Không chắc chắn nếu điều này là những gì bạn đã yêu cầu , nhưng bằng cách sửa đổi lớp RuntimeTypeAdapterFactory, tôi đã tạo một hệ thống cho phân lớp dựa trên các điều kiện trong nguồn Json. RuntimeTypeAdapterFactory.class:
/*
* 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 java.io.IOException;
import java.util.LinkedHashMap;
import java.util.Map;
import com.google.gson.Gson;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParseException;
import com.google.gson.JsonPrimitive;
import com.google.gson.TypeAdapter;
import com.google.gson.TypeAdapterFactory;
import com.google.gson.internal.Streams;
import com.google.gson.reflect.TypeToken;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonWriter;
/**
* 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 RuntimeTypeAdapter} 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
* RuntimeTypeAdapter<Shape> shapeAdapter
* = RuntimeTypeAdapter.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
* shapeAdapter.registerSubtype(Rectangle.class, "Rectangle");
* shapeAdapter.registerSubtype(Circle.class, "Circle");
* shapeAdapter.registerSubtype(Diamond.class, "Diamond");
* }</pre>
* Finally, register the type adapter in your application's GSON builder:
* <pre> {@code
* Gson gson = new GsonBuilder()
* .registerTypeAdapter(Shape.class, shapeAdapter)
* .create();
* }</pre>
* Like {@code GsonBuilder}, this API supports chaining: <pre> {@code
* RuntimeTypeAdapter<Shape> shapeAdapter = RuntimeTypeAdapterFactory.of(Shape.class)
* .registerSubtype(Rectangle.class)
* .registerSubtype(Circle.class)
* .registerSubtype(Diamond.class);
* }</pre>
*/
public final class RuntimeTypeAdapterFactory<T> implements TypeAdapterFactory {
private final Class<?> baseType;
private final RuntimeTypeAdapterPredicate predicate;
private final Map<String, Class<?>> labelToSubtype = new LinkedHashMap<String, Class<?>>();
private final Map<Class<?>, String> subtypeToLabel = new LinkedHashMap<Class<?>, String>();
private RuntimeTypeAdapterFactory(Class<?> baseType, RuntimeTypeAdapterPredicate predicate) {
if (predicate == null || baseType == null) {
throw new NullPointerException();
}
this.baseType = baseType;
this.predicate = predicate;
}
/**
* 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, RuntimeTypeAdapterPredicate predicate) {
return new RuntimeTypeAdapterFactory<T>(baseType, predicate);
}
/**
* 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<T>(baseType, null);
}
/**
* 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());
}
public <R> TypeAdapter<R> create(Gson gson, TypeToken<R> type) {
if (type.getRawType() != baseType) {
return null;
}
final Map<String, TypeAdapter<?>> labelToDelegate
= new LinkedHashMap<String, TypeAdapter<?>>();
final Map<Class<?>, TypeAdapter<?>> subtypeToDelegate
= new LinkedHashMap<Class<?>, TypeAdapter<?>>();
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 = Streams.parse(in);
String label = predicate.process(jsonElement);
@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 { // Unimplemented as we don't use write.
/*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 (jsonObject.has(typeFieldName)) {
throw new JsonParseException("cannot serialize " + srcType.getName()
+ " because it already defines a field named " + typeFieldName);
}
JsonObject clone = new JsonObject();
clone.add(typeFieldName, new JsonPrimitive(label));
for (Map.Entry<String, JsonElement> e : jsonObject.entrySet()) {
clone.add(e.getKey(), e.getValue());
}*/
Streams.write(null, out);
}
};
}
}
RuntimeTypeAdapterPredicate.class:
package com.google.gson.typeadapters;
import com.google.gson.JsonElement;
/**
* Created by Johan on 2014-02-13.
*/
public abstract class RuntimeTypeAdapterPredicate {
public abstract String process(JsonElement element);
}
Ví dụ (lấy từ một dự án tôi hiện đang làm việc trên):
ItemTypePredicate.class:
package org.libpoe.serial;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.typeadapters.RuntimeTypeAdapterPredicate;
/**
* Created by Johan on 2014-02-13.
*/
public class ItemTypePredicate extends RuntimeTypeAdapterPredicate {
@Override
public String process(JsonElement element) {
JsonObject obj = element.getAsJsonObject();
int frameType = obj.get("frameType").getAsInt();
switch(frameType) {
case 4: return "Gem";
case 5: return "Currency";
}
if (obj.get("typeLine").getAsString().contains("Map")
&& obj.get("descrText").getAsString() != null
&& obj.get("descrText").getAsString().contains("Travel to this Map")) {
return "Map";
}
return "Equipment";
}
}
Cách sử dụng:
RuntimeTypeAdapterFactory<Item> itemAdapter = RuntimeTypeAdapterFactory.of(Item.class, new ItemTypePredicate())
.registerSubtype(Currency.class)
.registerSubtype(Equipment.class)
.registerSubtype(Gem.class)
.registerSubtype(Map.class);
Gson gson = new GsonBuilder()
.enableComplexMapKeySerialization()
.registerTypeAdapterFactory(itemAdapter).create();
Lớp cơ sở hierachy là Mục. Tiền tệ, thiết bị, đá quý và bản đồ tất cả mở rộng này.
Nếu đây là một thành phần có mục đích chung, hãy nghĩ về cách bạn muốn người dùng định cấu hình nó. Mặc định hợp lý cũng đáng để suy nghĩ. Nó sẽ có ý nghĩa để có nhiều trường hợp bộ giải mã, một trong mỗi lớp học? – Jukka
Thats làm thế nào tôi làm điều này hiện nay, một ví dụ cho mỗi loại lớp. Vấn đề là người dùng thư viện của tôi bây giờ cần phải thực hiện các chi tiết nội bộ như bộ giải mã và bộ mã hóa và định cấu hình chúng vào mùa xuân mỗi khi một lớp mới được thêm vào. Tôi muốn tha cho họ và thay vào đó làm một dàn diễn viên đơn giản. – Abe