如何使用Gson结合实体类解析含其他数据类型的JSON数组

待解析的JSON结构 #

{
 "results": [
    {
      "c": 75.0875,
      "h": 75.15,
      "l": 73.7975,
      "n": 1,
      "o": 74.06,
      "t": 1577941200000,
      "v": 135647456,
      "vw": 74.6099
    },
    {
      "c": 74.3575,
      "h": 75.145,
      "l": 74.125,
      "n": 1,
      "o": 74.2875,
      "t": 1578027600000,
      "v": 146535512,
      "vw": 74.7026
    }
  ],
  "status": "OK",
  "ticker": "AAPL"
}

现有代码与问题 #

主类代码 #

Transcript transcript = new Transcript();
Gson gson = new Gson();
// HTTP Requests here
transcript = gson.fromJson(getResponse.body(), Transcript.class);
// "status" verification
System.out.println(transcript.getResults());

Transcript类（错误写法） #

public class Transcript {
    public Type results = new TypeToken<ArrayList<DataObject>>(){}.getType();
    public String ticker = "AAPL";
    public String status;

    // Getters and setters too
}

DataObject类（错误写法） #

public class DataObject {
    public String tag;
    public double value;

    public DataObject(String tag, double value){
        this.tag = tag;
        this.value = value;
    }

    public String toString() {
        return "tag = " + tag + ", value = " + value;
    }
}

遇到的错误 #

• 当前核心错误：

  Caused by: com.google.gson.JsonIOException: Interfaces can't be instantiated! Register an InstanceCreator or a TypeAdapter for this type. Interface name: java.lang.reflect.Type

• 将字段改为private时的错误：

  com.google.gson.JsonIOException: Failed making field 'piemanray314.testingjavafx.testingjavafx.Transcript#results' accessible; either increase its visibility or write a custom TypeAdapter for its declaring type.

正确解决方案 #

1. 修正DataObject类 #

JSON的results数组内对象的字段是c、h、l等，需将DataObject字段名与JSON严格对应，同时保留无参构造（Gson依赖它实例化对象）：

public class DataObject {
    public double c;
    public double h;
    public double l;
    public int n;
    public double o;
    public long t;
    public long v;
    public double vw;

    // 必须保留无参构造
    public DataObject() {}

    @Override
    public String toString() {
        return "c=" + c + ", h=" + h + ", l=" + l + ", n=" + n + ", o=" + o + ", t=" + t + ", v=" + v + ", vw=" + vw;
    }
}

2. 修正Transcript类 #

直接用List<DataObject>声明results字段，无需使用Type类型，同时规范字段访问权限：

import java.util.List;

public class Transcript {
    private List<DataObject> results;
    private String ticker;
    private String status;

    // 无参构造（建议保留）
    public Transcript() {}

    // Getter/Setter方法，供外部访问私有字段
    public List<DataObject> getResults() {
        return results;
    }

    public void setResults(List<DataObject> results) {
        this.results = results;
    }

    public String getTicker() {
        return ticker;
    }

    public void setTicker(String ticker) {
        this.ticker = ticker;
    }

    public String getStatus() {
        return status;
    }

    public void setStatus(String status) {
        this.status = status;
    }
}

3. 主类代码调整 #

原有主类代码可直接使用，Gson会自动完成解析：

Gson gson = new Gson();
// 假设getResponse.body()为JSON字符串或Reader类型
Transcript transcript = gson.fromJson(getResponse.body(), Transcript.class);

// 验证解析结果
System.out.println("Status: " + transcript.getStatus());
System.out.println("Ticker: " + transcript.getTicker());
System.out.println("Results:");
for (DataObject obj : transcript.getResults()) {
    System.out.println(obj);
}

4. 私有字段的访问处理 #

若使用私有字段，可通过两种方式让Gson正常赋值：

• 保留上述Getter/Setter方法，Gson会自动调用Setter赋值
• 配置Gson并添加注解，示例如下：

// 主类中配置Gson
Gson gson = new GsonBuilder()
        .setFieldNamingPolicy(FieldNamingPolicy.IDENTITY)
        .excludeFieldsWithoutExposeAnnotation()
        .create();

同时在实体类私有字段上添加@Expose注解：

import com.google.gson.annotations.Expose;

public class Transcript {
    @Expose
    private List<DataObject> results;
    @Expose
    private String ticker;
    @Expose
    private String status;

    // Getter/Setter方法...
}

内容的提问来源于stack exchange，提问作者Piemanray314