發送電子郵件至arraylist從數據庫檢索

Question

我正在一個項目中，我需要從數據庫中檢索電子郵件地址，然後發送電子郵件給他們。我用arraylist檢索了這些電子郵件地址。像這樣：

import java.sql.Connection; 
import java.sql.DriverManager; 
import java.sql.ResultSet; 
import java.sql.SQLException; 
import java.sql.Statement; 
import java.util.ArrayList; 
import java.util.List; 

import javaapplication1.Person; 

public class ABC { 
    public static void main(String[] args) throws SQLException { 
     ArrayList<Person> personlist = new ArrayList<Person>(); 
     //List<Person> personlist = new List<Person>(); 
     try { 


      Class.forName("oracle.jdbc.driver.OracleDriver"); 
      Connection con=DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:xe","gsjsc","gsjschanna"); 
      Statement st=con.createStatement(); 

      ResultSet srs = st.executeQuery("SELECT * FROM person2"); 
      while (srs.next()) { 
       Person person = new Person(); 
       person.setName(srs.getString("name")); 
       person.setJobtitle(srs.getString("jobtitle")); 
       // person.setFrequentflyer(srs.getInt("frequentflyer")); 
       personlist.add(person); 
      } 

      System.out.println(personlist.size()); 
      for (int a=0;a<personlist.size();a++) 
      { 
      System.out.println(personlist.get(a).getName()); 
      System.out.println(personlist.get(a).getJobtitle()); 
      // System.out.println(personlist.get(2).getName()); 
      // System.out.println(personlist.get(3).getName()); 
      } 
      //System.out.println(personlist.get(4)); 

     //System.out.println(namelist.); 
     } catch (Exception e) { 
      System.err.println("Got an exception! "); 
      System.err.println(e.getMessage()); 
     } 
    } 
} 

Person.java：包含所有的setter和getters。

編輯

現在我要發送電子郵件到對象人的ArrayList中檢索這些電子郵件地址。 我有一個代碼，像這樣的數組列表中發送郵件給多個收件人：

package javaapplication1; 
import java.util.ArrayList; 
import java.util.List; 
import java.util.Properties; 
import java.util.Scanner; 
import javax.mail.Address; 
import javax.mail.Authenticator; 
import javax.mail.Message; 
import javax.mail.MessagingException; 
import javax.mail.PasswordAuthentication; 
import javax.mail.Session; 
import javax.mail.Transport; 
import javax.mail.internet.AddressException; 
import javax.mail.internet.InternetAddress; 
import javax.mail.internet.MimeMessage; 

public class SendEmailToGroupDemo { 

public static void main(String[] args) { 

    // Create a SendEmail object and call start 
    // method to send a mail in Java. 
    SendEmailToGroupDemo sendEmailToGroup = new SendEmailToGroupDemo(); 
    sendEmailToGroup.start(); 

} 

private void start() { 

    // For establishment of email client with 
    // Google's gmail use below properties. 
    // For TLS Connection use below properties 
    // Create a Properties object 
    Properties props = new Properties(); 

    // these properties are required 
    // providing smtp auth property to true 
    props.put("mail.smtp.auth", "true"); 
    // providing tls enability 
    props.put("mail.smtp.starttls.enable", "true"); 
    // providing the smtp host i.e gmail.com 
    props.put("mail.smtp.host", "smtp.gmail.com"); 
    // providing smtp port as 587 
    props.put("mail.smtp.port", "587"); 

    // For SSL Connection use below properties 

    /*props.put("mail.smtp.host", "smtp.gmail.com"); 
    props.put("mail.smtp.socketFactory.port", "465"); 
    props.put("mail.smtp.socketFactory.class", 
    "javax.net.ssl.SSLSocketFactory"); 
    props.put("mail.smtp.auth", "true"); 
    props.put("mail.smtp.port", "465");*/ 

    // Create Scanner object to take necessary 
    // values from the user. 
    Scanner scanner = new Scanner(System.in); 

    System.out.println("Please provide your Username for Authentication ..."); 
    final String Username = scanner.next(); 

    System.out.println("Please provide your Password for Authentication ..."); 
    final String Password = scanner.next(); 

    System.out.println("Please provide Email Address from which you want to send Email ..."); 
    final String fromEmailAddress = scanner.next(); 

    System.out.println("Please provide Email Addresses to which you want to send Email ..."); 
    System.out.println("If you are done type : Done or done"); 

    // ArrayLists to store email addresses entered by user 
    ArrayList< String> emails = (ArrayList<String>) getEmails(); 

    System.out.println("Please provide Subject for your Email ... "); 
    final String subject = scanner.next(); 

    System.out.println("Please provide Text Message for your Email ... "); 
    final String textMessage = scanner.next(); 

    // Create a Session object based on the properties and 
    // Authenticator object 
    Session session = Session.getDefaultInstance(props, 
    new LoginAuthenticator(Username,Password)); 

    try { 

    // Create a Message object using the session created above 
    Message message = new MimeMessage(session); 

    // setting email address to Message from where message is being sent 
    message.setFrom(new InternetAddress(fromEmailAddress)); 

