Json转换利器Gson之实例六-注册TypeAdapter及处理Enum类型

枚举类型给我们的程序带来了好处,如何用Gson来实现与Json的互转呢?请看本文.

本文重点掌握如何自己写一个TypeAdapter及注册TypeAdapter和处理Enum类型.

实体类:

public enum PackageState { PLAY, UPDATE, UPDATING, DOWNLOAD, DOWNLOADING, }
public class PackageItem { private String name; private PackageState state; private String size; public String getName() { return name; } public void setName(String name) { this.name = name; } public PackageState getState() { return state; } public void setState(PackageState state) { this.state = state; } public String getSize() { return size; } public void setSize(String size) { this.size = size; } @Override public String toString() { return "PackageItem [name=" + name + ", size=" + size + ", state=" + state + "]"; } }
自己写一个转换器实现JsonSerializer<T>接口和jsonDeserializer<T>接口:

mport java.lang.reflect.Type; import com.google.gson.JsonDeserializationContext; import com.google.gson.JsonDeserializer; import com.google.gson.JsonElement; import com.google.gson.JsonParseException; import com.google.gson.JsonPrimitive; import com.google.gson.JsonSerializationContext; import com.google.gson.JsonSerializer; public class EnumSerializer implements JsonSerializer<PackageState>, JsonDeserializer<PackageState> { // 对象转为Json时调用,实现JsonSerializer<PackageState>接口 @Override public JsonElement serialize(PackageState state, Type arg1, JsonSerializationContext arg2) { return new JsonPrimitive(state.ordinal()); } // json转为对象时调用,实现JsonDeserializer<PackageState>接口 @Override public PackageState deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException { if (json.getAsInt() < PackageState.values().length) return PackageState.values()[json.getAsInt()]; return null; } } 测试类:
import com.google.gson.Gson; import com.google.gson.GsonBuilder; public class GsonTest6 { public static void main(String[] args) { GsonBuilder gsonBuilder = new GsonBuilder(); gsonBuilder.registerTypeAdapter(PackageState.class, new EnumSerializer()); Gson gson = gsonBuilder.create(); PackageItem item = new PackageItem(); item.setName("item_name"); item.setSize("500M"); item.setState(PackageState.UPDATING);// 这个 state是枚举值 String s = gson.toJson(item); System.out.println(s); System.out.println("--------------------------------"); PackageItem retItem = gson.fromJson(s, PackageItem.class); System.out.println(retItem); } }

输出结果(结果中已经将state的对应枚举类型转为了int类型):

{"name":"item_name","state":2,"size":"500M"} -------------------------------- PackageItem [name=item_name, size=500M, state=UPDATING]

Json转换利器Gson之实例一-简单对象转化和带泛型的List转化 (http://blog.csdn.net/lk_blog/article/details/7685169)
Json转换利器Gson之实例二-Gson注解和GsonBuilder (http://blog.csdn.ne