Created tests for AnnotationHandler class and added a default template

exception-handler/src/main/java/com/raychatter/common/annotation/AnnotationHandler.java

@@ -1,6 +1,8 @@
 package com.raychatter.common.annotation;
 
 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;
 
@@ -13,45 +15,64 @@ import java.util.Scanner;
 public class AnnotationHandler implements HandlerExceptionResolver {
 
    @Override
-   public ModelAndView resolveException(final HttpServletRequest request,
-                                        final HttpServletResponse response,
-                                        final Object handler,
-                                        final Exception thrownException) {
+   public ModelAndView resolveException(final HttpServletRequest request, final HttpServletResponse response, final Object handler, final Exception thrownException) {
+      final ExceptionHandler annotation = thrownException.getClass().getAnnotation(ExceptionHandler.class);
 
-      final ExceptionHandler exceptionHandlerAnnotation = thrownException.getClass().getAnnotation(ExceptionHandler.class);
-      if (exceptionHandlerAnnotation == null) {
+//    This still returns an empty ModelAndView
+      if (annotation == null) {
          return new ModelAndView();
       }
 
-      return doStuffWithAnnotation(exceptionHandlerAnnotation, thrownException, response);
+      return doStuffWithAnnotation(annotation, thrownException, response);
    }
 
    private ModelAndView doStuffWithAnnotation(final ExceptionHandler exceptionHandlerAnnotation, final Exception thrownException, final HttpServletResponse response) {
 
+//    This is only outside of the try because the null annotation case is handled in resolveException
       response.setContentType(exceptionHandlerAnnotation.contentType());
       response.setStatus(exceptionHandlerAnnotation.httpStatus().value());
+
       try {
          response.getWriter().write(formatMessage(thrownException));
       } catch (IOException e) {
-         e.printStackTrace();
+         response.setContentType(MediaType.APPLICATION_XML_VALUE);
+         response.setStatus(HttpStatus.INTERNAL_SERVER_ERROR.value());
+
+         try {
+            response.getWriter().write(formatDefaultMessage(thrownException));
+         } catch (IOException ex) {
+            ex.printStackTrace();
+         }
       }
+
       return new ModelAndView();
    }
 
-//   Customize your output message here. If you have multiple dynamic parameters to
-//   put into your template, you can assign them all in this method.
-   private String formatMessage(final Exception thrownException) {
+   protected String formatMessage(final Exception thrownException) throws IOException {
       return String.format(readTemplate(), thrownException.getMessage());
    }
 
-   // Reads the template file until the end of the line
-   private String readTemplate() {
+   protected String formatDefaultMessage(final Exception thrownException) throws IOException {
+      return String.format(readDefaultTemplate(), thrownException.getMessage());
+   }
+
+   protected String readTemplate() throws IOException {
+      final InputStream templateFile = new ClassPathResource("error.template").getInputStream();
+      return new Scanner(templateFile, "UTF-8").useDelimiter("\\A").next().trim();
+   }
+
+// Extract into a new protected method to grab input stream; spy that new method, returning null?
+   protected String readDefaultTemplate() {
       try {
-        final InputStream templateFile = new ClassPathResource("error.template").getInputStream();
-        return new Scanner(templateFile, "UTF-8").useDelimiter("\\A").next().trim();
-      } catch (IOException exception) {
-        return "Default Error Message: %s";
+         final InputStream templateFile = getInputStream("defaults/default.template");
+         return new Scanner(templateFile, "UTF-8").useDelimiter("\\A").next().trim();
+      } catch (IOException ex) {
+         return "Error: %s";
       }
    }
 
+   protected InputStream getInputStream(String filepath) throws IOException {
+      return new ClassPathResource(filepath).getInputStream();
+   }
+
 }

exception-handler/src/main/resources/defaults/default.template

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<error>
+%s
+</error>

exception-handler/src/test/java/com/raychatter/common/annotation/AnnotationHandlerTest.java

@@ -1,13 +1,52 @@
 package com.raychatter.common.annotation;
 
-import junit.framework.TestCase;
+import junit.framework.Assert;
 import org.junit.Test;
 
-public class AnnotationHandlerTest extends TestCase {
+import java.io.IOException;
+
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.spy;
+
+public class AnnotationHandlerTest {
 
    @Test
-   public void shouldReturnModelAndViewIfAnnotationIsNull() {
-      AnnotationHandler annotationHandler = new AnnotationHandler();
+   public void formatMessage_ShouldRenderUserTemplate_WhenUserTemplateGiven() throws Exception {
+      final String givenUserTemplate = "A TEMPLATE: %s";
+      final String exceptionMessage = "AN ERROR MESSAGE";
+      final String expectedResult = "A TEMPLATE: AN ERROR MESSAGE";
+
+      AnnotationHandler sut = spy(new AnnotationHandler());
+      doReturn(givenUserTemplate).when(sut).readTemplate();
+
+      final String actual = sut.formatMessage(new Exception(exceptionMessage));
+
+      Assert.assertEquals(expectedResult, actual);
    }
 
-}
+   @Test public void formatDefaultMessage_ShouldRenderDefaultUserTemplate_WhenNoUserTemplateGiven() throws Exception {
+      final String defaultTemplate = "DEFAULT TEMPLATE: %s";
+      final String exceptionMessage = "AN ERROR MESSAGE";
+      final String expectedMessage = "DEFAULT TEMPLATE: AN ERROR MESSAGE";
+
+      AnnotationHandler spyAnnotationHandler = spy(new AnnotationHandler());
+      doReturn(defaultTemplate).when(spyAnnotationHandler).readDefaultTemplate();
+
+      final String actual = spyAnnotationHandler.formatDefaultMessage(new Exception(exceptionMessage));
+
+      Assert.assertEquals(expectedMessage, actual);
+   }
+
+   @Test public void readDefaultTemplate_ShouldCatchIOException_WhenDefaultTemplateNotFound() throws Exception {
+      final String expectedTemplate = "Error: %s";
+      final String defaultFilepath = "defaults/default.template";
+
+      AnnotationHandler spyAnnotationHandler = spy(new AnnotationHandler());
+      doThrow(new IOException()).when(spyAnnotationHandler).getInputStream(defaultFilepath);
+
+      final String actualTemplate = spyAnnotationHandler.readDefaultTemplate();
+
+      Assert.assertEquals(expectedTemplate, actualTemplate);
+   }
+}