implement sending email using Java Mail

Author: jamesjieye

pom.xml

@@ -43,6 +43,15 @@
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-security</artifactId>
     </dependency>
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-mail</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-configuration-processor</artifactId>
+      <optional>true</optional>
+    </dependency>
     <dependency>
       <groupId>mysql</groupId>
       <artifactId>mysql-connector-java</artifactId>
@@ -56,6 +65,10 @@
       <artifactId>commons-io</artifactId>
       <version>${commons-io.version}</version>
     </dependency>
+    <dependency>
+      <groupId>org.freemarker</groupId>
+      <artifactId>freemarker</artifactId>
+    </dependency>
 
     <dependency>
       <groupId>org.springframework.boot</groupId>

src/main/java/com/taskagile/config/ApplicationProperties.java

@@ -0,0 +1,28 @@
+package com.taskagile.config;
+
+import javax.validation.constraints.Email;
+import javax.validation.constraints.NotBlank;
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.validation.annotation.Validated;
+
+@Configuration
+@ConfigurationProperties(prefix="app")
+@Validated
+public class ApplicationProperties {
+
+  /**
+   * Default `from` value of emails sent out by the system
+   */
+  @Email
+  @NotBlank
+  private String mailFrom;
+
+  public void setMailFrom(String mailFrom) {
+    this.mailFrom = mailFrom;
+  }
+
+  public String getMailFrom() {
+    return mailFrom;
+  }
+}

src/main/java/com/taskagile/domain/common/mail/DefaultMailManager.java

@@ -1,12 +1,59 @@
 package com.taskagile.domain.common.mail;
 
+import freemarker.template.Configuration;
+import freemarker.template.Template;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Value;
 import org.springframework.stereotype.Component;
+import org.springframework.ui.freemarker.FreeMarkerTemplateUtils;
+import org.springframework.util.Assert;
+
+import java.util.HashMap;
+import java.util.Map;
 
 @Component
 public class DefaultMailManager implements MailManager {
 
+  private final static Logger log = LoggerFactory.getLogger(DefaultMailManager.class);
+
+  private String mailFrom;
+  private Mailer mailer;
+  private Configuration configuration;
+
+  public DefaultMailManager(@Value("${app.mail-from}") String mailFrom,
+                            Mailer mailer,
+                            Configuration configuration) {
+    this.mailFrom = mailFrom;
+    this.mailer = mailer;
+    this.configuration = configuration;
+  }
+
   @Override
   public void send(String emailAddress, String subject, String template, MessageVariable... variables) {
-    // TODO implement this
+    Assert.hasText(emailAddress, "Parameter `emailAddress` must not be blank");
+    Assert.hasText(subject, "Parameter `subject` must not be blank");
+    Assert.hasText(template, "Parameter `template` must not be blank");
+
+    String messageBody = createMessageBody(template, variables);
+    Message message = new SimpleMessage(emailAddress, subject, messageBody, mailFrom);
+    mailer.send(message);
+  }
+
+  private String createMessageBody(String templateName, MessageVariable... variables) {
+    try {
+      Template template = configuration.getTemplate(templateName);
+      Map<String, Object> model = new HashMap<>();
+      if (variables != null) {
+        for (MessageVariable variable : variables) {
+          model.put(variable.getKey(), variable.getValue());
+        }
+      }
+      return FreeMarkerTemplateUtils.processTemplateIntoString(template, model);
+    } catch (Exception e) {
+      log.error("Failed to create message body from template `" + templateName + "`", e);
+      return null;
+    }
   }
+
 }

src/main/java/com/taskagile/domain/common/mail/Mailer.java

@@ -0,0 +1,11 @@
+package com.taskagile.domain.common.mail;
+
+public interface Mailer {
+
+  /**
+   * Send a message
+   *
+   * @param message the message instance
+   */
+  void send(Message message);
+}

