GSON使用方法

转载网址：https://blog.youkuaiyun.com/sagomilk/article/details/51297472

GSON

basic

maven

<dependency>  
    <groupId>com.google.code.gson</groupId>  
    <artifactId>gson</artifactId>  
    <version>2.6.2</version>  
  </dependency> 

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fromJson，toJson sample

Gson gson = new Gson();
TargetType target = gson.fromJson(JSON_DATA_STRING, TargetType);
String targetString = gson.toJson(TargetObject);

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Custom

类型格式TypeToken

Type listType = new TypeToken<ArrayList<Person>>(){}.getType();

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时间输出格式

GsonBuilder builder = new GsonBuilder();
builder.setDateFormat("yyyy年MM月dd HH:mm:ss"); 
Gson gson = builder.create();

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别名

String JSON_DATA_STRING = {
    nick_name: "sagomilk"
}

public class Person {   
    @SerializedName("nick_name")
    public String name;
}

gson.fromJson(JSON_DATA_STRING, Person.class);

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支持null输出

Gson includeNullsGson = gsonBuilder.serializeNulls().create();

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禁用html转义

Gson unescapingGson = new GsonBuilder().disableHtmlEscaping().create();

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停用属性

transient String nickName;

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或者 static ，如果需要输出

import java.lang.reflect.Modifier;
Gson gson = new GsonBuilder()
    .excludeFieldsWithModifiers(Modifier.STATIC)
    .create();

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多版本支持

class VersionClass{
    @Since(1.0) 
    String versionOneField = "1.0";

    @Since(2.0) 
    String versionTwoField = "2.0";
}

Gson gson = new GsonBuilder().setVersion(1.0).create();

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Serializer

private class DateTimeSerializer implements JsonSerializer<DateTime> {
  public JsonElement serialize(DateTime src, Type typeOfSrc, JsonSerializationContext context) {
    return new JsonPrimitive(src.toString());
  }
}

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Deserializer

private class DateTimeDeserializer implements JsonDeserializer<DateTime> {
  public DateTime deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
      throws JsonParseException {
    return new DateTime(json.getAsJsonPrimitive().getAsString());
  }
}

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Serialization 和 Deserialization

GsonBuilder gson = new GsonBuilder();
gson.registerTypeAdapter(MyType2.class, new MyTypeAdapter());
gson.registerTypeAdapter(MyType.class, new MySerializer());
gson.registerTypeAdapter(MyType.class, new MyDeserializer());
gson.registerTypeAdapter(MyType.class, new MyInstanceCreator());

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Array

1. 直接解析成数组

   Person[] foos = gson.fromJson(JSON_DATA_STRING, Person[].class);
   List<Person> fooList = Arrays.asList(foos);
   

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2. 解析成为List

   Type listType = new TypeToken<ArrayList<Person>>(){}.getType();
   ArrayList<Person> foos = gson.fromJson(JSON_DATA_STRING, listType);
   

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Other

Map

如果没有对应的Object class，可以直接使用Map.class,但是使用的时候需要执行转换

Map m = gson.fromJson(JSON_DATA_STRING, Map.class);

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命名风格setFieldNamingPolicy

 new GsonBuilder().setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_DASHES).create();

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美化

GsonBuilder gsonBuilder = new GsonBuilder();
Gson prettyGson = gsonBuilder.setPrettyPrinting().create();

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Streaming

FileWriter writer = new FileWriter("./data.json")) { 
gson.toJson(new Person(), writer);