How to map an ArrayList of primitives to a single column?

Question

Let\'s say I have the following situation:

Object Car has an ArrayList of prices, which are all numbers. Is it possible in Hibernate to save all the prices in a sin

Answer 1

I updated Chris's code to utilize the Jackson JSON library for lists and maps:

import java.util.List;

import javax.persistence.AttributeConverter;
import javax.persistence.Converter;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

@Converter
public class ListToJsonConverter implements AttributeConverter, String> {

    private static ObjectMapper mapper = new ObjectMapper();

    @Override
    public String convertToDatabaseColumn(List attribute) {
        if (attribute == null) {
            return null;
        }
        try {
            return mapper.writeValueAsString(attribute);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
        return null;
    }

    @SuppressWarnings("unchecked")
    @Override
    public List convertToEntityAttribute(String dbData) {
        if (dbData == null || dbData.isEmpty()) {
            return null;
        }
        try {
            return mapper.readValue(dbData, List.class);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}

import java.util.Map;

import javax.persistence.AttributeConverter;
import javax.persistence.Converter;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

@Converter
public class MapToJsonConverter implements AttributeConverter, String> {

    private static ObjectMapper mapper = new ObjectMapper();

    @Override
    public String convertToDatabaseColumn(Map attribute) {
        if (attribute == null) {
            return null;
        }
        try {
            return mapper.writeValueAsString(attribute);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
        return null;
    }

    @SuppressWarnings("unchecked")
    @Override
    public Map convertToEntityAttribute(String dbData) {
        if (dbData == null || dbData.isEmpty()) {
            return null;
        }
        try {
            return mapper.readValue(dbData, Map.class);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}

@Column(name = "example_list")
@Convert(converter = ListToJsonConverter.class)
public List getExampleList() {
    return exampleList;
}

@Column(name = "example_map")
@Convert(converter = MapToJsonConverter.class)
public Map getExampleMap() {
    return exampleMap;
}

This allows storing just about any types in a human-readable way in a string column, and makes it so you don't need a separate class for every type of list or hashmap. It also automatically escapes the strings.