From afbe183231899dd6a4a38708feed22d830babe73 Mon Sep 17 00:00:00 2001
From: haerong22 <haerong22@naver.com>
Date: Fri, 19 Feb 2021 20:38:47 +0900
Subject: [PATCH] code manipulation: relfection(annotation)

---
 .../main/java/org/example/AnnotationApp.java  | 30 +++++++++++++++++++
 .../src/main/java/org/example/Book.java       |  3 ++
 .../example/{App.java => ClassApiApp.java}    |  2 +-
 .../main/java/org/example/MyAnnotation.java   | 13 ++++++++
 .../{AppTest.java => ClassApiAppTest.java}    |  2 +-
 5 files changed, 48 insertions(+), 2 deletions(-)
 create mode 100644 code-manipulation/reflection-example/src/main/java/org/example/AnnotationApp.java
 rename code-manipulation/reflection-example/src/main/java/org/example/{App.java => ClassApiApp.java} (99%)
 create mode 100644 code-manipulation/reflection-example/src/main/java/org/example/MyAnnotation.java
 rename code-manipulation/reflection-example/src/test/java/org/example/{AppTest.java => ClassApiAppTest.java} (90%)

diff --git a/code-manipulation/reflection-example/src/main/java/org/example/AnnotationApp.java b/code-manipulation/reflection-example/src/main/java/org/example/AnnotationApp.java
new file mode 100644
index 00000000..fab12ed8
--- /dev/null
+++ b/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);
+    }
+}
diff --git a/code-manipulation/reflection-example/src/main/java/org/example/Book.java b/code-manipulation/reflection-example/src/main/java/org/example/Book.java
index f43e1411..004ab874 100644
--- a/code-manipulation/reflection-example/src/main/java/org/example/Book.java
+++ b/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";
diff --git a/code-manipulation/reflection-example/src/main/java/org/example/App.java b/code-manipulation/reflection-example/src/main/java/org/example/ClassApiApp.java
similarity index 99%
rename from code-manipulation/reflection-example/src/main/java/org/example/App.java
rename to code-manipulation/reflection-example/src/main/java/org/example/ClassApiApp.java
index 0ae8e2e0..3247ec5b 100644
--- a/code-manipulation/reflection-example/src/main/java/org/example/App.java
+++ b/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 {
 
 
diff --git a/code-manipulation/reflection-example/src/main/java/org/example/MyAnnotation.java b/code-manipulation/reflection-example/src/main/java/org/example/MyAnnotation.java
new file mode 100644
index 00000000..532e3ed0
--- /dev/null
+++ b/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;
+}
diff --git a/code-manipulation/reflection-example/src/test/java/org/example/AppTest.java b/code-manipulation/reflection-example/src/test/java/org/example/ClassApiAppTest.java
similarity index 90%
rename from code-manipulation/reflection-example/src/test/java/org/example/AppTest.java
rename to code-manipulation/reflection-example/src/test/java/org/example/ClassApiAppTest.java
index 6a1d2d79..e52da309 100644
--- a/code-manipulation/reflection-example/src/test/java/org/example/AppTest.java
+++ b/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 :-)