[w06][sujin] Spring Event

topics/06-event/members/sujin/build.gradle

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+// 6주차 학습용 — Spring Event (publishEvent / @EventListener / @TransactionalEventListener / @Async)
+// 도메인: #2 결제(payment). STAGE 1 은 jdbc 없어도 되지만, STAGE 2 트랜잭션 결합부터 H2 사용.
+
+plugins {
+    id 'java'
+    id 'application'
+}
+
+java {
+    toolchain {
+        languageVersion = JavaLanguageVersion.of(21)
+    }
+}
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    implementation 'org.springframework.boot:spring-boot-starter:3.2.0'
+
+    // STAGE 2 트랜잭션 결합 — H2 인메모리
+    implementation 'org.springframework.boot:spring-boot-starter-jdbc:3.2.0'
+    runtimeOnly 'com.h2database:h2:2.2.224'
+
+    // STAGE 4 비교용 — 5 주차 @Audited(AOP) vs 6 주차 이벤트 결과 비교
+    implementation 'org.springframework.boot:spring-boot-starter-aop:3.2.0'
+}
+
+application {
+    // 실행 시 -PmainClass=stage.s1.Stage1HelloEvent 로 덮어씀
+    mainClass = providers.gradleProperty('mainClass').orElse('stage.s1.Stage1HelloEvent')
+}
+
+// -parameters: @EventListener(condition = "...") SpEL / 파라미터 바인딩 안전장치 (5 주차에서 익힘)
+tasks.withType(JavaCompile).configureEach {
+    options.compilerArgs << '-parameters'
+}

topics/06-event/members/sujin/src/main/java/infra/MeasurementLog.java

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+package infra;
+
+import java.io.IOException;
+import java.net.URL;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardOpenOption;
+import java.time.LocalDateTime;
+import java.time.format.DateTimeFormatter;
+
+/**
+ * 측정 / 관찰 결과를 본인 폴더의 measurements.md 에 자동 누적 기록.
+ * (1~3 주차 example 과 동일한 자동 위치 감지 패턴)
+ *
+ * <h3>자동 위치 감지</h3>
+ * IntelliJ Working Directory 설정과 무관하게, 이 클래스의 실제 위치에서
+ * 위로 올라가며 build.gradle 가진 폴더를 찾아 그 안에 measurements.md 를 만든다.
+ *
+ * <h3>6 주차(Spring Event) 형식</h3>
+ * 동시성 측정(누락/실패/ms)이 아니라 자유 텍스트 관찰이 많으므로 {@code save(stage, note)} 사용.
+ * <pre>
+ *   MeasurementLog.save("s1", "HelloEvent 발행 → 동기 리스너 호출 순서 확인 (thread=main)");
+ *   // → measurements.md 에 "- [06-08 14:00] s1 · HelloEvent 발행 → ..." 한 줄 append
+ * </pre>
+ * 시간 측정이 필요한 STAGE 3(@Async) 에선 {@code save(stage, note, millis)} 로 ms 도 기록.
+ */
+public final class MeasurementLog {
+
+    private static final Path FILE = resolveFile();
+    private static final DateTimeFormatter TIME = DateTimeFormatter.ofPattern("MM-dd HH:mm");
+
+    private MeasurementLog() {}
+
+    /** 자유 텍스트 관찰 (STAGE 1~2 주로 사용). */
+    public static void save(String stage, String note) {
+        String line = String.format("- [%s] %s · %s%n",
+            LocalDateTime.now().format(TIME), stage, note);
+        append(line);
+    }
+
+    /** 시간 측정 포함 (STAGE 3 @Async — publisher 블록 시간 등). */
+    public static void save(String stage, String note, double millis) {
+        String line = String.format("- [%s] %s · %s (%.1fms)%n",
+            LocalDateTime.now().format(TIME), stage, note, millis);
+        append(line);
+    }
+
+    private static void append(String line) {
+        try {
+            if (!Files.exists(FILE)) {
+                Files.writeString(FILE,
+                    "# 측정 기록 (6주차 — Spring Event)\n\n자동 누적. 옆에 해석 메모는 직접 추가하세요.\n\n");
+            }
+            Files.writeString(FILE, line, StandardOpenOption.APPEND);
+            System.out.println("→ " + FILE.toAbsolutePath() + " 에 기록됨");
+        } catch (IOException e) {
+            System.err.println("⚠️ measurements.md 기록 실패: " + e.getMessage());
+        }
+    }
+
+    private static Path resolveFile() {
+        try {
+            var domain = MeasurementLog.class.getProtectionDomain();
+            if (domain == null) return Path.of("measurements.md");
+            var codeSource = domain.getCodeSource();
+            if (codeSource == null) return Path.of("measurements.md");
+            URL location = codeSource.getLocation();
+            if (location == null) return Path.of("measurements.md");
+
+            Path start = Path.of(location.toURI());
+            if (Files.isRegularFile(start)) {
+                start = start.getParent();
+            }
+
+            Path current = start;
+            for (int i = 0; i < 10 && current != null; i++) {
+                if (Files.exists(current.resolve("build.gradle"))
+                    || Files.exists(current.resolve("build.gradle.kts"))) {
+                    return current.resolve("measurements.md");
+                }
+                current = current.getParent();
+            }
+        } catch (Exception ignored) {}
+        return Path.of("measurements.md");
+    }
+}

