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@Hello("Annotation Processing!") December 10, 2016 Tatsuya Maki

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2. Annotation Processorをつくる 1. Annotation Processingをしる 3. Annotation Processorをつかう

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2. Annotation Processorをつくる 1. Annotation Processingをしる 3. Annotation Processorをつかう

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AutoValue https://github.com/google/auto

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@AutoValue
 public abstract class User {
 public abstract String name();
 
 public abstract int age();
 }

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final class AutoValue_User extends User {
 private final String name;
 private final int age;
 
 AutoValue_User(String name, int age) {
 if (name == null) {
 throw new NullPointerException("Null name");
 }
 this.name = name;
 this.age = age;
 }
 
 @Override
 public String name() {
 return name;
 }
 
 @Override
 public int age() {
 return age;
 }
 
 @Override
 public String toString() {
 return "User{" + "name=" + name + ", " + "age=" + age + "}";
 }
 
 @Override
 public boolean equals(Object o) {
 if (o == this) {
 return true;
 }


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Butter Knife https://github.com/JakeWharton/butterknife/

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public class MainActivity extends AppCompatActivity {
 @BindView(R.id.fab)
 FloatingActionButton fab;
 
 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 ButterKnife.bind(this);
 }
 
 @OnClick(R.id.fab)
 void showSnackBar(View view) {
 Snackbar.make(view, "FloatingActionButton is clicked!", Snackbar.LENGTH_LONG)
 .setAction("Action", null).show();
 }
 }

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public class MainActivity_ViewBinding implements Unbinder {
 protected T target;
 private View view2131492974;
 
 @UiThread
 public MainActivity_ViewBinding(final T target, View source) {
 this.target = target;
 View view;
 view = Utils.findRequiredView(source, R.id.fab, "field 'fab' and method 'showSnackBar'");
 target.fab = Utils.castView(view, R.id.fab, "field 'fab'", FloatingActionButton.class);
 view2131492974 = view;
 view.setOnClickListener(new DebouncingOnClickListener() {
 @Override
 public void doClick(View p0) {
 target.showSnackBar(p0);
 }
 });
 }
 
 @Override
 @CallSuper
 public void unbind() {
 T target = this.target;
 if (target == null) throw new IllegalStateException("Bindings already cleared.");
 target.fab = null;
 view2131492974.setOnClickListener(null);
 view2131492974 = null;
 this.target = null;
 }
 }

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Dagger 2 https://github.com/google/dagger

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@ActivityScope
 @Component(modules = {ActivityModule.class})
 public interface ActivityComponent {
 void inject(@NonNull MainActivity activity);
 }

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public final class DaggerActivityComponent implements ActivityComponent {
 private DaggerActivityComponent(Builder builder) {
 assert builder != null;
 }
 
 public static Builder builder() {
 return new Builder();
 }
 
 public static ActivityComponent create() {
 return builder().build();
 }
 
 @Override
 public void inject(MainActivity activity) {
 MembersInjectors.noOp().injectMembers(activity);
 }
 
 public static final class Builder {
 private Builder() {
 }
 
 public ActivityComponent build() {
 return new DaggerActivityComponent(this);
 }
 
 public Builder activityModule(ActivityModule activityModule) {
 Preconditions.checkNotNull(activityModule);
 return this;
 }
 }
 }

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Annotation Processingは、 JSR 269で定義されている仕様。 コンパイル時にアノテーションを処理する。 Pluggable Annotation Processor APIのこと。

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*.java *.class

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*.java Parse & Enter 構文解析し、シンボルテーブルへ入力 *.class

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*.java Parse & Enter Annotation Processing アノテーションを処理 *.class

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*.java Parse & Enter Annotation Processing 新しいファイルが生成されると再処理 *.class

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*.java *.class Parse & Enter Annotation Processing Analyze & Generate 構文木を分析し、classファイルに変換

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ソースコードを生成するので安心。 実行時に余計な処理をしないので高速。 コンパイル時に型が検証できるので安全。 Reflectionと比較して、

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2. Annotation Processorをつくる 1. Annotation Processingをしる 3. Annotation Processorをつかう

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Annotationの実装 2 1 3 AnnotationProcessorの実装 AnnotationProcessorを登録

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Annotationの実装 2 1 3 AnnotationProcessorの実装 AnnotationProcessorを登録

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@Target(ElementType.TYPE)
 @Retention(RetentionPolicy.CLASS)
 public @interface MyAnnotation {
 String message();
 }

