JAX-RS Tip of the Day: Automatic Mapping of Jettison JSON Objects

One of the more interesting features in JAX-RS (Jersey) is the ability to automatically "wrap" POJOs. This combined with automatic wrapping of JAXB annotated beans, and using Jackson to create JSON objects is a powerful mix. However, sometimes we want to wrap an object, and add some additional metadata.

This tip is a very simple tip which allows you to create Jettison JSONObject, and JSONArray objects to create new objects, "wrap" existing objects, or add additional metadata. I mention "wrap" the objects, please don't confuse this with JSONP.

To enable automatic POJO mapping, and Jettison objects add the following to the web.xml

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<servlet>     <servlet-name>ServletAdaptor</servlet-name>     <servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class>     <init-param>         <description>             Allow automatic POJO Mapping features.         </description>         <param-name>com.sun.jersey.api.json.POJOMappingFeature</param-name>         <param-value>true</param-value>     </init-param>     <init-param>         <description>             Set the packages to point to resources which you want to allow             mapping of Jettison based objects. Separate the values for multiple             packages with a comma (,).         </description>         <param-name>com.sun.jersey.config.property.packages</param-name>         <param-value>com.bluelotussoftware.example.jaxrs.resources</param-value>     </init-param>     <load-on-startup>1</load-on-startup> </servlet>

This simple configuration will give you considerable flexibility in how you handle your objects. This will now allow you to produce JSONObjects like the code example below:

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@GET @Path("{id}") @Produces({MediaType.APPLICATION_JSON}) public JSONObject findJSONObject(@PathParam("id") Integer id) {     Customer c = super.find(id);     JSONObject jSONObject = new JSONObject();     try {         jSONObject.put("customerId", c.getCustomerId());         jSONObject.put("name", c.getName());         jSONObject.put("addressLine1", c.getAddressline1());         jSONObject.put("addressLine2", c.getAddressline2());         jSONObject.put("city", c.getCity());         jSONObject.put("state", c.getState());         jSONObject.put("phone", c.getPhone());         jSONObject.put("fax", c.getFax());         jSONObject.put("email", c.getEmail());         jSONObject.put("creditLimit", c.getCreditLimit());     } catch (JSONException ex) {         throw new WebApplicationException(ex, Response.Status.INTERNAL_SERVER_ERROR);     }     return jSONObject; }