#22 mvc: handler adapter

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

@@ -4,6 +4,7 @@ import org.example.mvc.controller.Controller;
 import org.example.mvc.controller.HandlerKey;
 import org.example.mvc.controller.RequestMethod;
 import org.example.mvc.view.JspViewResolver;
+import org.example.mvc.view.ModelAndView;
 import org.example.mvc.view.View;
 import org.example.mvc.view.ViewResolver;
 import org.slf4j.Logger;
@@ -27,12 +28,14 @@ public class DispatcherServlet extends HttpServlet {
 
     private RequestMappingHandlerMapping requestMappingHandlerMapping;
     private List<ViewResolver> viewResolvers;
+    private List<HandlerAdapter> handlerAdapters;
 
     @Override
     public void init() throws ServletException {
         requestMappingHandlerMapping = new RequestMappingHandlerMapping();
         requestMappingHandlerMapping.init();
 
+        handlerAdapters = List.of(new SimpleControllerHandlerAdaptor());
         viewResolvers = Collections.singletonList(new JspViewResolver());
     }
 
@@ -49,11 +52,16 @@ public class DispatcherServlet extends HttpServlet {
                 return;
             }
 
-            String viewName = handler.handleRequest(req, resp);
+            HandlerAdapter handlerAdapter = handlerAdapters.stream()
+                    .filter(ha -> ha.supports(handler))
+                    .findFirst()
+                    .orElseThrow(() -> new ServletException("No adapter for handler [" + handler + "]"));
+
+            ModelAndView modelAndView = handlerAdapter.handle(req, resp, handler);
 
             for (ViewResolver viewResolver : viewResolvers) {
-                View view = viewResolver.resolveView(viewName);
-                view.render(new HashMap<>(), req, resp);
+                View view = viewResolver.resolveView(modelAndView.getViewName());
+                view.render(modelAndView.getModel(), req, resp);
             }
 
         } catch (Exception e) {

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

@@ -0,0 +1,13 @@
+package org.example.mvc;
+
+import org.example.mvc.view.ModelAndView;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+public interface HandlerAdapter {
+
+    boolean supports(Object handler);
+
+    ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception;
+}

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

@@ -0,0 +1,22 @@
+package org.example.mvc;
+
+import org.example.mvc.controller.Controller;
+import org.example.mvc.view.ModelAndView;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+public class SimpleControllerHandlerAdaptor implements HandlerAdapter {
+    @Override
+    public boolean supports(Object handler) {
+        return (handler instanceof Controller);
+    }
+
+    @Override
+    public ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
+        String viewName = ((Controller) handler).handleRequest(request, response);
+
+        return new ModelAndView(viewName);
+    }
+
+}

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

@@ -0,0 +1,23 @@
+package org.example.mvc.view;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+public class ModelAndView {
+
+    private Object view;
+    private final Map<String, Object> model = new HashMap<>();
+
+    public ModelAndView(String viewName) {
+        view = viewName;
+    }
+
+    public Map<String, ?> getModel() {
+        return Collections.unmodifiableMap(model);
+    }
+
+    public String getViewName() {
+        return (this.view instanceof String ? (String) this.view : null);
+    }
+}