我不确定这是否可行，但我想在我的应用程序的Main类中实例化一个类，它只会运行一次。我遇到了特别的问题，因为我的应用程序多次调用main作为应用程序重启的方法，这是以ConToDatabase.main(args);
课程＆amp;方法我想运行一次包含一个计时器任务，确定何时发送电子邮件。其构造如下：
class EmailSending extends TimerTask
{
public static FileInputStream propFile;
static Connection conn = null;
static Statement query = null;
static String path;
static FunctionLogging logger = new FunctionLogging(path, true);
static Statement stmnt;
public void run()
{
try
{
logger.writeToFile("Entered Class|EmailSending");
Date date = new Date();
SimpleDateFormat mailDate = new SimpleDateFormat();
mailDate = new SimpleDateFormat("dd-MM-yy HH:mm:ss");
String mail = mailDate.format(date);
propFile = new FileInputStream("config.ini");
Properties config = new Properties(System.getProperties());
config.load(propFile);
String host = config.getProperty("host");
String port = config.getProperty("port");
path = config.getProperty("path");
String DB_URL = config.getProperty("DB_URL");
String USER = config.getProperty("USER");
String PASS = config.getProperty("PASS");
path = config.getProperty("path");
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection(DB_URL, USER, PASS);
String sender = config.getProperty("sender");
Properties toRecipients = System.getProperties();
Session current = Session.getDefaultInstance(toRecipients);
toRecipients.setProperty("mail.smtp.host", host);
toRecipients.setProperty("mail.smtp.port", port);
MimeMessage message = new MimeMessage(current);
message.setFrom(new InternetAddress(sender));
String[] recipients = config.getProperty("EmailList").split(";");
for(int i=0;i<recipients.length;i++)
{
message.setRecipient(Message.RecipientType.TO, new InternetAddress(recipients[i].trim()));
logger.writeToFile("EmailSending Class|Method: run|Recipient: ["+recipients[i].trim()+"] found");
message.setSubject("Results of Audit Trail "+mail);
message.setText(messageBody().toString());
logger.writeToFile("EmailSending Class|emailSend Method|Sending emails");
Transport.send(message);
}
}
catch (MessagingException me)
{
System.out.println(me.getMessage());
}
catch (FileNotFoundException fnf)
{
System.out.println(fnf.getMessage());
}
catch (IOException ioe)
{
System.out.println(ioe.getMessage());
}
catch (SQLException sqle)
{
System.out.println(sqle.getMessage());
}
catch (ClassNotFoundException cnf)
{
System.out.println(cnf.getMessage());
}
}
public static void emailSend(int control) throws IOException
{
logger.writeToFile("EmailSend Class|Method: emailSend|Timer Started");
Timer timer = new Timer();
timer.schedule(new EmailSending(), 0, control*60000);
logger.writeToFile("EmailSend Class|Method: emailSend|Timer Completed. Sleeping for ["+control+"] minute(s)");
}
private static StringBuilder messageBody() throws SQLException
{
stmnt = conn.createStatement();
String SQL = "Select Action from Java_Test_AuditTrail";
ResultSet rs1 = stmnt.executeQuery(SQL);
rs1.last();
int rowNumb = rs1.getRow();
int list = 0;
int delete = 0;
int update = 0;
int load = 0;
int upload = 0;
int display = 0;
int add = 0;
rs1.beforeFirst();
rs1.next();
int seeker=1;
while(rs1.next()&&seeker<=rowNumb)
{
String actExecuted = rs1.getString("Action");
if(actExecuted.equals("LIST"))
{
list++;
}
if(actExecuted.equals("DELETE"))
{
delete++;
}
if(actExecuted.equals("UPDATE"))
{
update++;
}
if(actExecuted.equals("RE-LOAD"))
{
load++;
}
if(actExecuted.equals("UPLOAD"))
{
upload++;
}
if(actExecuted.equals("DISPLAY AUDIT"))
{
display++;
}
if(actExecuted.equals("USER_CREATED"))
{
add++;
}
}
StringBuilder builder = new StringBuilder();
builder.append("Since Creation of the database, there have been: ["+list+"] List requests executed"+"\n");
builder.append("\n");
builder.append("Since Creation of the database, there have been: ["+delete+"] Delete requests executed"+"\n");
builder.append("\n");
builder.append("Since Creation of the database, there have been: ["+update+"] Update requests executed"+"\n");
builder.append("\n");
builder.append("Since Creation of the database, there have been: ["+load+"] Re-load requests executed"+"\n");
builder.append("\n");
builder.append("Since Creation of the database, there have been: ["+upload+"] Upload requests executed"+"\n");
builder.append("\n");
builder.append("Since Creation of the database, there have been: ["+display+"] Audit-Display requests executed"+"\n");
builder.append("\n");
builder.append("Since Creation of the database, there have been: ["+add+"] User-Creation requests executed"+"\n");
return builder;
}
}
答案 0 :(得分：1)
也许在工作结束时调用'取消'方法？
TimerTask的javadoc具有以下'取消'：
http://docs.oracle.com/javase/7/docs/api/java/util/TimerTask.html
public boolean cancel（）
取消此计时器任务。如果任务已安排一次性 执行，尚未运行，或尚未安排，它会 永远不会跑。如果任务已经安排重复执行，那么 永远不会再跑。 （如果此调用发生时任务正在运行， 任务将运行完成，但永远不会再运行。）
请注意，从a的run方法中调用此方法 重复计时器任务绝对保证计时器任务将 不要再跑了。
这种方法可以重复调用;第二次和后续的电话 没有效果。