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@Target(ElementType.TYPE)
 @Retention(RetentionPolicy.CLASS)
 public @interface MyAnnotation {
 String message();
 }

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@Target(ElementType.TYPE)
 @Retention(RetentionPolicy.CLASS)
 public @interface MyAnnotation {
 String message();
 }

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@Target(ElementType.TYPE)
 @Retention(RetentionPolicy.CLASS)
 public @interface MyAnnotation {
 String message();
 }

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@Target(ElementType.TYPE)
 @Retention(RetentionPolicy.CLASS)
 public @interface MyAnnotation {
 String message();
 }

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Annotationの実装 2 1 3 AnnotationProcessorの実装 AnnotationProcessorを登録

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public interface Processor {
 Set getSupportedOptions();
 
 Set getSupportedAnnotationTypes();
 
 SourceVersion getSupportedSourceVersion();
 
 void init(ProcessingEnvironment processingEnv);
 
 boolean process(Set annotations, RoundEnvironment roundEnv);
 
 Iterable getCompletions(Element element, AnnotationMirror annotation, ExecutableElement member, String userText);
 }

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public class MyAnnotationProcessor extends AbstractProcessor { @Override
 public Set getSupportedAnnotationTypes() {
 return Collections.singleton(MyAnnotation.class.getCanonicalName());
 } @Override
 public SourceVersion getSupportedSourceVersion() {
 return SourceVersion.latestSupported();
 } @Override
 public synchronized void init(ProcessingEnvironment environment) {
 super.init(environment);
 messager = environment.getMessager();
 elements = environment.getElementUtils();
 types = environment.getTypeUtils();
 filer = environment.getFiler();
 } @Override
 public boolean process(Set annotations, RoundEnvironment environment) { ... } }

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public class MyAnnotationProcessor extends AbstractProcessor { @Override
 public Set getSupportedAnnotationTypes() {
 return Collections.singleton(MyAnnotation.class.getCanonicalName());
 } @Override
 public SourceVersion getSupportedSourceVersion() {
 return SourceVersion.latestSupported();
 } @Override
 public synchronized void init(ProcessingEnvironment environment) {
 super.init(environment);
 messager = environment.getMessager();
 elements = environment.getElementUtils();
 types = environment.getTypeUtils();
 filer = environment.getFiler();
 } @Override
 public boolean process(Set annotations, RoundEnvironment environment) { ... } }

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public class MyAnnotationProcessor extends AbstractProcessor { @Override
 public Set getSupportedAnnotationTypes() {
 return Collections.singleton(MyAnnotation.class.getCanonicalName());
 } @Override
 public SourceVersion getSupportedSourceVersion() {
 return SourceVersion.latestSupported();
 } @Override
 public synchronized void init(ProcessingEnvironment environment) {
 super.init(environment);
 messager = environment.getMessager();
 elements = environment.getElementUtils();
 types = environment.getTypeUtils();
 filer = environment.getFiler();
 } @Override
 public boolean process(Set annotations, RoundEnvironment environment) { ... } }

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public class MyAnnotationProcessor extends AbstractProcessor { @Override
 public Set getSupportedAnnotationTypes() {
 return Collections.singleton(MyAnnotation.class.getCanonicalName());
 } @Override
 public SourceVersion getSupportedSourceVersion() {
 return SourceVersion.latestSupported();
 } @Override
 public synchronized void init(ProcessingEnvironment environment) {
 super.init(environment);
 messager = environment.getMessager();
 elements = environment.getElementUtils();
 types = environment.getTypeUtils();
 filer = environment.getFiler();
 } @Override
 public boolean process(Set annotations, RoundEnvironment environment) { ... } }

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public class MyAnnotationProcessor extends AbstractProcessor { @Override
 public Set getSupportedAnnotationTypes() {
 return Collections.singleton(MyAnnotation.class.getCanonicalName());
 } @Override
 public SourceVersion getSupportedSourceVersion() {
 return SourceVersion.latestSupported();
 } @Override
 public synchronized void init(ProcessingEnvironment environment) {
 super.init(environment);
 messager = environment.getMessager();
 elements = environment.getElementUtils();
 types = environment.getTypeUtils();
 filer = environment.getFiler();
 } @Override
 public boolean process(Set annotations, RoundEnvironment environment) { ... } }