src/main/java/com/taskagile/domain/common/mail/Message.java

@@ -0,0 +1,32 @@
+package com.taskagile.domain.common.mail;
+
+public interface Message {
+
+  /**
+   * Get the recipient of the message
+   *
+   * @return recipient's email address
+   */
+  String getTo();
+
+  /**
+   * Get the subject of the message
+   *
+   * @return message's subject
+   */
+  String getSubject();
+
+  /**
+   * Get the body of the message
+   *
+   * @return the body of the message
+   */
+  String getBody();
+
+  /**
+   * Get the from of this message
+   *
+   * @return where this message is from
+   */
+  String getFrom();
+}

src/main/java/com/taskagile/domain/common/mail/SimpleMessage.java

@@ -0,0 +1,61 @@
+package com.taskagile.domain.common.mail;
+
+import java.util.Objects;
+
+public class SimpleMessage implements Message {
+
+  private String to;
+  private String subject;
+  private String body;
+  private String from;
+
+  public SimpleMessage(String to, String subject, String body, String from) {
+    this.to = to;
+    this.subject = subject;
+    this.body = body;
+    this.from = from;
+  }
+
+  @Override
+  public String getTo() {
+    return to;
+  }
+
+  @Override
+  public String getSubject() {
+    return subject;
+  }
+
+  @Override
+  public String getBody() {
+    return body;
+  }
+
+  public String getFrom() {
+    return from;
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) return true;
+    if (!(o instanceof SimpleMessage)) return false;
+    SimpleMessage that = (SimpleMessage) o;
+    return Objects.equals(to, that.to) &&
+      Objects.equals(subject, that.subject) &&
+      Objects.equals(body, that.body);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(to, subject, body);
+  }
+
+  @Override
+  public String toString() {
+    return "SimpleMessage{" +
+      "to='" + to + '\'' +
+      ", subject='" + subject + '\'' +
+      ", body='" + body + '\'' +
+      '}';
+  }
+}

src/main/java/com/taskagile/infrastructure/mail/AsyncMailer.java

@@ -0,0 +1,52 @@
+package com.taskagile.infrastructure.mail;
+
+import com.taskagile.domain.common.mail.Mailer;
+import com.taskagile.domain.common.mail.Message;
+import org.apache.commons.lang3.StringUtils;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.mail.MailException;
+import org.springframework.mail.SimpleMailMessage;
+import org.springframework.mail.javamail.JavaMailSender;
+import org.springframework.scheduling.annotation.Async;
+import org.springframework.stereotype.Component;
+import org.springframework.util.Assert;
+
+@Component
+public class AsyncMailer implements Mailer {
+
+  private static final Logger log = LoggerFactory.getLogger(AsyncMailer.class);
+
+  private JavaMailSender mailSender;
+
+  public AsyncMailer(JavaMailSender mailSender) {
+    this.mailSender = mailSender;
+  }
+
+  @Async
+  @Override
+  public void send(Message message) {
+    Assert.notNull(message, "Parameter `message` must not be null");
+
+    try {
+      SimpleMailMessage mailMessage = new SimpleMailMessage();
+
+      if (StringUtils.isNotBlank(message.getFrom())) {
+        mailMessage.setFrom(message.getFrom());
+      }
+      if (StringUtils.isNotBlank(message.getSubject())) {
+        mailMessage.setSubject(message.getSubject());
+      }
+      if (StringUtils.isNotEmpty(message.getBody())) {
+        mailMessage.setText(message.getBody());
+      }
+      if (message.getTo() != null) {
+        mailMessage.setTo(message.getTo());
+      }
+
+      mailSender.send(mailMessage);
+    } catch (MailException e) {
+      log.error("Failed to send mail message", e);
+    }
+  }
+}

src/main/resources/application.properties

@@ -1,7 +1,19 @@
+app.mail-from[email protected]
+
 spring.datasource.url=jdbc:mysql://localhost:3306/task_agile?useSSL=false
 spring.datasource.username=<username>
 spring.datasource.password=<password>
 spring.datasource.driver-class-name=com.mysql.jdbc.Driver
 
