JDK中的Timer和TimerTask

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　Timer是jdk中提供的一个定时器工具，使用的时候会在主线程之外起一个单独的线程执行指定的计划任务，可以指定执行一次或者反复执行多次。

　TimerTask是一个实现了Runnable接口的抽象类，代表一个可以被Timer执行的任务。

一个Timer调度的例子

1 import java.util.Timer;
2 import java.util.TimerTask;
3
4 public class TestTimer {
5
6     public static void main(String args[]){
7         System.out.println("About to schedule task.");
8         new Reminder(3);
9         System.out.println("Task scheduled.");
10     }
11
12     public static class Reminder{
13         Timer timer;
14
15         public Reminder(int sec){
16             timer = new Timer();
17             timer.schedule(new TimerTask(){
18                 public void run(){
19                     System.out.println("Time's up!");
20                     timer.cancel();
21                 }
22             }, sec*1000);
23         }
24     }
25 }

运行之后，在console会首先看到：

About to schedule task.

Task scheduled.

然后3秒钟后，看到

Time's up!
__________________________________________________________________________________________________________________

另一个栗子

List<Map<String, Object>> merList = tranService.transExQuery(params);
Timer timer = new Timer();
OrgMerchantMsgTimerTask task = new OrgMerchantMsgTimerTask(timer, merList);
// 延迟0毫秒开始任务，间隔100毫秒重发一次
timer.schedule(task, 0, 100);

/**
* 定时发送消息任务
*
* @author lijinyang
*/
private class OrgMerchantMsgTimerTask extends TimerTask {
private Timer timer;
private String url = "http://127.0.0.1:****/olt/skcb/callBackNotice?merchOrderId=";
private List<Map<String, Object>> merList;

public OrgMerchantMsgTimerTask(Timer timer,
List<Map<String, Object>> merList) {
this.timer = timer;
this.merList = merList;
}

@Override
public void run() {
if (merList.isEmpty()) {
timer.cancel();
} else {
Map<String, Object> aTran = merList.get(0);
String noticeUrl = url + aTran.get("trans_no");
try {
log.error("----向下游推送异步消息, {}-----", noticeUrl);
HttpUtils.httpGetMethod(noticeUrl, "utf-8");
} catch (Exception e) {
log.error("----向下游推送异步消息失败, {}-----", noticeUrl);
}
merList.remove(aTran);
}
}
}

import org.apache.commons.httpclient.methods.GetMethod;
import org.apache.commons.httpclient.params.HttpMethodParams;
import org.apache.commons.httpclient.HttpClient;

public static String httpGetMethod(String url, String charset) throws Exception {
HttpClient client = new HttpClient();
client.getParams().setParameter(HttpMethodParams.HTTP_CONTENT_CHARSET, charset);
GetMethod getMethod = null;
try {
getMethod = new GetMethod(url);
System.out.println("---开始向--"+url+"推送结果-----");
int statusCode = client.executeMethod(getMethod);
if (statusCode != HttpStatus.SC_OK) {
String msg = "访问失败！！HTTP_STATUS=" + statusCode;
System.out.println(msg);
System.out.println("---向"+url+"推送消息失败---");
return null;
}// if
String context = getMethod.getResponseBodyAsString();
return context;

} finally {
if (getMethod != null)
getMethod.releaseConnection();
}// finally
}// method