如何通过键从gson对象获取值 [英] How to get a value from gson object by key

问题描述

我一直在尝试遵循这个解决方案

然而，它似乎没有道理。

我从一个字符串中定义一个新的gson对象：

字符串示例： http://api.soundrop.fm/spaces/XJTt3mXTOZpvgmOc

  public void convertToJson（）
 {
 Gson gson = new Gson（）; 
 Object gsonContent = gson.fromJson（stringContent，RadioContent.class）; 
} 
  

然后尝试并返回一个值：

  public Object getValue（String find）
 {
 return gsonContent.find; 
} 
  

最后将其命名为：

  public static void print（String find =title）
 {
 Object value = radioContent.getValue（find）; 
 
 System.out.println（value）; 
} 
  

然而，我收到一个错误：

  java：找不到符号
符号：变量find 
位置：变量gsonContent，类型为java.lang.Object 
  

完整课程：
主要课程： http://pastebin.com/v4LrZm6k
广播级： http：// pastebin.com/2BWwb6eD

解决方案

这是Java。根据对象引用的声明类型来解析字段。

根据你的编译器错误， gsonContent 是一个类型为 Object 的变量。 对象没有 find 字段。

您'已经告诉Gson什么类型的反序列化了，所以只要使 gsonContent 变量具有这种类型即可

  RadioContent gsonContent = gson.fromJson（stringContent，RadioContent.class）; 
  

另外，好像你在隐藏实例 gsonContent


---

您也可以执行以下操作：

  JsonObject jsonObject = gson.fromJson（stringContent，JsonObject.class）; 
 jsonObject.get（fieldName）; //为该名称返回一个JsonElement 
  

I have been trying to follow along with this solution How to find specified name and its value in JSON-string from Java?

However it does not seem to make sense.

I define a new gson object from a string:

Example of string here: http://api.soundrop.fm/spaces/XJTt3mXTOZpvgmOc

public void convertToJson()
{
    Gson gson = new Gson();
    Object gsonContent = gson.fromJson( stringContent, RadioContent.class );
}

And then try and return a value:

public Object getValue( String find )
{
    return gsonContent.find;
}

Finally its called with:

public static void print( String find = "title" )
{
    Object value = radioContent.getValue( find );

    System.out.println( value );
}

However I am getting an error:

java: cannot find symbol
  symbol:   variable find
  location: variable gsonContent of type java.lang.Object

Full classes: Main class: http://pastebin.com/v4LrZm6k Radio class: http://pastebin.com/2BWwb6eD

解决方案

This is Java. Fields are resolved based on the declared type of the object reference.

Based on your compiler error, gsonContent is a variable of type Object. Object does not have a find field.

You're already telling Gson what type to deserialize to, so just make the gsonContent variable be of that type

RadioContent gsonContent = gson.fromJson( stringContent, RadioContent.class );

Also, it seems like you are shadowing the instance gsonContent field with a local variable.

---

You can do the following as well

JsonObject jsonObject = gson.fromJson( stringContent, JsonObject.class);
jsonObject.get(fieldName); // returns a JsonElement for that name

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