小编ham*_*ack的帖子

我正在尝试使用Jackson 2.1.4将不可变的POJO与JSON序列化,而不必编写自定义序列化程序并尽可能少注释.我还想避免为了满足Jackson库而添加不必要的getter或默认构造函数.

我现在卡在异常上:

JsonMappingException:找不到类型[simple type,class Circle]的合适构造函数:无法从JSON对象实例化(需要添加/启用类型信息？)

代码:

public abstract class Shape {}


public class Circle extends Shape {
  public final int radius; // Immutable - no getter needed

  public Circle(int radius) {
    this.radius = radius;
  }
}


public class Rectangle extends Shape {
  public final int w; // Immutable - no getter needed
  public final int h; // Immutable - no getter needed

  public Rectangle(int w, int h) {
    this.w = w;
    this.h = h;
  }
}

测试代码:

ObjectMapper mapper …