how to return json objects from java rest api

Question

I am trying to return a JSON object from a jax-rs but I get an internal server error whenever I try to access.

This is my method, I am using javax.ws.rs.GET.

@GET
@Produces("application/json")
public Testy getJson() {
   return new Testy("hello");
}

This is the class:

public class Testy {

    private final String value;

    public Testy(String value){

        this.value = value;
    }

  public String getValue(){

      return value;
   }

}

My Pom.xml has this dependency, I have tried various dependencies, but none work. There are various maven resources for jersey, there's jersey-client jersey-core.

<dependency>
 <groupId>com.fasterxml.jackson.jaxrs</groupId>
 <artifactId>jackson-jaxrs-json-provider</artifactId>
 <version>2.3.3</version>
</dependency>

I am using Glassfish 4.

Questions about working with Jersey:

I have seen some places where they mention you need to have initialize POJO support, it seems like its for jersey 1.* but I am not sure. I don't need this if I am using 2.* ?

Do I have to modify the web.xml to point to the jersey servlet ?

How can I produce and consume JSON objects using POJO classes !?

Edit

Here is my auto generated config class.

Answer 1

I had to add the JacksonFeature resource to my ApplicationConfig Class.

    @javax.ws.rs.ApplicationPath("webresources")
public class ApplicationConfig extends Application {

    @Override
    public Set<Class<?>> getClasses() {
        Set<Class<?>> resources = new java.util.HashSet<>();              
       addRestResourceClasses(resources);
       resources.add(org.glassfish.jersey.jackson.JacksonFeature.class);
        return resources;
    }

    /**
     * Do not modify addRestResourceClasses() method.
     * It is automatically populated with
     * all resources defined in the project.
     * If required, comment out calling this method in getClasses().
     */
    private void addRestResourceClasses(Set<Class<?>> resources) {
        resources.add(com.wfscorp.restapitwo.GenericResource.class);
    }

}

Then everything worked!

Note

When I used the com.fasterxml.jackson.jaxrs dependency I was unable to deploy my application. I started getting a WELD-001408 Unsatisfied dependencies for type error so I had to exclude the jersey media multi part.

These are the dependencies in my pom.xml

 <dependencies>
    <dependency>
        <groupId>org.glassfish.jersey.media</groupId>
        <artifactId>jersey-media-json-jackson</artifactId>
        <version>2.13</version>
        <type>jar</type>
    </dependency>
    <dependency>
        <groupId>javax</groupId>
        <artifactId>javaee-web-api</artifactId>
        <version>7.0</version>
        <scope>provided</scope>
    </dependency> 

    <dependency>
        <groupId>com.fasterxml.jackson.jaxrs</groupId>
        <artifactId>jackson-jaxrs-json-provider</artifactId>
        <version>2.4.0</version>
    </dependency>

    <dependency>
        <groupId>org.glassfish.jersey.media</groupId>
        <artifactId>jersey-media-multipart</artifactId>
        <version>2.7</version>
        <scope>provided</scope>
    </dependency>

</dependencies>

Answer 2

This will guide through the entire process Reference ,Simple and Easy - http://examples.javacodegeeks.com/enterprise-java/rest/jersey/json-example-with-jersey-jackson/

Answer 3

It may be that you need to expose the value property of your Testy object with a getter.