La désérialisation de JSON avec carte de la “clé” & “valeur” propriétés ne fonctionne pas avec Jackson

Questions

Pour commencer, le sérialisé la sérialisation JSON ci-dessous un sens?
Si oui, pourquoi ne suis-je pas l'obtention de la Carte de retour?
Ce que je peux faire à ce sujet sur la désérialisation de côté?

La sérialisation JSON de Map<String, String> propriété (extrait):

{
  "attributes": {
    "entry": [
      {
        "key": "operating system",
        "value": "GNU/Linux"
      },
      {
        "key": "allergies",
        "value": "weed"
      }
    ]
  }
}

POJO pour la désérialisation:

class Contact implements Comparable<Contact>, Serializable {
    @JsonProperty("attributes")
    private Map<String, String> attributes;
    ...
}

Les Causes de cette exception:

Thread-4889 An exception occurred during request network execution :Could not read JSON: Can not deserialize instance of java.lang.String out of START_ARRAY token
at [Source: libcore.net.http.FixedLengthInputStream@43822760; line: 1, column: 17] (through reference chain: com.example.model.Contact["attributes"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.lang.String out of START_ARRAY token
at [Source: libcore.net.http.FixedLengthInputStream@43822760; line: 1, column: 17] (through reference chain: com.example.model.Contact["attributes"])
org.springframework.http.converter.HttpMessageNotReadableException: Could not read JSON: Can not deserialize instance of java.lang.String out of START_ARRAY token
at [Source: libcore.net.http.FixedLengthInputStream@43822760; line: 1, column: 17] (through reference chain: com.example.model.Contact["attributes"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.lang.String out of START_ARRAY token
at [Source: libcore.net.http.FixedLengthInputStream@43822760; line: 1, column: 17] (through reference chain: com.example.model.Contact["attributes"])
at org.springframework.http.converter.json.MappingJackson2HttpMessageConverter.readInternal(MappingJackson2HttpMessageConverter.java:126)
at org.springframework.http.converter.AbstractHttpMessageConverter.read(AbstractHttpMessageConverter.java:147)
at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:76)
at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:484)
at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:439)
at org.springframework.web.client.RestTemplate.getForObject(RestTemplate.java:237)
at com.example.providers.Query$1.loadDataFromNetwork(Query.java:99)
at com.octo.android.robospice.request.CachedSpiceRequest.loadDataFromNetwork(CachedSpiceRequest.java:45)
at com.octo.android.robospice.request.RequestRunner.processRequest(RequestRunner.java:130)
at com.octo.android.robospice.request.RequestRunner$1.run(RequestRunner.java:197)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:390)
at java.util.concurrent.FutureTask.run(FutureTask.java:234)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
at java.lang.Thread.run(Thread.java:841)
Caused by: com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.lang.String out of START_ARRAY token
at [Source: libcore.net.http.FixedLengthInputStream@43822760; line: 1, column: 17] (through reference chain: com.example.model.Contact["attributes"])
at com.fasterxml.jackson.databind.DeserializationContext.mappingException(DeserializationContext.java:691)
at com.fasterxml.jackson.databind.deser.std.StringDeserializer.deserialize(StringDeserializer.java:46)
at com.fasterxml.jackson.databind.deser.std.StringDeserializer.deserialize(StringDeserializer.java:11)
at com.fasterxml.jackson.databind.deser.std.MapDeserializer._readAndBindStringMap(MapDeserializer.java:430)
at com.fasterxml.jackson.databind.deser.std.MapDeserializer.deserialize(MapDeserializer.java:312)
at com.fasterxml.jackson.databind.deser.std.MapDeserializer.deserialize(MapDeserializer.java:26)
at com.fasterxml.jackson.databind.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:525)
at com.fasterxml.jackson.databind.deser.impl.FieldProperty.deserializeAndSet(FieldProperty.java:106)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:242)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:118)
at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:227)
at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.des

Les attributs de l'Objet lors de l'inspection dans le débogueur après la désérialisation:

La désérialisation de JSON avec carte de la “clé” & “valeur” propriétés ne fonctionne pas avec Jackson

Nouvelle inspection après la modification:

@JsonProperty("attributes")
private Map<String, List<Map<String, String>>> attributes;

La désérialisation de JSON avec carte de la “clé” & “valeur” propriétés ne fonctionne pas avec Jackson

Dépendances:

com.fasterxml.jackson.core:jackson-core:2.3.0
com.fasterxml.jackson.core:jackson-databind:2.3.0
com.fasterxml.jackson.core:jackson-annotations:2.3.0

OriginalL'auteur joelpet | 2013-12-20

Si nous allons convertir Map en json:

    Map<String, String> map = new HashMap<String, String>();
map.put("operating system", "GNU/Linux");
map.put("allergies", "weed");

La sortie sera:

{"operating system":"GNU/Linux","allergies":"weed"}

Comme on peut le voir il n'y a pas de key/value.

Solution

WrapperObject

@JsonIgnoreProperties(ignoreUnknown = true)
public class WrapperObject { //we can give any name to class, its only external {}    
private Attributes attributes;
public WrapperObject() {}
public Attributes getAttributes() {
return attributes;
}    
}

Attributs

@JsonIgnoreProperties(ignoreUnknown = true)  
public class Attributes {
public Attributes() {}
private ArrayList<Entry> entry;  
public ArrayList<Entry> getEntry() {
return entry;
}    
}

Entrée

@JsonIgnoreProperties(ignoreUnknown = true)    
public  class Entry {
private String key;
private String value;
public Entry() {}
public String getKey() {
return key;
}
public String getValue() {
return value;
}
}

Lanceur

public static void main(String[] args) throws JsonParseException, JsonMappingException,     IOException {
String str = "{" + 
"  \"attributes\": {" + 
"    \"entry\": [" + 
"      {" + 
"        \"key\": \"operating system\"," + 
"        \"value\": \"GNU/Linux\"" + 
"      }," + 
"      {" + 
"        \"key\": \"allergies\"," + 
"        \"value\": \"weed\"" + 
"      }" + 
"    ]" + 
"  }" + 
"}";
ObjectMapper mapper = new ObjectMapper();
WrapperObject mj = mapper.readValue(str, WrapperObject.class);
if(mj == null){
System.err.println("null");
}
//dummy check
System.out.println(mj.getAttributes().getEntry().get(0).getKey());
}

De sortie:

operating system

OriginalL'auteur Maxim Shoustin

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