[3주차] 관심사 분리 1 : 리플렉션 및 빈 주입 구현

.gitignore

@@ -42,3 +42,6 @@ bin/
 
 ### Mac OS ###
 .DS_Store\ntomcat.8080/
+
+## tomcat
+**/tomcat.8080

build.gradle.kts

@@ -15,6 +15,9 @@ dependencies {
     testImplementation("org.junit.jupiter:junit-jupiter")
     testRuntimeOnly("org.junit.platform:junit-platform-launcher")
 
+    // 리플렉션
+    implementation("org.reflections:reflections:0.10.2")
+
     // ObjectMapper
     implementation("com.fasterxml.jackson.core:jackson-databind:2.18.3")
 

src/main/java/com/diy/app/Lecture.java

@@ -0,0 +1,37 @@
+package com.diy.app;
+
+import com.diy.framework.web.annotation.MethodOrder;
+
+import java.math.BigDecimal;
+
+
+public class Lecture {
+
+    private Long id;
+    private String name;
+    private BigDecimal price;
+
+    public Lecture() {
+    }
+
+    public Long getId() {
+        return id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public BigDecimal getPrice() {
+        return price;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    @MethodOrder(1)
+    private String getDisplayName() {
+        return "lecture";
+    }
+}

src/main/java/com/diy/app/LectureApplication.java

@@ -0,0 +1,32 @@
+package com.diy.app;
+
+import com.diy.framework.web.annotation.Component;
+import com.diy.framework.web.beans.factory.BeanFactory;
+import com.diy.framework.web.beans.factory.BeanScanner;
+import com.diy.framework.web.mvc.Controller;
+import com.diy.framework.web.server.TomcatWebServer;
+import com.diy.framework.web.servlet.DispatcherServlet;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Set;
+
+public class LectureApplication {
+
+    public static void main(String[] args) throws Exception {
+        final BeanScanner beanScanner = new BeanScanner("com.diy.app");
+        final Set<Class<?>> beanClasses = beanScanner.scanClassesTypeAnnotatedWith(Component.class);
+
+        final BeanFactory beanFactory = new BeanFactory();
+        beanFactory.initialize(beanClasses);
+
+        final LectureService lectureService = (LectureService) beanFactory.getBean(LectureService.class);
+
+        final Map<String, Controller> controllerMapping = new HashMap<>();
+        controllerMapping.put("/lectures", new LectureController(lectureService));
+
+        final DispatcherServlet servlet = new DispatcherServlet(controllerMapping);
+        final TomcatWebServer tomcatWebServer = new TomcatWebServer(servlet);
+        tomcatWebServer.start();
+    }
+}

src/main/java/com/diy/app/LectureController.java

@@ -0,0 +1,55 @@
+package com.diy.app;
+
+import com.diy.framework.web.mvc.Controller;
+import com.diy.framework.web.mvc.view.ModelAndView;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Map;
+
+public class LectureController implements Controller {
+
+    private final LectureService lectureService;
+
+    public LectureController(final LectureService lectureService) {
+        this.lectureService = lectureService;
+    }
+
+    @Override
+    public ModelAndView handleRequest(final HttpServletRequest request, final HttpServletResponse response) throws Exception {
+        if ("POST".equals(request.getMethod())) {
+            return doPost(request, response);
+        } else if ("GET".equals(request.getMethod())) {
+            return doGet(request, response);
+        }
+
+        throw new RuntimeException("404 Not Found");
+    }
+
+    private ModelAndView doPost(final HttpServletRequest req, final HttpServletResponse resp) throws ServletException, IOException {
+        final byte[] bodyBytes = req.getInputStream().readAllBytes();
+        final String body = new String(bodyBytes, StandardCharsets.UTF_8);
+
+        final Lecture lecture = new ObjectMapper().readValue(body, Lecture.class);
+        lectureService.save(lecture);
+
+        return new ModelAndView("redirect:/lectures");
+    }
+
+    private ModelAndView doGet(final HttpServletRequest req, final HttpServletResponse resp) throws Exception {
+        final Collection<Lecture> lectures = lectureService.findAll();
+        final Map<String, Object> model = new HashMap<>();
+        final Object lectureModels = lectures.stream()
+                .map(lecture -> Map.of("id", lecture.getId(), "name", lecture.getName(), "price", lecture.getPrice()))
+                .toList();
+        model.put("lectures", lectureModels);
+
+        return new ModelAndView("lecture-list", model);
+    }
+}

src/main/java/com/diy/app/LectureRepository.java

@@ -0,0 +1,25 @@
+package com.diy.app;
+
+import com.diy.framework.web.annotation.Component;
+
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Map;
+
+@Component
+public class LectureRepository {
+
+    // 메모리에 Lecture 데이터를 저장하는 임시 저장소
+    private final Map<Long, Lecture> lectures = new HashMap<>();
+
+    public Lecture save(final Lecture lecture) {
+        final long id = lectures.size();
+        lectures.put(id, lecture);
+        lecture.setId(id);
+        return lecture;
+    }
+
+    public Collection<Lecture> findAll() {
+        return lectures.values();
+    }
+}

src/main/java/com/diy/app/LectureService.java

@@ -0,0 +1,25 @@
+package com.diy.app;
+
+import com.diy.framework.web.annotation.Autowired;
+import com.diy.framework.web.annotation.Component;
+
+import java.util.Collection;
+
+@Component
+public class LectureService {
+
+    private final LectureRepository lectureRepository;
+
+    @Autowired
+    public LectureService(final LectureRepository lectureRepository) {
+        this.lectureRepository = lectureRepository;
+    }
+
+    public Lecture save(final Lecture lecture) {
+        return lectureRepository.save(lecture);
+    }
+
+    public Collection<Lecture> findAll() {
+        return lectureRepository.findAll();
+    }
+}

