Interface Mapper.Direct<T>

Enclosing interface:
Mapper<T>
public static interface Mapper.Direct<T>

Optional: append instance as JSON directly, without building a map first.

A generated mapper knows every property name and type at build time, so it can append them in order rather than filling a LinkedHashMap -- with a hash per key -- and having the writer walk it back rediscovering each value's type. On a small object that map round trip is the majority of the serialisation cost, not the escaping.

Measured through Mappers#toJson on a four-property object, output asserted identical: 2.05x / 1.51x / 2.81x faster (263 -> 128, 214 -> 142, 224 -> 80 ns per call).

That measurement ran on Java SE, so the map it avoids is the JDK's LinkedHashMap. On a translated device build the map is vm/JavaAPI's, which overrides the natives HashMap gets and costs about 1.5x a HashMap to build -- so the saving there is at least this, not less.

Implemented as a separate interface rather than a method on Mapper so hand-written mappers keep compiling; Mappers#toJson uses it when the mapper offers it and falls back to toMap when it does not.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    toJson(T instance, StringBuilder out)
    Appends instance as a JSON value -- an object, or the four characters null.

  • Method Details

    • toJson

      void toJson(T instance, StringBuilder out)
      Appends instance as a JSON value -- an object, or the four characters null. Must produce exactly what JSONWriter.toJson(toMap(instance)) would.