Added samples for annotation processing article. (#705)

* Added annotation processing examples. Fixed core-java8 build on OS X

* Moved projects to separate submodule

annotations/annotation-processing/pom.xml

@@ -0,0 +1,50 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xmlns="http://maven.apache.org/POM/4.0.0"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <version>1.0.0-SNAPSHOT</version>
+        <artifactId>annotations</artifactId>
+        <relativePath>../</relativePath>
+    </parent>
+
+    <artifactId>annotation-processing</artifactId>
+
+    <properties>
+        <auto-service.version>1.0-rc2</auto-service.version>
+        <maven-compiler-plugin.version>3.5.1</maven-compiler-plugin.version>
+    </properties>
+
+    <dependencies>
+
+        <dependency>
+            <groupId>com.google.auto.service</groupId>
+            <artifactId>auto-service</artifactId>
+            <version>${auto-service.version}</version>
+            <scope>provided</scope>
+        </dependency>
+
+    </dependencies>
+
+    <build>
+
+        <plugins>
+
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>${maven-compiler-plugin.version}</version>
+                <configuration>
+                    <source>1.8</source>
+                    <target>1.8</target>
+                </configuration>
+            </plugin>
+
+        </plugins>
+
+    </build>
+
+</project>

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

@@ -0,0 +1,132 @@
+package com.baeldung.annotation.processor;
+
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
+import javax.annotation.processing.*;
+import javax.lang.model.SourceVersion;
+import javax.lang.model.element.Element;
+import javax.lang.model.element.TypeElement;
+import javax.lang.model.type.ExecutableType;
+import javax.tools.Diagnostic;
+import javax.tools.JavaFileObject;
+
+import com.google.auto.service.AutoService;
+
+@SupportedAnnotationTypes("com.baeldung.annotation.processor.BuilderProperty")
+@SupportedSourceVersion(SourceVersion.RELEASE_8)
+@AutoService(Processor.class)
+public class BuilderProcessor extends AbstractProcessor {
+
+    @Override
+    public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
+        for (TypeElement annotation : annotations) {
+
+            Set<? extends Element> annotatedElements = roundEnv.getElementsAnnotatedWith(annotation);
+
+            Map<Boolean, List<Element>> annotatedMethods = annotatedElements.stream()
+                    .collect(Collectors.partitioningBy(element ->
+                            ((ExecutableType) element.asType()).getParameterTypes().size() == 1
+                                    && element.getSimpleName().toString().startsWith("set")));
+
+            List<Element> setters = annotatedMethods.get(true);
+            List<Element> otherMethods = annotatedMethods.get(false);
+
+            otherMethods.forEach(element ->
+                    processingEnv.getMessager().printMessage(Diagnostic.Kind.ERROR,
+                            "@BuilderProperty must be applied to a setXxx method with a single argument", element));
+
+            if (setters.isEmpty()) {
+                continue;
+            }
+
+            String className = ((TypeElement) setters.get(0).getEnclosingElement()).getQualifiedName().toString();
+
+            Map<String, String> setterMap = setters.stream().collect(Collectors.toMap(
+                    setter -> setter.getSimpleName().toString(),
+                    setter -> ((ExecutableType) setter.asType())
+                            .getParameterTypes().get(0).toString()
+            ));
+
+            try {
+                writeBuilderFile(className, setterMap);
+            } catch (IOException e) {
+                e.printStackTrace();
+            }
+
+        }
+
+        return true;
+    }
+
+    private void writeBuilderFile(String className, Map<String, String> setterMap) throws IOException {
+
+        String packageName = null;
+        int lastDot = className.lastIndexOf('.');
+        if (lastDot > 0) {
+            packageName = className.substring(0, lastDot);
+        }
+
+        String simpleClassName = className.substring(lastDot + 1);
+        String builderClassName = className + "Builder";
+        String builderSimpleClassName = builderClassName.substring(lastDot + 1);
+
+        JavaFileObject builderFile = processingEnv.getFiler().createSourceFile(builderClassName);
+        try (PrintWriter out = new PrintWriter(builderFile.openWriter())) {
+
+            if (packageName != null) {
+                out.print("package ");
+                out.print(packageName);
+                out.println(";");
+                out.println();
+            }
+
+            out.print("public class ");
+            out.print(builderSimpleClassName);
+            out.println(" {");
+            out.println();
+
+            out.print("    private ");
+            out.print(simpleClassName);
+            out.print(" object = new ");
+            out.print(simpleClassName);
+            out.println("();");
+            out.println();
+
+            out.print("    public ");
+            out.print(simpleClassName);
+            out.println(" build() {");
+            out.println("        return object;");
+            out.println("    }");
+            out.println();
+
+            setterMap.entrySet().forEach(setter -> {
+                String methodName = setter.getKey();
+                String argumentType = setter.getValue();
+
+                out.print("    public ");
+                out.print(builderSimpleClassName);
+                out.print(" ");
+                out.print(methodName);
+
+                out.print("(");
+
+                out.print(argumentType);
+                out.println(" value) {");
+                out.print("        object.");
+                out.print(methodName);
+                out.println("(value);");
+                out.println("        return this;");
+                out.println("    }");
+                out.println();
+            });
+
+            out.println("}");
+
+        }
+    }
+
+}