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public class MyAnnotationProcessor extends AbstractProcessor { @Override
 public Set getSupportedAnnotationTypes() {
 return Collections.singleton(MyAnnotation.class.getCanonicalName());
 } @Override
 public SourceVersion getSupportedSourceVersion() {
 return SourceVersion.latestSupported();
 } @Override
 public synchronized void init(ProcessingEnvironment environment) {
 super.init(environment);
 messager = environment.getMessager();
 elements = environment.getElementUtils();
 types = environment.getTypeUtils();
 filer = environment.getFiler();
 } @Override
 public boolean process(Set annotations, RoundEnvironment environment) { ... } }

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public class MyAnnotationProcessor extends AbstractProcessor { @Override
 public boolean process(Set annotations, RoundEnvironment environment) {
 final Set elements = environment.getElementsAnnotatedWith(MyAnnotation.class);
 elements.forEach(element -> {
 final Name className = element.getSimpleName();
 final Name packageName = this.elements.getPackageOf(element).getQualifiedName();
 try {
 final JavaFileObject file = filer.createSourceFile(packageName + ".MyAnnotation_" + className);
 try (final Writer writer = file.openWriter()) {
 writer.append("package ").append(packageName).append(";\n\n")
 .append("public class MyAnnotation_").append(className).append(" {\n\n")
 .append(" @Override\n")
 .append(" public String toString() {\n");
 
 final MyAnnotation annotation = element.getAnnotation(MyAnnotation.class);
 final String message = annotation.message();
 writer.append(" return \"").append(message).append("\";\n")
 .append(" }\n")
 .append("}\n");
 writer.flush();
 }
 } catch (IOException e) {
 messager.printMessage(Diagnostic.Kind.ERROR, "Failed to generate a file:" + packageName);
 }
 });
 return false;
 }
 }

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public class MyAnnotationProcessor extends AbstractProcessor { @Override
 public boolean process(Set annotations, RoundEnvironment environment) {
 final Set elements = environment.getElementsAnnotatedWith(MyAnnotation.class);
 elements.forEach(element -> {
 final Name className = element.getSimpleName();
 final Name packageName = this.elements.getPackageOf(element).getQualifiedName();
 try {
 final JavaFileObject file = filer.createSourceFile(packageName + ".MyAnnotation_" + className);
 try (final Writer writer = file.openWriter()) {
 writer.append("package ").append(packageName).append(";\n\n")
 .append("public class MyAnnotation_").append(className).append(" {\n\n")
 .append(" @Override\n")
 .append(" public String toString() {\n");
 
 final MyAnnotation annotation = element.getAnnotation(MyAnnotation.class);
 final String value = annotation.value();
 writer.append(" return \"").append(value).append("\";\n")
 .append(" }\n")
 .append("}\n");
 writer.flush();
 }
 } catch (IOException e) {
 messager.printMessage(Diagnostic.Kind.ERROR, "Failed to generate a file:" + packageName);
 }
 });
 return false;
 }
 }

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public class MyAnnotationProcessor extends AbstractProcessor { @Override
 public boolean process(Set annotations, RoundEnvironment environment) {
 final Set elements = environment.getElementsAnnotatedWith(MyAnnotation.class);
 elements.forEach(element -> {
 final Name className = element.getSimpleName();
 final Name packageName = this.elements.getPackageOf(element).getQualifiedName();
 try {
 final JavaFileObject file = filer.createSourceFile(packageName + ".MyAnnotation_" + className);
 try (final Writer writer = file.openWriter()) {
 writer.append("package ").append(packageName).append(";\n\n")
 .append("public class MyAnnotation_").append(className).append(" {\n\n")
 .append(" @Override\n")
 .append(" public String toString() {\n");
 
 final MyAnnotation annotation = element.getAnnotation(MyAnnotation.class);
 final String value = annotation.value();
 writer.append(" return \"").append(value).append("\";\n")
 .append(" }\n")
 .append("}\n");
 writer.flush();
 }
 } catch (IOException e) {
 messager.printMessage(Diagnostic.Kind.ERROR, "Failed to generate a file:" + packageName);
 }
 });
 return false;
 }
 }

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public class MyAnnotationProcessor extends AbstractProcessor { @Override
 public boolean process(Set annotations, RoundEnvironment environment) {
 final Set elements = environment.getElementsAnnotatedWith(MyAnnotation.class);
 elements.forEach(element -> {
 final Name className = element.getSimpleName();
 final Name packageName = this.elements.getPackageOf(element).getQualifiedName();
 try {
 final JavaFileObject file = filer.createSourceFile(packageName + ".MyAnnotation_" + className);
 try (final Writer writer = file.openWriter()) {
 writer.append("package ").append(packageName).append(";\n\n")
 .append("public class MyAnnotation_").append(className).append(" {\n\n")
 .append(" @Override\n")
 .append(" public String toString() {\n");
 
 final MyAnnotation annotation = element.getAnnotation(MyAnnotation.class);
 final String value = annotation.value();
 writer.append(" return \"").append(value).append("\";\n")
 .append(" }\n")
 .append("}\n");
 writer.flush();
 }
 } catch (IOException e) {
 messager.printMessage(Diagnostic.Kind.ERROR, "Failed to generate a file:" + packageName);
 }
 });
 return false;
 }
 }

