fix(exception-handling): Add ResourceNotFoundException handler for structured error responses [MDD-78]

src/main/java/io/spring/api/exception/CustomizeExceptionHandler.java

@@ -21,6 +21,10 @@
 import org.springframework.web.context.request.WebRequest;
 import org.springframework.web.servlet.mvc.method.annotation.ResponseEntityExceptionHandler;
 
+/**
+ * Global exception handler for REST API controllers.
+ */
+
 @RestControllerAdvice
 public class CustomizeExceptionHandler extends ResponseEntityExceptionHandler {
 
@@ -59,6 +63,18 @@ public ResponseEntity<Object> handleInvalidAuthentication(
             });
   }
 
+  @ExceptionHandler(ResourceNotFoundException.class)
+  public ResponseEntity<Object> handleResourceNotFound(
+      ResourceNotFoundException e, WebRequest request) {
+    return ResponseEntity.status(HttpStatus.NOT_FOUND)
+        .body(
+            new HashMap<String, Object>() {
+              {
+                put("message", "Resource not found");
+              }
+            });
+  }
+
   @Override
   protected ResponseEntity<Object> handleMethodArgumentNotValid(
       MethodArgumentNotValidException e,

src/main/java/io/spring/graphql/exception/GraphQLCustomizeExceptionHandler.java

@@ -9,6 +9,7 @@
 import graphql.execution.DataFetcherExceptionHandlerResult;
 import io.spring.api.exception.FieldErrorResource;
 import io.spring.api.exception.InvalidAuthenticationException;
+import io.spring.api.exception.ResourceNotFoundException;
 import io.spring.graphql.types.Error;
 import io.spring.graphql.types.ErrorItem;
 import java.util.ArrayList;
@@ -38,6 +39,14 @@ public DataFetcherExceptionHandlerResult onException(
               .path(handlerParameters.getPath())
               .build();
       return DataFetcherExceptionHandlerResult.newResult().error(graphqlError).build();
+    } else if (handlerParameters.getException() instanceof ResourceNotFoundException) {
+      GraphQLError graphqlError =
+          TypedGraphQLError.newBuilder()
+              .errorType(ErrorType.NOT_FOUND)
+              .message("Resource not found")
+              .path(handlerParameters.getPath())
+              .build();
+      return DataFetcherExceptionHandlerResult.newResult().error(graphqlError).build();
     } else if (handlerParameters.getException() instanceof ConstraintViolationException) {
       List<FieldErrorResource> errors = new ArrayList<>();
       for (ConstraintViolation<?> violation :

src/test/java/io/spring/api/ProfileApiTest.java

@@ -8,6 +8,7 @@
 
 import io.restassured.module.mockmvc.RestAssuredMockMvc;
 import io.spring.JacksonCustomizations;
+import io.spring.api.exception.CustomizeExceptionHandler;
 import io.spring.api.security.WebSecurityConfig;
 import io.spring.application.ProfileQueryService;
 import io.spring.application.data.ProfileData;
@@ -23,7 +24,7 @@
 import org.springframework.test.web.servlet.MockMvc;
 
 @WebMvcTest(ProfileApi.class)
-@Import({WebSecurityConfig.class, JacksonCustomizations.class})
+@Import({WebSecurityConfig.class, JacksonCustomizations.class, CustomizeExceptionHandler.class})
 public class ProfileApiTest extends TestWithCurrentUser {
   private User anotherUser;
 
@@ -93,4 +94,44 @@ public void should_unfollow_user_success() throws Exception {
 
     verify(userRepository).removeRelation(eq(followRelation));
   }
+
+  @Test
+  public void should_get_404_when_follow_nonexistent_user() throws Exception {
+    when(userRepository.findByUsername(eq("nonexistent")))
+        .thenReturn(Optional.empty());
+    given()
+        .header("Authorization", "Token " + token)
+        .when()
+        .post("/profiles/{username}/follow", "nonexistent")
+        .prettyPeek()
+        .then()
+        .statusCode(404)
+        .body("message", equalTo("Resource not found"));
+  }
+
+  @Test
+  public void should_get_404_when_unfollow_nonexistent_user() throws Exception {
+    when(userRepository.findByUsername(eq("nonexistent")))
+        .thenReturn(Optional.empty());
+    given()
+        .header("Authorization", "Token " + token)
+        .when()
+        .delete("/profiles/{username}/follow", "nonexistent")
+        .prettyPeek()
+        .then()
+        .statusCode(404)
+        .body("message", equalTo("Resource not found"));
+  }
+
+  @Test
+  public void should_get_404_when_get_nonexistent_profile() throws Exception {
+    when(profileQueryService.findByUsername(eq("nonexistent"), eq(null)))
+        .thenReturn(Optional.empty());
+    RestAssuredMockMvc.when()
+        .get("/profiles/{username}", "nonexistent")
+        .prettyPeek()
+        .then()
+        .statusCode(404)
+        .body("message", equalTo("Resource not found"));
+  }
 }