Flexjson or Gson : Protect object references after object serialization

Question

I serializing a list with flexjson. After serialization, I printing object hashcode() and I would check to see if the objects are equal.

Problem, after the operation the object reference are changing. I don't want it.

My code;

    String sameOfString="sameOfString";
    List<Object> list=new ArrayList<Object>();
    list.add(sameOfString);
    list.add(sameOfString);
    list.add("differentString");

    for(Object str:list){
        System.out.println(str.hashCode());
    }
    **System.out.println(list.get(0)==list.get(1));**
    System.out.println(list.get(0)==list.get(2));
    System.out.println("--");
    String json= new JSONSerializer().exclude("*.class").deepSerialize(list);
    List<String> listDeserilized = (List<String>) new JSONDeserializer().deserialize(json);
    for(Object str:listDeserilized){
        System.out.println(str.hashCode());
    }
    **System.out.println(listDeserilized.get(0)==listDeserilized.get(1));**
    System.out.println(listDeserilized.get(0)==listDeserilized.get(2));

And output..

1018069468

1018069468

199675306

true

false

-

1018069468

1018069468

199675306

false

false

How can solve this problem?

Answer 1

I solved my problem with jackson lib.

@JsonIdentityInfo annotation protecting object relations(in other words; protecting references) and after deserialization, object locations dont changing in memory.

the final code :

package com.maar.projectbuilder;

import com.fasterxml.jackson.annotation.JsonIdentityInfo;
import com.fasterxml.jackson.annotation.JsonTypeInfo;
import com.fasterxml.jackson.annotation.JsonTypeName;
import com.fasterxml.jackson.annotation.ObjectIdGenerators;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.annotation.JsonDeserialize;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

/**
 * Created by Firat on 11.9.2014.
 */
public class Testt {
    @JsonDeserialize(as=StringClazz.class)
    @JsonTypeInfo(use=JsonTypeInfo.Id.CLASS, include=JsonTypeInfo.As.PROPERTY, property="@class")
    @JsonIdentityInfo(generator=ObjectIdGenerators.IntSequenceGenerator.class, property="@id")
    @JsonTypeName(value = "StringClazz")
    private static class StringClazz{
        private String data="";

        public StringClazz() {
        }

        public String getData() {
            return data;
        }

        public void setData(String data) {
            this.data = data;
        }
    }
    public static void main(String[] args) throws IOException {
        StringClazz someOfString=new StringClazz();
        someOfString.setData("someOfString");
        StringClazz differentString=new StringClazz();
        differentString.setData("differentString");

        List<StringClazz> list=new ArrayList<StringClazz>();
        list.add(someOfString);
        list.add(someOfString);
        list.add(differentString);

        for(Object str:list){
            System.out.println(str.hashCode());
        }
        System.out.println(list.get(0)==list.get(1));
        System.out.println(list.get(0)==list.get(2));
        System.out.println("-------");
        String json= null;
        try {
            json = new ObjectMapper().enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL).writeValueAsString(list);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
        System.out.println(json);
        List<StringClazz> listDeserilized =new ObjectMapper().enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL).readValue(json, new TypeReference<List<StringClazz>>() {
        });
        for(Object str:listDeserilized){
            System.out.println(str.hashCode());
        }
        System.out.println(listDeserilized.get(0)==listDeserilized.get(1));
        System.out.println(listDeserilized.get(0)==listDeserilized.get(2));
    }
}