code manipulation: relfection(annotation)

code-manipulation/reflection-example/src/main/java/org/example/AnnotationApp.java

@@ -0,0 +1,30 @@
+package org.example;
+
+import java.util.Arrays;
+
+public class AnnotationApp {
+
+    public static void main(String[] args) {
+
+        // 원하는 필드의 애노테이션의 값 가져오기
+        Arrays.stream(Book.class.getDeclaredFields()).forEach(f -> {
+            Arrays.stream(f.getAnnotations()).forEach(a -> {
+                if (a instanceof MyAnnotation) {
+                    MyAnnotation myAnnotation = (MyAnnotation) a;
+                    System.out.println(myAnnotation.name());
+                    System.out.println(myAnnotation.number());
+                }
+            });
+        });
+
+
+//        // 필드에 사용한 애노테이션 가져오기
+//        Arrays.stream(Book.class.getDeclaredFields()).forEach(f -> {
+//            Arrays.stream(f.getAnnotations()).forEach(System.out::println);
+//        });
+
+
+//        // 클래스에 있는 애노테이션 가져오기
+//        Arrays.stream(Book.class.getAnnotations()).forEach(System.out::println);
+    }
+}

code-manipulation/reflection-example/src/main/java/org/example/Book.java

@@ -1,7 +1,10 @@
 package org.example;
 
+
+@MyAnnotation(name = "lee", number = 20)
 public class Book {
 
+    @MyAnnotation
     private static String B = "BOOK";
 
     private static final String C = "BOOK";

code-manipulation/reflection-example/src/main/java/org/example/ClassApiApp.java

@@ -4,7 +4,7 @@ import java.lang.reflect.Field;
 import java.lang.reflect.Modifier;
 import java.util.Arrays;
 
-public class App {
+public class ClassApiApp {
     public static void main( String[] args ) throws ClassNotFoundException {
 
 

code-manipulation/reflection-example/src/main/java/org/example/MyAnnotation.java

@@ -0,0 +1,13 @@
+package org.example;
+
+import java.lang.annotation.*;
+
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ElementType.TYPE, ElementType.FIELD})
+@Inherited
+public @interface MyAnnotation {
+
+    String name() default "kim"; // 기본값을 주지 않으면 애노테이션 사용시 반드시 값을 넣어야 한다.
+
+    int number() default 100;
+}

code-manipulation/reflection-example/src/test/java/org/example/ClassApiAppTest.java

@@ -7,7 +7,7 @@ import org.junit.Test;
 /**
  * Unit test for simple App.
  */
-public class AppTest 
+public class ClassApiAppTest
 {
     /**
      * Rigorous Test :-)