+++ /dev/null
-/*
- * Copyright (C) 2011 Google Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package com.google.gson;
-
-import com.google.gson.reflect.TypeToken;
-
-/**
- * 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} 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);
- * }
- * }
- * }</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 {@link #create}. Factories should expect {@code
- * create()} 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()} where {@code type} 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()} so that the type adapter's {@code
- * read()} and {@code write()} 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 {@link
- * com.google.gson.GsonBuilder} for them to take effect: <pre> {@code
- *
- * GsonBuilder builder = new GsonBuilder();
- * builder.registerTypeAdapterFactory(new LowercaseEnumTypeAdapterFactory());
- * ...
- * Gson gson = builder.create();
- * }</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}
- * collection type. The factory can be used to create type adapters for
- * multisets of any element type: the type adapter for {@code
- * Multiset<String>} is different from the type adapter for {@code
- * Multiset<URL>}.
- *
- * <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} is passed in to {@code create} 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;
- * }
- * };
- * }
- * }
- * }</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()} method; this ensures potentially-expensive type adapter
- * creation happens only once.
- *
- * @since 2.1
- */
-public interface TypeAdapterFactory {
-
- /**
- * Returns a type adapter for {@code type}, or null if this factory doesn't
- * support {@code type}.
- */
- <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type);
-}
projects / unical.git / blobdiff