Map key serialization in Java. Working example

JacksonMapTestJava.java

package test;

import java.io.IOException;
import java.util.TreeMap;

import com.fasterxml.jackson.core.*;
import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.annotation.*;
import com.fasterxml.jackson.databind.deser.std.StdKeyDeserializer;
import com.fasterxml.jackson.databind.ser.std.StdSerializer;

@SuppressWarnings("hiding")
public 
class JacksonMapTestJava
{
  public static void 
  main(String[] args) 
    throws JsonGenerationException, JsonMappingException, IOException 
  {
    Pair pair = new Pair(2, 3);
    TreeMap<Pair, String> map = new TreeMap<JacksonMapTestJava.Pair, String>();
    map.put(pair, "Horsey");
    Thingie thingie = new Thingie();
    thingie.setMap(map);
    ObjectMapper mapper = new ObjectMapper();
    String str = mapper.writeValueAsString(thingie);
    System.out.println(str);
    Thingie result = mapper.readValue(str, Thingie.class);
    System.out.println(result.getMap());
  }
  
  
  public static class
  Thingie
  {
    public TreeMap<Pair, String> 
    getMap() 
    {
      return map;
    }

    public void 
    setMap(TreeMap<Pair, String> map) 
    {
      this.map = map;
    }

    @JsonSerialize(keyUsing=PairKS.class)
    @JsonDeserialize(keyUsing=PairKD.class)
    private TreeMap<Pair, String> map;
  }
  
  public static class
  Pair
  {
    public
    Pair()
    {}
    
    public 
    Pair(int arg1, int arg2) 
    {
      this.arg1 = arg1;
      this.arg2 = arg2;
    }

    public int 
    getArg1() 
    {
      return arg1;
    }
    
    public void 
    setArg1(int arg1) 
    {
      this.arg1 = arg1;
    }
    
    public int 
    getArg2() 
    {
      return arg2;
    }
    
    public void 
    setArg2(int arg2) 
    {
      this.arg2 = arg2;
    }
    
    @Override
    public String 
    toString() 
    {
      return "Pair(" + arg1 + ", " + arg2 + ")"; 
    }
    
    private int arg1;
    private int arg2;
  }
  
  public static class PairKD 
    extends StdKeyDeserializer
  {
    PairKD()
    {
      super(Pair.class);
    }
    
    @Override
    public Pair
    _parse(String key, DeserializationContext ctxt) 
      throws JsonMappingException
    {
      ObjectMapper mapper = new ObjectMapper();
      try {
        return mapper.readValue(key, Pair.class);
      }
      catch (Exception ex) {
        throw ctxt.weirdKeyException(_keyClass, key, ex.getMessage());
      }
    }
  }

  public static class PairKS
    extends StdSerializer<Pair>
  {
    PairKS()
    {
      super(Pair.class);
    }
    
    @Override
    public void
    serialize(Pair value, JsonGenerator jgen, SerializerProvider provider)
      throws JsonGenerationException, IOException
    {
      ObjectMapper mapper = new ObjectMapper();
      jgen.writeFieldName(mapper.writeValueAsString(value));
    }
  }
}

dude please set up a formatter :-D