使用场景：
在平常web开发过程中，有时操作员要做一个后台会运行很长时间的任务（如上传一个大文件到后台处理），而此时前台页面仍需要给用户及时的进度信息反馈，同时还要避免前台页面超时。
框架介绍：
本架构采用Struts+Spring+AJAX(jquery)方式实现，前台提交任务到后台，然后通过AJAX方式周期性获取任务进度，展示给用户看。
本框架支持提交任务、查看任务进展、停止任务、删除任务。
使用java线程池的技术来执行任务，避免不停的生成新的线程;
代码下载（内含使用样例）：
https://github.com/jerrymousecn/daemo_tasks
下载包说明：
1）demo/daemonTasks.war为tomcat发布包(zip格式)，可以直接放到tomcat的webapps目录；
2）demo/demo_source目录是eclipse样例项目代码
3）source目录是本框架源代码
主要代码：
1.DaemonTask.java
后台任务基础类
package cn.jerry.tools.tasks;
import java.util.Date;
public abstract class DaemonTask implements Runnable {
private String taskID;
private String taskName;
private String taskDesc;
private boolean isStartedFlag = false;;
private boolean isTerminated = false;;
private int progress;
private Date startTime;
private Date terminatedTime;
protected boolean toStopFlag = false;
protected abstract void execute();
protected void setProgress(int progress) {
this.progress = progress;
}
public void run() {
this.isStartedFlag = true;
this.execute();
this.isTerminated = true;
this.terminatedTime = new Date();
}
public String getTaskID() {
return taskID;
}
public void setTaskID(String taskID) {
this.taskID = taskID;
}
public boolean isStarted() {
return isStartedFlag;
}
public boolean getIsTerminated() {
return isTerminated;
}
public void setToStopFlag(boolean toStopFlag) {
this.toStopFlag = toStopFlag;
}
public Date getStartTime() {
return startTime;
}
public Date getTerminatedTime() {
return terminatedTime;
}
public int getProgress() {
return progress;
}
public String getTaskName() {
return taskName;
}
public void setTaskName(String taskName) {
this.taskName = taskName;
}
public String getTaskDesc() {
return taskDesc;
}
public void setTaskDesc(String taskDesc) {
this.taskDesc = taskDesc;
}
}
2.TaskManager.java
后台任务管理类，支持添加任务，停止任务，删除任务，查看任务，对已完成任务进行定期清理，获取任务进度
package cn.jerry.tools.tasks;
import java.util.Collections;
import java.util.Date;
import java.util.Map;
import java.util.Timer;
import java.util.TimerTask;
import java.util.UUID;
import java.util.Map.Entry;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class TaskManager {
private static TaskManager taskManager = new TaskManager();
private ExecutorService executorService = Executors.newCachedThreadPool();
private ConcurrentMap<String, DaemonTask> taskMap = new ConcurrentHashMap<String, DaemonTask>();
private final int TASK_NOT_FOUND = -1;
private TaskCleaner taskCleaner = new TaskCleaner(taskMap);
private Timer timer = new Timer();
private final int CLEAN_PERIOD = 200000; //in milliseconds
private String getUniqueID() {
return UUID.randomUUID().toString();
}
private TaskManager() {
startTerminatedTaskCleanTimer();
}
private void startTerminatedTaskCleanTimer() {
timer.schedule(taskCleaner, 0, CLEAN_PERIOD);
}
private void stopTerminatedTaskCleanTimer() {
timer.cancel();
}
public static TaskManager getInstance() {
return taskManager;
}
public synchronized String addTaskAndStart(DaemonTask task) {
String taskID = getUniqueID();
task.setTaskID(taskID);
taskMap.put(taskID, task);
executorService.execute(task);
return taskID;
}
public synchronized void stopTask(String taskID) {
DaemonTask task = getTask(taskID);
if (task != null) {
task.setToStopFlag(true);
}
}
public synchronized void delFinishedTask(String taskID) {
DaemonTask task = getTask(taskID);
if (task != null) {
if (task.getIsTerminated()) {
taskMap.remove(taskID);
}
}
}
public DaemonTask getTask(String taskID) {
return taskMap.get(taskID);
}
public Map<String, DaemonTask> getTasksForView() {
Map<String, DaemonTask> map = Collections.unmodifiableMap(taskMap);
return map;
}
public int getProgress(String taskID) {
int progress = TASK_NOT_FOUND;
DaemonTask task = getTask(taskID);
if (task != null) {
progress = task.getProgress();
}
return progress;
}
}
class TaskCleaner extends TimerTask {
private ConcurrentMap<String, DaemonTask> taskMap;
public TaskCleaner(ConcurrentMap<String, DaemonTask> taskMap) {
this.taskMap = taskMap;
}
@Override
public void run() {
for (Entry<String, DaemonTask> entry : taskMap.entrySet()) {
String taskID = entry.getKey();
DaemonTask task = entry.getValue();
if (task.getIsTerminated()) {
Date terminatedTime = task.getTerminatedTime();
Date now = new Date();
long timeOffset = getTimeOffset(terminatedTime, now);
if (timeOffset > 10000) {
taskMap.remove(taskID);
System.out.println("task: " + taskID + " is removed");
}
}
}
}
private long getTimeOffset(Date date1, Date date2) {
long time1 = date1.getTime();
long time2 = date2.getTime();
long offset = time2 - time1;
if (offset < 0) {
offset = -offset;
}
return offset;
}
}
3.任务样例TestTask.java
关键点需要注意： 方法中需要自行计算进度（完成时，进度应设置为100），并且要对toStopFlag进行判断，用于终止任务。
package cn.jerry.tools.tasks;
public class TestTask extends DaemonTask {
@Override
protected void execute() {
for (int i = 0; i < 10; i++) {
if(this.toStopFlag==false)
{
int progress = (i + 1) * 100 / 10;
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
this.setProgress(progress);
}
}
}
}
4.前台查询状态页面getTaskResult.jsp：
<%@ taglib prefix="s" uri="/struts-tags" %>
<html>
<head>
<script type="text/javascript" src="js/jquery-1.11.1.min.js"></script>
<link rel="stylesheet" href="css/jquery-ui.css">
<script src="js/jquery-ui.js"></script>
<link rel="stylesheet" href="css/style.css">
<script type="text/javascript">
var intervalId;
function trim(str){
return str.replace(/(^s*)|(s*$)/g, "");
}
function getprogress() {
htmlobj=$.ajax({url:"getTaskProgress.jsp?taskid="+'<s:property value="taskid"/>',cache:false,async:false});
str = trim(htmlobj.responseText);
$("#myDiv").html(str);
$( "#progressbar" ).progressbar({
value: parseInt(str)
});
if(parseInt(str)>=100)
{
clearInterval(intervalId);
}
}
$(document).ready(function(){
intervalId = setInterval(getprogress, 1000);
});
</script>
</head>
<body>
Task [<s:property value="taskName"/>]progress:
<div id="progressbar"></div>
<div id="myDiv"></div>
</body>
</html>
5.相关截图
1）进度页面截图：
2）查看任务列表
声明：
本框架中使用的进度条代码实现来自以下网站，版权不属于本人，本框架仅用于学习交流。
http://jqueryui.com/progressbar/#animated