Mixin Issue

[mnadeem]

User Class

 public class User {
private Integer userId;
private String password;

public User(Integer userId, String password) {
    this.userId = userId;
    this.password = password;
}

public Integer getUserId() {
    return userId;
}

public String getPassword() {
    return password;
}

@Override
public String toString() {
    return "User [userId=" + userId + ", password=" + password + "]";
}
}

Corresponding mixing

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;

public abstract class UserMixin {


@JsonCreator
public UserMixin(
        @JsonProperty("userId") Integer userId
        , @JsonProperty("password") String password) {
    System.out.println("mixed-in constructor.");
}

}

TEST class

import java.io.IOException;

import com.fasterxml.jackson.databind.ObjectMapper;

 public class JacksonMixIn {
public static void main(String[] args) throws IOException {


    User user = new User(1,  "password");

    ObjectMapper mapper = new ObjectMapper();
    final String json = mapper.writeValueAsString(user);
    System.out.println(json);

    ObjectMapper mapper2 = new ObjectMapper();
    mapper2.addMixIn(User.class, UserMixin.class);


    System.out.println(mapper2.writeValueAsString(user));


    final User deserializedUser = mapper2.readValue(json, User.class);
    System.out.println(deserializedUser);
}

}

If I run the class everything as expected

{"userId":1,"password":"password"}
{"userId":1,"password":"password"}
User [userId=1, password=password]

Removed the following two getters from User class

public Integer getUserId() {
    return userId;
}

public String getPassword() {
    return password;
}

Exception in thread "main" com.fasterxml.jackson.databind.JsonMappingException: No serializer found for class com.github.dexecutor.redisson.User and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) )
at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:269)
at com.fasterxml.jackson.databind.ser.impl.UnknownSerializer.failForEmpty(UnknownSerializer.java:68)
at com.fasterxml.jackson.databind.ser.impl.UnknownSerializer.serialize(UnknownSerializer.java:32)
at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:130)
at com.fasterxml.jackson.databind.ObjectMapper._configAndWriteValue(ObjectMapper.java:3631)
at com.fasterxml.jackson.databind.ObjectMapper.writeValueAsString(ObjectMapper.java:2998)
at com.github.dexecutor.redisson.JacksonMixIn.main(JacksonMixIn.java:14)

How do I marshal/un marshall objects in this case??

Note: I cant add the getter: it would be 3rd party class

[cowtowncoder]

As per exception, you may disable the features (SerializationFeature.FAIL_ON_EMPTY_BEANS), to get an empty JSON Object (since there are no getters).

But it depends: would you want to get some properties serialized, or is empty Object fine?

[mnadeem]

Is there any way (With the help of mixing or some other way), can I serilize/deserialize User object with out modifying(i.e. Adding getter/setter) it

[cowtowncoder]

@mnadeem asking same question again without more information is not going to get you an answer.
As far as I can see:

1. Deserialization works just fine, unless I am missing something.
2. Serialization would succeed if you did WHAT THE EXCEPTION SUGGEST YOU TO DO. You did read the message did you?

So what is your remaining problem?

[mnadeem]

Well my problem (As I stated earlier) is I have got 3rd party library, and for some reason those have to be marshalled/marshalled into json, and I cannot provided getters only for the sake of marshalling/unmarshalling. I was expecting the framework to be smart enough (Use reflection, what not).

If the framework cannot provide such basic thing, that means, (as I understand) is not the write one for the use case (And I have to escalate it, not to be used any further)

Well I don't have to go any further (I got the answer), I understand, why the framework is like this, partly because people like @cowtowncoder is maintaining it, smart enough in giving childish answer

Dude, I read that, I have seen it, and that is the reason I have made that one, to appear in bold, not sure if you have seen it.

I feel there should be a guide line to respond to issues as well.

[cowtowncoder]

@mnadeem You do not make any sense whatever. So your not asking any more questions without adequate information is a big win for me. Feel free to use some other library and pester its maintainers.

[mnadeem]

For those of you interested in solution (and don't care about use case), use the following code, and things would work like a charm

   ObjectMapper mapper = new ObjectMapper();
   mapper.setVisibility(mapper.getSerializationConfig().getDefaultVisibilityChecker().withFieldVisibility(JsonAutoDetect.Visibility.ANY).withGetterVisibility(JsonAutoDetect.Visibility.NONE)
            .withSetterVisibility(JsonAutoDetect.Visibility.NONE)
            .withCreatorVisibility(JsonAutoDetect.Visibility.NONE));

Above code wont force you to have public getter of private field.

[cowtowncoder]

@mnadeem thank you for sharing the solution for anyone else looking.

For sake of completeness, there is also @JsonAutoDetect, applicable to classes directly and via mix-ins.

[mnadeem]

I have documented about this in this blog