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Added samples for annotation processing article. (eugenp#705)
* Added annotation processing examples. Fixed core-java8 build on OS X * Moved projects to separate submodule
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‎annotations/annotation-processing/pom.xml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xmlns="http://maven.apache.org/POM/4.0.0"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<parent>
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<groupId>com.baeldung</groupId>
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<version>1.0.0-SNAPSHOT</version>
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<artifactId>annotations</artifactId>
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<relativePath>../</relativePath>
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</parent>
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<artifactId>annotation-processing</artifactId>
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<properties>
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<auto-service.version>1.0-rc2</auto-service.version>
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<maven-compiler-plugin.version>3.5.1</maven-compiler-plugin.version>
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</properties>
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<dependencies>
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<dependency>
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<groupId>com.google.auto.service</groupId>
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<artifactId>auto-service</artifactId>
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<version>${auto-service.version}</version>
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<scope>provided</scope>
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</dependency>
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</dependencies>
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<build>
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<plugins>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-compiler-plugin</artifactId>
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<version>${maven-compiler-plugin.version}</version>
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<configuration>
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<source>1.8</source>
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<target>1.8</target>
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</configuration>
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</plugin>
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</plugins>
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</build>
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</project>

‎annotations/annotation-processing/src/main/java/com/baeldung/annotation/processor/BuilderProcessor.java‎

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package com.baeldung.annotation.processor;
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import java.io.IOException;
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import java.io.PrintWriter;
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import java.util.List;
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import java.util.Map;
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import java.util.Set;
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import java.util.stream.Collectors;
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import javax.annotation.processing.*;
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import javax.lang.model.SourceVersion;
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import javax.lang.model.element.Element;
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import javax.lang.model.element.TypeElement;
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import javax.lang.model.type.ExecutableType;
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import javax.tools.Diagnostic;
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import javax.tools.JavaFileObject;
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import com.google.auto.service.AutoService;
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@SupportedAnnotationTypes("com.baeldung.annotation.processor.BuilderProperty")
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@SupportedSourceVersion(SourceVersion.RELEASE_8)
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@AutoService(Processor.class)
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public class BuilderProcessor extends AbstractProcessor {
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@Override
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public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
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for (TypeElement annotation : annotations) {
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Set<? extends Element> annotatedElements = roundEnv.getElementsAnnotatedWith(annotation);
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Map<Boolean, List<Element>> annotatedMethods = annotatedElements.stream()
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.collect(Collectors.partitioningBy(element ->
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((ExecutableType) element.asType()).getParameterTypes().size() == 1
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&& element.getSimpleName().toString().startsWith("set")));
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List<Element> setters = annotatedMethods.get(true);
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List<Element> otherMethods = annotatedMethods.get(false);
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otherMethods.forEach(element ->
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processingEnv.getMessager().printMessage(Diagnostic.Kind.ERROR,
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"@BuilderProperty must be applied to a setXxx method with a single argument", element));
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if (setters.isEmpty()) {
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continue;
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}
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String className = ((TypeElement) setters.get(0).getEnclosingElement()).getQualifiedName().toString();
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Map<String, String> setterMap = setters.stream().collect(Collectors.toMap(
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setter -> setter.getSimpleName().toString(),
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setter -> ((ExecutableType) setter.asType())
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.getParameterTypes().get(0).toString()
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));
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try {
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writeBuilderFile(className, setterMap);
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} catch (IOException e) {
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e.printStackTrace();
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}
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}
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return true;
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}
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private void writeBuilderFile(String className, Map<String, String> setterMap) throws IOException {
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String packageName = null;
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int lastDot = className.lastIndexOf('.');
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if (lastDot > 0) {
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packageName = className.substring(0, lastDot);
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}
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String simpleClassName = className.substring(lastDot + 1);
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String builderClassName = className + "Builder";
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String builderSimpleClassName = builderClassName.substring(lastDot + 1);
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JavaFileObject builderFile = processingEnv.getFiler().createSourceFile(builderClassName);
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try (PrintWriter out = new PrintWriter(builderFile.openWriter())) {
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if (packageName != null) {
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out.print("package ");
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out.print(packageName);
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out.println(";");
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out.println();
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}
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out.print("public class ");
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out.print(builderSimpleClassName);
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out.println(" {");
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out.println();
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out.print(" private ");
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out.print(simpleClassName);
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out.print(" object = new ");
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out.print(simpleClassName);
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out.println("();");
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out.println();
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out.print(" public ");
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out.print(simpleClassName);
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out.println(" build() {");
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out.println(" return object;");
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out.println(" }");
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out.println();
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setterMap.entrySet().forEach(setter -> {
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String methodName = setter.getKey();
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String argumentType = setter.getValue();
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out.print(" public ");
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out.print(builderSimpleClassName);
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out.print(" ");
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out.print(methodName);
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out.print("(");
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out.print(argumentType);
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out.println(" value) {");
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out.print(" object.");
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out.print(methodName);
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out.println("(value);");
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out.println(" return this;");
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out.println(" }");
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out.println();
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});
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out.println("}");
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}
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}
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}

