Created LoginExceptionView to explain to client why login or refresh have failed.

src/main/java/app/mealsmadeeasy/api/auth/AuthController.java

@@ -46,29 +46,24 @@ public final class AuthController {
                 .body(loginView);
     }
 
+    @ExceptionHandler(LoginException.class)
+    public ResponseEntity<LoginExceptionView> onLoginException(LoginException ex) {
+        final LoginExceptionView loginExceptionView = new LoginExceptionView(ex.getReason(), ex.getMessage());
+        return ResponseEntity.status(HttpStatus.UNAUTHORIZED).body(loginExceptionView);
+    }
+
     @PostMapping("/login")
-    public ResponseEntity<LoginView> login(@RequestBody LoginBody loginBody) {
-        try {
+    public ResponseEntity<LoginView> login(@RequestBody LoginBody loginBody) throws LoginException {
         final LoginDetails loginDetails = this.authService.login(loginBody.getUsername(), loginBody.getPassword());
         return this.getLoginViewResponseEntity(loginDetails);
-        } catch (LoginException loginException) {
-            return ResponseEntity.status(HttpStatus.UNAUTHORIZED).build();
-        }
     }
 
     @PostMapping("/refresh")
     public ResponseEntity<LoginView> refresh(
             @CookieValue(value = "refresh-token", required = false) @Nullable String oldRefreshToken
-    ) {
-        if (oldRefreshToken != null) {
-            try {
+    ) throws LoginException {
         final LoginDetails loginDetails = this.authService.refresh(oldRefreshToken);
         return this.getLoginViewResponseEntity(loginDetails);
-            } catch (LoginException loginException) {
-                return ResponseEntity.status(HttpStatus.UNAUTHORIZED).build();
-            }
-        }
-        return ResponseEntity.status(HttpStatus.UNAUTHORIZED).build();
     }
 
     @PostMapping("/logout")

src/main/java/app/mealsmadeeasy/api/auth/AuthService.java

@@ -1,7 +1,9 @@
 package app.mealsmadeeasy.api.auth;
 
+import org.jetbrains.annotations.Nullable;
+
 public interface AuthService {
     LoginDetails login(String username, String password) throws LoginException;
     void logout(String refreshToken);
-    LoginDetails refresh(String refreshToken) throws LoginException;
+    LoginDetails refresh(@Nullable String refreshToken) throws LoginException;
 }

src/main/java/app/mealsmadeeasy/api/auth/AuthServiceImpl.java

@@ -2,7 +2,7 @@ package app.mealsmadeeasy.api.auth;
 
 import app.mealsmadeeasy.api.jwt.JwtService;
 import app.mealsmadeeasy.api.user.UserEntity;
-import io.jsonwebtoken.JwtException;
+import org.jetbrains.annotations.Nullable;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.security.authentication.AuthenticationManager;
 import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
@@ -45,10 +45,9 @@ public final class AuthServiceImpl implements AuthService {
     @Override
     public LoginDetails login(String username, String password) throws LoginException {
         try {
-            final Authentication authentication = this.authenticationManager.authenticate(new UsernamePasswordAuthenticationToken(
-                    username,
-                    password
-            ));
+            final Authentication authentication = this.authenticationManager.authenticate(
+                    new UsernamePasswordAuthenticationToken(username, password)
+            );
             final UserEntity principal = (UserEntity) authentication.getPrincipal();
             return new LoginDetails(
                     username,
@@ -56,7 +55,7 @@ public final class AuthServiceImpl implements AuthService {
                     this.createRefreshToken(principal)
             );
         } catch (AuthenticationException e) {
-            throw new LoginException(e);
+            throw new LoginException(LoginExceptionReason.INVALID_CREDENTIALS, e);
         }
     }
 
@@ -66,16 +65,23 @@ public final class AuthServiceImpl implements AuthService {
     }
 
     @Override
-    public LoginDetails refresh(String refreshToken) throws LoginException {
-        try {
+    public LoginDetails refresh(@Nullable String refreshToken) throws LoginException {
+        if (refreshToken == null) {
+            throw new LoginException(LoginExceptionReason.NO_REFRESH_TOKEN, "No refresh token provided.");
+        }
+
         final RefreshTokenEntity old = this.refreshTokenRepository.findByToken(refreshToken)
-                    .orElseThrow(() -> new LoginException("No such refresh-token: " + refreshToken));
+                .orElseThrow(() -> new LoginException(
+                        LoginExceptionReason.INVALID_REFRESH_TOKEN,
+                        "No such refresh-token: " + refreshToken
+                ));
         if (old.isRevoked()) {
-                throw new LoginException("RefreshToken is revoked.");
+            throw new LoginException(LoginExceptionReason.INVALID_REFRESH_TOKEN, "RefreshToken is revoked.");
         }
         if (old.getExpires().isBefore(LocalDateTime.now())) {
-                throw new LoginException("RefreshToken is expired.");
+            throw new LoginException(LoginExceptionReason.EXPIRED_REFRESH_TOKEN, "RefreshToken is expired.");
         }
+
         final UserEntity principal = old.getOwner();
         this.refreshTokenRepository.delete(old);
 
@@ -85,9 +91,6 @@ public final class AuthServiceImpl implements AuthService {
                 this.jwtService.generateAccessToken(username),
                 this.createRefreshToken(principal)
         );
-        } catch (JwtException e) {
-            throw new LoginException(e);
-        }
     }
 
 }

src/main/java/app/mealsmadeeasy/api/auth/LoginException.java

@@ -2,16 +2,20 @@ package app.mealsmadeeasy.api.auth;
 
 public final class LoginException extends Exception {
 
-    public LoginException(String message) {
+    private final LoginExceptionReason reason;
+
+    public LoginException(LoginExceptionReason reason, String message) {
         super(message);
+        this.reason = reason;
     }
 
-    public LoginException(String message, Throwable cause) {
-        super(message, cause);
-    }
-
-    public LoginException(Throwable cause) {
+    public LoginException(LoginExceptionReason reason, Throwable cause) {
         super(cause);
+        this.reason = reason;
+    }
+
+    public LoginExceptionReason getReason() {
+        return this.reason;
     }
 
 }

src/main/java/app/mealsmadeeasy/api/auth/LoginExceptionReason.java

@@ -0,0 +1,8 @@
+package app.mealsmadeeasy.api.auth;
+
+public enum LoginExceptionReason {
+    INVALID_CREDENTIALS,
+    EXPIRED_REFRESH_TOKEN,
+    INVALID_REFRESH_TOKEN,
+    NO_REFRESH_TOKEN
+}

src/main/java/app/mealsmadeeasy/api/auth/LoginExceptionView.java

@@ -0,0 +1,21 @@
+package app.mealsmadeeasy.api.auth;
+
+public class LoginExceptionView {
+
+    private final LoginExceptionReason reason;
+    private final String message;
+
+    public LoginExceptionView(LoginExceptionReason reason, String message) {
+        this.reason = reason;
+        this.message = message;
+    }
+
+    public LoginExceptionReason getReason() {
+        return this.reason;
+    }
+
+    public String getMessage() {
+        return this.message;
+    }
+
+}