Anotações Java Além da Reflexão

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1. Anotações Java Além da Reflexão Wellington Costa Pereira
2. Wellington Costa Pereira • +4 anos de experiência • Mestrando em Ciências da Computação (UECE) • Programar é vida! • Open source <3 • Compartilhar conhecimento <3 Github: https://github.com/WellingtonCosta Linkedin: https://www.linkedin.com/in/wellingtoncosta128 Email: wellington.costa128@gmail.com
4. Sem mais delongas...
6. Anotações?
7. Anotações Introduzida na versão 5 do Java, as anotações, ou Annotations, são uma forma de representar metadados que podem vir a serem interpretados por um compilador, visando realizar alguma ação a partir desses metadados. As annotations também podem servir como uma forma para substituição das tradicionais configurações baseadas em XML ou até mesmo para geração de arquivos, muitas vezes arquivos de código-fonte.
8. Lombok @ToString @EqualsAndHashCode public class Pessoa { @Getter @Setter private Long id; @Getter @Setter private String nome; @Getter @Setter private String email; @Getter @Setter private String telefone; }
9. JPA @Entity @Table(name = "tb_pessoa") public class Pessoa { @Id private Long id; @Column private String nome; @Column private String email; @Column private String telefone; }
10. Spring @RestController @RequestMapping("/api/pessoas") public class PessoaController { @GetMapping public List<Pessoa> listarTodos() { // … } }
11. Butter Knife public class PessoaActivity extends Activity { @BindView(R.id.nome) TextView nome; @BindView(R.id.email) TextView email; @BindView(R.id.telefone) TextView telefone; @Override protected void onCreate(Bundle savedInstance) { // … ButterKnife.inject(this); } }
12. Java 5
13. Java 5
14. Java 5 • JSR 14: Generics • JSR 175: Annotations • JSR 201: ◦ Autoboxing / Unboxing ◦ Enumerations ◦ Static Imports ◦ Enhanced For Loops • apt command-line tool • Dentre outras funcionalidades bacanas!
15. JSR 269 • 6 meses após o lançamento do Java 5 • “Pluggable Annotation Processing API” • Google, Oracle, dentre outras organizações patrocinaram • Simplificar e padronizar o processamento de anotações • Agora o apt faz parte do javac
16. Componentes
17. Componentes • Annotation • Processor • APT (Annotation Processing Tool) • Annotated Elements
18. Annotation
19. @Target(ElementType.TYPE) @Retention(RetentionPolicy.SOURCE) public @interface HelloWorld { }
20. @Target(ElementType.TYPE) @Retention(RetentionPolicy.SOURCE) public @interface HelloWorld { }
21. @Target(ElementType.TYPE) @Retention(RetentionPolicy.SOURCE) public @interface HelloWorld { }
22. @Target(ElementType.TYPE) @Retention(RetentionPolicy.SOURCE) public @interface HelloWorld { }
23. Processor
24. interface Processor { Set<String> getSupportedOptions(); Set<String> getSupportedAnnotationTypes(); SourceVersion getSupportedSourceVersion(); void init(ProcesssingEnvironment processingEnv); boolean process(Set<? extends TypeElement> annotations, RoundEnvironment env); Iterable<? extends Completion> getCompletions(Element element, AnnotationMirror annotation, ExecutableElement member, String userText); }
25. interface Processor { Set<String> getSupportedOptions(); Set<String> getSupportedAnnotationTypes(); SourceVersion getSupportedSourceVersion(); void init(ProcesssingEnvironment processingEnv); boolean process(Set<? extends TypeElement> annotations, RoundEnvironment env); Iterable<? extends Completion> getCompletions(Element element, AnnotationMirror annotation, ExecutableElement member, String userText); }
26. Processing Environment
27. interface ProcessingEnvironment { Map<String, String> getOptions(); SourceVersion getSourceVersion(); Locale getLocale(); Messager getMessager(); Filer getFiler(); Elements getElementUtils(); Types getTypeUtils(); }
28. interface ProcessingEnvironment { Map<String, String> getOptions(); SourceVersion getSourceVersion(); Locale getLocale(); Messager getMessager(); Filer getFiler(); Elements getElementUtils(); Types getTypeUtils(); }
