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JSON serialization of different attributes of a single entity for different requests using Jackson

There are several REST calls that require the same JSON entity with a different set of attributes. Example of the entity:
public class JsonEntity
{
public String id;
public String name;
public String type;
public String model;
}
JsonEntity is a part of the complex responses of different calls. The first call requires the whole JsonEntity without changes. Second call requires JsonEntity without type and model attributes. Thrid one requires JsonEntity without name attribute.
Is there any way to retrieve the same JSON entity with a particular set of attributes depending on the particular context (except separating JsonEntity) using Jackson?

I see 3 ways of doing this:
1. Use #JsonGetter
This annotation tells jackson to use a metho rather than a field for serialization.
Create 3 subclasses of JsonEntity, one for each response. Change JsonEntity and use #IgnoreField on every field, make them protected if possible. On each subclasses, create specific getter for the fields you need, example:
public class JsonEntitySecondCall extends JsonEntity
{
#JsonGetter("id")
public String getId(){
return id;
}
#JsonGetter("name")
public String getName(){
return name;
}
}
Also, create a clone/copy constructor for JsonEntity. For your second call, create a new JsonEntitySecondCall by cloning the original JsonEntity, and use it in your API. Because of the anotation, the created Object will only serialisze the given fields. I don't this you can just cast your object, because Jackson uses reflection.
2. Use #AnyGetter
the AnyGetter annotaiton allows you to define a map of what will be serialized:
private Map<String, Object> properties = new HashMap<>();
#JsonAnyGetter
public Map<String, Object> properties() {
return properties;
}
Now you just need to tell your JsonEntity what properties it needs to return before each call (you could create 3 methods, one for each context, and use an enum to set which one must be used.).
3. Use #JsonInclude(Include.NON_NULL)
This annotation tells Jackson not to serialize a field if it is null. You can then clone your object and set null the fields you don't want to send. (this only works if you shouldn't send null elements to the API)
For more on Jackson annotations use this link.

AWS DynamoDBMapper save method keeps throwing `DynamoDBMappingException: not supported; requires #DynamoDBTyped or #DynamoDBTypeConverted`

I followed everything that is outlined here - https://github.com/derjust/spring-data-dynamodb/wiki/Use-Hash-Range-keys. But still no luck.
I have a DynamoDB table with a hash key and a sort key.
Here is my entity class RecentlyPlayed.class
#DynamoDBTable(tableName="some-table")
public class RecentlyPlayed {
#Id
private RecentlyPlayedId recentlyPlayedId;
// ----- Constructor methods -----
#DynamoDBHashKey(attributeName="keyA")
// Getter and setter
#DynamoDBRangeKey(attributeName="keyB")
// Getter and setter
}
Here is my key class RecentlyPlayedId.class
public class RecentlyPlayedId implements Serializable {
private static final long serialVersionUID = 1L;
private String keyA;
private String keyB;
public RecentlyPlayedId(String keyA, String keyB) {
this.keyA = keyA;
this.keyB = keyB;
}
#DynamoDBHashKey
// Getter and setter
#DynamoDBRangeKey
// Getter and setter
}
Here is my repository interface RecentlyPlayedRepository
#EnableScan
public interface RecentlyPlayedRepository extends CrudRepository<RecentlyPlayed, RecentlyPlayedId> {
List<RecentlyPlayed> findAllByKeyA(#Param("keyA") String keyA);
// Finding the entry for keyA with highest keyB
RecentlyPlayed findTop1ByKeyAOrderByKeyBDesc(#Param("keyA") String keyA);
}
I am trying to save an object like this
RecentlyPlayed rp = new RecentlyPlayed(...);
dynamoDBMapper.save(rp); // Throws that error
recentlyPlayedRepository.save(rp); // Also throws the same error
I am using Spring v2.0.1.RELEASE. The wiki in the original docs warns about this error and describes what to do to mitigate. I did exactly what they said. But still no luck.
The link to that wiki is here - https://github.com/derjust/spring-data-dynamodb/wiki/Use-Hash-Range-keys

DynamoDB only supports primitive data types, it does not know how to convert your complex field (recentlyPlayedId) into a primitive, such as a String.
To show that this is the case, you can add the annotation #DynamoDBIgnore to your recentlyPlayedId attribute like this:
#DynamoDBIgnore
private RecentlyPlayedId recentlyPlayedId;
You also need to remove the #id annotation.
Your save function will then work, but the recentlyPlayedId will not be stored in the item. If you do want to save this field, you need to use the #DynamoDBTypeConverted annotation and write a converter class. The converter class defines how to convert the complex field into a String, and then uncovert the String into the complex field.

