SampleJsonTest.java

import com.google.gson.Gson;
import com.google.gson.annotations.SerializedName;

import org.junit.Before;
import org.junit.Test;

import static org.junit.Assert.assertEquals;

public class SampleJsonTest {
    private static final String SAMPLE_JSON = "{ \"first_name\": \"Atomic\", \"last_name\": \"Robot\" }";

    private Gson gson;

    @Before
    public void setup() {
        gson = new Gson();
    }

    @Test
    public void testParsingJsonAsMutablePerson() {
        MutablePerson person = gson.fromJson(SAMPLE_JSON, MutablePerson.class);
        assertEquals("Atomic", person.firstName);
        assertEquals("Robot", person.lastName);
    }
    
    @Test
    public void testParsingJsonAsImmutablePerson() {
        // Works due to the magic of the ReflectiveTypeAdapterFactory
        ImmutablePerson person = gson.fromJson(SAMPLE_JSON, ImmutablePerson.class);
        assertEquals("Atomic", person.firstName);
        assertEquals("Robot", person.lastName);
    }

    static class MutablePerson {
        @SerializedName("first_name") String firstName;
        @SerializedName("last_name") String lastName;
    }

    static class ImmutablePerson {
        final @SerializedName("first_name") String firstName;
        final @SerializedName("last_name") String lastName;

        // Not called by GSON...
        public ImmutablePerson(String firstName, String lastName) {
            this.firstName = firstName;
            this.lastName = lastName;
        }
    }
}