+spring.jpa.open-in-view=false
+spring.jpa.hibernate.ddl-auto=none
+spring.jpa.database-platform=org.hibernate.dialect.MySQL5InnoDBDialect
+
+spring.freemarker.template-loader-path=classpath:/mail-templates/
+
+spring.mail.host=localhost
+spring.mail.port=1025
+spring.mail.properties.mail.smtp.auth=false
+
 logging.level.com.taskagile=DEBUG
 logging.level.org.springframework.security=DEBUG

src/main/resources/mail-templates/welcome.ftl

@@ -0,0 +1,6 @@
+<h1>Welcome!</h1>
+<p>Here is your registration information:</p>
+<ul>
+  <li>Username: ${user.username}</li>
+  <li>Email Address: ${user.emailAddress}</li>
+</ul>

src/test/java/com/taskagile/domain/common/mail/DefaultMailManagerTests.java

@@ -0,0 +1,90 @@
+package com.taskagile.domain.common.mail;
+
+import freemarker.template.Configuration;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.ArgumentCaptor;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.TestConfiguration;
+import org.springframework.context.annotation.Bean;
+import org.springframework.test.context.ActiveProfiles;
+import org.springframework.test.context.junit4.SpringRunner;
+import org.springframework.ui.freemarker.FreeMarkerConfigurationFactoryBean;
+
+import static org.junit.Assert.assertEquals;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+
+@RunWith(SpringRunner.class)
+@ActiveProfiles("test")
+public class DefaultMailManagerTests {
+
+  @TestConfiguration
+  static class DefaultMessageCreatorConfiguration {
+    @Bean
+    public FreeMarkerConfigurationFactoryBean getFreemarkerConfiguration() {
+      FreeMarkerConfigurationFactoryBean factoryBean = new FreeMarkerConfigurationFactoryBean();
+      factoryBean.setTemplateLoaderPath("/mail-templates/");
+      return factoryBean;
+    }
+  }
+
+  @Autowired
+  private Configuration configuration;
+  private Mailer mailerMock;
+  private DefaultMailManager instance;
+
+  @Before
+  public void setUp() {
+    mailerMock = mock(Mailer.class);
+    instance = new DefaultMailManager("[email protected]", mailerMock, configuration);
+  }
+
+  @Test(expected = IllegalArgumentException.class)
+  public void send_nullEmailAddress_shouldFail() {
+    instance.send(null, "Test subject", "test.ftl");
+  }
+
+  @Test(expected = IllegalArgumentException.class)
+  public void send_emptyEmailAddress_shouldFail() {
+    instance.send("", "Test subject", "test.ftl");
+  }
+
+  @Test(expected = IllegalArgumentException.class)
+  public void send_nullSubject_shouldFail() {
+    instance.send("[email protected]", null, "test.ftl");
+  }
+
+  @Test(expected = IllegalArgumentException.class)
+  public void send_emptySubject_shouldFail() {
+    instance.send("[email protected]", "", "test.ftl");
+  }
+
+  @Test(expected = IllegalArgumentException.class)
+  public void send_nullTemplateName_shouldFail() {
+    instance.send("[email protected]", "Test subject", null);
+  }
+
+  @Test(expected = IllegalArgumentException.class)
+  public void send_emptyTemplateName_shouldFail() {
+    instance.send("[email protected]", "Test subject", "");
+  }
+
+  @Test
+  public void send_validParameters_shouldSucceed() {
+    String to = "[email protected]";
+    String subject = "Test subject";
+    String templateName = "test.ftl";
+
+    instance.send(to, subject, templateName, MessageVariable.from("name", "test"));
+    ArgumentCaptor<Message> messageArgumentCaptor = ArgumentCaptor.forClass(Message.class);
+    verify(mailerMock).send(messageArgumentCaptor.capture());
+
+    Message messageSent = messageArgumentCaptor.getValue();
+    assertEquals(to, messageSent.getTo());
+    assertEquals(subject, messageSent.getSubject());
+    assertEquals("[email protected]", messageSent.getFrom());
+    assertEquals("Hello, test\n", messageSent.getBody());
+  }
+}