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 <H2>
 <FONT SIZE="-1">
 com.google.gson</FONT>
 <BR>
 Interface TypeAdapterFactory</H2>
 <HR>
 <DL>
 <DT><PRE>public interface <B>TypeAdapterFactory</B></DL>
 </PRE>

 <P>
 Creates type adapters for set of related types. Type adapter factories are
  most useful when several types share similar structure in their JSON form.

  <h3>Example: Converting enums to lowercase</h3>
  In this example, we implement a factory that creates type adapters for all
  enums. The type adapters will write enums in lowercase, despite the fact
  that they're defined in <code>CONSTANT_CASE</code> in the corresponding Java
  model: <pre>   <code>public class LowercaseEnumTypeAdapterFactory implements TypeAdapter.Factory {
      public &lt;T&gt; TypeAdapter&lt;T&gt; create(Gson gson, TypeToken&lt;T&gt; type) {
        Class&lt;T&gt; rawType = (Class&lt;T&gt;) type.getRawType();
        if (!rawType.isEnum()) {
          return null;
        }

        final Map&lt;String, T&gt; lowercaseToConstant = new HashMap&lt;String, T&gt;();
        for (T constant : rawType.getEnumConstants()) {
          lowercaseToConstant.put(toLowercase(constant), constant);
        }

        return new TypeAdapter&lt;T&gt;() {
          public void write(JsonWriter out, T value) throws IOException {
            if (value == null) {
              out.nullValue();
            } else {
              out.value(toLowercase(value));
            }
          }

          public T read(JsonReader reader) throws IOException {
            if (reader.peek() == JsonToken.NULL) {
              reader.nextNull();
              return null;
            } else {
              return lowercaseToConstant.get(reader.nextString());
            }
          }
        };
      }

      private String toLowercase(Object o) {
        return o.toString().toLowerCase(Locale.US);
      }
    }
  </code></pre>

  <p>Type adapter factories select which types they provide type adapters
  for. If a factory cannot support a given type, it must return null when
  that type is passed to <A HREF="../../../com/google/gson/TypeAdapterFactory.html#create(com.google.gson.Gson, com.google.gson.reflect.TypeToken)"><CODE>create(com.google.gson.Gson, com.google.gson.reflect.TypeToken<T>)</CODE></A>. Factories should expect <code>create()</code> to be called on them for many types and should return null for
  most of those types. In the above example the factory returns null for
  calls to <code>create()</code> where <code>type</code> is not an enum.

  <p>A factory is typically called once per type, but the returned type
  adapter may be used many times. It is most efficient to do expensive work
  like reflection in <code>create()</code> so that the type adapter's <code>read()</code> and <code>write()</code> methods can be very fast. In this example the
  mapping from lowercase name to enum value is computed eagerly.

  <p>As with type adapters, factories must be <i>registered</i> with a <A HREF="../../../com/google/gson/GsonBuilder.html" title="class in com.google.gson"><CODE>GsonBuilder</CODE></A> for them to take effect: <pre>   <code>GsonBuilder builder = new GsonBuilder();
   builder.registerTypeAdapterFactory(new LowercaseEnumTypeAdapterFactory());
   ...
   Gson gson = builder.create();
  </code></pre>
  If multiple factories support the same type, the factory registered earlier
  takes precedence.

  <h3>Example: composing other type adapters</h3>
  In this example we implement a factory for Guava's <code>Multiset</code>
  collection type. The factory can be used to create type adapters for
  multisets of any element type: the type adapter for <code>Multiset&lt;String&gt;</code> is different from the type adapter for <code>Multiset&lt;URL&gt;</code>.

