创建一个类型意识的杰克逊解串器

Question

我想配置一个杰克逊解串器，根据注释字段的目标类型采取不同的行为。

public class Car { 
    @JsonSerialize(using=IdSerializer.class) 
    @JsonDeserialize(using=IdDeserializer.class) 
    String id 
} 

public class Bus { 
    @JsonSerialize(using=IdSerializer.class) 
    @JsonDeserialize(using=IdDeserializer.class) 
    Id id 
} 

杰克逊串行知道从它被转换数据类型，所以这是工作：

public class IdSerializer extends JsonSerializer<Object> { 
    @Override 
    public void serialize(Object value, JsonGenerator jsonGen, SerializerProvider provider) throws IOException { 

     // value is the annotated field class 
     if(value instanceof String) 
      jsonGen.writeObject(...); 
     else if (value instanceof Id) 
      jsonGen.writeObject(...); 
     else 
      throw new IllegalArgumentException(); 
    } 
} 

杰克逊解串器似乎不知道目标类型分为它将数据转换：

public class IdDeserializer extends JsonDeserializer<Object> { 
    @Override 
    public Object deserialize(JsonParser jp, DeserializationContext context) throws IOException { 

     // what is the annotated field class? 
    } 
} 

Answer 1

在序列化程序中，您可以添加有关在反序列化期间帮助您的类型的额外信息。从您发布的IdSerializer

大厦...

public class IdSerializer extends JsonSerializer<Object> { 

    @Override 
    public void serialize(Object value, JsonGenerator jsonGen, SerializerProvider provider) throws IOException { 

     // value is the annotated field class 
     if(value instanceof String){ 
      jsonGen.writeStartObject(); 
      jsonGen.writeFieldName("id"); 
      jsonGen.writeObject(value); 
      jsonGen.writeFieldName("type"); 
      jsonGen.writeString("String"); 
      jsonGen.writeEndObject(); 
     } 
     else if (value instanceof Id){ 
      Id id = (Id) value; 
      jsonGen.writeStartObject(); 
      jsonGen.writeFieldName("id"); 
      jsonGen.writeString(id.getStuff()); 
      jsonGen.writeFieldName("type"); 
      jsonGen.writeString("Id"); 
      jsonGen.writeEndObject(); 
     } 
     else{ 
      throw new IllegalArgumentException(); 
     } 
    } 
} 

在你解串器，您可以分析这种“类型”字段，并返回正确的 类型的对象。