Java 응용 프로그램 설계

Question

저는 Object Programming과 Java를 처음 접했으므로 여기에서 조언과 피드백을 수집하려고합니다. 기본적으로 다른 간격으로 다른 작업을 수행하는 백그라운드 서비스를 작성하려고합니다. 나는 코딩 표준을 따르고 있거나 효율적이라고 100 % 확신하지 못했습니다.

홈페이지/시작 클래스 :

public class Start { 

    public static void main(String[] args) { 
     Service s = new Service(); 
     s.Start(); 
    } 

} 

데이터베이스 클래스 :

import java.sql.Connection; 
import java.sql.DriverManager; 
import java.sql.SQLException; 

public class Database { 

    /* Database settings */ 
    private final String HOSTNAME = "localhost"; 
    private final String DATABASE = "java_database"; 
    private final String USERNAME = "java_username"; 
    private final String PASSWORD = "java_password"; 

    /* Database connection */ 
    public Connection getConnection() { 
     try { 
      return DriverManager.getConnection("jdbc:mysql://" + HOSTNAME + "/" + DATABASE + "?user=" + USERNAME + "&password=" + PASSWORD + "&useSSL=false&useUnicode=true&characterSetResults=utf8"); 
     } catch (SQLException ex) { 
      ex.printStackTrace(); 
     } 
     return null; 
    } 


} 

서비스 클래스 :

import java.sql.PreparedStatement; 
import java.sql.ResultSet; 
import java.sql.SQLException; 
import java.sql.Statement; 

public class Service { 

    private int taskId; 
    private int taskType; 


    /* Start Service */ 
    public void Start() { 
     try { 
      System.out.println("Starting Service..."); 
      while(true) { 
       System.out.print("Checking for tasks... "); 
       getNextTask(); 
       if (this.taskId > 0) { 
        System.out.println("Task ID " + this.taskId + " found."); 
        switch (this.taskType) { 
         case 1: 
          System.out.println("Task 1"); 
          SampleTask s = new SampleTask(); 
          s.Start(); 
          s = null; 
          break; 
         default: 
          System.out.println("Error: Unknown Task"); 
        }     
        setUsedTask(); 
       } else { 
        System.out.println("No tasks to perform at this time."); 
       } 
       this.taskId = 0; 
       this.taskType = 0; 
       Thread.sleep(5000); 
      } 
     } catch (InterruptedException ex) { 
      ex.printStackTrace(); 
     } 
    } 


    /* Gets the next available task from the database */ 
    public void getNextTask() { 
     try { 
      Database db = new Database(); 
      String query = "select taskId, taskType " 
        + "from tasks " 
        + "where (time_to_sec(timediff(now(), taskLastRun)) > taskFrequency or taskLastRun is null) and taskEnabled = 1 " 
        + "limit 1"; 
      Statement stmt = db.getConnection().createStatement(); 
      ResultSet rset = stmt.executeQuery(query); 
      if (rset.next()) { 
       this.taskId = rset.getInt(1); 
       this.taskType = rset.getInt(2); 
      } 
     } catch (SQLException ex) { 
      ex.printStackTrace(); 
     } 
    } 


    /* Set task as complete */ 
    public void setUsedTask() { 
     try { 
      Database db = new Database(); 
      String query = "update tasks " 
        + "set taskLastRun = now() " 
        + "where taskId = ? " 
        + "limit 1"; 
      PreparedStatement pstmt = db.getConnection().prepareStatement(query); 
      pstmt.setInt(1, this.taskId); 
      pstmt.executeUpdate(); 
     } catch (SQLException ex) { 
      ex.printStackTrace(); 
     } 
    } 


} 

Answer 1

(대기와 Thread.sleep를() 접근 방식을 대체하는 고려) 그리고 here과 같이 notify() 접근법을 사용한다.

public class Service { 

    private int taskId; 
    private int taskType; 
    private final Object serviceMonitor; 


    /* Start Service */ 
    public void Start() { 
     synchronized(serviceMonitor){ 
      try { 
      System.out.println("Starting Service..."); 
      while(true) { 
       System.out.print("Checking for tasks... "); 
       getNextTask(); 
       if (this.taskId > 0) { 
        System.out.println("Task ID " + this.taskId + " found."); 
        switch (this.taskType) { 
         case 1: 
          System.out.println("Task 1"); 
          SampleTask s = new SampleTask(); 
          s.Start(); 
          s = null; 
          break; 
         default: 
          System.out.println("Error: Unknown Task"); 
        }     
        setUsedTask(); 
       } else { 
        System.out.println("No tasks to perform at this time."); 
       } 
       this.taskId = 0; 
       this.taskType = 0; 
       serviceMonitor.wait(); 
      } 
      } 
     } 
     catch (InterruptedException ex) { 
      ex.printStackTrace(); 
     } 
    } 

public void getNextTask() { 
    synchronized(serviceMonitor){ 
    try { 
     Database db = new Database(); 
     String query = "select taskId, taskType " 
       + "from tasks " 
       + "where (time_to_sec(timediff(now(), taskLastRun)) > taskFrequency or taskLastRun is null) and taskEnabled = 1 " 
       + "limit 1"; 
     Statement stmt = db.getConnection().createStatement(); 
     ResultSet rset = stmt.executeQuery(query); 
     if (rset.next()) { 
      this.taskId = rset.getInt(1); 
      this.taskType = rset.getInt(2); 
      serviceMonitor.notifyAll(); 
     } 
     } 
    } catch (SQLException ex) { 
     ex.printStackTrace(); 
    } 
} 

Answer 2

public class Main { 
    public static void main(String[] args) { 
     Service service = new Service(Arrays.asList(new SampleTask(),new AnotherTask())); 
     service.execute(); 
    } 
} 



class Service { 
    private List<Task> taskList; 

    public Service(List<Task> taskList) { 
     this.taskList = taskList; 
    } 
    public void addTask(Task task) { 
     taskList.add(task); 
    } 
    public void execute() { 
     for (Task task : taskList) { 
      new Timer().schedule(task, task.getDelay(), task.getPeriod()); 
     } 
    } 
    public void clearTasks() { 
     taskList.clear(); 
    } 
} 


abstract class Task extends TimerTask { 
    abstract long getDelay(); 
    abstract long getPeriod(); 
} 


class SampleTask extends Task { 
    public void run() { 
     System.out.println("Sample task executed"); 
    } 

    long getDelay() { 
     return 1000; 
    } 

    long getPeriod() { 
     return 60000; 
    } 
} 

class AnotherTask extends Task { 
    public void run() { 
     System.out.println("Another task is executed"); 
    } 

    long getDelay() { 
     return 1000; 
    } 

    long getPeriod() { 
     return 500000; 
    } 
}