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    <p>In the Gson project code base is <a href="https://github.com/google/gson/blob/master/extras/src/main/java/com/google/gson/typeadapters/RuntimeTypeAdapterFactory.java" rel="noreferrer">the RuntimeTypeAdapter</a>, which reportedly works well for polymorphic serialization and deserialization. I don't think I've yet tried to use it. See <a href="http://code.google.com/p/google-gson/issues/detail?id=231" rel="noreferrer">http://code.google.com/p/google-gson/issues/detail?id=231</a> for more info. Note, it hasn't yet been included in any Gson releases.</p> <p>If use of it doesn't fit your needs, then custom deserialization processing is necessary. Following is one such approach, assuming you want to use the JSON structure demonstrated. (I'd take a somewhat different approach, if the JSON structure could be different.)</p> <pre><code>import java.lang.reflect.Type; import java.util.HashMap; import java.util.List; import java.util.Map; import com.google.gson.Gson; import com.google.gson.GsonBuilder; import com.google.gson.JsonDeserializationContext; import com.google.gson.JsonDeserializer; import com.google.gson.JsonElement; import com.google.gson.JsonObject; import com.google.gson.JsonParseException; import com.google.gson.reflect.TypeToken; public class App { public static void main(String[] args) { Barn[] barns = {new Barn(), new Barn()}; barns[0].type = "horse"; barns[0].animal = new Horse(); barns[1].type = "cow"; barns[1].animal = new Cow(); String json = new Gson().toJson(barns); // [{"type":"horse","animal":{}},{"type":"cow","animal":{}}] BarnDeserializer deserializer = new BarnDeserializer("type"); deserializer.registerBarnType("horse", Horse.class); deserializer.registerBarnType("cow", Cow.class); Gson gson = new GsonBuilder().registerTypeAdapter(Barn.class, deserializer).create(); List&lt;Barn&gt; barns2= gson.fromJson(json, new TypeToken&lt;List&lt;Barn&gt;&gt;(){}.getType()); for (Barn barn : barns2) { System.out.println(barn.animal.getClass()); } } } class BarnDeserializer implements JsonDeserializer&lt;Barn&gt; { String barnTypeElementName; Gson gson; Map&lt;String, Class&lt;? extends Animal&gt;&gt; barnTypeRegistry; BarnDeserializer(String barnTypeElementName) { this.barnTypeElementName = barnTypeElementName; gson = new Gson(); barnTypeRegistry = new HashMap&lt;&gt;(); // Java 7 required for this syntax. } void registerBarnType(String barnTypeName, Class&lt;? extends Animal&gt; animalType) { barnTypeRegistry.put(barnTypeName, animalType); } @Override public Barn deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException { JsonObject barnObject = json.getAsJsonObject(); JsonElement animalTypeElement = barnObject.get(barnTypeElementName); Barn barn = new Barn(); barn.type = animalTypeElement.getAsString(); Class&lt;? extends Animal&gt; animalType = barnTypeRegistry.get(barn.type); barn.animal = gson.fromJson(barnObject.get("animal"), animalType); return barn; } } class Barn {String type; Animal animal;} class Animal {} class Horse extends Animal {} class Cow extends Animal {} </code></pre>
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    1. POHow to handle deserializing with polymorphism?
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    1. USVincent Hiribarren
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