java - 在java中使用fromJson时自动转换

Question

我有一个带有一些 int 参数的类，我正在尝试使用 fromJson 将一些值加载到此类中。当参数为自然数时效果很好，但当参数非自然数时抛出异常。

代码示例:

public class WebElemetsPoss{
    int screenWidth;
    int screenHeight;
    ...
}

Gson gson = new Gson();
// value = {"screenWidth":360,"screenHeight":519.894, .... }
WebElemetsPoss wep = gson.fromJson(value, WebElemetsPoss.class);

有没有办法在使用 fromJson 时执行从 double 到 int 的自动转换？

Answer 1

获得结果的最简单方法是使用一些辅助类:

public class WebElemetsPoss {
    int screenWidth;
    int screenHeight;

    public WebElemetsPoss(double screenWidth, double screenHeight) {
        this.screenWidth = (int)screenWidth;
        this.screenHeight = (int)screenHeight;
    }

    public WebElemetsPoss(DoubleLoader loader) {
        this(loader.screenWidth, this.screenHeight);
    }

    public static class DoubleLoader {
        double screenWidth;
        double screenHeight;
    }
}

....

Gson gson = new Gson();
WebElemetsPoss wep = new WebElemetsPoss(gson.fromJson(value, WebElemetsPoss.DoubleLoader.class));

另一种可能的解决方案是添加自定义类型适配器:

class WebElemetsPossAdapter extends TypeAdapter<WebElemetsPoss> {
    @Override
    public WebElemets read (JsonReader reader) throws IOException {
        int screenWidth = 0, screenHeight = 0;
        reader.beginObject();
        while (reader.hasNext()) {
            String name = reader.nextName();
            if (name.equals("screenWidth")) {
                screenWidth = (int)reader.nextDouble();
            } else if (name.equals("screenHeight")) {
                screenHeight = (int)reader.nextDouble();
            } else {
                reader.skipValue();
            }
        }
        reader.endObject();
        return new WebElemets(screenWidth, screenHeight);
    }

    @Override
    public void write(JsonWriter out, WebElemets value) throws IOException {
    }
}

//...

Gson gson = new GsonBuilder().registerTypeAdapter(WebElemetsPoss.class, new WebElemetsPossAdapter()).create();
//...