使用继承的自定义 JsonDeserializer 导致 StackOverflowError

Question

我在使用自定义 JsonDeserializer 时遇到问题。我正在尝试根据 Rest 服务调用接收到的 JSON 消息来使用抽象类的不同实现（如果数据是一个Array使用的，如果它是String另一个使用）：

@Path("/rest/cipher")
public interface CipherManager {

    @POST
    @Consumes("application/json")
    @Produces("application/json")
    @Path("/encrypt")
    public Response cipher(AbstractCipherRequestBean jsonRequestData);
}

解串器看起来像这样：

public class CipherRequestDeserializer extends JsonDeserializer<AbstractCipherRequestBean> {

@Override
public AbstractCipherRequestBean deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException, JsonProcessingException {
    ObjectMapper mapper = (ObjectMapper) jp.getCodec();
    ObjectNode root = (ObjectNode) mapper.readTree(jp);
    Class<? extends AbstractCipherRequestBean> abstractCipherRequestBeanClass = null;
    Iterator<Entry<String, JsonNode>> elementsIterator = root.getFields();
    while (elementsIterator.hasNext()) {
        Entry<String, JsonNode> element = elementsIterator.next();
        String name = element.getKey();
        if(name.equals("b64Data")){
            if(element.getValue().isArray()){
                abstractCipherRequestBeanClass = CipherMultRequestBean.class;
            }else{
                abstractCipherRequestBeanClass = CipherRequestBean.class;
            }
        }
    }
    if (abstractCipherRequestBeanClass == null){
        return null;
    }
    return mapper.readValue(root, abstractCipherRequestBeanClass);
}

}

继承如下：

public class RequestBean {
    protected String b64Data;
    ...
}

@JsonDeserialize(using = CipherRequestDeserializer.class)
public abstract class AbstractCipherRequestBean extends RequestBean{
    ...
}

public class CipherRequestBean extends AbstractCipherRequestBean{
    ...
}

public class CipherMultRequestBean extends AbstractCipherRequestBean {
    private List<String> b64Data;
    ...
}

我相信，由于两个实现都继承了@JsonDeserialize注释，因此每次调用都会再次mapper.readValue(root, abstractCipherRequestBeanClass)调用该deserialize方法，并以 StackOverflowError 结束。

有没有办法避免这种情况？因为最后我mapper用一个实际的类调用，我认为它会使用默认mapper实现，而不是CipherRequestDeserializer一个。

Answer 1

我终于找到了解决方案。像这样注释我的两个子类就足够了：

@JsonDeserialize(as = CipherRequestBean.class)
public class CipherRequestBean extends AbstractCipherRequestBean{
...
}

@JsonDeserialize(as = CipherMultRequestBean.class)
public class CipherMultRequestBean extends AbstractCipherRequestBean {
private List<String> b64Data;
...
}