2022-12-27-Tue-11:19-SingletonContainerTest

src/test/java/hello/core/singleton/StatefulService.java

@@ -0,0 +1,16 @@
+package hello.core.singleton;
+
+public class StatefulService {
+
+    private int price; // 싱글톤 패턴에서 공유 필드는 정말 조심해서 쓰고 늘 stateless 상태로 쓰자
+
+    public void order(String name, int price) {
+        System.out.println("price = " + price + "name = " + name);
+        this.price = price;
+    }
+
+    public int getPrice() {
+        return price; // 여기가 문제
+    }
+
+}

src/test/java/hello/core/singleton/StatefulServiceTest.java

@@ -0,0 +1,38 @@
+package hello.core.singleton;
+
+import org.assertj.core.api.Assertions;
+import org.junit.jupiter.api.Test;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.annotation.Bean;
+
+class StatefulServiceTest {
+
+    @Test
+    void statefulServiceSingleton() {
+        ApplicationContext ac = new AnnotationConfigApplicationContext(TestConfig.class);
+        StatefulService statefulService1 = ac.getBean(StatefulService.class);
+        StatefulService statefulService2 = ac.getBean(StatefulService.class);
+
+        // Thread A : A 사용자가 10,000원 주문
+        statefulService2 .order("userA", 10000);
+
+        // Thread B : B 사용자가 20,000원 주문
+        statefulService2.order("userB", 20000);
+
+        // Thread : 사용자 A 주문 금액 조회 : 20,000원이 나오므르 문제 발생
+        int price = statefulService1.getPrice();
+        System.out.println("price = " + price);
+
+        Assertions.assertThat(statefulService1.getPrice()).isEqualTo(20000);
+    }
+
+    static class TestConfig{
+
+        @Bean
+        public StatefulService statefulService() {
+            return new StatefulService();
+        }
+
+    }
+}