.setFirstName("Lisa");
// Displays {"first_name":"Lisa","last_name":"Simpson"}
Window.alert(new JSONObject(customer).toString());

Answer 2

I seem to be answering this question a lot...

There's a page on code.google.com titled Using GWT for JSON Mashups. It's (unfortunately) way over my head, as I'm not that familiar with GWT, so it may not be helpful.

Answer 3

Try this serializer from Google Code: http://code.google.com/p/json-io/

If you need to write or read JSON format in Java, this is the tool to use. No need to create extra classes, etc. Convert a Java object graph to JSON format in one call. Do the opposite - create a JSON String or Stream to Java objects. This is the fastest library I have seen yet to do this. It is faster than ObjectOutputStream and ObjectInputStream in most cases, which use binary format.

Very handy utility.

Answer 4

The simplest way would be to use GWT's built-in JSON API. Here's the documentation. And here is a great tutorial on how to use it.

It's as simple as this:

String json = //json string
JSONValue value = JSONParser.parse(json);

The JSONValue API is pretty cool. It lets you chain validations as you extract values from the JSON object so that exceptions will be thrown if anything's amiss with the format.

Answer 5

You may want to checkout this project https://gerrit.googlesource.com/gwtjsonrpc/

It's a library created in order to support a code review system for Android, Gerrit, but it's a stand-alone module meant to be embedded into any GWT project, not just Gerrit.

A reasonable tutorial is probably the README in the top level of the directory. It's quite similar to standard GWT RPC but it uses JSON encoding. It also has built-in XSRF protection.

Answer 6

Another thing to try is the new AutoBean framework introduced with GWT 2.1.

You define interfaces for your beans and a factory that vends them, and GWT generates implementations for you.

interface MyBean {
  String getFoo();
  void setFoo(String foo);
}

interface MyBiggerBean {
  List<MyBean> getBeans();
  void setBeans(List<MyBean> beans>;
}

interface Beanery extends AutoBeanFactory{
  AutoBean<MyBean> makeBean();
  AutoBean<MyBiggerBean> makeBigBean();
}

Beanery beanFactory = GWT.create(Beanery.class);

void go() {
  MyBean bean = beanFactory.makeBean().as();
  bean.setFoo("Hello, beans");
}

The AutoBeanCodex can be used to serialize them to and from json.

AutoBean<MyBean> autoBean = AutoBeanUtils.getAutoBean(bean);
String asJson = AutoBeanCodex.encode(autoBean).getPayload();

AutoBean<MyBean> autoBeanCloneAB = 
  AutoBeanCodex.decode(beanFactory, MyBean.class, asJson );

MyBean autoBeanClone = autoBeanCloneAB.as(); 
assertTrue(AutoBeanUtils.deepEquals(autoBean, autoBeanClone));

They work on the server side too — use AutoBeanFactoryMagic.create(Beanery.class) instead of GWT.create(Beanery.class).