src/main/java/com/diy/framework/web/annotation/Autowired.java

@@ -0,0 +1,9 @@
+package com.diy.framework.web.annotation;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+// 의존성 주입에 사용할 생성자를 표시하는 애너테이션
+@Retention(RetentionPolicy.RUNTIME)
+public @interface Autowired {
+}

src/main/java/com/diy/framework/web/annotation/Component.java

@@ -0,0 +1,9 @@
+package com.diy.framework.web.annotation;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+// 런타임에 bean으로 등록할 클래스를 구분하기 위한 애너테이션
+@Retention(RetentionPolicy.RUNTIME)
+public @interface Component {
+}

src/main/java/com/diy/framework/web/annotation/MethodOrder.java

@@ -0,0 +1,12 @@
+package com.diy.framework.web.annotation;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+// 실행 중에도 리플렉션으로 읽을 수 있게 설정
+@Retention(RetentionPolicy.RUNTIME)
+public @interface MethodOrder {
+
+    // @MethodOrder(1) 처럼 순서 값을 넣기 위한 값
+    int value();
+}

src/main/java/com/diy/framework/web/beans/factory/BeanFactory.java

@@ -0,0 +1,85 @@
+package com.diy.framework.web.beans.factory;
+
+import com.diy.framework.web.annotation.Autowired;
+
+import java.lang.reflect.Constructor;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Set;
+
+public class BeanFactory {
+
+    private final Map<Class<?>, Object> beans = new HashMap<>();
+    private Set<Class<?>> beanClasses;
+
+    public void addBean(final Class<?> clazz, final Object bean) {
+        // 생성한 빈 저장
+        beans.put(clazz, bean);
+    }
+
+    public void initialize(final Set<Class<?>> beanClasses) throws Exception {
+        this.beanClasses = beanClasses;
+
+        // 빈 클래스들로 객체 생성 후 저장
+        for (Class<?> beanClass : beanClasses) {
+            if (getBean(beanClass) == null) {
+                Object bean = createBean(beanClass);
+                addBean(beanClass, bean);
+            }
+        }
+    }
+
+    public Object getBean(final Class<?> clazz) {
+        // 저장된 빈 조회
+        return beans.get(clazz);
+    }
+
+    private Object createBean(final Class<?> beanClass) throws Exception {
+        // 사용할 생성자 찾기
+        Constructor<?> constructor = findConstructor(beanClass);
+
+        // 생성자 파라미터 타입 가져오기
+        Class<?>[] parameterTypes = constructor.getParameterTypes();
+
+        // 파라미터 없는 생성자면 바로 객체 생성
+        if (parameterTypes.length == 0) {
+            return constructor.newInstance();
+        }
+
+        // 생성자 파라미터에 넣을 빈들 찾기
+        Object[] parameters = new Object[parameterTypes.length];
+        for (int i = 0; i < parameterTypes.length; i++) {
+            parameters[i] = getOrCreateBean(parameterTypes[i]);
+        }
+
+        // 찾은 빈들을 생성자에 넣어서 객체 생성
+        return constructor.newInstance(parameters);
+    }
+
+    private Object getOrCreateBean(final Class<?> beanClass) throws Exception {
+        Object bean = getBean(beanClass);
+        if (bean != null) {
+            return bean;
+        }
+
+        if (!beanClasses.contains(beanClass)) {
+            throw new IllegalArgumentException("빈 클래스를 찾을 수 없습니다: " + beanClass.getName());
+        }
+
+        bean = createBean(beanClass);
+        addBean(beanClass, bean);
+        return bean;
+    }
+
+    private Constructor<?> findConstructor(final Class<?> beanClass) throws NoSuchMethodException {
+        // Autowired 붙은 생성자 찾기
+        for (Constructor<?> constructor : beanClass.getDeclaredConstructors()) {
+            if (constructor.isAnnotationPresent(Autowired.class)) {
+                return constructor;
+            }
+        }
+
+        // 없으면 기본 생성자 사용
+        return beanClass.getDeclaredConstructor();
+    }
+}

src/main/java/com/diy/framework/web/beans/factory/BeanScanner.java

@@ -0,0 +1,25 @@
+package com.diy.framework.web.beans.factory;
+
+import org.reflections.Reflections;
+
+import java.lang.annotation.Annotation;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+public class BeanScanner {
+
+    private final Reflections reflections;
+
+    public BeanScanner(final String... basePackages) {
+        // 스캔할 패키지 설정
+        reflections = new Reflections(basePackages);
+    }
+
+    public Set<Class<?>> scanClassesTypeAnnotatedWith(final Class<? extends Annotation> annotation) {
+        // 특정 애너테이션이 붙은 클래스 찾기
+        return reflections.getTypesAnnotatedWith(annotation)
+                .stream()
+                .filter(type -> (!type.isAnnotation() && !type.isInterface()))
+                .collect(Collectors.toSet());
+    }
+}

src/main/java/com/diy/framework/web/mvc/Controller.java

@@ -0,0 +1,11 @@
+package com.diy.framework.web.mvc;
+
+import com.diy.framework.web.mvc.view.ModelAndView;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+@FunctionalInterface
+public interface Controller {
+    ModelAndView handleRequest(final HttpServletRequest request, final HttpServletResponse response) throws Exception;
+}