如何重写日期的 autobean 编码器和解码器

public class DateBean {
    private java.util.Date date;

    public java.util.Date getDate() {
        return date;
    }

    public void setDate(java.util.Date date) {
        this.date = date;
    }
}

import com.google.auto.value.AutoValue;
import com.google.common.base.Optional;
import com.google.gson.Gson;
import com.google.gson.TypeAdapter;
import com.google.gson.annotations.SerializedName;

@AutoValue
public abstract class DateBean {
    @SerializedName("date")
    public abstract Optional<java.util.Date> getDate();

    public static Builder builder() {
        return new AutoValue_DateBean.Builder();
    }

    @AutoValue.Builder
    public abstract static class Builder {
        public abstract Builder setDate(java.util.Date date);
        public abstract DateBean build();
    }

    public static TypeAdapter<DateBean> typeAdapter(Gson gson) {
        return new AutoValue_DateBean.GsonTypeAdapter(gson);
    }
}

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

public class Main {
    public static void main(String[] args) {
        Gson gson = new GsonBuilder()
                .registerTypeAdapter(DateBean.class, DateBean.typeAdapter(new Gson()))
                .create();

        DateBean dateBean = DateBean.builder().setDate(new java.util.Date()).build();
        String json = gson.toJson(dateBean);
        System.out.println(json);

        DateBean deserializedDateBean = gson.fromJson(json, DateBean.class);
        System.out.println(deserializedDateBean.getDate());
    }
}