[DI - Step 1] 효오 미션 제출합니다.

nextstep-di/src/main/java/nextstep/di/factory/BeanFactory.java

@@ -4,6 +4,10 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
+import java.util.ArrayList;
+import java.util.List;
 import java.util.Map;
 import java.util.Set;
 
@@ -24,6 +28,34 @@ public <T> T getBean(Class<T> requiredType) {
     }
 
     public void initialize() {
+        for (Class<?> preInstanticateBean : preInstanticateBeans) {
+            beans.put(preInstanticateBean, createBean(preInstanticateBean));
+        }
+    }
+
+    private Object createBean(Class<?> preInstanticateBean) {
+        try {
+            Constructor<?> injectedConstructor = BeanFactoryUtils.getInjectedConstructor(preInstanticateBean);
+            if (injectedConstructor == null) {
+                return createDefaultConstructorInstance(preInstanticateBean);
+            }
+            return createInstance(injectedConstructor);
+        } catch (Exception e) {
+            logger.error("### Bean create fail : {}", e.getMessage());
+            throw new IllegalArgumentException("Bean create fail!");
+        }
+    }
+
+    private Object createDefaultConstructorInstance(Class<?> preInstanticateBean) throws IllegalAccessException, InstantiationException {
+        return preInstanticateBean.newInstance();
+    }
 
+    private Object createInstance(Constructor<?> injectedConstructor) throws IllegalAccessException, InvocationTargetException, InstantiationException {
+        Class<?>[] parameterTypes = injectedConstructor.getParameterTypes();
+        List<Object> parameters = new ArrayList<>();
+        for (Class<?> parameterType : parameterTypes) {
+            parameters.add(getBean(parameterType));
+        }
+        return injectedConstructor.newInstance(parameters.toArray());
     }
 }