topics/06-event/members/sujin/src/main/java/stage/s1/Stage1HelloEvent.java

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+package stage.s1;
+
+import infra.MeasurementLog;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.context.ApplicationEventPublisher;
+import org.springframework.context.event.EventListener;
+import org.springframework.stereotype.Component;
+import org.springframework.stereotype.Service;
+
+// (1) 이벤트 — record 로 충분 (Spring 4.2+). 완성본.
+record HelloEvent(String message) {}
+
+// (2) Publisher — ApplicationEventPublisher 주입
+@Service
+class HelloService {
+    private final ApplicationEventPublisher publisher;
+
+    HelloService(ApplicationEventPublisher publisher) {
+        this.publisher = publisher;
+    }
+
+    void sayHello(String name) {
+        System.out.println("[publisher] sayHello — " + name
+                + " / thread=" + Thread.currentThread().getName());
+
+        publisher.publishEvent(new HelloEvent("hello " + name));
+
+        System.out.println("[publisher] return"
+                + " / thread=" + Thread.currentThread().getName());
+    }
+}
+
+// (3) Listener — @EventListener 메서드 1 개
+@Component
+class HelloListener {
+
+    @EventListener
+    void onHello(HelloEvent event) {
+        String message = event.message();
+
+        System.out.println("[listener] received — " + message + " / threads=" + Thread.currentThread().getName());
+    }
+}
+
+// (4) main
+@SpringBootApplication
+public class Stage1HelloEvent {
+    public static void main(String[] args) {
+        var ctx = SpringApplication.run(Stage1HelloEvent.class, args);
+        ctx.getBean(HelloService.class).sayHello("world");
+
+        MeasurementLog.save("s1-1", "HelloEvent 발행 → 동기 리스너 호출 순서 println 확인");
+
+    }
+}

topics/06-event/members/sujin/src/main/java/stage/s1/Stage1_2_Order.java

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+package stage.s1;
+
+import infra.MeasurementLog;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.context.ApplicationEventPublisher;
+import org.springframework.context.event.EventListener;
+import org.springframework.core.annotation.Order;
+import org.springframework.stereotype.Component;
+import org.springframework.stereotype.Service;
+
+// 1-2 전용 이벤트 — 1-1 의 HelloEvent 와 분리해서 리스너 교차 발화 방지.
+// (payload 타입이 곧 라우팅 키 — 1-5 에서 다시 나올 개념)
+record OrderDemoEvent(String message) {}
+
+@Service
+class OrderDemoPublisher {
+    private final ApplicationEventPublisher publisher;
+
+    OrderDemoPublisher(ApplicationEventPublisher publisher) {
+        this.publisher = publisher;
+    }
+
+    void publish() {
+        System.out.println("[publisher] publish");
+        publisher.publishEvent(new OrderDemoEvent("hi"));
+        System.out.println("[publisher] return");
+    }
+}
+
+@Component
+class ListenerA {
+    @EventListener
+    @Order(2)
+    void on(OrderDemoEvent e) {
+        System.out.println("[A] " + e.message());
+    }
+}
+
+@Component
+class ListenerB {
+    @EventListener
+    @Order(1)
+    void on(OrderDemoEvent e) {
+        System.out.println("[B] " + e.message());
+    }
+}
+
+@Component
+class ListenerC {
+    @EventListener
+    @Order(0)
+    void on(OrderDemoEvent e) {
+        System.out.println("[C] " + e.message());
+    }
+}
+
+@SpringBootApplication
+public class Stage1_2_Order {
+    public static void main(String[] args) {
+        var ctx = SpringApplication.run(Stage1_2_Order.class, args);
+        ctx.getBean(OrderDemoPublisher.class).publish();
+
+        MeasurementLog.save("s1-2", "@Order로 리스너 호출 순서 제어 확인 (작은 값 먼저)");
+    }
+}

