How do you return JSON from REST call?

Question

this may be a stupid question, but I couldn't find a clear answer on the web. I'm building a REST api with javax.ws.rs. I've got a class that looks like this

public class Person{

    private String name;

    private List<Telephone> telephones;

    constructor + getters + setters
}

I'm implementing a getAllPerson REST call that should return json. This is what I'm doing right now:

Path("/persons")
@GET
@Produces({MediaType.APPLICATION_JSON})
public List<Person> getAllPersons() {
    return facade.getAllPersons();
}

I don't think this is the right way to do it, because it gives me an error (HTTP Status 500 - Internal Server Error...)

And I also have no idea how the program would know how to convert a list of person objects that contains another list of telephone objects to JSON.

So what is the right way to return a list like that in JSON, should I manually build the json String? And what should the return type of the getAllPersons() be?

Sorry if this is a really stupid question, but I couldn't find an answer that was clear to me. Thanks in advance.

EDIT: The error I got is:

Severe:   MessageBodyWriter not found for media type=application/json, type=class java.util.ArrayList, genericType=java.util.List<com.myproject.domain.Person>.

EDIT2: I've added @XmlRootElement to my Person class and I added an empty constructor

I also added this to my pom file:

<dependency>
     <groupId>com.fasterxml.jackson.jaxrs</groupId>
     <artifactId>jackson-jaxrs-json-provider</artifactId>
     <version>2.6.4</version>
 </dependency>

See in your logfile too see what is happend and post the stacktrace if you not find a solution by your own — Jens, Dec 11 '15 at 09:57
You need use some JSON deserializer like Jackson. This is who knows how deserialize/serialize entities. — Héctor, Dec 11 '15 at 09:58
Your annotation says @Produces({MediaType.APPLICATION_JSON}) but you are returning a list of Person objects. You need to return a JSON object. — codingsplash, Dec 11 '15 at 10:27
@Bosiwow Have a look at this question: http://stackoverflow.com/questions/18741954/configure-jackson-as-json-provider-in-jax-rs-2-0 — Oskar Kjellin, Dec 11 '15 at 10:38

score -1 · Answer 1 · answered Dec 11 '15 at 10:23

-1

As you rightly guessed, you are getting a internal error as you are not returning a JSON. You need to create and return a JSON object with the necessary data. You can create a JSON in Java by two ways:

Use JSON Object
Serialize a class into JSON Object

A sample way of creating JSON Object is:

import org.json.simple.JSONObject;
JSONObject sampleJSON= new JSONObject();
sampleJSON.put("name", "Hello");
sampleJSON.put("age", 23);

To return the JSON object use:

Path("/persons")
@GET
@Produces({MediaType.APPLICATION_JSON})
public JSONObject returnJSONData() {
    JSONObject sampleJSON= new JSONObject();
    sampleJSON.put("name", "Hello");
    sampleJSON.put("age", 23);
    return sampleJSON;
}

answered Dec 11 '15 at 10:23

codingsplash

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Isn't there an automatic way to convert from Java objects to json? – Bosiwow Dec 11 '15 at 10:34
Yes, using a library like Jackson. For an example see here: http://www.studytrails.com/java/json/jackson-create-json.jsp – codingsplash Dec 11 '15 at 10:36
1

:o, Think I got it working: http://www.tutorialspoint.com/jackson/jackson_tutorial.pdf was a better tutorial for me, thanks for the help :) – Bosiwow Dec 11 '15 at 10:47

How do you return JSON from REST call?

1 Answers1