The class which has Enum variable.

Hoge.java

import flexjson.JSONDeserializer;
import flexjson.JSONSerializer;

public class Hoge {
	private Color color;
	
	public Hoge(){}

	public Color getColor() {
		return color;
	}

	public void setColor(Color color) {
		this.color = color;
	}
	
	public String toJson(){
		return new JSONSerializer().exclude("*.class")
					.serialize(this);
	}
	
	public static Hoge fromJson(String json){
		return new JSONDeserializer<Hoge>()
				.use(null, Hoge.class)
				.deserialize(json);
	}
	
	public enum Color {
		RED,
		BLUE,
		GREEN;
	}
}

HogeTest.java

import static org.junit.Assert.assertEquals;
import jp.co.pooh.FlexJsonTest.Hoge.Color;

import org.junit.Test;

public class HogeTest {
	@Test
	public void testToJson() {
		Hoge hoge = new Hoge();
		hoge.setColor(Color.BLUE);
		String json = hoge.toJson();
		
		assertEquals("{\"color\":\"BLUE\"}", json);
	}

	@Test
	public void testFromJson() {
		String json = "{\"color\":\"BLUE\"}";
		Hoge created = Hoge.fromJson(json);
		
		assertEquals(Color.BLUE, created.getColor());
	}

	@Test(expected=IllegalArgumentException.class)
	public void testFailFromJsonByIllegalEnumId() {
		String json = "{\"color\":\"blue\"}";//lowercase!!
		Hoge.fromJson(json);
	}
}