Using json with Play 2 - json

Question

I'm trying to create a simple application that allows me to create, read, update and delete various users. I have a basic UI-based view, controller and model that work, but wanted to be more advanced than this and provide a RESTful json interface.
However, despite reading everything I can find in the Play 2 documentation, the Play 2 Google groups and the stackoverflow website, I still can't get this to work.
I've updated my controller based on previous feedback and I now believe it is based on the documentation.
Here is my updated controller:
package controllers;
import models.Member;
import play.*;
import play.mvc.*;
import play.libs.Json;
import play.data.Form;
public class Api extends Controller {
/* Return member info - version to serve Json response */
public static Result member(Long id){
ObjectNode result = Json.newObject();
Member member = Member.byid(id);
result.put("id", member.id);
result.put("email", member.email);
result.put("name", member.name);
return ok(result);
}
// Create a new body parser of class Json based on the values sent in the POST
#BodyParser.Of(Json.class)
public static Result createMember() {
JsonNode json = request().body().asJson();
// Check that we have a valid email address (that's all we need!)
String email = json.findPath("email").getTextValue();
if(name == null) {
return badRequest("Missing parameter [email]");
} else {
// Use the model's createMember class now
Member.createMember(json);
return ok("Hello " + name);
}
}
....
But when I run this, I get the following error:
incompatible types [found: java.lang.Class<play.libs.Json>] [required: java.lang.Class<?extends play.mvc.BodyParser>]
In /Users/Mark/Development/EclipseWorkspace/ms-loyally/loyally/app/controllers/Api.java at line 42.
41 // Create a new body parser of class Json based on the values sent in the POST
42 #BodyParser.Of(Json.class)
43 public static Result createMember() {
44 JsonNode json = request().body().asJson();
45 // Check that we have a valid email address (that's all we need!)
46 String email = json.findPath("email").getTextValue();
As far as I can tell, I've copied from the documentation so I would appreciate any help in getting this working.

Answer 1

There appear to be conflicts in the use of the Json class in the Play 2 documentation. To get the example above working correctly, the following imports are used:
import play.mvc.Controller;
import play.mvc.Result;
import play.mvc.BodyParser;
import play.libs.Json;
import play.libs.Json.*;
import static play.libs.Json.toJson;
import org.codehaus.jackson.JsonNode;
import org.codehaus.jackson.node.ObjectNode;
#BodyParser.Of(play.mvc.BodyParser.Json.class)
public static index sayHello() {
JsonNode json = request().body().asJson();
ObjectNode result = Json.newObject();
String name = json.findPath("name").getTextValue();
if(name == null) {
result.put("status", "KO");
result.put("message", "Missing parameter [name]");
return badRequest(result);
} else {
result.put("status", "OK");
result.put("message", "Hello " + name);
return ok(result);
}
}
Note the explicit calling of the right Json class in #BodyParser
I'm not sure if this is a bug or not? But this is the only way I could get the example to work.

Answer 2

Import those two
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.node.ObjectNode;
According to this documentation: http://fasterxml.github.io/jackson-databind/javadoc/2.0.0/com/fasterxml/jackson/databind/node/ObjectNode.html

Answer 3

Try this:
import play.*;
import play.mvc.*;
import org.codehaus.jackson.JsonNode; //Fixing "error: cannot find symbol" for JsonNode
// Testing JSON
#BodyParser.Of(BodyParser.Json.class) //Or you can import play.mvc.BodyParser.Json
public static Result sayHello() {
JsonNode json = request().body().asJson();
String name = json.findPath("name").getTextValue();
if(name==null) {
return badRequest("Missing parameter [name]");
} else {
return ok("Hello " + name);
}
}

Answer 4

AFAIK, the code you are using has not reached any official Play version (neither 2.0 or 2.0.1) according to this: https://github.com/playframework/Play20/pull/212
Instead, you can do this (not tested):
if(request().getHeader(play.mvc.Http.HeaderNames.ACCEPT).equalsIgnoreCase("application/json")) {

Answer 5

Did you try checking out the documentation for it?
Serving a JSON response looks like:
#BodyParser.Of(Json.class)
public static index sayHello() {
JsonNode json = request().body().asJson();
ObjectNode result = Json.newObject();
String name = json.findPath("name").getTextValue();
if(name == null) {
result.put("status", "KO");
result.put("message", "Missing parameter [name]");
return badRequest(result);
} else {
result.put("status", "OK");
result.put("message", "Hello " + name);
return ok(result);
}
}

Answer 6

You have imported play.libs.Json and then use the BodyParser.Of annotation with this Json.class.
The above annotation expects a class which extends a play.mvc.BodyParser. So simply replace #BodyParser.Of(Json.class) by #BodyParser.Of(BodyParser.Json.class).