Jackson objectMapper使用多种配置

Question

我有两个类：A类，其中包含B类。我需要将json解组为A类，但我需要A类具有一组反序列化特性，而类B具有一组不同的特性。有可能吗？最好的方法是什么？Thx！

Answer 1

实际上，如果您想在每次调用的基础上更改SerializationFeature或DeserializationFeature，您不希望使用ObjectMapper中的方法，而是像这样构造ObjectReader和/或ObjectWriter：

static final ObjectMapper mapper = ...; // only create once, acts as factor
// later on
byte[] json = mapper.writer(SerializationFeature.INDENT_OUTPUT)
    .without(SerializationFeature. WRAP_EXCEPTIONS)
    .writeValueAsBytes(value);
MyType result = mapper.readerFor(MyType.class)
    .with(DeserializationFeature.UNWRAP_ROOT_VALUE)
    // and more 'with' or 'without' calls
    readValue(json);

请注意，尽管ObjectMapper的构造是昂贵的，并且实例绝对需要重用，但ObjectReader和ObjectWriter的构造是廉价的，并且意味着在每次读/写的基础上进行。因此，虽然它们可以重用（实例是完全线程安全的、不可变的），但不一定有太多需求。

Answer 2

最终，我为内部类型定义了自己的反序列化程序，并在内部定义了自己新的静态ObjectMapper来保存所需的配置，从而解决了这个问题。

public ObjectMapper MyObjectMapper() {
    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper            
            .setAnnotationIntrospector(new JaxbAnnotationIntrospector(TypeFactory.defaultInstance()))           
    SimpleModule simpleModule = new SimpleModule("PostSurveyModule", Version.unknownVersion());
    simpleModule.addDeserializer(MyInnerObject.class, new MyInnerObjectDeserializer());
    objectMapper.registerModule(simpleModule);
    return objectMapper;
}
public static class MyInnerObjectDeserializer extends JsonDeserializer<MyInnerObject> {
    static ObjectMapper objectMapper = new ObjectMapper();
    static {
        objectMapper                
                .setVisibilityChecker(objectMapper.getDeserializationConfig().getDefaultVisibilityChecker()
                .withGetterVisibility(JsonAutoDetect.Visibility.PUBLIC_ONLY));
        objectMapper.addMixInAnnotations(MyInnerObject.class, MyInnerObjectMixin.class); //some mixin to add
        
    }   
    @Override
    public MyInnerObject deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException, JsonProcessingException {
        MyInnerObject myInnerObject = objectMapper.readValue(jp, MyInnerObject.class);
        return myInnerObject;
    }
}