From 4f9b7ab878885ebad6ad76079a6d042a68cd0cc6 Mon Sep 17 00:00:00 2001
From: gitchan <eunkeeeee@gmail.com>
Date: Tue, 26 Sep 2023 15:17:42 +0900
Subject: [PATCH] =?UTF-8?q?feat:=20DI=20Stage3=20=ED=86=B5=EA=B3=BC?=
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---
 .../java/di/stage3/context/DIContainer.java   | 42 ++++++++++++++++++-
 .../java/di/stage3/context/Stage3Test.java    |  2 +-
 2 files changed, 41 insertions(+), 3 deletions(-)

diff --git a/study/src/test/java/di/stage3/context/DIContainer.java b/study/src/test/java/di/stage3/context/DIContainer.java
index b62feb1ed3..db13a1b613 100644
--- a/study/src/test/java/di/stage3/context/DIContainer.java
+++ b/study/src/test/java/di/stage3/context/DIContainer.java
@@ -1,6 +1,10 @@
 package di.stage3.context;
 
+import java.lang.reflect.Constructor;
+import java.lang.reflect.Field;
+import java.lang.reflect.InvocationTargetException;
 import java.util.Set;
+import java.util.stream.Collectors;
 
 /**
  * 스프링의 BeanFactory, ApplicationContext에 해당되는 클래스
@@ -10,11 +14,45 @@ class DIContainer {
     private final Set<Object> beans;
 
     public DIContainer(final Set<Class<?>> classes) {
-        this.beans = Set.of();
+        this.beans = classes.stream()
+                .map(this::createInstance)
+                .collect(Collectors.toSet());
+        for (Object bean : this.beans) {
+            Field[] fields = bean.getClass().getDeclaredFields();
+            for (Field field : fields) {
+                Object object = getBean(field.getType());
+                if (object == null) {
+                    return;
+                }
+                try {
+                    field.setAccessible(true);
+                    field.set(bean, object);
+                    field.setAccessible(false);
+                } catch (IllegalAccessException e) {
+                    throw new RuntimeException(e);
+                }
+            }
+        }
+    }
+
+    private Object createInstance(Class<?> aClass) {
+        try {
+            Constructor<?> constructor = aClass.getDeclaredConstructor();
+            constructor.setAccessible(true);
+            Object instance = constructor.newInstance();
+            constructor.setAccessible(false);
+            return instance;
+        } catch (NoSuchMethodException | InstantiationException | IllegalAccessException |
+                 InvocationTargetException e) {
+            throw new RuntimeException(e);
+        }
     }
 
     @SuppressWarnings("unchecked")
     public <T> T getBean(final Class<T> aClass) {
-        return null;
+        return (T) beans.stream()
+                .filter(aClass::isInstance)
+                .findAny()
+                .orElse(null);
     }
 }
diff --git a/study/src/test/java/di/stage3/context/Stage3Test.java b/study/src/test/java/di/stage3/context/Stage3Test.java
index 2363e8666f..c1451aaa44 100644
--- a/study/src/test/java/di/stage3/context/Stage3Test.java
+++ b/study/src/test/java/di/stage3/context/Stage3Test.java
@@ -19,7 +19,7 @@ class Stage3Test {
     void stage3() {
         final var user = new User(1L, "gugu");
 
-        final var diContainer = createDIContainer();
+        DIContainer diContainer = createDIContainer();
 
         /**
          * 제어의 역전(IoC)