29. Elements? Types?
30. Elements public class HelloClass implements Runnable { private final String name; public HelloClass(String name) { this.name = name; } @Override public void run() { System.out.println(“Hello, ” + name); } }
31. public class HelloClass implements Runnable { TypeElement private final String name; public HelloClass(String name) { this.name = name; } @Override public void run() { System.out.println(“Hello, ” + name); } } Elements
32. public class HelloClass implements Runnable { TypeElement private final String name; VariableElement public HelloClass(String name) { this.name = name; } @Override public void run() { System.out.println(“Hello, ” + name); } } Elements
33. public class HelloClass implements Runnable { TypeElement private final String name; VariableElement public HelloClass(String name) { this.name = name; ExecutableElement } @Override public void run() { System.out.println(“Hello, ” + name); } } Elements
34. public class HelloClass implements Runnable { TypeElement private final String name; VariableElement public HelloClass(String name) { this.name = name; ExecutableElement } @Override public void run() { System.out.println(“Hello, ” + name); ExecutableElement } } Elements
35. public class HelloClass implements Runnable { private final String name; public HelloClass(String name) { this.name = name; } @Override public void run() { System.out.println(“Hello, ” + name); } } Types
36. public class HelloClass implements Runnable { private final String name; public HelloClass(String name) { this.name = name; } @Override public void run() { System.out.println(“Hello, ” + name); } } Types
37. public class HelloClass implements Runnable { private final String name; public HelloClass(String name) { this.name = name; } @Override public void run() { System.out.println(“Hello, ” + name); } } Types
38. public class HelloClass implements Runnable { private final String name; public HelloClass(String name) { this.name = name; } @Override public void run() { System.out.println(“Hello, ” + name); } } Types
39. public class HelloClass implements Runnable { private final String name; public HelloClass(String name) { this.name = name; } @Override public void run() { System.out.println(“Hello, ” + name); } } Types
40. public class HelloClass implements Runnable { private final String name; public HelloClass(String name) { this.name = name; } @Override public void run() { System.out.println(“Hello, ” + name); } } Types
41. Criando nosso Processor
42. public class HelloWorldProcessor extends AbstractProcessor { }
43. public class HelloWorldProcessor extends AbstractProcessor { @Override public SourceVersion getSupportedSourceVersion() { return SourceVersion.latestSupported(); } }
44. public class HelloWorldProcessor extends AbstractProcessor { @Override public SourceVersion getSupportedSourceVersion() { return SourceVersion.latestSupported(); } @Override public Set<String> getSupportedAnnotationTypes() { return Collections.singleton(HelloWorld.class.getName()); } }
45. public class HelloWorldProcessor extends AbstractProcessor { @Override public SourceVersion getSupportedSourceVersion() { return SourceVersion.latestSupported(); } @Override public Set<String> getSupportedAnnotationTypes() { return Collections.singleton(HelloWorld.class.getName()); } @Override public boolean process( Set<? extends TypeElement> annotations, RoundEnvironment env) { } }
46. public class HelloWorldProcessor extends AbstractProcessor { // . . . @Override public boolean process( Set<? extends TypeElement> annotations, RoundEnvironment env) { } }
47. public class HelloWorldProcessor extends AbstractProcessor { // . . . @Override public boolean process( Set<? extends TypeElement> annotations, RoundEnvironment env) { Set<? extends Element> elements = env.getElementsAnnotatedWith(HelloWorld.class); } }
48. public class HelloWorldProcessor extends AbstractProcessor { // . . . @Override public boolean process( Set<? extends TypeElement> annotations, RoundEnvironment env) { Set<? extends Element> elements = env.getElementsAnnotatedWith(HelloWorld.class); for(Element element : elements) { System.out.println(element); } } }
49. public class HelloWorldProcessor extends AbstractProcessor { // . . . @Override public boolean process( Set<? extends TypeElement> annotations, RoundEnvironment env) { Set<? extends Element> elements = env.getElementsAnnotatedWith(HelloWorld.class); for(Element element : elements) { System.out.println(element); } return false; } }