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public class MyAnnotationProcessor extends AbstractProcessor { @Override
 public boolean process(Set annotations, RoundEnvironment environment) {
 final Set elements = environment.getElementsAnnotatedWith(MyAnnotation.class);
 elements.forEach(element -> {
 final Name className = element.getSimpleName();
 final Name packageName = this.elements.getPackageOf(element).getQualifiedName();
 try {
 final JavaFileObject file = filer.createSourceFile(packageName + ".MyAnnotation_" + className);
 try (final Writer writer = file.openWriter()) {
 writer.append("package ").append(packageName).append(";\n\n")
 .append("public class MyAnnotation_").append(className).append(" {\n\n")
 .append(" @Override\n")
 .append(" public String toString() {\n");
 
 final MyAnnotation annotation = element.getAnnotation(MyAnnotation.class);
 final String value = annotation.value();
 writer.append(" return \"").append(value).append("\";\n")
 .append(" }\n")
 .append("}\n");
 writer.flush();
 }
 } catch (IOException e) {
 messager.printMessage(Diagnostic.Kind.ERROR, "Failed to generate a file:" + packageName);
 }
 });
 return false;
 }
 }

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public class MyAnnotationProcessor extends AbstractProcessor { @Override
 public boolean process(Set annotations, RoundEnvironment environment) {
 final Set elements = environment.getElementsAnnotatedWith(MyAnnotation.class);
 elements.forEach(element -> {
 final Name className = element.getSimpleName();
 final Name packageName = this.elements.getPackageOf(element).getQualifiedName();
 try {
 final JavaFileObject file = filer.createSourceFile(packageName + ".MyAnnotation_" + className);
 try (final Writer writer = file.openWriter()) {
 writer.append("package ").append(packageName).append(";\n\n")
 .append("public class MyAnnotation_").append(className).append(" {\n\n")
 .append(" @Override\n")
 .append(" public String toString() {\n");
 
 final MyAnnotation annotation = element.getAnnotation(MyAnnotation.class);
 final String value = annotation.value();
 writer.append(" return \"").append(value).append("\";\n")
 .append(" }\n")
 .append("}\n");
 writer.flush();
 }
 } catch (IOException e) {
 messager.printMessage(Diagnostic.Kind.ERROR, "Failed to generate a file:" + packageName);
 }
 });
 return false;
 }
 }

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public class MyAnnotationProcessor extends AbstractProcessor { @Override
 public boolean process(Set annotations, RoundEnvironment environment) {
 final Set elements = environment.getElementsAnnotatedWith(MyAnnotation.class);
 elements.forEach(element -> {
 final Name className = element.getSimpleName();
 final Name packageName = this.elements.getPackageOf(element).getQualifiedName();
 try {
 final JavaFileObject file = filer.createSourceFile(packageName + ".MyAnnotation_" + className);
 try (final Writer writer = file.openWriter()) {
 writer.append("package ").append(packageName).append(";\n\n")
 .append("public class MyAnnotation_").append(className).append(" {\n\n")
 .append(" @Override\n")
 .append(" public String toString() {\n");
 
 final MyAnnotation annotation = element.getAnnotation(MyAnnotation.class);
 final String message = annotation.message();
 writer.append(" return \"").append(message).append("\";\n")
 .append(" }\n")
 .append("}\n");
 writer.flush();
 }
 } catch (IOException e) {
 messager.printMessage(Diagnostic.Kind.ERROR, "Failed to generate a file:" + packageName);
 }
 });
 return false;
 }
 }