‎annotations/annotation-processing/src/main/java/com/baeldung/annotation/processor/BuilderProperty.java‎

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package com.baeldung.annotation.processor;
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import java.lang.annotation.*;
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@Target(ElementType.METHOD)
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@Retention(RetentionPolicy.SOURCE)
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public @interface BuilderProperty {
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}

‎annotations/annotation-user/pom.xml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<parent>
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<artifactId>annotations</artifactId>
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<groupId>com.baeldung</groupId>
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<version>1.0.0-SNAPSHOT</version>
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<relativePath>../</relativePath>
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</parent>
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<artifactId>annotation-user</artifactId>
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<dependencies>
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<dependency>
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<groupId>com.baeldung</groupId>
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<artifactId>annotation-processing</artifactId>
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<version>${project.parent.version}</version>
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</dependency>
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<dependency>
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<groupId>junit</groupId>
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<artifactId>junit</artifactId>
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<version>4.12</version>
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<scope>test</scope>
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</dependency>
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</dependencies>
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<build>
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<plugins>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-compiler-plugin</artifactId>
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<version>3.5.1</version>
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<configuration>
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<source>1.8</source>
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<target>1.8</target>
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</configuration>
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</plugin>
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</plugins>
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</build>
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</project>

‎annotations/annotation-user/src/main/java/com/baeldung/annotation/Person.java‎

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package com.baeldung.annotation;
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import com.baeldung.annotation.processor.BuilderProperty;
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public class Person {
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private int age;
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private String name;
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public int getAge() {
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return age;
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}
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@BuilderProperty
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public void setAge(int age) {
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this.age = age;
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}
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public String getName() {
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return name;
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}
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@BuilderProperty
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public void setName(String name) {
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this.name = name;
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}
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}

‎annotations/annotation-user/src/test/java/com/baeldung/annotation/PersonBuilderTest.java‎

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package com.baeldung.annotation;
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import org.junit.Test;
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import static org.junit.Assert.assertEquals;
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public class PersonBuilderTest {
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@Test
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public void whenBuildPersonWithBuilder_thenObjectHasPropertyValues() {
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Person person = new PersonBuilder()
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.setAge(25)
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.setName("John")
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.build();
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assertEquals(25, person.getAge());
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assertEquals("John", person.getName());
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}
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}

‎annotations/pom.xml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<parent>
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<artifactId>parent-modules</artifactId>
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<groupId>com.baeldung</groupId>
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<version>1.0.0-SNAPSHOT</version>
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</parent>
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<modelVersion>4.0.0</modelVersion>
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<artifactId>annotations</artifactId>
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<packaging>pom</packaging>
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<modules>
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<module>annotation-processing</module>
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<module>annotation-user</module>
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</modules>
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</project>

‎core-java-8/pom.xml‎

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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<groupId>com.baeldung</groupId>
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<version>1.0.0-SNAPSHOT</version>
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<artifactId>core-java8</artifactId>
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<version>0.1-SNAPSHOT</version>
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<name>core-java8</name>
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</build>
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<properties>
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<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
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<!-- logging -->
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<org.slf4j.version>1.7.13</org.slf4j.version>
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<logback.version>1.0.13</logback.version>

‎core-java-8/src/test/resources/.gitignore‎

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This file was deleted.

‎core-java-8/src/test/resources/test.txt‎

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