final version

pom.xml

@@ -7,10 +7,57 @@
     <groupId>org.sadtech.example</groupId>
     <artifactId>create-annotation</artifactId>
     <version>0.0.1-SNAPSHOT</version>
+    <packaging>jar</packaging>
 
     <properties>
         <maven.compiler.source>11</maven.compiler.source>
         <maven.compiler.target>11</maven.compiler.target>
     </properties>
 
+    <dependencies>
+        <dependency>
+            <groupId>com.google.auto.service</groupId>
+            <artifactId>auto-service</artifactId>
+            <version>1.0</version>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>30.1.1-jre</version>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-source-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <id>attach-sources</id>
+                        <goals>
+                            <goal>jar</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-javadoc-plugin</artifactId>
+                <configuration>
+                    <javadocExecutable>${java.home}/bin/javadoc</javadocExecutable>
+                </configuration>
+                <executions>
+                    <execution>
+                        <id>attach-javadocs</id>
+                        <goals>
+                            <goal>jar</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+
 </project>

src/main/java/org/sadtech/example/annotation/ClassCreator.java

@@ -0,0 +1,52 @@
+package org.sadtech.example.annotation;
+
+import org.sadtech.example.annotation.domain.ClassDto;
+import org.sadtech.example.annotation.domain.FieldDto;
+
+import javax.annotation.processing.ProcessingEnvironment;
+import javax.tools.JavaFileObject;
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.util.Set;
+
+/**
+ * // TODO: 20.06.2021 Добавить описание.
+ *
+ * @author upagge 20.06.2021
+ */
+public class ClassCreator {
+
+    private ClassCreator() {
+
+    }
+
+    public static void record(ClassDto classDto, ProcessingEnvironment environment) {
+        JavaFileObject builderFile = null;
+        try {
+            builderFile = environment.getFiler().createSourceFile(classDto.getClassName());
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+
+        try (PrintWriter out = new PrintWriter(builderFile.openWriter())) {
+            out.println("package " + classDto.getClassPackage() + ";");
+            out.println();
+            out.print("public class " + classDto.getClassName() + " {");
+            out.println();
+            out.println();
+            generateNames(classDto.getFields(), out);
+            out.println();
+            out.println("}");
+            out.println();
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+
+    private static void generateNames(Set<FieldDto> fields, PrintWriter out) {
+        for (FieldDto field : fields) {
+            out.println("   public static final String " + field.getFieldStringName() + " = \"" + field.getFieldName() + "\";");
+        }
+    }
+
+}

src/main/java/org/sadtech/example/annotation/FieldNames.java

@@ -0,0 +1,14 @@
+package org.sadtech.example.annotation;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Target(ElementType.TYPE)
+@Retention(RetentionPolicy.CLASS)
+public @interface FieldNames {
+
+    String postfix() default "Fields";
+
+}

src/main/java/org/sadtech/example/annotation/domain/ClassDto.java

@@ -0,0 +1,35 @@
+package org.sadtech.example.annotation.domain;
+
+import java.util.Set;
+
+public class ClassDto {
+
+    private String className;
+    private Set<FieldDto> fields;
+    private String classPackage;
+
+    public String getClassName() {
+        return className;
+    }
+
+    public void setClassName(String className) {
+        this.className = className;
+    }
+
+    public Set<FieldDto> getFields() {
+        return fields;
+    }
+
+    public void setFields(Set<FieldDto> fields) {
+        this.fields = fields;
+    }
+
+    public String getClassPackage() {
+        return classPackage;
+    }
+
+    public void setClassPackage(String classPackage) {
+        this.classPackage = classPackage;
+    }
+
+}

src/main/java/org/sadtech/example/annotation/domain/FieldDto.java

@@ -0,0 +1,30 @@
+package org.sadtech.example.annotation.domain;
+
+/**
+ * // TODO: 07.06.2021 Добавить описание.
+ *
+ * @author upagge 07.06.2021
+ */
+public class FieldDto {
+
+    private final String fieldStringName;
+    private final String fieldName;
+
+    private FieldDto(String fieldStringName, String fieldName) {
+        this.fieldStringName = fieldStringName;
+        this.fieldName = fieldName;
+    }
+
+    public static FieldDto of(String fieldStringName, String fieldName) {
+        return new FieldDto(fieldStringName, fieldName);
+    }
+
+    public String getFieldStringName() {
+        return fieldStringName;
+    }
+
+    public String getFieldName() {
+        return fieldName;
+    }
+
+}

src/main/java/org/sadtech/example/annotation/processor/FieldNameProcessor.java

@@ -0,0 +1,67 @@
+package org.sadtech.example.annotation.processor;
+
+import com.google.auto.service.AutoService;
+import com.google.common.base.CaseFormat;
+import org.sadtech.example.annotation.ClassCreator;
+import org.sadtech.example.annotation.FieldNames;
+import org.sadtech.example.annotation.domain.ClassDto;
+import org.sadtech.example.annotation.domain.FieldDto;
+
+import javax.annotation.processing.AbstractProcessor;
+import javax.annotation.processing.Processor;
+import javax.annotation.processing.RoundEnvironment;
+import javax.annotation.processing.SupportedAnnotationTypes;
+import javax.annotation.processing.SupportedSourceVersion;
+import javax.lang.model.SourceVersion;
+import javax.lang.model.element.Element;
+import javax.lang.model.element.TypeElement;
+import javax.lang.model.type.TypeMirror;
+import java.util.Arrays;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+@SupportedAnnotationTypes("org.sadtech.example.annotation.FieldNames")
+@SupportedSourceVersion(SourceVersion.RELEASE_11)
+@AutoService(Processor.class)
+public class FieldNameProcessor extends AbstractProcessor {
+
+    @Override
+    public boolean process(Set<? extends TypeElement> set, RoundEnvironment roundEnvironment) {
+        for (TypeElement annotation : set) {
+            Set<? extends Element> annotatedElements = roundEnvironment.getElementsAnnotatedWith(annotation);
+            for (Element annotatedElement : annotatedElements) {
+                final TypeMirror mirror = annotatedElement.asType();
+                final String annotatedElementName = annotatedElement.getSimpleName().toString();
+                final FieldNames settings = annotatedElement.getAnnotation(FieldNames.class);
+                final String newClassName = annotatedElementName + settings.postfix();
+
+                final Set<FieldDto> fields = annotatedElement.getEnclosedElements().stream()
+                        .filter(this::isField)
+                        .map(
+                                element -> {
+                                    final String fieldName = element.getSimpleName().toString();
+                                    final String fieldStringName = CaseFormat.LOWER_CAMEL.to(CaseFormat.UPPER_UNDERSCORE, fieldName);
+                                    return FieldDto.of(fieldStringName, fieldName);
+                                }
+                        ).collect(Collectors.toSet());
+
+                final ClassDto newClass = new ClassDto();
+                newClass.setClassName(newClassName);
+                newClass.setFields(fields);
+                newClass.setClassPackage(getPackage(mirror));
+                ClassCreator.record(newClass, processingEnv);
+            }
+        }
+        return true;
+    }
+
+    public boolean isField(Element element) {
+        return element != null && element.getKind().isField();
+    }
+
+    public static String getPackage(TypeMirror typeMirror) {
+        final String[] split = typeMirror.toString().split("\\.");
+        return String.join(".", Arrays.copyOf(split, split.length - 1));
+    }
+
+}