hardcode

A friendly warning: This is an alpha quality software. Things may break, or be already broken!

A java library to hardcode data into the classfiles.

Sometimes, one need to load data fast. For instance, startup time is critical for Android applications. This library can help out. It prints out the source code that creates the data.

It's about an order of magnitude faster than java serialization, about 2-3 times as fast as FST (TODO: an actual benchmark). Obviously, this is suitable only for the static data.

Source code is handled by JavaPoet, output takes form of a com.squareup.javapoet.TypeSpec that can be simply printed out or processed further.

Hello world

Following source code

package org.deletethis.hardcode.examples;

import com.squareup.javapoet.JavaFile;
import org.deletethis.hardcode.Hardcode;

public class HelloWorld {
    public static void main(String[] args) {
        // create the hardcode object
        Hardcode hardcode = Hardcode.defaultConfig();

        // create a class
        JavaFile helloFile = hardcode.createJavaFile("com.example.helloworld", "HelloWorldSupplier", "Hello world!\n");

        // write class somewhere
        System.out.println(helloFile);
    }
}

Produces an implementation of the Provider which provides a single String.

package com.example.helloworld;

import java.lang.Override;
import java.lang.String;
import java.lang.SuppressWarnings;
import java.util.function.Supplier;

public class HelloWorldSupplier implements Supplier<String> {
  @SuppressWarnings("unchecked")
  @Override
  public String get() {
    return "Hello world!\n";
  }
}

Compatibility

This library requires Java 8 to generate code. Generated code can be configured to support Java as low as 1.5.

Supported types:

• java.lang.String, enum
• primitive types int, float, long, char, double, float, short, byte
• many collection
• few other useful types - URI, URL and Date
• POJOs, see below

POJOs

User defined POJOs are supported, however they must follow some conventions:

• source must be compiled with -parameters
• all arguments constructor must be present
• getter are not used, we read fields by default

TODO: support getter/setters as well

Project structure

Everything has maven group id of org.deletethis.hardcode.

There are following artifacts:

• hardcode-annotations - very simple library with essential annotations - to be used as runtime dependency
• hardcode - main library, should not be used during runtime
• hardcode-guava - support for several Guava types
• testing-utilities - not very interesting to public, makes writing unit tests easier

Features

• can split an object data into multiple functions, to work around the 64k method size limit
• object graph support
  • handles multiple references to the single object
  • unfortunately, cycles are not supported
• can create Grahviz representation of your object tree
• supports most common of the collections
• supports some of Guava immutable types
• support for custom serializers, either via API or java.util.ServiceLoader
• Provider is optional, in order to support Java 7 - or Android up to API level 23

Todo

• support for more more types
  • frequently used JDK types, such as Date or URL
  • support more Guava types
• rewrite @HardcodeSplit - especially error checking
• better error checking in general - should be done during graph building, not afterwards
• upload to maven repo
• improve this readme
• document @HardcodeSplit and @HardcodeRoot
• better test coverage
• javadoc for public APIs