supporting the nullable flag in Schema#toString()

Author: erosb

core/src/main/java/org/everit/json/schema/Schema.java

@@ -220,6 +220,7 @@ public void describeTo(JSONPrinter writer) {
         writer.ifPresent("description", description);
         writer.ifPresent("id", id);
         writer.ifPresent("default", defaultValue);
+        writer.ifPresent("nullable", nullable);
         describePropertiesTo(writer);
         writer.endObject();
     }

core/src/test/java/org/everit/json/schema/StringSchemaTest.java

@@ -28,6 +28,10 @@
 import static org.junit.Assert.assertTrue;
 
 public class StringSchemaTest {
+    
+    private static Schema loadWithNullableSupport(JSONObject rawSchemaJson) {
+        return SchemaLoader.builder().nullableSupport(true).schemaJson(rawSchemaJson).build().load().build();
+    }
 
     @Test
     public void formatFailure() {
@@ -123,6 +127,22 @@ public void toStringTest() {
         assertTrue(ObjectComparator.deepEquals(rawSchemaJson, new JSONObject(actual)));
     }
 
+    @Test
+    public void toStringWithNullableTrueTest() {
+        JSONObject rawSchemaJson = ResourceLoader.DEFAULT.readObj("tostring/stringschema.json");
+        rawSchemaJson.put("nullable", true);
+        String actual = loadWithNullableSupport(rawSchemaJson).toString();
+        assertTrue(ObjectComparator.deepEquals(rawSchemaJson, new JSONObject(actual)));
+    }
+
+    @Test
+    public void toStringWithNullableFalseTest() {
+        JSONObject rawSchemaJson = ResourceLoader.DEFAULT.readObj("tostring/stringschema.json");
+        rawSchemaJson.put("nullable", false);
+        String actual = loadWithNullableSupport(rawSchemaJson).toString();
+        assertTrue(ObjectComparator.deepEquals(rawSchemaJson, new JSONObject(actual)));
+    }
+
     @Test
     public void toStringNoFormat() {
         JSONObject rawSchemaJson = ResourceLoader.DEFAULT.readObj("tostring/stringschema.json");