杰克逊ObjectMapper设置JsonFormat.Shape.ARRAY不带注释 [英] Jackson ObjectMapper set JsonFormat.Shape.ARRAY without annotation

问题描述

我需要使用两个杰克逊2对象映射器. 两个映射器都使用相同的类集. 首先，我需要使用标准序列化. 在第二个中，我想对所有类使用ARRAY形状类型(请参见

I need to use two jackson 2 object mappers. Both mappers work with the same set of classes. In the first I need to use standard serialization. In the second i want to use ARRAY shape type for all classes (see https://fasterxml.github.io/jackson-annotations/javadoc/2.2.0/com/fasterxml/jackson/annotation/JsonFormat.Shape.html#ARRAY).

但是我想为第二个ObjectMapper全局设置此功能.就像mapper.setShape(...)

But i want to global set this feature for my second ObjectMapper. Something like mapper.setShape(...)

该怎么做?

UPD:

我找到了一种覆盖该类配置的方法:

I found a way to override the config for the class:

mapper.configOverride(MyClass.class)
   .setFormat(JsonFormat.Value.forShape(JsonFormat.Shape.ARRAY));

因此，我可以使用Reflection API更改所有类.

So I can change for all my classes using Reflection API.

令人尴尬的是我覆盖了全局设置，但是我不能直接设置它.

It is embarrassing that I override the global setting, but I can not directly set it.

推荐答案

由于@JsonFormat注释在字段上有效，因此无法在全局级别将其设置为Shape.Array.这意味着所有字段都将被序列化并反序列化为数组值(想象一下，如果一个字段已经是一个列表，在这种情况下，它将被包装到另一个我们可能不想要的列表中).

As @JsonFormat annotation works on field, you can't set it to Shape.Array at global level. This would mean all the fields would be serialized and deserialised into array values (imagine if a field is already a list, in this case, it will be wrapped into another list which is something we might not want).

但是，您可以为类型(将值转换为数组)编写自己的serializer并在ObjectMapper中对其进行配置，例如:

You can however, write your own serializer for a type (that converts a value into an array) and configure it in ObjectMapper, e.g.:

class CustomDeserializer extends JsonSerializer<String>{

    @Override
    public void serialize(String value, JsonGenerator gen, SerializerProvider serializers)
            throws IOException, JsonProcessingException {
        gen.writeStartArray();
        gen.writeString(value);
        gen.writeEndArray();
    }
}

并将其配置为ObjectMaper实例，例如:

And configure it to ObjectMaper instance, e.g.:

ObjectMapper mapper = new ObjectMapper();
SimpleModule module = new SimpleModule();
module.addSerializer(String.class, new CustomDeserializer());
mapper.registerModule(module);

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