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Diffstat (limited to 'mod/src/main/java/com')
-rw-r--r-- | mod/src/main/java/com/google/gson/typeadapters/RuntimeTypeAdapterFactory.java | 272 |
1 files changed, 272 insertions, 0 deletions
diff --git a/mod/src/main/java/com/google/gson/typeadapters/RuntimeTypeAdapterFactory.java b/mod/src/main/java/com/google/gson/typeadapters/RuntimeTypeAdapterFactory.java new file mode 100644 index 0000000..51f05ff --- /dev/null +++ b/mod/src/main/java/com/google/gson/typeadapters/RuntimeTypeAdapterFactory.java @@ -0,0 +1,272 @@ +/* + * 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.typeadapters; + +import com.google.gson.*; +import com.google.gson.reflect.TypeToken; +import com.google.gson.stream.JsonReader; +import com.google.gson.stream.JsonWriter; + +import java.io.IOException; +import java.util.LinkedHashMap; +import java.util.Map; + +/** + * Adapts values whose runtime type may differ from their declaration type. This + * is necessary when a field's type is not the same type that GSON should create + * when deserializing that field. For example, consider these types: + * <pre> {@code + * abstract class Shape { + * int x; + * int y; + * } + * class Circle extends Shape { + * int radius; + * } + * class Rectangle extends Shape { + * int width; + * int height; + * } + * class Diamond extends Shape { + * int width; + * int height; + * } + * class Drawing { + * Shape bottomShape; + * Shape topShape; + * } + * }</pre> + * <p>Without additional type information, the serialized JSON is ambiguous. Is + * the bottom shape in this drawing a rectangle or a diamond? <pre> {@code + * { + * "bottomShape": { + * "width": 10, + * "height": 5, + * "x": 0, + * "y": 0 + * }, + * "topShape": { + * "radius": 2, + * "x": 4, + * "y": 1 + * } + * }}</pre> + * This class addresses this problem by adding type information to the + * serialized JSON and honoring that type information when the JSON is + * deserialized: <pre> {@code + * { + * "bottomShape": { + * "type": "Diamond", + * "width": 10, + * "height": 5, + * "x": 0, + * "y": 0 + * }, + * "topShape": { + * "type": "Circle", + * "radius": 2, + * "x": 4, + * "y": 1 + * } + * }}</pre> + * Both the type field name ({@code "type"}) and the type labels ({@code + * "Rectangle"}) are configurable. + * + * <h3>Registering Types</h3> + * Create a {@code RuntimeTypeAdapterFactory} by passing the base type and type field + * name to the {@link #of} factory method. If you don't supply an explicit type + * field name, {@code "type"} will be used. <pre> {@code + * RuntimeTypeAdapterFactory<Shape> shapeAdapterFactory + * = RuntimeTypeAdapterFactory.of(Shape.class, "type"); + * }</pre> + * Next register all of your subtypes. Every subtype must be explicitly + * registered. This protects your application from injection attacks. If you + * don't supply an explicit type label, the type's simple name will be used. + * <pre> {@code + * shapeAdapterFactory.registerSubtype(Rectangle.class, "Rectangle"); + * shapeAdapterFactory.registerSubtype(Circle.class, "Circle"); + * shapeAdapterFactory.registerSubtype(Diamond.class, "Diamond"); + * }</pre> + * Finally, register the type adapter factory in your application's GSON builder: + * <pre> {@code + * Gson gson = new GsonBuilder() + * .registerTypeAdapterFactory(shapeAdapterFactory) + * .create(); + * }</pre> + * Like {@code GsonBuilder}, this API supports chaining: <pre> {@code + * RuntimeTypeAdapterFactory<Shape> shapeAdapterFactory = RuntimeTypeAdapterFactory.of(Shape.class) + * .registerSubtype(Rectangle.class) + * .registerSubtype(Circle.class) + * .registerSubtype(Diamond.class); + * }</pre> + * + * <h3>Serialization and deserialization</h3> + * In order to serialize and deserialize a polymorphic object, + * you must specify the base type explicitly. + * <pre> {@code + * Diamond diamond = new Diamond(); + * String json = gson.toJson(diamond, Shape.class); + * }</pre> + * And then: + * <pre> {@code + * Shape shape = gson.fromJson(json, Shape.class); + * }</pre> + */ +public final class RuntimeTypeAdapterFactory<T> implements TypeAdapterFactory { + private final Class<?> baseType; + private final String typeFieldName; + private final Map<String, Class<?>> labelToSubtype = new LinkedHashMap<>(); + private final Map<Class<?>, String> subtypeToLabel = new LinkedHashMap<>(); + private final boolean maintainType; + + private RuntimeTypeAdapterFactory(Class<?