topics/06-event/members/sujin/src/main/java/stage/s1/Stage1_3_Exception.java

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+package stage.s1;
+
+import infra.MeasurementLog;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.context.ApplicationEventPublisher;
+import org.springframework.context.event.EventListener;
+import org.springframework.core.annotation.Order;
+import org.springframework.stereotype.Component;
+import org.springframework.stereotype.Service;
+
+record ExceptionDemoEvent(String message) {}
+
+@Service
+class ExceptionDemoPublisher {
+    private final ApplicationEventPublisher publisher;
+
+    ExceptionDemoPublisher(ApplicationEventPublisher publisher) {
+        this.publisher = publisher;
+    }
+
+    void publish() {
+        System.out.println("[publisher] publish");
+        publisher.publishEvent(new ExceptionDemoEvent("hi"));
+        System.out.println("[publisher] return");   // ← 이 줄이 찍히는지 관찰 포인트
+    }
+}
+
+@Component
+class FirstListener {
+    @EventListener
+    @Order(1)
+    void on(ExceptionDemoEvent e) {
+        System.out.println("[L1 order=1] received");
+    }
+}
+
+@Component
+class FailingListener {
+    @EventListener
+    @Order(2)
+    void on(ExceptionDemoEvent e) {
+        System.out.println("[L2 order=2] received — throwing");
+
+        throw new RuntimeException("일부러 실패");
+    }
+}
+
+@Component
+class ThirdListener {
+    @EventListener
+    @Order(3)
+    void on(ExceptionDemoEvent e) {
+        System.out.println("[L3 order=3] received");   // ← 이게 찍히나? 관찰 포인트
+    }
+}
+
+@SpringBootApplication
+public class Stage1_3_Exception {
+    public static void main(String[] args) {
+        var ctx = SpringApplication.run(Stage1_3_Exception.class, args);
+
+        try {
+            ctx.getBean(ExceptionDemoPublisher.class).publish();
+        } catch (Exception e) {
+            System.out.println("[main] caught — " + e.getMessage());   // ← 전파됐나? 관찰 포인트
+        }
+
+        MeasurementLog.save("s1-3", "동기 기준동작: 예외 전파 O, 체인 중단 O — STAGE3 @Async 면 전파 X 예정");
+    }
+}

topics/06-event/members/sujin/src/main/java/stage/s1/Stage1_4_OldStyle.java

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+package stage.s1;
+
+import infra.MeasurementLog;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.context.ApplicationEvent;
+import org.springframework.context.ApplicationEventPublisher;
+import org.springframework.context.ApplicationListener;
+import org.springframework.context.event.EventListener;
+import org.springframework.stereotype.Component;
+import org.springframework.stereotype.Service;
+
+class LegacyDemoEvent extends ApplicationEvent {
+    private final String message;
+
+    LegacyDemoEvent(Object source, String message) {
+        super(source);                  // ApplicationEvent는 source(발행 주체) 필수
+        this.message = message;
+    }
+
+    String message() { return message; }
+}
+
+@Service
+class LegacyDemoPublisher {
+    private final ApplicationEventPublisher publisher;
+
+    LegacyDemoPublisher(ApplicationEventPublisher publisher) {
+        this.publisher = publisher;
+    }
+
+    void publish() {
+        System.out.println("[publisher] publish");
+        publisher.publishEvent(new LegacyDemoEvent(this, "hi"));
+        System.out.println("[publisher] return");
+    }
+}
+
+// (A) 옛 방식 — ApplicationListener<E> 인터페이스 직접 구현
+@Component
+class OldStyleListener implements ApplicationListener<LegacyDemoEvent> {
+    @Override
+    public void onApplicationEvent(LegacyDemoEvent event) {
+        System.out.println("[OldStyle] " + event.message());
+    }
+}
+
+// (B) 비교용 — 같은 이벤트를 @EventListener 로 받기 (완성 제공)
+@Component
+class AnnotationStyleListener {
+    @EventListener
+    void on(LegacyDemoEvent e) {
+        System.out.println("[Annotation] " + e.message());
+    }
+}
+
+@SpringBootApplication
+public class Stage1_4_OldStyle {
+    public static void main(String[] args) {
+        var ctx = SpringApplication.run(Stage1_4_OldStyle.class, args);
+        ctx.getBean(LegacyDemoPublisher.class).publish();
+
+       MeasurementLog.save("s1-4", "ApplicationListener<E> vs @EventListener — 동작 동일(같은 메커니즘), 단\n" +
+           "  인터페이스는 클래스당 이벤트 1개 고정");
+    }
+}