feat(validation): add request and domain validation for email use case

application/src/main/java/com/pablotj/restemailbridge/application/usecase/SendEmailUseCase.java

@@ -5,6 +5,7 @@ import com.pablotj.restemailbridge.application.port.in.EmailDefaultConfigPort;
 import com.pablotj.restemailbridge.application.port.out.EmailPort;
 import com.pablotj.restemailbridge.domain.model.Email;
 import com.pablotj.restemailbridge.domain.repository.EmailRepository;
+import com.pablotj.restemailbridge.domain.service.EmailValidatorService;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -18,20 +19,13 @@ public class SendEmailUseCase {
 
     private static final Logger log = LoggerFactory.getLogger(SendEmailUseCase.class);
 
+    private final EmailValidatorService emailValidatorService;
     private final EmailDefaultConfigPort emailConfigurationPort;
     private final EmailPort emailService;
     private final EmailRepository emailRepository;
 
-    /**
+    public SendEmailUseCase(EmailValidatorService emailValidatorService, EmailDefaultConfigPort emailConfigurationPort, EmailPort emailService, EmailRepository emailRepository) {
-     * Constructor injecting required ports.
+        this.emailValidatorService = emailValidatorService;
-     *
-     * @param emailConfigurationPort Port to retrieve configuration
-     * @param emailService           Service to send emails
-     * @param emailRepository        Repository to persist emails
-     */
-    public SendEmailUseCase(EmailDefaultConfigPort emailConfigurationPort,
-                            EmailPort emailService,
-                            EmailRepository emailRepository) {
         this.emailConfigurationPort = emailConfigurationPort;
         this.emailService = emailService;
         this.emailRepository = emailRepository;
@@ -44,16 +38,19 @@ public class SendEmailUseCase {
      */
     public void handle(EmailDTO emailDTO) {
         String to = emailConfigurationPort.getDefaultRecipient();
+
+        Email email = Email.builder()
+                .from(emailDTO.from())
+                .to(to)
+                .subject(emailDTO.subject())
+                .body(emailDTO.body())
+                .build();
+
+        emailValidatorService.validate(email);
+
         log.info("Sending email from {} to {}", emailDTO.from(), to);
 
-        Email email = emailService.sendEmail(
+        email = emailService.sendEmail(email);
-                Email.builder()
-                        .from(emailDTO.from())
-                        .to(to)
-                        .subject(emailDTO.subject())
-                        .body(emailDTO.body())
-                        .build()
-        );
 
         emailRepository.save(email);
         log.info("Email successfully sent and persisted to repository for recipient {}", to);

domain/src/main/java/com/pablotj/restemailbridge/domain/service/EmailValidatorService.java

@@ -0,0 +1,22 @@
+package com.pablotj.restemailbridge.domain.service;
+
+import com.pablotj.restemailbridge.domain.model.Email;
+
+
+public class EmailValidatorService {
+
+    /**
+     * Validates business rules for Email.
+     */
+    public void validate(Email email) {
+        if (email == null) throw new IllegalArgumentException("Email cannot be null");
+        if (email.getTo() == null || !email.getTo().matches(".+@.+\\..+"))
+            throw new IllegalArgumentException("Recipient email is invalid");
+        if (email.getFrom() == null || email.getFrom().isBlank())
+            throw new IllegalArgumentException("Sender email is required");
+        if (email.getSubject() == null || email.getSubject().isBlank())
+            throw new IllegalArgumentException("Subject is required");
+        if (email.getBody() == null || email.getBody().isBlank())
+            throw new IllegalArgumentException("Body is required");
+    }
+}

infrastructure/src/main/java/com/pablotj/restemailbridge/infrastructure/config/UseCaseConfig.java

@@ -4,6 +4,7 @@ import com.pablotj.restemailbridge.application.port.in.EmailDefaultConfigPort;
 import com.pablotj.restemailbridge.application.port.out.EmailPort;
 import com.pablotj.restemailbridge.application.usecase.SendEmailUseCase;
 import com.pablotj.restemailbridge.domain.repository.EmailRepository;
+import com.pablotj.restemailbridge.domain.service.EmailValidatorService;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 
@@ -12,6 +13,6 @@ public class UseCaseConfig {
 
     @Bean
     public SendEmailUseCase sendEmailUseCase(EmailDefaultConfigPort emailConfigurationPort, EmailPort emailService, EmailRepository emailRepository) {
-        return new SendEmailUseCase(emailConfigurationPort, emailService, emailRepository);
+        return new SendEmailUseCase(new EmailValidatorService(), emailConfigurationPort, emailService, emailRepository);
     }
 }

infrastructure/src/main/java/com/pablotj/restemailbridge/infrastructure/persistence/MailJpa.java

@@ -19,15 +19,15 @@ public class MailJpa {
     @GeneratedValue(strategy = GenerationType.IDENTITY)
     private Long id;
 
-    @Column(nullable = false)
+    @Column(length = 100, nullable = false)
     private String sender;
 
-    @Column(nullable = false)
+    @Column(length = 100, nullable = false)
     private String recipient;
 
-    @Column(nullable = false)
+    @Column(length = 50, nullable = false)
     private String subjet;
 
-    @Column(nullable = false)
+    @Column(length = 40000, nullable = false)
     private String body;
 }

infrastructure/src/main/java/com/pablotj/restemailbridge/infrastructure/rest/GlobalExceptionHandler.java

@@ -0,0 +1,20 @@
+package com.pablotj.restemailbridge.infrastructure.rest;
+
+import java.util.HashMap;
+import java.util.Map;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.MethodArgumentNotValidException;
+import org.springframework.web.bind.annotation.ExceptionHandler;
+import org.springframework.web.bind.annotation.RestControllerAdvice;
+
+@RestControllerAdvice
+public class GlobalExceptionHandler {
+
+    @ExceptionHandler(MethodArgumentNotValidException.class)
+    public ResponseEntity<Map<String, String>> handleValidationExceptions(MethodArgumentNotValidException ex) {
+        Map<String, String> errors = new HashMap<>();
+        ex.getBindingResult().getFieldErrors().forEach(error ->
+                errors.put(error.getField(), error.getDefaultMessage()));
+        return ResponseEntity.badRequest().body(errors);
+    }
+}

infrastructure/src/main/java/com/pablotj/restemailbridge/infrastructure/rest/dto/SendMailRequest.java

@@ -1,8 +1,12 @@
 package com.pablotj.restemailbridge.infrastructure.rest.dto;
 
+import jakarta.validation.constraints.Email;
+import jakarta.validation.constraints.NotBlank;
+import org.hibernate.validator.constraints.Length;
+
 public record SendMailRequest(
-        String from,
+        @NotBlank @Email @Length(min = 4, max = 100) String from,
-        String subject,
+        @NotBlank @Length(min=1, max = 30) String subject,
-        String body
+        @NotBlank @Length(min=1, max = 4000) String body
 ) {
 }