Removing getters/setters for the #Id field fixed the problem for me. This is suggested in https://github.com/derjust/spring-data-dynamodb/wiki/Use-Hash-Range-keys

not supported; requires #DynamoDBTyped or #DynamoDBTypeConverted",
i was getting this error when i defined model class with field JsonNode,i converted it to MAP<String,String>,now it is working fine

How to parse DTO to Pojo objects

Well, I'm trying to parse objects and I'm having so much issues.
My classes are like this:
-Entidad-
public class Entidad{
private Long codEntidad;
private Set<Comunicacion> comunicacion;
/*------------ Getter and Setters --------------*/
}
-Comunicacion-
public class Comunicacion {
private Entidad entidad;
private Long codComunicacion;
/*------------ Getter and Setters --------------*/
}
I need to parse to DTO objects:
-EntidadDTO-
public class EntidadDTO{
private Long codEntidad;
private Set<ComunicacionDTO> comunicacionDto;
/*------------ Getter and Setters --------------*/
}
-ComunicacionDTO-
public class ComunicacionDTO {
private EntidadDto entidadDto;
private Long codComunicacion;
/*------------ Getter and Setters --------------*/
}
I tried to use:
BeanUtils.copyProperties(entidad, entidadDto);
It seems that the parse is success but the property entidadDto.getComunicacionDto(); is a hashMap of Comunicacion (not ComunicacionDTO)
Should I try to make a custom parse with reflection?
Also I'd like to use this to parse more objects with a similar structure.
Thanks!

Try dozer. You can define mappings from bean to bean using it.
http://dozer.sourceforge.net/

Why you want to parse java object and move data to other java object?
Parsing is for unstructured strings not for objects.
Use setters/getters to move data from one object to the other, using reflection will make you cry when you start doing refactorings.

Want to hide some fields of an object that are being mapped to JSON by Jackson

I have a User class that I want to map to JSON using Jackson.
public class User {
private String name;
private int age;
private int securityCode;
// getters and setters
}
I map this to a JSON string using -
User user = getUserFromDatabase();
ObjectMapper mapper = new ObjectMapper();
String json = mapper.writeValueAsString(user);
I don't want to map the securityCode variable. Is there any way of configuring the mapper so that it ignores this field?
I know I can write custom data mappers or use the Streaming API but I would like to know if it possible to do it through configuration?

You have two options:
Jackson works on setters-getters of fields. So, you can just remove getter of field which you want to omit in JSON. ( If you don't need getter at other place.)
Or, you can use the #JsonIgnore annotation of Jackson on getter method of that field and you see there in no such key-value pair in resulted JSON.
#JsonIgnore
public int getSecurityCode(){
return securityCode;
}

Adding this here because somebody else may search this again in future, like me. This Answer is an extension to the Accepted Answer
You have two options:
1. Jackson works on setters-getters of fields. So, you can just remove getter of field which you want to omit in JSON. ( If you don't need getter at other place.)
2. Or, you can use the `#JsonIgnore` [annotation of Jackson][1] on getter method of that field and you see there in no such key-value pair in resulted JSON.
#JsonIgnore
public int getSecurityCode(){
return securityCode;
}
Actually, newer version of Jackson added READ_ONLY and WRITE_ONLY annotation arguments for JsonProperty. So you could also do something like this.
#JsonProperty(access = Access.WRITE_ONLY)
private String securityCode;
instead of
#JsonIgnore
public int getSecurityCode(){
return securityCode;
}

you also can gather all properties on an annotation class
#JsonIgnoreProperties( { "applications" })
public MyClass ...
String applications;

If you don't want to put annotations on your Pojos you can also use Genson.
Here is how you can exclude a field with it without any annotations (you can also use annotations if you want, but you have the choice).
Genson genson = new Genson.Builder().exclude("securityCode", User.class).create();
// and then
String json = genson.serialize(user);

Field Level:
public class User {
private String name;
private int age;
#JsonIgnore
private int securityCode;
// getters and setters
}
Class Level:
#JsonIgnoreProperties(value = { "securityCode" })
public class User {
private String name;
private int age;
private int securityCode;
}

if you are using GSON you have to mark the field/member declarations as #Expose and use the GsonBuilder().excludeFieldsWithoutExposeAnnotation().create()
Don't forget to mark your sub classes with #Expose otherwise the fields won't show.

I suggest you use this.
#JsonProperty(access = JsonProperty.Access.WRITE_ONLY)
private int securityCode;
This allows you to set the value of securityCode(especially if you use lombok #Setter) and also prevent the field from showing up in the GET request.

