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JsonDeserializer (Gson 2.3.1 API)
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com.google.gson</FONT>
<BR>
Interface JsonDeserializer<T></H2>
<DL>
<DT><DT><B>Type Parameters:</B><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.</DL>
<HR>
<DL>
<DT><PRE>public interface <B>JsonDeserializer<T></B></DL>
</PRE>
<P>
<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.
<P>
<P>
<DL>
<DT><B>Author:</B></DT>
<DD>Inderjeet Singh, Joel Leitch</DD>
</DL>
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<CODE> <A HREF="../../../com/google/gson/JsonDeserializer.html" title="type parameter in JsonDeserializer">T</A></CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../com/google/gson/JsonDeserializer.html#deserialize(com.google.gson.JsonElement, java.lang.reflect.Type, com.google.gson.JsonDeserializationContext)">deserialize</A></B>(<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>
<BR>
Gson invokes this call-back method during deserialization when it encounters a field of the
specified type.</TD>
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<A NAME="deserialize(com.google.gson.JsonElement, java.lang.reflect.Type, com.google.gson.JsonDeserializationContext)"><!-- --></A><H3>
deserialize</H3>
<PRE>
<A HREF="../../../com/google/gson/JsonDeserializer.html" title="type parameter in JsonDeserializer">T</A> <B>deserialize</B>(<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>
<DL>
<DD>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).
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>json</CODE> - The Json data being deserialized<DD><CODE>typeOfT</CODE> - The type of the Object to deserialize to
<DT><B>Returns:</B><DD>a deserialized object of the specified type typeOfT which is a subclass of <code>T</code>
<DT><B>Throws:</B>
<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></DL>
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