使用Jackson将json嵌入节点作为值反序列化为Map [英] Deserializing json embedded node as value into Map using Jackson
问题描述
亲爱的朋友，我需要你的建议。
Dear folks I need you advice.
我正在尝试为地图实现自定义 Jackson 反序列化器但有困难。作为输入数据，我有以下json：
I'm, trying to implement custom Jackson deserializer for maps but having difficulties with it. As an input data I have the following json:
{
"someMap": {
"one_value": "1",
"another_value: "2"
},
"anotherMap": "{\"100000000\": 360000,\"100000048\": 172800,\"100000036\": 129600,\"100000024\": 86400,\"100000012\": 43200}"
}
正如你在第二种情况下所看到的，它在节点值中有json映射（我是按照意图这样做的。因为我想要替换它来自env变量的值：anotherMap：$ {SOME_MAP： - {\100000000 \：360000，\100000048 \：172800，\100000036 \： 129600，\100000024 \：86400，\100000012 \：43200}}）。据我所知，我必须在两个地图反序列化流程之间进行区分。所以对于第一个地图我需要使用默认的一个地图反序列化器，第二个地图反序列化器，自定义的地图反序列化器从值中正确解析地图。我写这段代码的那一刻：
As you can see in the second case it has json map inside node value(I'm doing it in that way by intention. Because I want to replace the value from env variable: "anotherMap": "${SOME_MAP:-{\"100000000\": 360000,\"100000048\": 172800,\"100000036\": 129600,\"100000024\": 86400,\"100000012\": 43200}}"). As I understand I have to differentiate somehow between that 2 maps deserialization flows. So for the first map I need to use default one map deserializer for the second one the custom one to have properly parsed map from the value. At the moment I wrote that code to do that:
// invokation code
new ObjectMapper().registerModule(new ConfigModule()).readValue(is, ConfigModuleTestConfigWrapper.class);
// module code
public class ConfigModule extends SimpleModule {
@Override
public void setupModule(SetupContext context) {
super.setupModule(context);
context.addDeserializers(new Deserializers.Base() {
@Override
public JsonDeserializer<?> findMapDeserializer(MapType type, DeserializationConfig config, BeanDescription beanDesc,
KeyDeserializer keyDeserializer, TypeDeserializer elementTypeDeserializer,
JsonDeserializer<?> elementDeserializer) throws JsonMappingException {
return new MapPropertyDeserializer(type);
}
});
}
private static class MapPropertyDeserializer extends StdScalarDeserializer<Map<String, Integer>> {
MapPropertyDeserializer(MapType type) {
super(type);
}
@Override
public Map<String, Integer> deserialize(JsonParser p, DeserializationContext ctxt) throws IOException {
JsonNode node = p.readValueAsTree();
if (node == null || node.isContainerNode()) {
// return <default jackson deserializer>
}
System.out.println("isContainerNode ?: " + node.isContainerNode());
System.out.println("isValueNode ?: " + node.isValueNode());
// some parsing flow goes below
JsonNode valueNode = node.get(1);
valueNode.asText();
return new HashMap<>();
}
}
// bean description
@JsonIgnoreProperties
public class ConfigSubstitutorModuleTestConfigWrapper {
private final Map<String, String> someMap;
private final Map<String, Integer> anotherMap;
@JsonCreator
public ConfigSubstitutorModuleTestConfigWrapper(
@JsonProperty("someMap") Map<String, String> someMap,
@JsonProperty("anotherMap") Map<String, Integer> anotherMap
) {
this.someMap = someMap;
this.anotherMap = anotherMap;
}
public Map<String, String> getSomeMap() {
return someMap;
}
public Map<String, Integer> getAnotherMap() {
return anotherMap;
}
}
问题是（据我所知:) :)我不知道如何从deserialize方法返回默认的地图反序列化器。
The problem is(as I understand:)) that I don't know how to return default map deserializer from the deserialize method.
有没有人知道我能做些什么来达到预期的目标？
Does anybody have any clue what I could do there to achieve desired goal ?
推荐答案
最后接受解决方案来解决它：
1）创建反序列化器类：
1) Create deserializer class:
/**
* The target of that deserializer is to do two-step deserialization.
* At first it just reads string and then does second deserialization in the proper {@link Map} type once string substitution done.
* <p>
* Note! In order to get object mapper reference you have to set it first on object mapper initialization stage:
* </p>
* <pre>
* objectMapper.setInjectableValues(new InjectableValues.Std().addValue(OBJECT_MAPPER_VALUE_ID, objectMapper));
* </pre>
*/
public class ValueAsMapDeserializer extends JsonDeserializer<Map> implements ContextualDeserializer {
public static final String OBJECT_MAPPER_VALUE_ID = "objectMapper";
static final String VALUE_PREFIX = "$|";
static final String VALUE_SUFFIX = "|";
private JavaType keyType;
private JavaType valueType;
@Override
public JsonDeserializer<?> createContextual(final DeserializationContext ctxt,
final BeanProperty property) throws JsonMappingException {
JavaType filedType = property.getType();
this.keyType = filedType.getKeyType();
this.valueType = filedType.getContentType();
return this;
}
@Override
public Map deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException {
// Can't use constructor init there because of intention to use that deserializer using annotation
// Also such tricky thing as 'injectable values' was used cause of no way to get the reference to object mapper from deserialization context out of the box
ObjectMapper objectMapper = (ObjectMapper) ctxt.findInjectableValue(OBJECT_MAPPER_VALUE_ID, null, null);
final Optional<String> substitutedValue = Substitutor.create(jp, VALUE_PREFIX, VALUE_SUFFIX).substitute();
MapType mapType = objectMapper.getTypeFactory().constructMapType(Map.class, keyType, valueType);
return objectMapper.readValue(substitutedValue.orElseThrow(() -> new RuntimeException("Failed to parse the value as map")), mapType);
}
}
2）标记bean字段以使用该反序列化器：
2) Mark bean field to use that deserializer:
@JsonDeserialize(using = ValueAsMapDeserializer.class)
private final Map<String, Integer> anotherMap;
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