使用jackson反序列化json以更正子类类型

Question

将字符串反序列化为对象 ..ObjectMapper objectMapper = new ObjectMapper();objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);System.out.println(json); // Output is belowStatus status = new ObjectMapper().readValue(json, Status.class);ProcessingStage s = (ProcessingStage) status.getStages().get(0);// orDataStage s = (DataStage) status.getStages().get(0);产生这些错误..java.lang.ClassCastException: Stage cannot be cast to ProcessingStagejava.lang.ClassCastException: Stage cannot be cast to DataStage我如何使用 Jackson 将 的子类反序列Stage化为正确的实例类型？我期待status.stages包含：[DataStage, DataStage, ProcessingStage]，但看起来它包含：[Stage, Stage, Stage]。上面的输出System.out.println(json);..{  "stages":  [    {      "name":"Pre",      "order":1,      "data":      [        {          "id":"0688709c-17be-472a-bf5e-7d7b11bd8ccf"        }      ],    },    {      "name":"Processing",      "order":2,      "data":      [        {          "id":"ac3ecbb5-2aa6-4faf-b443-391472065219"        }      ],    },    {      "name":"Post",      "order":3,      "status":"not-started"    }  ]}Status.javaimport java.util.List;import com.fasterxml.jackson.annotation.JsonProperty;public class Status {    @JsonProperty("stages")    private List<Stage> stages;    public Status() {}    public List<Stage> getStages() {        return stages;    }    public void setStages(List<Stage> stages) {        this.stages = stages;    }}Stage.javaimport com.fasterxml.jackson.annotation.JsonIgnoreProperties;import com.fasterxml.jackson.annotation.JsonProperty;import com.fasterxml.jackson.annotation.JsonSubTypes;@JsonIgnoreProperties(ignoreUnknown = true)@JsonSubTypes({    @JsonSubTypes.Type(value = ProcessingStage.class, name = "ProcessingStage"),    @JsonSubTypes.Type(value = DataStage.class, name = "DataStage") })

Answer 1

您可以尝试先使用 instanceOf 评估对象的类

 if(status.getStages().get(0) instanceOf ProcessingStage) {

  ProcessingStage s = (ProcessingStage) status.getStages().get(0);

 }

或评估其他班级

DataStage