【转】 Json转换利器Gson之实例五-注册TypeAdapter及处理Enum类型

枚举类型给咱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.

本文重点掌握如何本身写一个TypeAdapter及注册TypeAdapter和处理Enum类型.

实体类:

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public enum PackageState {     PLAY, UPDATE, UPDATING, DOWNLOAD, DOWNLOADING, }

　

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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 + "]";     } }

　本身写一个转换器实现JsonSerializer<T>接口和jsonDeserializer<T>接口:

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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:

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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):

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

　　

分类: JSP

标签: Enum, Gson, json, TypeAdapter, 实例