Clean project

src/main/java/com/github/raychatter/AnnotationHandler.java

@@ -0,0 +1,94 @@
+package com.github.raychatter;
+
+import org.springframework.core.io.ClassPathResource;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.MediaType;
+import org.springframework.web.servlet.HandlerExceptionResolver;
+import org.springframework.web.servlet.ModelAndView;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Scanner;
+
+public class AnnotationHandler implements HandlerExceptionResolver {
+
+   protected static final String DEFAULT_ERROR_STRING = "<error>%s</error>";
+   protected static final String USER_TEMPLATE = "error.template";
+   protected static final String DEFAULT_TEMPLATE = "defaults/default.template";
+   private static final String UTF_8 = "UTF-8";
+
+   //TODO: When there's a wrapper exception leave it unannotated… call the e.getCause() method… until there is an annotated exception or if there are no more causes (e.geCause()==null)??.
+   @Override
+   public ModelAndView resolveException(final HttpServletRequest request, final HttpServletResponse response, final Object handler, final Exception thrownException) {
+      final ExceptionHandler annotation = getAnnotationFrom(thrownException);
+
+      try {
+         if (annotation == null) {
+            thrownException.printStackTrace();
+            return respondWithDefault(thrownException, response);
+         }
+
+         return handleException(annotation, thrownException, response);
+      } catch (IOException e) {
+         // potentially something went wrong in response itself
+         e.printStackTrace();
+      }
+
+      return new ModelAndView();
+   }
+
+   protected ModelAndView handleException(final ExceptionHandler annotation, final Exception thrownException, final HttpServletResponse response) throws IOException {
+      response.setContentType(annotation.contentType());
+      response.setStatus(annotation.httpStatus().value());
+
+      try {
+         final String message = formatMessage(thrownException);
+         response.getWriter().write(message);
+      } catch (IOException e) {
+         return respondWithDefault(thrownException, response);
+      }
+
+      return new ModelAndView();
+   }
+
+   protected ModelAndView respondWithDefault(final Exception thrownException, final HttpServletResponse response) throws IOException {
+      response.setContentType(MediaType.APPLICATION_XML_VALUE);
+      response.setStatus(HttpStatus.INTERNAL_SERVER_ERROR.value());
+      response.getWriter().write(formatDefaultMessage(thrownException));
+
+      return new ModelAndView();
+   }
+
+   protected ExceptionHandler getAnnotationFrom(Exception thrownException) {
+      return thrownException.getClass().getAnnotation(ExceptionHandler.class);
+   }
+
+   protected String formatMessage(final Exception thrownException) throws IOException {
+      return String.format(readTemplate(), thrownException.getMessage());
+   }
+
+   protected String formatDefaultMessage(final Exception thrownException) throws IOException {
+      return String.format(readDefaultTemplate(), thrownException.getMessage());
+   }
+
+   protected String readTemplate() throws IOException {
+      final InputStream templateFile = getResource(USER_TEMPLATE);
+      return new Scanner(templateFile, UTF_8).useDelimiter("\\A").next().trim();
+   }
+
+   protected String readDefaultTemplate() {
+      try {
+         final InputStream templateFile = getResource(DEFAULT_TEMPLATE);
+         return new Scanner(templateFile, UTF_8).useDelimiter("\\A").next().trim();
+      } catch (IOException ex) {
+         return DEFAULT_ERROR_STRING;
+      }
+   }
+
+   protected InputStream getResource(final String resource) throws IOException {
+      return new ClassPathResource(resource).getInputStream();
+   }
+
+}