OptionalCodec.java

package com.alibaba.fastjson.parser.deserializer;

import java.io.IOException;
import java.lang.reflect.Type;
import java.util.Optional;
import java.util.OptionalDouble;
import java.util.OptionalInt;
import java.util.OptionalLong;

import com.alibaba.fastjson.JSONException;
import com.alibaba.fastjson.parser.DefaultJSONParser;
import com.alibaba.fastjson.parser.JSONToken;
import com.alibaba.fastjson.serializer.JSONSerializer;
import com.alibaba.fastjson.serializer.ObjectSerializer;
import com.alibaba.fastjson.util.TypeUtils;

public class OptionalCodec implements ObjectSerializer, ObjectDeserializer {

    public static OptionalCodec instance = new OptionalCodec();

    @SuppressWarnings("unchecked")
    public <T> T deserialze(DefaultJSONParser parser, Type type, Object fieldName) {
        
        if (type == OptionalInt.class) {
            Object obj = parser.parseObject(Integer.class);
            Integer value = TypeUtils.castToInt(obj);
            if (value == null) {
                return (T) OptionalInt.empty();
            } else {
                return (T) OptionalInt.of(value);
            }
        }
        
        if (type == OptionalLong.class) {
            Object obj = parser.parseObject(Long.class);
            Long value = TypeUtils.castToLong(obj);
            if (value == null) {
                return (T) OptionalLong.empty();
            } else {
                return (T) OptionalLong.of(value);
            }
        }
        
        if (type == OptionalDouble.class) {
            Object obj = parser.parseObject(Double.class);
            Double value = TypeUtils.castToDouble(obj);
            if (value == null) {
                return (T) OptionalDouble.empty();
            } else {
                return (T) OptionalDouble.of(value);
            }
        }
        
        type = TypeUtils.unwrapOptional(type);
        Object value = parser.parseObject(type);
        
        if (value == null) {
            return (T) Optional.empty();
        }
        
        return (T) Optional.of(value);
    }

    public int getFastMatchToken() {
        return JSONToken.LBRACE;
    }

    public void write(JSONSerializer serializer, Object object, Object fieldName, Type fieldType,
                      int features) throws IOException {

        if (object == null) {
            serializer.writeNull();
            return;
        }

        if (object instanceof Optional) {
            Optional<?> optional = (Optional<?>) object;
            Object value = optional.get();
            serializer.write(value);
            return;
        }

        if (object instanceof OptionalDouble) {
            OptionalDouble optional = (OptionalDouble) object;
            if (optional.isPresent()) {
                double value = optional.getAsDouble();
                serializer.write(value);
            } else {
                serializer.writeNull();
            }
            return;
        }
        
        if (object instanceof OptionalInt) {
            OptionalInt optional = (OptionalInt) object;
            if (optional.isPresent()) {
                int value = optional.getAsInt();
                serializer.getWriter().writeInt(value);
            } else {
                serializer.writeNull();
            }
            return;
        }
        
        if (object instanceof OptionalLong) {
            OptionalLong optional = (OptionalLong) object;
            if (optional.isPresent()) {
                long value = optional.getAsLong();
                serializer.getWriter().writeLong(value);
            } else {
                serializer.writeNull();
            }
            return;
        }
        
        throw new JSONException("not support optional : " + object.getClass());
    }

}