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| <h2 title="Interface JsonDeserializer" class="title">Interface JsonDeserializer<T></h2> |
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| <dl> |
| <dt><span class="paramLabel">Type Parameters:</span></dt> |
| <dd><code>T</code> - type for which the deserializer is being registered. It is possible that a |
| deserializer may be asked to deserialize a specific generic type of the T.</dd> |
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| <hr> |
| <br> |
| <pre>public interface <span class="typeNameLabel">JsonDeserializer<T></span></pre> |
| <div class="block"><p>Interface representing a custom deserializer for Json. You should write a custom |
| deserializer, if you are not happy with the default deserialization done by Gson. You will |
| also need to register this deserializer through |
| <a href="../../../com/google/gson/GsonBuilder.html#registerTypeAdapter-java.lang.reflect.Type-java.lang.Object-"><code>GsonBuilder.registerTypeAdapter(Type, Object)</code></a>.</p> |
| |
| <p>Let us look at example where defining a deserializer will be useful. The <code>Id</code> class |
| defined below has two fields: <code>clazz</code> and <code>value</code>.</p> |
| |
| <pre> |
| public class Id<T> { |
| private final Class<T> clazz; |
| private final long value; |
| public Id(Class<T> clazz, long value) { |
| this.clazz = clazz; |
| this.value = value; |
| } |
| public long getValue() { |
| return value; |
| } |
| } |
| </pre> |
| |
| <p>The default deserialization of <code>Id(com.foo.MyObject.class, 20L)</code> will require the |
| Json string to be <code>{"clazz":com.foo.MyObject,"value":20}</code>. Suppose, you already know |
| the type of the field that the <code>Id</code> will be deserialized into, and hence just want to |
| deserialize it from a Json string <code>20</code>. You can achieve that by writing a custom |
| deserializer:</p> |
| |
| <pre> |
| class IdDeserializer implements JsonDeserializer<Id>() { |
| public Id deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) |
| throws JsonParseException { |
| return new Id((Class)typeOfT, id.getValue()); |
| } |
| </pre> |
| |
| <p>You will also need to register <code>IdDeserializer</code> with Gson as follows:</p> |
| |
| <pre> |
| Gson gson = new GsonBuilder().registerTypeAdapter(Id.class, new IdDeserializer()).create(); |
| </pre> |
| |
| <p>New applications should prefer <a href="../../../com/google/gson/TypeAdapter.html" title="class in com.google.gson"><code>TypeAdapter</code></a>, whose streaming API |
| is more efficient than this interface's tree API.</div> |
| <dl> |
| <dt><span class="simpleTagLabel">Author:</span></dt> |
| <dd>Inderjeet Singh, Joel Leitch</dd> |
| </dl> |
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| <td class="colFirst"><code><a href="../../../com/google/gson/JsonDeserializer.html" title="type parameter in JsonDeserializer">T</a></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../com/google/gson/JsonDeserializer.html#deserialize-com.google.gson.JsonElement-java.lang.reflect.Type-com.google.gson.JsonDeserializationContext-">deserialize</a></span>(<a href="../../../com/google/gson/JsonElement.html" title="class in com.google.gson">JsonElement</a> json, |
| <a href="http://docs.oracle.com/javase/1.5.0/docs/api/java/lang/reflect/Type.html?is-external=true" title="class or interface in java.lang.reflect">Type</a> typeOfT, |
| <a href="../../../com/google/gson/JsonDeserializationContext.html" title="interface in com.google.gson">JsonDeserializationContext</a> context)</code> |
| <div class="block">Gson invokes this call-back method during deserialization when it encounters a field of the |
| specified type.</div> |
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| <a name="deserialize-com.google.gson.JsonElement-java.lang.reflect.Type-com.google.gson.JsonDeserializationContext-"> |
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| <h4>deserialize</h4> |
| <pre><a href="../../../com/google/gson/JsonDeserializer.html" title="type parameter in JsonDeserializer">T</a> deserialize(<a href="../../../com/google/gson/JsonElement.html" title="class in com.google.gson">JsonElement</a> json, |
| <a href="http://docs.oracle.com/javase/1.5.0/docs/api/java/lang/reflect/Type.html?is-external=true" title="class or interface in java.lang.reflect">Type</a> typeOfT, |
| <a href="../../../com/google/gson/JsonDeserializationContext.html" title="interface in com.google.gson">JsonDeserializationContext</a> context) |
| throws <a href="../../../com/google/gson/JsonParseException.html" title="class in com.google.gson">JsonParseException</a></pre> |
| <div class="block">Gson invokes this call-back method during deserialization when it encounters a field of the |
| specified type. |
| <p>In the implementation of this call-back method, you should consider invoking |
| <a href="../../../com/google/gson/JsonDeserializationContext.html#deserialize-com.google.gson.JsonElement-java.lang.reflect.Type-"><code>JsonDeserializationContext.deserialize(JsonElement, Type)</code></a> method to create objects |
| for any non-trivial field of the returned object. However, you should never invoke it on the |
| the same type passing <code>json</code> since that will cause an infinite loop (Gson will call your |
| call-back method again).</div> |
| <dl> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>json</code> - The Json data being deserialized</dd> |
| <dd><code>typeOfT</code> - The type of the Object to deserialize to</dd> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>a deserialized object of the specified type typeOfT which is a subclass of <code>T</code></dd> |
| <dt><span class="throwsLabel">Throws:</span></dt> |
| <dd><code><a href="../../../com/google/gson/JsonParseException.html" title="class in com.google.gson">JsonParseException</a></code> - if json is not in the expected format of <code>typeofT</code></dd> |
| </dl> |
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