Jackson deserialize with spring interface list

Question

I need to save and load objects from redis.

The object contains a list of GrantedAuthority (by the way), which is the interface:

public class UserAccountAuthentication implements Authentication { private List<GrantedAuthority> authorities; private boolean authenticated = true; ... } 

Jackson successfully serializes the object, but does not deserialize it with the following exception:

 abstract types can only be instantiated with additional type information 

I know that I can specify the type by adding:

 @JsonTypeInfo( 

But I cannot do this in this case, because GrantedAuthority is the Spring interface, and I cannot change it.

---

serialized json:

 { "authorities": [ { "authority": "ROLE_NORMAL_USER" } ], "authenticated": true, "securityToken": { "expiration": 1458635906853, "token": "sxKi3Pddfewl2rgpatVE7KiSR5qGmhpGl0spiHUTLAAW8zuoLFE0VLFYcfk72VLnli66fcVmb8aK9qFavyix3bOwgp1DRGtGacPI", "roles": [ "ROLE_NORMAL_USER" ], "expired": false, "expirationDateFormatted": "2016-03-22 08:38:26.853 UTC" }, "name": "admin", "expired": false 

}

---

abstract GrantedAuthority populated only by SimpleGrantedAuthority .

so i tried:

 objectMapper.registerSubtypes(SimpleGrantedAuthority.class); 

and still no luck.

Answer 1

I think you need to add a custom deserializer

 public class UserAccountAuthenticationSerializer extends JsonDeserializer<UserAccountAuthentication> { @Override public UserAccountAuthentication deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException { UserAccountAuthentication userAccountAuthentication = new UserAccountAuthentication(); ObjectCodec oc = jsonParser.getCodec(); JsonNode node = oc.readTree(jsonParser); userAccountAuthentication.setAuthenticated(node.get("authenticated").booleanValue()); Iterator<JsonNode> elements = node.get("authorities").elements(); while (elements.hasNext()) { JsonNode next = elements.next(); JsonNode authority = next.get("authority"); userAccountAuthentication.getAuthorities().add(new SimpleGrantedAuthority(authority.asText())); } return userAccountAuthentication; } 

}

This is my json

 {"authenticated":true,"authorities":[{"authority":"role1"},{"authority":"role2"}],"details":null,"principal":null,"credentials":null,"name":null} 

Then at the top of your POJO

 @JsonDeserialize(using = UserAccountAuthenticationSerializer.class) public class UserAccountAuthentication implements Authentication { 

Here is the test

 @Test public void test1() throws IOException { UserAccountAuthentication userAccountAuthentication = new UserAccountAuthentication(); userAccountAuthentication.setAuthenticated(true); userAccountAuthentication.getAuthorities().add(new SimpleGrantedAuthority("role1")); userAccountAuthentication.getAuthorities().add(new SimpleGrantedAuthority("role2")); String json1 = new ObjectMapper().writeValueAsString(userAccountAuthentication); UserAccountAuthentication readValue = new ObjectMapper().readValue(json1, UserAccountAuthentication.class); String json2 = new ObjectMapper().writeValueAsString(readValue); assertEquals(json1, json2); 

}