改善此方案性能的方法

for循环由于两个原因而花费时间。
1）个人电子邮件通过减少传输连接来
改善它2）个人提交通过以下方法来改善它

所以理想的情况是同时处理这两种情况，我建议批量处理1000次，然后再打数字

例

int BATCH_SIZE = 1000conn = DriverManager.getConnection("username","password");conn.setAutoCommit(false);Statement stmt = conn.createStatement(        ResultSet.TYPE_SCROLL_INSENSITIVE,        ResultSet.CONCUR_UPDATABLE);int count = 0;Map<String, String> emails_map = new HashMap(BATCH_SIZE)<String, String>;for (Map.Entry<String, List<ClassOBj>> entry : testMap        .entrySet()) {    String email = get_useremail();    String const_val = do_magic(); // this is how you are computing some constant    String body = construct_body();    count++;    String SQL = "YOUR UPDATe STATEMENT";    stmt.executeUpdate(SQL);      emails_map.put(email, body); // can create     if (count % BATCH_SIZE == 0) {        //commits all transcations        conn.commit();        //bulk send emails sending         //http://stackoverflow.com/questions/13287515/how-to-send-bulk-mails-using-javax-mail-api-efficiently-can-we-use-reuse-auth        bulk_emails_send(emails_map)    }}public void bulk_emails_send(Map<String, String> emails_map) {    // Get the default Session object through your setting    Session session = Session.getDefaultInstance(properties);    Transport t = session.getTransport();    t.connect();    try {        for (String email_id in emails_map) { Message m = new MimeMessage(session); //add to, from , subject, body m.saveChanges(); t.sendMessage(m, m.getAllRecipients());        }    } finally {        t.close();    }}