java - 从 json 字符串解析时未调用对象构造函数

Question

为什么没有调用 IACircle 构造函数？
这就是我加载 Json 的方式..

BufferedReader br = new BufferedReader(in);
LevelDefinition ld = new Gson().fromJson(br, LevelDefinition.class);

Json 字符串..

{
    "iaCircles": [
        {
            "x": -32.0,
            "y": -5.0,
            "angle": 0.0,
            "radius": 2.5,
            "density": 0.0,
            "friction": 0.0,
            "restitution": 1.0,
            "textureSelection": "CIRCLE",
            "inflictsDamage": true,
            "fixedRotation":true
        },
        {
            "x": 55.0,
            "y": -5.0,
            "angle": 0.0,
            "radius": 2.5,
            "density": 0.0,
            "friction": 0.0,
            "restitution": 1.0,
            "textureSelection": "CIRCLE",
            "inflictsDamage": true,
            "fixedRotation":true
        }
    ]
}

Java 类解析为 ..

public class LevelDefinition {

    private Vector<IACircle> iaCircles;
}

IACircle 定义..

public class IACircle {
    public IACircle (
        float x, float y, float angle, float radius,
        float density, float friction, float restitution,
        String textureSelection, boolean inflictsDamage, boolean fixedRotation) { 
        System.out.println("constructor called, circle");
    }
}

Answer 1

您应该为您的类定义默认的无参数构造函数。 GSON 仅调用无参数构造函数来初始化类。你有一个带参数的构造函数，这就是它不被调用的原因；它创建一个ObjectConstructor来初始化。试试这个:

public class IACircle {
    public IACircle () { 
        System.out.println("constructor called, circle");
    }
}