  <p>The type adapter <i>delegates</i> to another type adapter for the
  multiset elements. It figures out the element type by reflecting on the
  multiset's type token. A <code>Gson</code> is passed in to <code>create</code> for
  just this purpose: <pre>   <code>public class MultisetTypeAdapterFactory implements TypeAdapter.Factory {
      public &lt;T&gt; TypeAdapter&lt;T&gt; create(Gson gson, TypeToken&lt;T&gt; typeToken) {
        Type type = typeToken.getType();
        if (typeToken.getRawType() != Multiset.class
            || !(type instanceof ParameterizedType)) {
          return null;
        }

        Type elementType = ((ParameterizedType) type).getActualTypeArguments()[0];
        TypeAdapter&lt;?&gt; elementAdapter = gson.getAdapter(TypeToken.get(elementType));
        return (TypeAdapter&lt;T&gt;) newMultisetAdapter(elementAdapter);
      }

      private &lt;E&gt; TypeAdapter&lt;Multiset&lt;E&gt;&gt; newMultisetAdapter(
          final TypeAdapter&lt;E&gt; elementAdapter) {
        return new TypeAdapter&lt;Multiset&lt;E&gt;&gt;() {
          public void write(JsonWriter out, Multiset&lt;E&gt; value) throws IOException {
            if (value == null) {
              out.nullValue();
              return;
            }

            out.beginArray();
            for (Multiset.Entry&lt;E&gt; entry : value.entrySet()) {
              out.value(entry.getCount());
              elementAdapter.write(out, entry.getElement());
            }
            out.endArray();
          }

          public Multiset&lt;E&gt; read(JsonReader in) throws IOException {
            if (in.peek() == JsonToken.NULL) {
              in.nextNull();
              return null;
            }

            Multiset&lt;E&gt; result = LinkedHashMultiset.create();
            in.beginArray();
            while (in.hasNext()) {
              int count = in.nextInt();
              E element = elementAdapter.read(in);
              result.add(element, count);
            }
            in.endArray();
            return result;
          }
        };
      }
    }
  </code></pre>
  Delegating from one type adapter to another is extremely powerful; it's
  the foundation of how Gson converts Java objects and collections. Whenever
  possible your factory should retrieve its delegate type adapter in the
  <code>create()</code> method; this ensures potentially-expensive type adapter
  creation happens only once.
 <P>

 <P>
 <DL>
 <DT><B>Since:</B></DT>
   <DD>2.1</DD>
 </DL>
 <HR>

 <P>

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 <CODE>&lt;T&gt; <A HREF="../../../com/google/gson/TypeAdapter.html" title="class in com.google.gson">TypeAdapter</A>&lt;T&gt;</CODE></FONT></TD>
 </TR>
 </TABLE>
 </CODE></FONT></TD>
 <TD><CODE><B><A HREF="../../../com/google/gson/TypeAdapterFactory.html#create(com.google.gson.Gson, com.google.gson.reflect.TypeToken)">create</A></B>(<A HREF="../../../com/google/gson/Gson.html" title="class in com.google.gson">Gson</A>&nbsp;gson,
        <A HREF="../../../com/google/gson/reflect/TypeToken.html" title="class in com.google.gson.reflect">TypeToken</A>&lt;T&gt;&nbsp;type)</CODE>

 <BR>
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Returns a type adapter for <code>type</code>, or null if this factory doesn't
  support <code>type</code>.</TD>
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 <A NAME="create(com.google.gson.Gson, com.google.gson.reflect.TypeToken)"><!-- --></A><H3>
 create</H3>
 <PRE>
 &lt;T&gt; <A HREF="../../../com/google/gson/TypeAdapter.html" title="class in com.google.gson">TypeAdapter</A>&lt;T&gt; <B>create</B>(<A HREF="../../../com/google/gson/Gson.html" title="class in com.google.gson">Gson</A>&nbsp;gson,
                           <A HREF="../../../com/google/gson/reflect/TypeToken.html" title="class in com.google.gson.reflect">TypeToken</A>&lt;T&gt;&nbsp;type)</PRE>
 <DL>
 <DD>Returns a type adapter for <code>type</code>, or null if this factory doesn't
  support <code>type</code>.
 <P>
 <DD><DL>
 </DL>
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	Interface TypeAdapterFactory</H2>
	<HR>
	<DL>
	<DT><PRE>public interface <B>TypeAdapterFactory</B></DL>
	</PRE>

	<P>
	Creates type adapters for set of related types. Type adapter factories are
	most useful when several types share similar structure in their JSON form.

