code manipulation : annotation processor #2

code-manipulation/annotation-processor/src/main/java/org/example/App.java

@@ -2,7 +2,7 @@ package org.example;
 
 public class App {
     public static void main( String[] args ) {
-//        Moja moja = new MojaFactory();
+        Moja moja = new MagicMoja();
-//        System.out.println(moja.pullOut());
+        System.out.println(moja.pullOut());
     }
 }

code-manipulation/annotation-processor/src/main/java/org/example/Moja.java

@@ -2,6 +2,5 @@ package org.example;
 
 @Magic
 public interface Moja {
-
     String pullOut();
 }

code-manipulation/magic-annotation/pom.xml

@@ -32,6 +32,12 @@
       <version>1.0-rc6</version>
     </dependency>
 
+    <dependency>
+      <groupId>com.squareup</groupId>
+      <artifactId>javapoet</artifactId>
+      <version>1.13.0</version>
+    </dependency>
+
   </dependencies>
 
 </project>

code-manipulation/magic-annotation/src/main/java/org/example/MagicMojaProcessor.java

@@ -1,16 +1,19 @@
 package org.example;
 
 import com.google.auto.service.AutoService;
+import com.squareup.javapoet.ClassName;
+import com.squareup.javapoet.JavaFile;
+import com.squareup.javapoet.MethodSpec;
+import com.squareup.javapoet.TypeSpec;
 
 import javax.annotation.processing.AbstractProcessor;
+import javax.annotation.processing.Filer;
 import javax.annotation.processing.Processor;
 import javax.annotation.processing.RoundEnvironment;
 import javax.lang.model.SourceVersion;
-import javax.lang.model.element.Element;
+import javax.lang.model.element.*;
-import javax.lang.model.element.ElementKind;
-import javax.lang.model.element.Name;
-import javax.lang.model.element.TypeElement;
 import javax.tools.Diagnostic;
+import java.io.IOException;
 import java.util.Set;
 
 @AutoService(Processor.class)
@@ -45,6 +48,36 @@ public class MagicMojaProcessor extends AbstractProcessor {
                 processingEnv.getMessager()
                         .printMessage(Diagnostic.Kind.NOTE, "Processing " + elementName);
             }
+
+            // element 의 className ( FQCN )
+            TypeElement typeElement = (TypeElement) element;
+            ClassName className = ClassName.get(typeElement);
+
+            // pullOut 메소드 생성
+            MethodSpec pullOut = MethodSpec.methodBuilder("pullOut")
+                    .addModifiers(Modifier.PUBLIC)
+                    .returns(String.class)
+                    .addStatement("return $S", "Rabbit!")
+                    .build();
+
+            // magicMoja 클래스 생성
+            TypeSpec magicMoja = TypeSpec.classBuilder("MagicMoja")
+                    .addModifiers(Modifier.PUBLIC)
+                    .addSuperinterface(className)
+                    .addMethod(pullOut)
+                    .build();
+
+            // 위에 정의한 소스코드로 실제 파일 생성
+            Filer filer = processingEnv.getFiler();
+
+            try {
+                JavaFile.builder(className.packageName(), magicMoja)
+                        .build()
+                        .writeTo(filer);
+            } catch (IOException e) {
+                processingEnv.getMessager()
+                        .printMessage(Diagnostic.Kind.ERROR, "FATAL ERROR: " + e);
+            }
         }
         return true;
     }