杰克逊仅使用字段名称对响应进行排序 [英] jackson to sort the response by using the field name alone

问题描述

我有几个pojo课程. 使用Jackson的@JsonUnwrapped批注省略了类名，但属性未按我的期望排序.

I have several pojo classes. The used the Jackson @JsonUnwrapped annotation to omit the class name but the properties are not sorting how I expect.

例如:

class a {
    @JsonUnwrapped
    B b;
    int c;
    //getters and setters
}

class B {
    int a;
    int d;
    // getters and setters
}

我的实际回答是:

{
c:1
a:2
d:2
}

但是我的预期答复是:

{
a:2
c:1
d:2
}

如何使响应中的字段按名称排序?

How can make it so that the fields in the response are sorted by name?

推荐答案

这有点棘手，因为Jackson将未包装对象的所有属性的序列化组合在一起. @JsonPropertyOrder注释无法覆盖此行为，因为它在未包装的字段上起作用，而不是字段的属性.解决方法是，您可以将对象序列化为中间的Map，自己对其进行排序，然后将其序列化为JSON，如下所示:

This is a bit tricky because Jackson groups the serialization of all properties of the unwrapped object together. The @JsonPropertyOrder annotation can't override this behavior because it works on the unwrapped field and not the field's properties. As a workaround, you can serialize the object to an intermediate Map, sort it yourself, and then serialize it to JSON as follows:

ObjectMapper objectMapper = new ObjectMapper();
Map map = objectMapper.convertValue(new a(), Map.class);
SortedMap sortedMap = new TreeMap(map);
System.out.println(objectMapper.writeValueAsString(sortedMap));

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