	<h3>Example: Converting enums to lowercase</h3>
	In this example, we implement a factory that creates type adapters for all
	enums. The type adapters will write enums in lowercase, despite the fact
	that they're defined in <code>CONSTANT_CASE</code> in the corresponding Java
	model: <pre> <code>public class LowercaseEnumTypeAdapterFactory implements TypeAdapter.Factory {
	public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
	Class<T> rawType = (Class<T>) type.getRawType();
	if (!rawType.isEnum()) {
	return null;
	}

	final Map<String, T> lowercaseToConstant = new HashMap<String, T>();
	for (T constant : rawType.getEnumConstants()) {
	lowercaseToConstant.put(toLowercase(constant), constant);
	}

	return new TypeAdapter<T>() {
	public void write(JsonWriter out, T value) throws IOException {
	if (value == null) {
	out.nullValue();
	} else {
	out.value(toLowercase(value));
	}
	}

	public T read(JsonReader reader) throws IOException {
	if (reader.peek() == JsonToken.NULL) {
	reader.nextNull();
	return null;
	} else {
	return lowercaseToConstant.get(reader.nextString());
	}
	}
	};
	}

	private String toLowercase(Object o) {
	return o.toString().toLowerCase(Locale.US);
	}
	}
	</code></pre>

	<p>Type adapter factories select which types they provide type adapters
	for. If a factory cannot support a given type, it must return null when
	that type is passed to <A HREF="../../../com/google/gson/TypeAdapterFactory.html#create(com.google.gson.Gson, com.google.gson.reflect.TypeToken)"><CODE>create(com.google.gson.Gson, com.google.gson.reflect.TypeToken<T>)</CODE></A>. Factories should expect <code>create()</code> to be called on them for many types and should return null for
	most of those types. In the above example the factory returns null for
	calls to <code>create()</code> where <code>type</code> is not an enum.

	<p>A factory is typically called once per type, but the returned type
	adapter may be used many times. It is most efficient to do expensive work
	like reflection in <code>create()</code> so that the type adapter's <code>read()</code> and <code>write()</code> methods can be very fast. In this example the
	mapping from lowercase name to enum value is computed eagerly.

	<p>As with type adapters, factories must be <i>registered</i> with a <A HREF="../../../com/google/gson/GsonBuilder.html" title="class in com.google.gson"><CODE>GsonBuilder</CODE></A> for them to take effect: <pre> <code>GsonBuilder builder = new GsonBuilder();
	builder.registerTypeAdapterFactory(new LowercaseEnumTypeAdapterFactory());
	...
	Gson gson = builder.create();
	</code></pre>
	If multiple factories support the same type, the factory registered earlier
	takes precedence.

	<h3>Example: composing other type adapters</h3>
	In this example we implement a factory for Guava's <code>Multiset</code>
	collection type. The factory can be used to create type adapters for
	multisets of any element type: the type adapter for <code>Multiset<String></code> is different from the type adapter for <code>Multiset<URL></code>.

