CODE GENERATION WITH JAVAC PLUGIN

Hello!I am Oleksandr Radchykov

committed.chinchilla@gmail.com

belict

Agenda

1. Motivation2. How to generate code?3. How to create plugin4. Demo

Motivation for code generation

Getting rid of boilerplate

class MyService { private final String name; private final Integer version;

public MyService(String name, Integer version) { this.name = name; This.version = version; }

public String getName() { return name; } public Integer getVersion() { return version; }}

@Getter@RequiredArgsConstructorclass MyService { private final String name; private final Integer version;}

6

Getting rid from annoying code duplication

public String validate(Object input) { if (income instanceof String

&& !((String) income).isEmpty()) { return (String) income; } …}

public String validate(Object input) { if (income instanceof String && !income.isEmpty()) { return income; } …}

8

Two ways to generate code

Annotation Processing

▷Java 5+

▷Takes java code and generates source files

▷You can not manipulate an existing java code

▷Use the model of processing rounds

Javac Plugin

▷Since Java 8▷Can give us access to AST trees parsed from

source code▷Can be used to add compile-time checks▷Can run on different phases of compilation

process

How to create javac plugin?

1. Implement Plugin interface

import com.sun.source.util.Plugin;

class MyPlugin implements Plugin { @Override public String getName() { return “pluginName”; }

@Override public void init(JavacTask javacTask,

String… strings) { /*...*/ }}

2. Create provider-configuration file

MyPlugin.jar- com/example

- MyPlugin.class- META-INF/services

- com.sun.source.util.Plugin

Provider-configuration file should declare all plugins you want to expose.

3. Compilation

$ javac -Xplugin:PluginName \ –cp /path/to/plugin \

Source.java

Demo

Questions?

Thanks

committed.chinchilla@gmail.com

belict