sending List/Map as POST parameter jersey

Question

I want to send a HashMap object to a ReST resource as a POST variable. I used the Form class to send the object. The client code:

public static         


        

Answer 1

Just to clear things a bit. The MultivaluedMap is meant to be used for obtaining general map of form parameters e.g. parameters submitted to your service via POST HTTP request. It is supposed to be used like this:

   @POST
   @Consumes("application/x-www-form-urlencoded")
   public void post(MultivaluedMap formParams) {
     // Store the message
   }

However, when your client application needs to provide your REST service with some sort of data (in your case a HashMap containing I suppose a lot of important information) it would Serialize it to XML first, then send it to the service which would then deserialize and use it. Unfortunately, Jersey is not able to automatically marshal/unmmarshal HashMaps so if you just provided HashMap parameter in your newProj method, you would get an exception.

So how to send a HashMap to your service? Well, the key is the JAXB @XmlRootElement and a custom XmlAdapter :-)

First you need to write your own wrapper for the map. The wrapper will be annotated with @XmlRootElement

@XmlRootElement
public class MyHashMapObject {
    private Map mapProperty;

    public MyHashMapObject() {
        mapProperty = new HashMap();
    }

    @XmlJavaTypeAdapter(MapAdapter.class) // NOTE: Our custom XmlAdaper
    public Map getMapProperty() {
        return mapProperty;
    }

    public void setMapProperty(Map map) {
        this.mapProperty = map;
    }
}

Then you need to define your "JAXB enabled" map elements:

public class MapElement {
    @XmlElement
    public String key;
    @XmlElement
    public String value;

    private MapElement() {
    }

    public MapElement(String key, String value) {
        this.key = key;
        this.value = value;
    }
}

And in the end define your custom XmlAdapter:

public class MapAdapter extends XmlAdapter> {
    public MapElement[] marshal(Map arg0) throws Exception {
        MapElement[] mapElements = new MapElement[arg0.size()];
        int i = 0;
        for (Map.Entry entry : arg0.entrySet())
            mapElements[i++] = new MapElement(entry.getKey(), entry.getValue());

        return mapElements;
    }

    public Map unmarshal(MapElement[] arg0) throws Exception {
        Map r = new HashMap();
        for (MapElement mapelement : arg0)
            r.put(mapelement.key, mapelement.value);
        return r;
    }
}

Once you have all of this in place (it must be used by your service and the client so put it to some shard jar), you can define your service like this:

@Path("/hello")
public class FormResource
{
    //@GET
    @POST
    @Produces(MediaType.APPLICATION_XML)
    @Consumes(MediaType.APPLICATION_XML)
    public MyHashMapObject post(
                MyHashMapObject anotherMap) {

        anotherMap.getMapProperty().put("e", "10");
        anotherMap.getMapProperty().put("f", "11");
        anotherMap.getMapProperty().put("g", "12");

        return anotherMap;
    }
}

You're all set to go now. Your client should go like this:

   public class Test {  
      public static void main(String[] args) {
            ClientConfig config = new DefaultClientConfig();
            Client client = Client.create(config);
            WebResource service = client.resource(getBaseURI());

            // Now do the MAP stuff
            MyHashMapObject map = new MyHashMapObject();
            map.getMapProperty().put("a", "1");
            map.getMapProperty().put("b", "2");

            ClientResponse response = service.path("rest").path("hello2")
                .type(MediaType.APPLICATION_XML)
                .accept(MediaType.APPLICATION_XML)
                .post(ClientResponse.class, map);

            Map myMap = response.getEntity(MyHashMapObject.class).getMapProperty();     
            for(Map.Entry entry : myMap.entrySet())
                System.out.format("Key: %s, Value: %s\n", entry.getKey(), entry.getValue());

        }

        private static URI getBaseURI() {
            return UriBuilder.fromUri(
                    "http://localhost:8080/org.nowaq.jersey.first").build();
        }
    }

Now you can easily pass your HashMap to your REST service. You can also make the implementation a bit more generic. Hope this helps.