	<p>The type adapter <i>delegates</i> to another type adapter for the
	multiset elements. It figures out the element type by reflecting on the
	multiset's type token. A <code>Gson</code> is passed in to <code>create</code> for
	just this purpose: <pre> <code>public class MultisetTypeAdapterFactory implements TypeAdapter.Factory {
	public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken) {
	Type type = typeToken.getType();
	if (typeToken.getRawType() != Multiset.class
	\|\| !(type instanceof ParameterizedType)) {
	return null;
	}

	Type elementType = ((ParameterizedType) type).getActualTypeArguments()[0];
	TypeAdapter<?> elementAdapter = gson.getAdapter(TypeToken.get(elementType));
	return (TypeAdapter<T>) newMultisetAdapter(elementAdapter);
	}

	private <E> TypeAdapter<Multiset<E>> newMultisetAdapter(
	final TypeAdapter<E> elementAdapter) {
	return new TypeAdapter<Multiset<E>>() {
	public void write(JsonWriter out, Multiset<E> value) throws IOException {
	if (value == null) {
	out.nullValue();
	return;
	}

	out.beginArray();
	for (Multiset.Entry<E> entry : value.entrySet()) {
	out.value(entry.getCount());
	elementAdapter.write(out, entry.getElement());
	}
	out.endArray();
	}

	public Multiset<E> read(JsonReader in) throws IOException {
	if (in.peek() == JsonToken.NULL) {
	in.nextNull();
	return null;
	}

	Multiset<E> result = LinkedHashMultiset.create();
	in.beginArray();
	while (in.hasNext()) {
	int count = in.nextInt();
	E element = elementAdapter.read(in);
	result.add(element, count);
	}
	in.endArray();
	return result;
	}
	};
	}
	}
	</code></pre>
	Delegating from one type adapter to another is extremely powerful; it's
	the foundation of how Gson converts Java objects and collections. Whenever
	possible your factory should retrieve its delegate type adapter in the
	<code>create()</code> method; this ensures potentially-expensive type adapter
	creation happens only once.
	<P>

	<P>
	<DL>
	<DT><B>Since:</B></DT>
	<DD>2.1</DD>
	</DL>
	<HR>

	<P>

	<!-- ========== METHOD SUMMARY =========== -->

	<A NAME="method_summary"><!-- --></A>
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	<TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor">
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	<B>Method Summary</B></FONT></TH>
	</TR>
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	<TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1">
	<CODE>
	<TABLE BORDER="0" CELLPADDING="0" CELLSPACING="0" SUMMARY="">
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	<TD NOWRAP><FONT SIZE="-1">
	<CODE><T> <A HREF="../../../com/google/gson/TypeAdapter.html" title="class in com.google.gson">TypeAdapter</A><T></CODE></FONT></TD>
	</TR>
	</TABLE>
	</CODE></FONT></TD>
	<TD><CODE><B><A HREF="../../../com/google/gson/TypeAdapterFactory.html#create(com.google.gson.Gson, com.google.gson.reflect.TypeToken)">create</A></B>(<A HREF="../../../com/google/gson/Gson.html" title="class in com.google.gson">Gson</A> gson,
	<A HREF="../../../com/google/gson/reflect/TypeToken.html" title="class in com.google.gson.reflect">TypeToken</A><T> type)</CODE>

	<BR>
	Returns a type adapter for <code>type</code>, or null if this factory doesn't
	support <code>type</code>.</TD>
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	<!-- ============ METHOD DETAIL ========== -->

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	<B>Method Detail</B></FONT></TH>
	</TR>
	</TABLE>

	<A NAME="create(com.google.gson.Gson, com.google.gson.reflect.TypeToken)"><!-- --></A><H3>
	create</H3>
	<PRE>
	<T> <A HREF="../../../com/google/gson/TypeAdapter.html" title="class in com.google.gson">TypeAdapter</A><T> <B>create</B>(<A HREF="../../../com/google/gson/Gson.html" title="class in com.google.gson">Gson</A> gson,
	<A HREF="../../../com/google/gson/reflect/TypeToken.html" title="class in com.google.gson.reflect">TypeToken</A><T> type)</PRE>
	<DL>
	<DD>Returns a type adapter for <code>type</code>, or null if this factory doesn't
	support <code>type</code>.
	<P>
	<DD><DL>
	</DL>
	</DD>
	</DL>
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