#22 mvc: view resolver

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

@@ -3,6 +3,9 @@ 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;
+import org.example.mvc.view.View;
+import org.example.mvc.view.ViewResolver;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -13,6 +16,9 @@ import javax.servlet.http.HttpServlet;
 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("/")
 public class DispatcherServlet extends HttpServlet {
@@ -20,11 +26,14 @@ public class DispatcherServlet extends HttpServlet {
     private static final Logger log = LoggerFactory.getLogger(DispatcherServlet.class);
 
     private RequestMappingHandlerMapping requestMappingHandlerMapping;
+    private List<ViewResolver> viewResolvers;
 
     @Override
     public void init() throws ServletException {
         requestMappingHandlerMapping = new RequestMappingHandlerMapping();
         requestMappingHandlerMapping.init();
+
+        viewResolvers = Collections.singletonList(new JspViewResolver());
     }
 
     @Override
@@ -35,12 +44,17 @@ public class DispatcherServlet extends HttpServlet {
             Controller handler =
                     requestMappingHandlerMapping.findHandler(new HandlerKey(RequestMethod.valueOf(req.getMethod()), req.getRequestURI()));
 
-            if (handler == null) return;
+            if (handler == null) {
+                resp.sendError(404);
+                return;
+            }
 
             String viewName = handler.handleRequest(req, resp);
 
-            RequestDispatcher requestDispatcher = req.getRequestDispatcher(viewName);
-            requestDispatcher.forward(req, resp);
+            for (ViewResolver viewResolver : viewResolvers) {
+                View view = viewResolver.resolveView(viewName);
+                view.render(new HashMap<>(), req, resp);
+            }
 
         } catch (Exception e) {
             log.error("exception occured: [{}]", e.getMessage(), e);

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

@@ -0,0 +1,23 @@
+package org.example.mvc.view;
+
+import javax.servlet.RequestDispatcher;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.util.Map;
+
+public class JspView implements View {
+
+    private final String name;
+
+    public JspView(String name) {
+        this.name = name;
+    }
+
+    @Override
+    public void render(Map<String, ?> model, HttpServletRequest request, HttpServletResponse response) throws Exception {
+        model.forEach(request::setAttribute);
+
+        RequestDispatcher requestDispatcher = request.getRequestDispatcher(name);
+        requestDispatcher.forward(request, response);
+    }
+}

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

@@ -0,0 +1,15 @@
+package org.example.mvc.view;
+
+import static org.example.mvc.view.RedirectView.*;
+
+public class JspViewResolver implements ViewResolver {
+    @Override
+    public View resolveView(String viewName) {
+
+        if (viewName.startsWith(DEFAULT_REDIRECT_PREFIX)) {
+            return new RedirectView(viewName);
+        }
+
+        return new JspView(viewName + ".jsp");
+    }
+}

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

@@ -0,0 +1,20 @@
+package org.example.mvc.view;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.util.Map;
+
+public class RedirectView implements View {
+
+    public static final String DEFAULT_REDIRECT_PREFIX = "redirect:";
+    private final String name;
+
+    public RedirectView(String name) {
+        this.name = name;
+    }
+
+    @Override
+    public void render(Map<String, ?> model, HttpServletRequest request, HttpServletResponse response) throws Exception {
+        response.sendRedirect(name.replace(DEFAULT_REDIRECT_PREFIX, ""));
+    }
+}

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

@@ -0,0 +1,10 @@
+package org.example.mvc.view;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.util.Map;
+
+public interface View {
+
+    void render(Map<String, ?> model, HttpServletRequest request, HttpServletResponse response) throws Exception;
+}

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

@@ -0,0 +1,6 @@
+package org.example.mvc.view;
+
+public interface ViewResolver {
+
+    View resolveView(String viewName);
+}