jackson IOException:无法将类com.mycompany.models.Person $ Address(类型为非静态成员类)反序列化为Bean

Question

我有一个看起来像这样的课程:

public class Person {
    public class Address {
        private String line1;
        private String line2;
        private String zipCode;
        private String state;

        // standard public getters and setters for the class here
   }

private String name;
private String address;

// standard public getters and setters for the class here

}

这就是我如何使用杰克逊.

public class JsonTest {
    public static <T> Object fromJson(String jsonAsString, Class<T> pojoClass)
throws JsonMappingException, JsonParseException, IOException {
        return m.readValue(jsonAsString, pojoClass);
    }

    public static String toJson(Object pojo, boolean prettyPrint)
throws JsonMappingException, JsonGenerationException, IOException {
        StringWriter sw = new StringWriter();
        JsonGenerator jg = jf.createJsonGenerator(sw);
        if (prettyPrint) {
            jg.useDefaultPrettyPrinter();
        }
        m.writeValue(jg, pojo);
        return sw.toString();
    }

    public static void main(String[] args) {
         Person p = new Person();
         String json = this.toJson(p, true); // converts ‘p’ to JSON just fine
         Person personFromJson = this.fromJson(json, Person.class); // throws exception!!!
    }
}

main方法的第3行(我尝试将json转换为Person对象),抛出此异常:

IOException: Can not deserialize Class com.mycompany.models.Person$Address (of type non-static member class) as a Bean

我究竟做错了什么？

Answer 1

因为内部类没有默认的零参数构造函数(它们具有对外部/父类的隐藏引用),Jackson无法实例化它们.

解决方案是使用static内部类:

public class Outer {
    static class Inner {
        private String foo;
        public String getFoo() { return foo; }
    }
}

原答案:

实现中存在一些问题,似乎您无法序列化这些类,请参阅cowtowncoder了解详细信息.