JsonMarshaller.java

package org.springframework.data.simpledb.core.entity.json;

import java.io.IOException;

import org.codehaus.jackson.JsonFactory;
import org.codehaus.jackson.annotate.JsonAutoDetect;
import org.codehaus.jackson.annotate.JsonMethod;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.mrbean.MrBeanModule;
import org.springframework.data.mapping.model.MappingException;
import org.springframework.util.Assert;

/**
 * Marshall and unmarshall objects, collections and map field wrappers
 */
public final class JsonMarshaller {

	static class JsonMarshallerHolder {

		private static JsonMarshaller instance = new JsonMarshaller();
	}

	private ObjectMapper jsonMapper;

	private JsonMarshaller() {
		JsonFactory factory = new JsonFactory();
		jsonMapper = new ObjectMapper(factory);
        jsonMapper.enableDefaultTypingAsProperty(ObjectMapper.DefaultTyping.NON_FINAL, "@class");
        JsonUnknownPropertyHandler jsonUnknownPropertyHandler = new JsonUnknownPropertyHandler();
		jsonMapper.getDeserializationConfig().addHandler(jsonUnknownPropertyHandler);
		jsonMapper.registerModule(new MrBeanModule());
	}

	public static JsonMarshaller getInstance() {
		return JsonMarshallerHolder.instance;
	}

    static JsonMarshaller createNew(){
        return new JsonMarshaller();
    }

	public <T> T unmarshall(String jsonString, Class<?> objectType) {
		Assert.notNull(jsonString);
		try {
			return (T) jsonMapper.readValue(jsonString, objectType);
		} catch(IOException e) {
			throw new MappingException("Could not unmarshall object : " + jsonString, e);
		}
	}

	public <T> String marshall(T input) {
		Assert.notNull(input);
		jsonMapper = new ObjectMapper().setVisibility(JsonMethod.FIELD, JsonAutoDetect.Visibility.ANY);
		jsonMapper.enableDefaultTypingAsProperty(ObjectMapper.DefaultTyping.NON_FINAL, "@class");
		try {
			return jsonMapper.writeValueAsString(input);
		} catch(Exception e) {
			throw new MappingException(e.getMessage(), e);
		}
	}

}