Jackson - 将属性序列化/反序列化为JSON值 [英] Jackson - serialize/deserialize property as JSON value

问题描述

使用Jackson 2，我正在寻找一种泛型方式将对象序列化为单个值（然后将它们序列化，以后只填充该单个字段），而不必重复创建JsonSerializer / JsonDeserializer处理每个案例。 @JsonIdentityInfo注释非常接近但是稍微错过了标记，因为据我所知，它将始终在第一次出现时序列化完整的子对象。

Using Jackson 2, I'm looking for a generic way to be serialize objects as a single value (then serialize them back later populating only that single field) without having to repetitively create a JsonSerializer / JsonDeserializer to handle each case. The @JsonIdentityInfo annotation comes pretty close but misses the mark a little bit since, as far as I can tell, it will always serialize the full child object on the first occurrence.

以下是我想要做的一个例子。给出类：

Here is an example of what I want to do. Given the classes:

class Customer {

    Long id = 99;
    String name = "Joe"; 
    // Lots more properties
}

class Order {
    String orderNum = "11111"
    @WhateverAnnotationsINeedHereToDoWhatIWant
    Customer customer;
}

我希望订单序列化为（或者我完全可以接受） ）：

I would like Order to serialize as either (either would be perfectly acceptable to me):

{"orderNum":"11111", "customer":"99"}
{"orderNum":"11111", "customer":{"id":99}}

@JsonIdentityInfo确实使得在客户端处理更加困难（我们可以假设客户知道如何将客户ID映射回完整的客户信息）。

What @JsonIdentityInfo does makes it more difficult to deal with on the client-side (we can assume that the client knows how to map the customer ID back into the full customer information).

对于显示的第二个JSON，@ JsonIgnoreProperties也可能非常接近，但这意味着我必须选择退出一切，而不是我想要的那个。

@JsonIgnoreProperties could also come pretty close for the second JSON shown but would mean I would have to opt-out of everything but the one I want.

当我反序列化时，我只希望客户仅使用id字段进行初始化。

When I deserialize back I would just want the Customer to be initialzed with the "id" field only.

任何神奇的方式来做到这一点我没有进入杰克逊的内心深处？据我所知，JsonDeserializer / JsonSerializer没有关于父级的上下文信息，因此似乎没有一种简单的方法来创建@JsonValueFromProperty（id）类型Jackson Mix-in然后只看一下该注释定制的Serializer / Deserializer。

Any magic way to do this that I'm missing without getting into the soupy internals of Jackson? As far as I can tell, JsonDeserializer/JsonSerializer has no contextual information on the parent so there doesn't seem to be an easy way to create a @JsonValueFromProperty("id") type Jackson Mix-in then just look at that annotation in the custom Serializer/Deserializer.

任何想法都将不胜感激。谢谢！

Any ideas would be greatly appreciated. Thanks!

推荐答案

我曾经需要对每种不同类型的请求返回的JSON进行细粒度控制，恐怕我已经结束了使用自定义序列化程序和反序列化程序。

I once needed fine-grained control over the JSON returned per different type of request, and I am afraid I ended up using custom Serializers and Deserializers.

一个简单的替代方法是将@JsonIgnore添加到Order的Customer字段，并将以下getter添加到Order：

A simple alternative would be adding @JsonIgnore to the Customer field of Order and add the following getter to Order:

@JsonProperty("customer")
public Long getCustomerId(){
  if (customer != null){
    return customer.getId();
  }
  else {
    return null;
  }
}

返回的JSON将是：

{"orderNum":"11111", "customer":"99"}

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