I had a similar case where I needed some property to be deserialized (JSON to Object) but not serialized (Object to JSON)
First i went for #JsonIgnore - it did prevent serialization of unwanted property, but failed to de-serialize it too. Trying value attribute didn't help either as it requires some condition.
Finally, working #JsonProperty with access attribute worked like a charm.

java.util.List is an interface, and JAXB can't handle interfaces

I seemed to get the following exception when trying to deploy my application:
Caused by: com.sun.xml.bind.v2.runtime.IllegalAnnotationsException: 2 counts of IllegalAnnotationExceptions
java.util.List is an interface, and JAXB can't handle interfaces.
this problem is related to the following location:
at java.util.List
at private java.util.List foobar.alkohol.register.webservice.jaxws.GetRelationsFromPersonResponse._return
at foobar.alkohol.register.webservice.jaxws.GetRelationsFromPersonResponse
java.util.List does not have a no-arg default constructor.
this problem is related to the following location:
at java.util.List
at private java.util.List foobar.alkohol.register.webservice.jaxws.GetRelationsFromPersonResponse._return
at foobar.alkohol.register.webservice.jaxws.GetRelationsFromPersonResponse
My code worked just well until I changed the return type from List to List<List<RelationCanonical>>
Here is the partial webservice:
#Name("relationService")
#Stateless
#WebService(name = "RelationService", serviceName = "RelationService")
#SOAPBinding(style = SOAPBinding.Style.DOCUMENT, use = SOAPBinding.Use.LITERAL, parameterStyle = SOAPBinding.ParameterStyle.WRAPPED)
public class RelationService implements RelationServiceLocal {
private boolean login(String username, String password) {
Identity.instance().setUsername(username);
Identity.instance().setPassword(password);
Identity.instance().login();
return Identity.instance().isLoggedIn();
}
private boolean logout() {
Identity.instance().logout();
return !Identity.instance().isLoggedIn();
}
#WebMethod
public List<List<RelationCanonical>> getRelationsFromPerson(#WebParam(name = "username")
String username, #WebParam(name = "password")
String password, #WebParam(name = "foedselsnummer")
String... foedselsnummer) {
......
......
......
}
I have also tried by removing the #SOAPBinding and trying default, but the same result occurs.
Appreciate any help
UPDATE
I want to note out something. I changed all List to ArrayList, and then it compiled. The reason why I say compiled and not worked is because it behaves strange. I get an Object of type:
RelationServiceStub.ArrayList
but the object has no get methods or does not behave as a List either. I also tried to cast it to a List but that didnt work.
Note that this is after I have used Axis 2 and wsdl2java So yes, now it compiles, but I dont know how to get the data out.

In my understanding, you will not be able to process a plain List via JAXB, as JAXB has no idea how to transform that into XML.
Instead, you will need to define a JAXB type which holds a List<RelationCanonical> (I'll call it Type1), and another one to hold a list of those types, in turn (as you're dealing with a List<List<...>>; I'll call this type Type2).
The result could then be an XML ouput like this:
<Type2 ...>
<Type1 ...>
<RelationCanonical ...> ... </RelationCanonical>
<RelationCanonical ...> ... </RelationCanonical>
...
</Type1>
<Type1>
<RelationCanonical ...> ... </RelationCanonical>
<RelationCanonical ...> ... </RelationCanonical>
...
</Type1>
...
</Type2>
Without the two enclosing JAXB-annotated types, the JAXB processor has no idea what markup to generate, and thus fails.
--Edit:
What I mean should look somewhat like this:
#XmlType
public class Type1{
private List<RelationCanonical> relations;
#XmlElement
public List<RelationCanonical> getRelations(){
return this.relations;
}
public void setRelations(List<RelationCanonical> relations){
this.relations = relations;
}
}
and
#XmlRootElement
public class Type2{
private List<Type1> type1s;
#XmlElement
public List<Type1> getType1s(){
return this.type1s;
}
public void setType1s(List<Type1> type1s){
this.type1s= type1s;
}
}
You should also check out the JAXB section in the J5EE tutorial and the Unofficial JAXB Guide.

If that suits your purpose you can always define an array like this:
YourType[]
JAXB can certainly figure out what that is and you should be able to immediatly use it client side. I would also recommend you to do it that way, since you should not be able to modify the array retrieved from a server via a List but via methods provided by the web service

If you want to do this for any class.
return items.size() > 0 ? items.toArray((Object[]) Array.newInstance(
items.get(0).getClass(), 0)) : new Object[0];

You can use "ArrayList" instead of inner "List"