    // setting the email addressess to which user wants to send message 
    message.setRecipients(Message.RecipientType.BCC, getEmailsList(emails)); 

    // setting the subject for the email 
    message.setSubject(subject); 

    // setting the text message which user wants to send to recipients 
    message.setText(textMessage); 

    // Using the Transport class send() method to send message 
    Transport.send(message); 

    System.out.println("\nYour Message delivered successfully ...."); 

    } catch (MessagingException e) { 

    throw new RuntimeException(e); 

    } 
} 

// This method takes a list of email addresses and 
// returns back an array of Address by looping the 
// list one by one and storing it into Address[] 
private Address[] getEmailsList(ArrayList<String> emails) { 

    Address[] emaiAddresses = new Address[emails.size()]; 

    for (int i =0;i < emails.size();i++) { 
    try { 
    emaiAddresses[i] = new InternetAddress(emails.get(i)); 
    } 
    catch (AddressException e) { 

    e.printStackTrace(); 
    } 
    } 
    return emaiAddresses; 
} 

// This method prompts user for email group to which he 
// wants to send message 
public List<String> getEmails() { 
    ArrayList<String> emails = new ArrayList<String>(); 

    int counter = 1; 
    String address = ""; 
    Scanner scanner = new Scanner(System.in); 

    // looping inifinitely times as long as user enters 
    // emails one by one 
    // the while loop breaks when user types done and 
    // press enter. 
    while(true) { 

    System.out.println("Enter E-Mail : " + counter); 
    address = scanner.next(); 

    if(address.equalsIgnoreCase("Done")){ 
    break; 
    } 
    else { 
    emails.add(address); 
    counter++; 
    } 
    } 

    return emails; 
} 
} 

// Creating a class for Username and Password authentication 
// provided by the user. 
class LoginAuthenticator extends Authenticator { 
PasswordAuthentication authentication = null; 

public LoginAuthenticator(String username, String password) { 
    authentication = new PasswordAuthentication(username,password); 
} 

@Override 
protected PasswordAuthentication getPasswordAuthentication() { 
    return authentication; 
} 
}  

這是一個完全不同的代碼。但是可以發送電子郵件給一羣人。但問題是我們必須手動輸入電子郵件地址。而我想將郵件發送到從ABC類檢索的地址。有人可以給我一個集成的代碼（對於這兩個類），這將是偉大的。

Answer 1

這應該將的Person轉換成String的ArrayList與來自所有人的電子郵件。

public ArrayList<String> getEmailsFromPersons(List<Person> persons) { 
    ArrayList<String> emails = new ArrayList<String>(); 
    for(Person person : persons) { 
     String email = person.getEmail(); 
     if(email != null && !email.trim().isEmpty()) { 
      emails.add(email); 
     } 
    } 
    return emails; 
} 

Answer 2

我在ArrayList中檢索這些電子郵件地址。像這樣：

我在Person對象中看不到任何電子郵件。但是仍然會嘗試從我編輯後理解的內容中回答你的問題。下面的代碼應該適合您的需求（請不要介意任何錯誤，因爲我在飛行時不做任何檢查）：

public class ABC { 
public static void main(String[] args) throws SQLException { 
    ArrayList<Person> personlist = new ArrayList<Person>(); 
    // Creating a separate list of emails for Persons 
    List<String> personEmails = new ArrayList<String>(); 

    //List<Person> personlist = new List<Person>(); 
    try { 


     Class.forName("oracle.jdbc.driver.OracleDriver"); 
     Connection con=DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:xe","gsjsc","gsjschanna"); 
     Statement st=con.createStatement(); 

     ResultSet srs = st.executeQuery("SELECT * FROM person2"); 
     String email = ""; 
     while (srs.next()) { 
      Person person = new Person(); 
      person.setName(srs.getString("name")); 
      person.setJobtitle(srs.getString("jobtitle")); 
      // person.setFrequentflyer(srs.getInt("frequentflyer")); 
      // I am assuming you would be setting email in person like this 
      email = srs.getString("email"); 
      person.setEmail(email); 
      // Add the email simultaneously to the separate list 
      personEmails.add(email); 
      personlist.add(person); 
     } 

     System.out.println(personlist.size()); 
     for (int a=0;a<personlist.size();a++) 
     { 
     System.out.println(personlist.get(a).getName()); 
     System.out.println(personlist.get(a).getJobtitle()); 
     // System.out.println(personlist.get(2).getName()); 
     // System.out.println(personlist.get(3).getName()); 
     } 
     //System.out.println(personlist.get(4)); 

    //System.out.println(namelist.); 
    } catch (Exception e) { 
     System.err.println("Got an exception! "); 
     System.err.println(e.getMessage()); 
    } 


    // call the email sender method of yours with the newly created list 
    SendEmailToGroupDemo sendEmailToGroup = new SendEmailToGroupDemo(); 
    // Obviously, make that start() method public having parameter of type List<String> instead of calling getEmails() within it 
    sendEmailToGroup.start(personEmails); 
    // Very little remains to be done, I hope you can figure it out easily 
} 
}