在杰克逊将 JSON 反序列化为 Class 中找不到类型 [simple type， class java.lang.

Question

要解析此 JSON 对象：

{"topology": [
{"id": "4cdbc040-657a-4847-b266-7e31d9e2c3d9","name": "PhysicalTOPO","layer": "datalink","nodes": null,"links": null,"sub-layer": "ethernet"},
{"id": "4acbd130-846b-3536-a142-8a42d8a3c4b8","name": "LogicalTOPO","layer": "ip","nodes": null,"links": null,"sub-layer": "ethernet"},
{"id": "9acbd139-946b-9536-a149-9a42d9a3c4b9","name": "NetworkTOPO","layer": "ip","nodes": null,"links": null,"sub-layer": "ethernet"}
]}

我创建了 VO 类和解析函数，如下所示：

public class TopologyVo extends Vo {
    @JsonProperty("topology")
    public Topology[] topology;
    //public List<Topology> topology; -- both have same exception
    public static class Topology extends Vo{
        @JsonProperty("id")
        public String id;
        @JsonProperty("name")
        public String name;
        @JsonProperty("layer")
        public String layer;
        @JsonProperty("nodes")
        public Object nodes; // it does not matter to map null to Object now
        @JsonProperty("links")
        public Object links;
        @JsonProperty("sub-layer")
        public String subLayer;
    }
}
// caller
...
TopologyVo vo = (TopologyVo)parse(content, TopologyVo.class);
...
public Object parse(String input, Class<?> mapClass) throws Exception {
    Object object = null;
    ObjectMapper mapper = new ObjectMapper();
    mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
    object = mapper.readValue(input, mapClass);
    return object;
}

导致异常：

com.fasterxml.jackson.databind.JsonMappingException: Can not find a (Map) Key deserializer for type [simple type, class java.lang.Class]
at com.fasterxml.jackson.databind.deser.DeserializerCache._handleUnknownKeyDeserializer(DeserializerCache.java:580)
at com.fasterxml.jackson.databind.deser.DeserializerCache.findKeyDeserializer(DeserializerCache.java:170)
at com.fasterxml.jackson.databind.DeserializationContext.findKeyDeserializer(DeserializationContext.java:404)
at com.fasterxml.jackson.databind.deser.std.MapDeserializer.createContextual(MapDeserializer.java:232)
at com.fasterxml.jackson.databind.DeserializationContext.handleSecondaryContextualization(DeserializationContext.java:572)
at com.fasterxml.jackson.databind.DeserializationContext.findContextualValueDeserializer(DeserializationContext.java:369)
at com.fasterxml.jackson.databind.deser.std.StdDeserializer.findDeserializer(StdDeserializer.java:697)
at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.resolve(BeanDeserializerBase.java:438)
at com.fasterxml.jackson.databind.deser.DeserializerCache._createAndCache2(DeserializerCache.java:294)
at com.fasterxml.jackson.databind.deser.DeserializerCache._createAndCacheValueDeserializer(DeserializerCache.java:243)
at com.fasterxml.jackson.databind.deser.DeserializerCache.findValueDeserializer(DeserializerCache.java:144)
at com.fasterxml.jackson.databind.DeserializationContext.findRootValueDeserializer(DeserializationContext.java:381)
at com.fasterxml.jackson.databind.ObjectMapper._findRootDeserializer(ObjectMapper.java:3095)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:2989)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2098)
at test.ApiTest.parse(ApiTest.java:195)

由于我的 VO 类中没有 Map，我不知道如何在类似问题的答案中实现"密钥反序列化器"（找不到类型 [simple type， class com.comcast.ivr.core.domain.AutoHandlingSlotKey] 的 （Map） 密钥反序列化器）。

这个问题是否来自VO中子类的数组（或列表/集合）？

Answer 1

这对我来说非常有效：

import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
public class Main {
    public static void main(String[] args) throws Exception {
        String jsonStr = "{"status": "OK","origin_addresses": [ "Vancouver, BC, Canada", "Seattle, État de Washington, États-Unis" ],"destination_addresses": [ "San Francisco, Californie, États-Unis", "Victoria, BC, Canada" ],"rows": [ {"elements": [ {"status": "OK","duration": {"value": 340110,"text": "3 jours 22 heures"},"distance": {"value": 1734542,"text": "1 735 km"}}, {"status": "OK","duration": {"value": 24487,"text": "6 heures 48 minutes"},"distance": {"value": 129324,"text": "129 km"}} ]}, {"elements": [ {"status": "OK","duration": {"value": 288834,"text": "3 jours 8 heures"},"distance": {"value": 1489604,"text": "1 490 km"}}, {"status": "OK","duration": {"value": 14388,"text": "4 heures 0 minutes"},"distance": {"value": 135822,"text": "136 km"}} ]} ]}";
        TopologyVo vo = (TopologyVo) parse(jsonStr, TopologyVo.class);
        System.out.println(vo);
    }
    public static Object parse(String input, Class<?> mapClass)
            throws Exception {
        Object object = null;
        ObjectMapper mapper = new ObjectMapper();
        mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES,
                false);
        object = mapper.readValue(input, mapClass);
        return object;
    }
}
class Vo {
}
class TopologyVo extends Vo {
    @JsonProperty("topology")
    public Topology[] topology;
    static class Topology extends Vo {
        @JsonProperty("id")
        public String id;
        @JsonProperty("name")
        public String name;
        @JsonProperty("layer")
        public String layer;
        @JsonProperty("nodes")
        public Object nodes; // it does not matter to map null to Object now
        @JsonProperty("links")
        public Object links;
        @JsonProperty("sub-layer")
        public String subLayer;
    }
}