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public class MyAnnotationProcessor extends AbstractProcessor { @Override
 public boolean process(Set annotations, RoundEnvironment environment) {
 final Set elements = environment.getElementsAnnotatedWith(MyAnnotation.class);
 elements.forEach(element -> {
 final Name className = element.getSimpleName();
 final Name packageName = this.elements.getPackageOf(element).getQualifiedName();
 try {
 final JavaFileObject file = filer.createSourceFile(packageName + ".MyAnnotation_" + className);
 try (final Writer writer = file.openWriter()) {
 writer.append("package ").append(packageName).append(";\n\n")
 .append("public class MyAnnotation_").append(className).append(" {\n\n")
 .append(" @Override\n")
 .append(" public String toString() {\n");
 
 final MyAnnotation annotation = element.getAnnotation(MyAnnotation.class);
 final String message = annotation.message();
 writer.append(" return \"").append(message).append("\";\n")
 .append(" }\n")
 .append("}\n");
 writer.flush();
 }
 } catch (IOException e) {
 messager.printMessage(Diagnostic.Kind.ERROR, "Failed to generate a file:" + packageName);
 }
 });
 return false;
 }
 }

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public class MyAnnotationProcessor extends AbstractProcessor { @Override
 public boolean process(Set annotations, RoundEnvironment environment) {
 final Set elements = environment.getElementsAnnotatedWith(MyAnnotation.class);
 elements.forEach(element -> {
 final Name className = element.getSimpleName();
 final Name packageName = this.elements.getPackageOf(element).getQualifiedName();
 try {
 final JavaFileObject file = filer.createSourceFile(packageName + ".MyAnnotation_" + className);
 try (final Writer writer = file.openWriter()) {
 writer.append("package ").append(packageName).append(";\n\n")
 .append("public class MyAnnotation_").append(className).append(" {\n\n")
 .append(" @Override\n")
 .append(" public String toString() {\n");
 
 final MyAnnotation annotation = element.getAnnotation(MyAnnotation.class);
 final String message = annotation.message();
 writer.append(" return \"").append(message).append("\";\n")
 .append(" }\n")
 .append("}\n");
 writer.flush();
 }
 } catch (IOException e) {
 messager.printMessage(Diagnostic.Kind.ERROR, "Failed to generate a file:" + packageName);
 }
 });
 return false;
 }
 }

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public class MyAnnotationProcessor extends AbstractProcessor { @Override
 public boolean process(Set annotations, RoundEnvironment environment) {
 final Set elements = environment.getElementsAnnotatedWith(MyAnnotation.class);
 elements.forEach(element -> {
 final Name className = element.getSimpleName();
 final Name packageName = this.elements.getPackageOf(element).getQualifiedName();
 try {
 final JavaFileObject file = filer.createSourceFile(packageName + ".MyAnnotation_" + className);
 try (final Writer writer = file.openWriter()) {
 writer.append("package ").append(packageName).append(";\n\n")
 .append("public class MyAnnotation_").append(className).append(" {\n\n")
 .append(" @Override\n")
 .append(" public String toString() {\n");
 
 final MyAnnotation annotation = element.getAnnotation(MyAnnotation.class);
 final String value = annotation.value();
 writer.append(" return \"").append(value).append("\";\n")
 .append(" }\n")
 .append("}\n");
 writer.flush();
 }
 } catch (IOException e) {
 messager.printMessage(Diagnostic.Kind.ERROR, "Failed to generate a file:" + packageName);
 }
 });
 return false;
 }
 }

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Annotationの実装 2 1 3 AnnotationProcessorの実装 AnnotationProcessorを登録

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. |--src | |-- main | | |-- java | | | `-- io.t28.example.MyAnnotationProcessor.java | | `-- resources | | `-- META-INF.services | | `-- javax.annotation.processing.Processor | `-- test | `-- java | `-- io.t28.example.MyAnnotationProcessorTest.java `-- build.gradle

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. |--src | |-- main | | |-- java | | | `-- io.t28.example.MyAnnotationProcessor.java | | `-- resources | | `-- META-INF.services | | `-- javax.annotation.processing.Processor | `-- test | `-- java | `-- io.t28.example.MyAnnotationProcessorTest.java `-- build.gradle

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2. Annotation Processorをつくる 1. Annotation Processingをしる 3. Annotation Processorをつかう

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dependencies {
 compile project(':library')
 annotationProcessor project(':processor') }

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@MyAnnotation(message = "Hello, world.")
 public class MyClass {
 }

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public class MyAnnotation_MyClass {
 
 @Override
 public String toString() {
 return "Hello, world.";
 }
 }


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まとめ

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2. コンパイル時にコードの検証や生成が可能 1. Pluggable Annotation Processing 3. ボイラープレートコードの生成に効果的

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おまけ

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AutoService https://github.com/google/auto/tree/master/service Compile Testing https://github.com/google/compile-testing JavaPoet https://github.com/square/javapoet

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@Thanks