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

@@ -0,0 +1,8 @@
+package com.baeldung.annotation.processor;
+
+import java.lang.annotation.*;
+
+@Target(ElementType.METHOD)
+@Retention(RetentionPolicy.SOURCE)
+public @interface BuilderProperty {
+}

annotations/annotation-user/pom.xml

@@ -0,0 +1,51 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <artifactId>annotations</artifactId>
+        <groupId>com.baeldung</groupId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>../</relativePath>
+    </parent>
+
+    <artifactId>annotation-user</artifactId>
+
+    <dependencies>
+
+        <dependency>
+            <groupId>com.baeldung</groupId>
+            <artifactId>annotation-processing</artifactId>
+            <version>${project.parent.version}</version>
+        </dependency>
+
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>4.12</version>
+            <scope>test</scope>
+        </dependency>
+
+    </dependencies>
+
+    <build>
+
+        <plugins>
+
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.5.1</version>
+                <configuration>
+                    <source>1.8</source>
+                    <target>1.8</target>
+                </configuration>
+            </plugin>
+
+        </plugins>
+
+    </build>
+
+</project>

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

@@ -0,0 +1,29 @@
+package com.baeldung.annotation;
+
+import com.baeldung.annotation.processor.BuilderProperty;
+
+public class Person {
+
+    private int age;
+
+    private String name;
+
+    public int getAge() {
+        return age;
+    }
+
+    @BuilderProperty
+    public void setAge(int age) {
+        this.age = age;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    @BuilderProperty
+    public void setName(String name) {
+        this.name = name;
+    }
+
+}

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

@@ -0,0 +1,22 @@
+package com.baeldung.annotation;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class PersonBuilderTest {
+
+    @Test
+    public void whenBuildPersonWithBuilder_thenObjectHasPropertyValues() {
+
+        Person person = new PersonBuilder()
+                .setAge(25)
+                .setName("John")
+                .build();
+
+        assertEquals(25, person.getAge());
+        assertEquals("John", person.getName());
+
+    }
+
+}

annotations/pom.xml

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <parent>
+        <artifactId>parent-modules</artifactId>
+        <groupId>com.baeldung</groupId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>annotations</artifactId>
+    <packaging>pom</packaging>
+
+    <modules>
+        <module>annotation-processing</module>
+        <module>annotation-user</module>
+    </modules>
+
+</project>

core-java-8/pom.xml

@@ -1,9 +1,10 @@
 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
+
     <groupId>com.baeldung</groupId>
+    <version>1.0.0-SNAPSHOT</version>
     <artifactId>core-java8</artifactId>
-    <version>0.1-SNAPSHOT</version>
 
     <name>core-java8</name>
 
@@ -111,6 +112,9 @@
     </build>
 
     <properties>
+
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+
         <!-- logging -->
         <org.slf4j.version>1.7.13</org.slf4j.version>
         <logback.version>1.0.13</logback.version>

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

@@ -1,13 +0,0 @@
-*.class
-
-#folders#
-/target
-/neoDb*
-/data
-/src/main/webapp/WEB-INF/classes
-*/META-INF/*
-
-# Packaged files #
-*.jar
-*.war
-*.ear

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

@@ -0,0 +1 @@
+Lorem ipsum dolor sit amet, consectetur adipiscing elit. Suspendisse facilisis neque sed turpis venenatis, non dignissim risus volutpat.

pom.xml

@@ -132,6 +132,7 @@
         <module>wicket</module>
         <module>xstream</module>
         <module>java-cassandra</module>
+        <module>annotations</module>
     </modules>
 
 </project>