用Gson解析JSON地图/字典？ [英] Parsing JSON maps / dictionaries with Gson?

问题描述

$ b

  {key1：value1，
key2：value2，
key3：
 {childKey1：childValue1，
childKey2：childValue2，
childKey3： childValue3} 
} 
 
 class Egg {
 @SerializedName（key1）
 private String mKey1; 
 
 @SerializedName（key2）
 private String mKey2; 
 
 @SerializedName（key3）
 // ??? 
} 
  

我正在阅读Gson文档，但无法弄清楚如何正确反序列化一个字典到一个地图。

解决方案

Gson很容易处理带有名称：值对的JSON对象的反序列化成Java Map 。

以下是使用原始问题中的JSON的一个示例。 （这个例子还演示了如何使用 FieldNamingStrategy 来避免为​​每个字段指定序列化名称，前提是字段到元素的名称映射是一致的。）

  import java.io.FileReader; 
 import java.lang.reflect.Field; 
 import java.util.Map; 
 
 import com.google.gson.FieldNamingStrategy; 
 import com.google.gson.Gson; 
 import com.google.gson.GsonBuilder; 
 $ b $ public class Foo 
 {
 public static void main（String [] args）throws Exception 
 {
 GsonBuilder gsonBuilder = new GsonBuilder（）; 
 gsonBuilder.setFieldNamingStrategy（new MyFieldNamingStrategy（））; 
 Gson gson = gsonBuilder.create（）; 
 egg egg = gson.fromJson（new FileReader（input.json），Egg.class）; 
 System.out.println（gson.toJson（egg））; 
} 
} 
 
 class Egg 
 {
 private String mKey1; 
 private String mKey2; 
私人地图< String，String> mKey3; 
} 
 
 class MyFieldNamingStrategy实现FieldNamingStrategy 
 {
 //将Java字段名转换为其JSON元素名称表示形式。 
 @Override 
 public String translateName（Field field）
 {
 String name = field.getName（）; 
 char newFirstChar = Character.toLowerCase（name.charAt（1））; 
返回newFirstChar + name.substring（2）; 
} 
} 
  

I need to parse a JSON Response that looks like:

{"key1": "value1", 
 "key2": "value2", 
 "key3": 
    {"childKey1": "childValue1", 
     "childKey2": "childValue2", 
     "childKey3": "childValue3" }
}

class Egg { 
    @SerializedName("key1")
    private String mKey1;

    @SerializedName("key2")
    private String mKey2;

    @SerializedName("key3")
    // ???
}

I'm reading through the Gson docs but cannot figure out how to properly deserialize a dictionary to a Map.

解决方案

Gson readily handles deserialization of a JSON object with name:value pairs into a Java Map.

Following is such an example using the JSON from the original question. (This example also demonstrates using a FieldNamingStrategy to avoid specifying the serialized name for every field, provided that the field-to-element name mapping is consistent.)

import java.io.FileReader;
import java.lang.reflect.Field;
import java.util.Map;

import com.google.gson.FieldNamingStrategy;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

public class Foo
{
  public static void main(String[] args) throws Exception
  {
    GsonBuilder gsonBuilder = new GsonBuilder();
    gsonBuilder.setFieldNamingStrategy(new MyFieldNamingStrategy());
    Gson gson = gsonBuilder.create();
    Egg egg = gson.fromJson(new FileReader("input.json"), Egg.class);
    System.out.println(gson.toJson(egg));
  }
}

class Egg
{
  private String mKey1;
  private String mKey2;
  private Map<String, String> mKey3;
}

class MyFieldNamingStrategy implements FieldNamingStrategy
{
  //Translates the Java field name into its JSON element name representation.
  @Override
  public String translateName(Field field)
  {
    String name = field.getName();
    char newFirstChar = Character.toLowerCase(name.charAt(1));
    return newFirstChar + name.substring(2);
  }
}

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