> baseType, String typeFieldName, boolean maintainType) { + if (typeFieldName == null || baseType == null) { + throw new NullPointerException(); + } + this.baseType = baseType; + this.typeFieldName = typeFieldName; + this.maintainType = maintainType; + } + + /** + * Creates a new runtime type adapter using for {@code baseType} using {@code + * typeFieldName} as the type field name. Type field names are case sensitive. + * {@code maintainType} flag decide if the type will be stored in pojo or not. + */ + public static <T> RuntimeTypeAdapterFactory<T> of(Class<T> baseType, String typeFieldName, boolean maintainType) { + return new RuntimeTypeAdapterFactory<>(baseType, typeFieldName, maintainType); + } + + /** + * Creates a new runtime type adapter using for {@code baseType} using {@code + * typeFieldName} as the type field name. Type field names are case sensitive. + */ + public static <T> RuntimeTypeAdapterFactory<T> of(Class<T> baseType, String typeFieldName) { + return new RuntimeTypeAdapterFactory<>(baseType, typeFieldName, false); + } + + /** + * Creates a new runtime type adapter for {@code baseType} using {@code "type"} as + * the type field name. + */ + public static <T> RuntimeTypeAdapterFactory<T> of(Class<T> baseType) { + return new RuntimeTypeAdapterFactory<>(baseType, "type", false); + } + + /** + * Registers {@code type} identified by {@code label}. Labels are case + * sensitive. + * + * @throws IllegalArgumentException if either {@code type} or {@code label} + * have already been registered on this type adapter. + */ + public RuntimeTypeAdapterFactory<T> registerSubtype(Class<? extends T> type, String label) { + if (type == null || label == null) { + throw new NullPointerException(); + } + if (subtypeToLabel.containsKey(type) || labelToSubtype.containsKey(label)) { + throw new IllegalArgumentException("types and labels must be unique"); + } + labelToSubtype.put(label, type); + subtypeToLabel.put(type, label); + return this; + } + + /** + * Registers {@code type} identified by its {@link Class#getSimpleName simple + * name}. Labels are case sensitive. + * + * @throws IllegalArgumentException if either {@code type} or its simple name + * have already been registered on this type adapter. + */ + public RuntimeTypeAdapterFactory<T> registerSubtype(Class<? extends T> type) { + return registerSubtype(type, type.getSimpleName()); + } + + @Override + public <R> TypeAdapter<R> create(Gson gson, TypeToken<R> type) { + // Workaround found at https://github.com/google/gson/issues/712#issuecomment-148955110 + if (null == type || !baseType.isAssignableFrom(type.getRawType())) { + // if (type.getRawType() != baseType) { + return null; + } + + final TypeAdapter<JsonElement> jsonElementAdapter = gson.getAdapter(JsonElement.class); + final Map<String, TypeAdapter<?>> labelToDelegate = new LinkedHashMap<>(); + final Map<Class<?>, TypeAdapter<?>> subtypeToDelegate = new LinkedHashMap<>(); + for (Map.Entry<String, Class<?>> entry : labelToSubtype.entrySet()) { + TypeAdapter<?> delegate = gson.getDelegateAdapter(this, TypeToken.get(entry.getValue())); + labelToDelegate.put(entry.getKey(), delegate); + subtypeToDelegate.put(entry.getValue(), delegate); + } + + return new TypeAdapter<R>() { + @Override public R read(JsonReader in) throws IOException { + JsonElement jsonElement = jsonElementAdapter.read(in); + JsonElement labelJsonElement; + if (maintainType) { + labelJsonElement = jsonElement.getAsJsonObject().get(typeFieldName); + } else { + labelJsonElement = jsonElement.getAsJsonObject().remove(typeFieldName); + } + + if (labelJsonElement == null) { + throw new JsonParseException("cannot deserialize " + baseType + + " because it does not define a field named " + typeFieldName); + } + String label = labelJsonElement.getAsString(); + @SuppressWarnings("unchecked") // registration requires that subtype extends T + TypeAdapter<R> delegate = (TypeAdapter<R>) labelToDelegate.get(label); + if (delegate == null) { + throw new JsonParseException("cannot deserialize " + baseType + " subtype named " + + label + "; did you forget to register a subtype?"); + } + return delegate.fromJsonTree(jsonElement); + } + + @Override public void write(JsonWriter out, R value) throws IOException { + Class<?> srcType = value.getClass(); + String label = subtypeToLabel.get(srcType); + @SuppressWarnings("unchecked") // registration requires that subtype extends T + TypeAdapter<R> delegate = (TypeAdapter<R>) subtypeToDelegate.get(srcType); + if (delegate == null) { + throw new JsonParseException("cannot serialize " + srcType.getName() + + "; did you forget to register a subtype?"); + } + JsonObject jsonObject = delegate.toJsonTree(value).getAsJsonObject(); + + if (maintainType) { + jsonElementAdapter.write(out, jsonObject); + return; + } + + JsonObject clone = new JsonObject(); + + if (jsonObject.has(typeFieldName)) { + throw new JsonParseException("cannot serialize " + srcType.getName() + + " because it already defines a field named " + typeFieldName); + } + clone.add(typeFieldName, new JsonPrimitive(label)); + + for (Map.Entry<String, JsonElement> e : jsonObject.entrySet()) { + clone.add(e.getKey(), e.getValue()); + } + jsonElementAdapter.write(out, clone); + } + }.nullSafe(); + } +} |