#22 mvc: annotation based

my-framework/mvc-practice/src/main/java/org/example/mvc/AnnotationHandler.java

@@ -0,0 +1,23 @@
+package org.example.mvc;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.lang.reflect.Constructor;
+import java.lang.reflect.Method;
+
+public class AnnotationHandler {
+    private final Class<?> clazz;
+    private final Method tagetMethod;
+
+    public AnnotationHandler(Class<?> clazz, Method targetMethod) {
+        this.clazz = clazz;
+        this.tagetMethod = targetMethod;
+    }
+
+    public String handle(HttpServletRequest request, HttpServletResponse response) throws Exception {
+        Constructor<?> declaredConstructor = clazz.getDeclaredConstructor();
+        Object handler = declaredConstructor.newInstance();
+
+        return (String) tagetMethod.invoke(handler, request, response);
+    }
+}

my-framework/mvc-practice/src/main/java/org/example/mvc/AnnotationHandlerAdapter.java

@@ -0,0 +1,19 @@
+package org.example.mvc;
+
+import org.example.mvc.view.ModelAndView;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+public class AnnotationHandlerAdapter implements HandlerAdapter {
+    @Override
+    public boolean supports(Object handler) {
+        return handler instanceof AnnotationHandler;
+    }
+
+    @Override
+    public ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
+        String viewName = ((AnnotationHandler) handler).handle(request, response);
+        return new ModelAndView(viewName);
+    }
+}

my-framework/mvc-practice/src/main/java/org/example/mvc/AnnotationHandlerMapping.java

@@ -0,0 +1,49 @@
+package org.example.mvc;
+
+import org.example.mvc.annotation.Controller;
+import org.example.mvc.annotation.RequestMapping;
+import org.example.mvc.controller.HandlerKey;
+import org.example.mvc.controller.RequestMethod;
+import org.reflections.Reflections;
+
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Set;
+
+public class AnnotationHandlerMapping implements HandlerMapping {
+
+    private final Object[] basePackage;
+
+    private Map<HandlerKey, AnnotationHandler> handlers = new HashMap<>();
+
+    public AnnotationHandlerMapping(Object... basePackage) {
+        this.basePackage = basePackage;
+    }
+
+    public void init() {
+        Reflections reflections = new Reflections(basePackage);
+
+        Set<Class<?>> classes = reflections.getTypesAnnotatedWith(Controller.class);
+
+        classes.forEach(clazz -> {
+            Arrays.stream(clazz.getDeclaredMethods()).forEach(method -> {
+                RequestMapping requestMapping = method.getDeclaredAnnotation(RequestMapping.class);
+
+                Arrays.stream(getRequestMethods(requestMapping))
+                        .forEach(requestMethod -> handlers.put(
+                                new HandlerKey(requestMethod, requestMapping.value()), new AnnotationHandler(clazz, method)
+                        ));
+            });
+        });
+    }
+
+    private RequestMethod[] getRequestMethods(RequestMapping requestMapping) {
+        return requestMapping.method();
+    }
+
+    @Override
+    public Object findHandler(HandlerKey handlerKey) {
+        return handlers.get(handlerKey);
+    }
+}

my-framework/mvc-practice/src/main/java/org/example/mvc/DispatcherServlet.java

@@ -1,6 +1,5 @@
 package org.example.mvc;
 
-import org.example.mvc.controller.Controller;
 import org.example.mvc.controller.HandlerKey;
 import org.example.mvc.controller.RequestMethod;
 import org.example.mvc.view.JspViewResolver;
@@ -10,7 +9,6 @@ import org.example.mvc.view.ViewResolver;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import javax.servlet.RequestDispatcher;
 import javax.servlet.ServletException;
 import javax.servlet.annotation.WebServlet;
 import javax.servlet.http.HttpServlet;
@@ -18,7 +16,6 @@ import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 import java.io.IOException;
 import java.util.Collections;
-import java.util.HashMap;
 import java.util.List;
 
 @WebServlet("/")
@@ -26,16 +23,27 @@ public class DispatcherServlet extends HttpServlet {
 
     private static final Logger log = LoggerFactory.getLogger(DispatcherServlet.class);
 
-    private RequestMappingHandlerMapping requestMappingHandlerMapping;
+    private List<HandlerMapping> handlerMappings;
     private List<ViewResolver> viewResolvers;
     private List<HandlerAdapter> handlerAdapters;
 
     @Override
     public void init() throws ServletException {
-        requestMappingHandlerMapping = new RequestMappingHandlerMapping();
+        RequestMappingHandlerMapping requestMappingHandlerMapping = new RequestMappingHandlerMapping();
         requestMappingHandlerMapping.init();
 