50. public class HelloWorldProcessor extends AbstractProcessor { @Override public SourceVersion getSupportedSourceVersion() { return SourceVersion.latestSupported(); } @Override public Set<String> getSupportedAnnotationTypes() { return Collections.singleton(HelloWorld.class.getName()); } @Override public boolean process( Set<? extends TypeElement> annotations, RoundEnvironment env) { Set<? extends Element> elements = env.getElementsAnnotatedWith(HelloWorld.class); for(Element element : elements) { System.out.println(element); } return false; } }
51. Anotando um elemento
52. @HelloWorld public class HelloWorldClass { // . . . }
53. @HelloWorld public class HelloWorldClass { // . . . }
54. @HelloWorld public class HelloWorldClass { // . . . }
55. Execução
56. • Acontece automaticamente quando javac é executado • ServiceLoader se encarrega de encontrar e instanciar os Processor Execução
57. • META-INF/services • Nome do arquivo ◦ javax.annotation.processing.Processor • Cada linha do arquivo deve ter o nome completo de cada Processor ◦ com.example.HelloWorldProcessor ServiceLoader
58. Processing Rounds
59. • Acontece em duas etapas • A primeira etapa processa os elementos anotados ◦ Novos arquivos de código fonte podem ser gerados ◦ Os arquivos compilados tem como saída seus bytecodes • A segunda etapa acontece para verificar se novos arquivos gerados ◦ Os eventuais arquivos gerados são compilados e tem como saída os arquivos bytecode Processing Rounds
62. Gerando nosso código
63. public class HelloWorldProcessor extends AbstractProcessor { // . . . @Override public boolean process( Set<? extends TypeElement> annotations, RoundEnvironment env) { Set<? extends Element> elements = env.getElementsAnnotatedWith(HelloWorld.class); for(Element element : elements) { // Analisar os atributos de ‘element’ // Gerar código a partir desses atributos } return false; } }
64. @Override public boolean process( Set<? extends TypeElement> annotations, RoundEnvironment env) { return false; }
65. @Override public boolean process( Set<? extends TypeElement> annotations, RoundEnvironment env) { List<ClassInfo> classesInfo = parseHelloWorldAnnotation(env); return false; }
66. @Override public boolean process( Set<? extends TypeElement> annotations, RoundEnvironment env) { List<ClassInfo> classesInfo = parseHelloWorldAnnotation(env); return false; } List<ClassInfo> parseHelloWorldAnnotation(RoundEnvironment env) { // . . . }
67. @Override public boolean process( Set<? extends TypeElement> annotations, RoundEnvironment env) { List<ClassInfo> classesInfo = parseHelloWorldAnnotation(env); for(ClassInfo classInfo : classesInfo) { generateHelloWorldCode(classInfo); } return false; } List<ClassInfo> parseHelloWorldAnnotation(RoundEnvironment env) { // . . . }
68. @Override public boolean process( Set<? extends TypeElement> annotations, RoundEnvironment env) { List<ClassInfo> classesInfo = parseHelloWorldAnnotation(env); for(ClassInfo classInfo : classesInfo) { generateHelloWorldCode(classInfo); } return false; } List<ClassInfo> parseHelloWorldAnnotation(RoundEnvironment env) { // . . . } void generateHelloWorldCode(ClassInfo classInfo) { // . . . }
69. Element
70. Element
71. Element ClassInfo package: “com.example” element: name: “FooHelloWorld”
72. Element ClassInfo package: “com.example” element: name: “FooHelloWorld” Generated Class
73. Usando algumas armas!
74. • Google Auto Common • Google Auto Service • JavaPoet Usando algumas armas
75. • Lembram? META-INF/services/javax.annotation.processing.Processor Google Auto Service
76. • Lembram? META-INF/services/javax.annotation.processing.Processor • AutoService gera esses arquivos através de anotações! Google Auto Service
77. • Lembram? META-INF/services/javax.annotation.processing.Processor • AutoService gera esses arquivos através de anotações! Google Auto Service public class HelloWorldProcessor extends AbstractProcessor { // . . . }
78. • Lembram? META-INF/services/javax.annotation.processing.Processor • AutoService gera esses arquivos através de anotações! Google Auto Service @AutoService(Processor.class) public class HelloWorldProcessor extends AbstractProcessor { // . . . }
79. TypeSpec.classBuilder(“FooHelloWorld”) .addModifiers(PUBLIC) .addMethod( MethodSpec.constructorBuilder() .addStatement( “System.out.println($S)”, “Hello, world!” ).build(); ).build(); JavaPoet
80. TypeSpec.classBuilder(“FooHelloWorld”) .addModifiers(PUBLIC) .addMethod( MethodSpec.constructorBuilder() .addStatement( “System.out.println($S)”, “Hello, world!” ).build(); ).build(); public class FooHelloWorld { FooHelloWorld() { System.out.println(“Hello, world!”); } } JavaPoet
81. E agora?
82. Perguntas?
84. Obrigado!