java定时器用法

男娘i 2022-09-26 03:55 196阅读 0赞

1、代码示例

//继承TimerTask
    public class TestTimerTask extends TimerTask{ 
    
        public void run() {
    
            while (true) {
                boolean result = getFlag();
                if (result) {
                    break;
                }
                try {
                    Thread.sleep(1000 * 60);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
    
            System.out.println("rfm数据返回ok，现在时间是：" + Calendar.getInstance().getTime());
            //需要执行的任务
        }
    
        public boolean getFlag(){
            Connection connn = null;
            PreparedStatement pss = null;
            ResultSet rss = null;
            boolean flag = false;
            ObjectMapper objectMapper = new ObjectMapper()
                    .setSerializationInclusion(JsonInclude.Include.NON_NULL)
                    .setDateFormat(new SimpleDateFormat("yyyy-MM-dd"))
                    .disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
                    .disable(SerializationFeature.FAIL_ON_EMPTY_BEANS)                         .setPropertyNamingStrategy(PropertyNamingStrategy.CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES);
            try {
                SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
                String date1 = null;
    
                Date date = Calendar.getInstance().getTime();
                date1 = simpleDateFormat.format(date);
    
                Class.forName("com.mysql.jdbc.Driver");
                String url = "jdbc:mysql://xxxxx";
                connn = DriverManager.getConnection(url, "xxxx", "xxxx");
    
                pss = connn.prepareStatement("select * from xxxx");
                rss = pss.executeQuery();
                Map<String, String> flagMap = new HashMap<>();
                while (rss.next()) {
                    flagMap.put(rss.getString(2), rss.getString(1));
                }
    
                System.out.println(objectMapper.writeValueAsString(flagMap));
                String flags = "";
                try {
                    flags = flagMap.get(date1);
                } catch (NullPointerException nu) {
    
                }
                if("1".equals(flags)){
                    flag = true;
                }
    
            }catch (Exception e) {
    
            } finally{
                try {
                    if(rss != null) {
                        rss.close();
                    }
                } catch (SQLException e) {
                    e.printStackTrace();
                }
                try {
                    if(pss != null) {
                        pss.close();
                    }
                } catch (SQLException e) {
                    e.printStackTrace();
                }
                try {
                    if(connn != null) {
                        connn.close();
                    }
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            return  flag;
        }
    
        public static void main (String[] ages){
    
            Timer timer = new Timer();//定时器
            TestTimerTask ts = new TestTimerTask();//定时任务目标
            Calendar calendar = Calendar.getInstance();
            calendar.set(Calendar.HOUR_OF_DAY, 6); //早晨6点
            calendar.set(Calendar.MINUTE, 20);
            calendar.set(Calendar.SECOND, 0);
            Date date = calendar.getTime();
            long period = 1000 * 60 * 60 * 24;//执行间隔24小时
    
            //如果第一次执行定时任务的时间 小于当前的时间
            //此时要在 第一次执行定时任务的时间加一天，以便此任务在下个时间点执行。如果不加一天，任务会立即执行。
            if (date.before(new Date())) {
                date = addDay(date, 1);
            }
    
            timer.scheduleAtFixedRate(ts, date, period);//设置执行参数并且开始定时任务
        }
    
        // 增加或减少天数
        public static Date addDay(Date date, int num) {
            Calendar startDT = Calendar.getInstance();
            startDT.setTime(date);
            startDT.add(Calendar.DAY_OF_MONTH, num);
            return startDT.getTime();
        }
    }