杰克逊序列化：如何忽略超类属性

问题描述

我想序列化一个不受我控制的POJO类，但希望避免序列化来自超类的任何属性，而不是来自最终类。示例：

I want to serialize a POJO class which is not under my control, but want to avoid serializing any of the properties which are coming from the superclass, and not from the final class. Example:

public class MyGeneratedRecord extends org.jooq.impl.UpdatableRecordImpl<...>,
    example.generated.tables.interfaces.IMyGenerated {
  public void setField1(...);
  public Integer getField1();

  public void setField2(...);
  public Integer getField2();
...
}

您可以从示例中猜出这是class是由JOOQ生成的，并且继承自复杂的基类UpdatableRecordImpl，它也有一些类似bean属性的方法，这会在序列化过程中引起问题。另外，我有几个类似的类，所以最好避免为我生成的所有POJO重复相同的解决方案。

You can guess from the example that that this class is generated by JOOQ, and inherits from a complex base class UpdatableRecordImpl which also has some bean property-like methods, which cause problems during the serialization. Also, I have several similar classes, so it would be good to avoid duplicating the same solution for all of my generated POJOs.

到目前为止，我找到了以下可能的解决方案：

I have found the following possible solutions so far:

• 使用mixin技术忽略来自超类的特定字段，如下所示：

这个问题是如果基类发生了变化（例如，一个新的getAnything（）方法出现在它中），它可能会破坏我的实现。

The problem with this is that if the base class changes (e.g., a new getAnything() method appears in it), it can break my implementation.

实现自定义序列化程序并在那里处理问题。这对我来说似乎有点矫枉过正。

implement a custom serializer and handle the issue there. This seems a bit overkill to me.

顺便提一句，我有一个界面，它描述了我想要序列化的属性，也许我可以混合@JsonSerialize（ as = IMyGenerated.class）注释......？我可以将它用于我的目的吗？

as incidentally I have an interface which describes exactly the properties I want to serialize, maybe I can mixin a @JsonSerialize(as=IMyGenerated.class) annotation...? Can I use this for my purpose?

但是，从纯粹的设计角度来看，最好的是能够告诉杰克逊我只想序列化最后一个类的属性，并忽略所有继承的属性。有没有办法做到这一点？

But, from pure design point of view, the best would be to be able to tell jackson that I want to serialize only the final class' properties, and ignore all the inherited ones. Is there a way to do that?

提前致谢。

推荐答案

您可以注册一个自定义的，它将忽略来自特定超级的所有属性类型。下面是一个示例：

You can register a custom Jackson annotation intropector which would ignore all the properties that come from the certain super type. Here is an example:

public class JacksonIgnoreInherited {

    public static class Base {
        public final String field1;

        public Base(final String field1) {
            this.field1 = field1;
        }
    }

    public static class Bean extends Base {
        public final String field2;

        public Bean(final String field1, final String field2) {
            super(field1);
            this.field2 = field2;
        }
    }

    private static class IgnoreInheritedIntrospector extends JacksonAnnotationIntrospector {
        @Override
        public boolean hasIgnoreMarker(final AnnotatedMember m) {
            return m.getDeclaringClass() == Base.class || super.hasIgnoreMarker(m);
        }
    }

    public static void main(String[] args) throws JsonProcessingException {
        final ObjectMapper mapper = new ObjectMapper();
        mapper.setAnnotationIntrospector(new IgnoreInheritedIntrospector());
        final Bean bean = new Bean("a", "b");
        System.out.println(mapper
                        .writerWithDefaultPrettyPrinter()
                        .writeValueAsString(bean));
    }

}

输出：

{
field2：b
}

{ "field2" : "b"}

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