spring core advanced : concurrency problem

spring-core/advanced/build.gradle

@@ -23,6 +23,9 @@ dependencies {
     compileOnly 'org.projectlombok:lombok'
     annotationProcessor 'org.projectlombok:lombok'
     testImplementation 'org.springframework.boot:spring-boot-starter-test'
+
+    testCompileOnly 'org.projectlombok:lombok'
+    testAnnotationProcessor 'org.projectlombok:lombok'
 }
 
 test {

spring-core/advanced/src/test/java/com/example/advanced/trace/threadlocal/FieldServiceTest.java

@@ -0,0 +1,42 @@
+package com.example.advanced.trace.threadlocal;
+
+import com.example.advanced.trace.threadlocal.code.FieldService;
+import lombok.extern.slf4j.Slf4j;
+import org.junit.jupiter.api.Test;
+
+@Slf4j
+public class FieldServiceTest {
+
+    private FieldService fieldService = new FieldService();
+
+    @Test
+    void field() {
+        log.info("main start");
+        Runnable userA = () -> {
+            fieldService.logic("userA");
+        };
+
+        Runnable userB = () -> {
+            fieldService.logic("userB");
+        };
+
+        Thread threadA = new Thread(userA);
+        threadA.setName("thread-A");
+        Thread threadB = new Thread(userB);
+        threadA.setName("thread-B");
+
+        threadA.start();
+//        sleep(2000);
+        threadB.start();
+        sleep(3000);
+        log.info("main exit");
+    }
+
+    private void sleep(int millis) {
+        try {
+            Thread.sleep(millis);
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        }
+    }
+}

spring-core/advanced/src/test/java/com/example/advanced/trace/threadlocal/code/FieldService.java

@@ -0,0 +1,25 @@
+package com.example.advanced.trace.threadlocal.code;
+
+import lombok.extern.slf4j.Slf4j;
+
+@Slf4j
+public class FieldService {
+
+    private String nameStore;
+
+    public String logic(String name) {
+        log.info("저장 name={} -> nameStore={}", name, nameStore);
+        nameStore = name;
+        sleep(1000);
+        log.info("조회 nameStore={}", nameStore);
+        return nameStore;
+    }
+
+    private void sleep(int millis) {
+        try {
+            Thread.sleep(millis);
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        }
+    }
+}