Annotation processor and compiler plugin
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This document discusses using annotation processors and compiler plugins to generate code. It provides examples of generating code to avoid boilerplate and duplication using annotation processors. It then outlines the basic steps to implement an annotation processor which includes implementing an interface, creating a provider configuration file, and compiling with the annotation processor on the classpath. Similarly, the basic steps for a compiler plugin are discussed, which involves implementing a plugin interface, creating a provider configuration file, and compiling with the plugin specified.
Annotation processor and compiler plugin
- 1. Annotation processor and compiler plugin as code generators.
- 2. Hello! I am Oleksandr Radchykov committed.chinchilla@gmail.com belict
- 3. Agenda 1.Motivation 2.How to generate code? 3.How to annotation processor 4.How to create plugin 5.Demo
- 5. 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; } }
- 6. @Getter @RequiredArgsConstructor class MyService { private final String name; private final Integer version; } 6
- 7. Getting rid from annoying code duplication public String validate(Object input) { if (income instanceof String && !((String) income).isEmpty()) { return (String) income; } … }
- 8. public String validate(Object input) { if (income instanceof String && !income.isEmpty()) { return income; } … } 8
- 9. Two ways to generate code
- 10. 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
- 11. 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
- 13. 1. Implement AbstractProcessor interface import javax.annotation.processing.AbstractProcessor; class MyProcessor implements AbstractProcessor { @Override public boolean process( Set<? Extends TypeElement> annotations, RoundEnvironment roundEnv) { /*...*/ } }
- 14. 2. Create provider-configuration file MyProcessor.jar - com/example - MyProcessor.class - META-INF/services - javax.annotation.processing.Processor Provider-configuration file should declare all annotation processors you want to expose.
- 15. 3. Compilation $ javac –cp processor.jar *sources*.java
- 16. Javac plugin
- 17. 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) { /*...*/ } }
- 18. 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.
- 19. 3. Compilation $ javac -Xplugin:PluginName –cp /path/to/plugin Source.java
- 20. Demo
- 21. Questions?