-        handlerAdapters = List.of(new SimpleControllerHandlerAdaptor());
+        AnnotationHandlerMapping annotationHandlerMapping = new AnnotationHandlerMapping();
+        annotationHandlerMapping.init();
+
+        handlerMappings = List.of(
+                requestMappingHandlerMapping,
+                annotationHandlerMapping
+        );
+
+        handlerAdapters = List.of(
+                new SimpleControllerHandlerAdapter(),
+                new AnnotationHandlerAdapter()
+        );
         viewResolvers = Collections.singletonList(new JspViewResolver());
     }
 
@@ -43,9 +51,15 @@ public class DispatcherServlet extends HttpServlet {
     protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         log.info("[DispatcherServlet] service started.");
 
+        String requestURI = req.getRequestURI();
+        RequestMethod requestMethod = RequestMethod.valueOf(req.getMethod());
+
         try {
-            Controller handler =
+            Object handler = handlerMappings.stream()
-                    requestMappingHandlerMapping.findHandler(new HandlerKey(RequestMethod.valueOf(req.getMethod()), req.getRequestURI()));
+                    .filter(hm -> hm.findHandler(new HandlerKey(requestMethod, requestURI)) != null)
+                    .map(hm -> hm.findHandler(new HandlerKey(requestMethod, requestURI)))
+                    .findFirst()
+                    .orElseThrow(() -> new ServletException("No handler for [" + requestMethod + ", " + requestURI + "]"));
 
             if (handler == null) {
                 resp.sendError(404);

my-framework/mvc-practice/src/main/java/org/example/mvc/HandlerMapping.java

@@ -0,0 +1,7 @@
+package org.example.mvc;
+
+import org.example.mvc.controller.HandlerKey;
+
+public interface HandlerMapping {
+    Object findHandler(HandlerKey handlerKey);
+}

my-framework/mvc-practice/src/main/java/org/example/mvc/RequestMappingHandlerMapping.java

@@ -5,12 +5,12 @@ import org.example.mvc.controller.*;
 import java.util.HashMap;
 import java.util.Map;
 
-public class RequestMappingHandlerMapping {
+public class RequestMappingHandlerMapping implements HandlerMapping {
 
     private Map<HandlerKey, Controller> mappings = new HashMap<>();
 
     void init() {
-        mappings.put(new HandlerKey(RequestMethod.GET, "/"), new HomeController());
+//        mappings.put(new HandlerKey(RequestMethod.GET, "/"), new HomeController());
         mappings.put(new HandlerKey(RequestMethod.GET, "/users"), new UserListController());
         mappings.put(new HandlerKey(RequestMethod.POST, "/users"), new UserCreateController());
         mappings.put(new HandlerKey(RequestMethod.GET, "/user/form"), new ForwardController("/user/form"));

my-framework/mvc-practice/src/main/java/org/example/mvc/SimpleControllerHandlerAdapter.java

@@ -6,7 +6,7 @@ import org.example.mvc.view.ModelAndView;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
-public class SimpleControllerHandlerAdaptor implements HandlerAdapter {
+public class SimpleControllerHandlerAdapter implements HandlerAdapter {
     @Override
     public boolean supports(Object handler) {
         return (handler instanceof Controller);

my-framework/mvc-practice/src/main/java/org/example/mvc/annotation/Controller.java

@@ -0,0 +1,11 @@
+package org.example.mvc.annotation;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Target({ElementType.TYPE})
+@Retention(RetentionPolicy.RUNTIME)
+public @interface Controller {
+}

my-framework/mvc-practice/src/main/java/org/example/mvc/annotation/RequestMapping.java

@@ -0,0 +1,17 @@
+package org.example.mvc.annotation;
+
+import org.example.mvc.controller.RequestMethod;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Target({ElementType.METHOD, ElementType.TYPE})
+@Retention(RetentionPolicy.RUNTIME)
+public @interface RequestMapping {
+
+    String value() default "";
+
+    RequestMethod[] method() default {};
+}

my-framework/mvc-practice/src/main/java/org/example/mvc/controller/HomeController.java

@@ -1,11 +1,16 @@
 package org.example.mvc.controller;
 
+import org.example.mvc.annotation.Controller;
+import org.example.mvc.annotation.RequestMapping;
+
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
-public class HomeController implements Controller{
+@Controller
-    @Override
+public class HomeController {
+
+    @RequestMapping(value = "/",method = RequestMethod.GET)
     public String handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception {
-        return "home.jsp";
+        return "home";
     }
 }