本文是在学习中的总结，欢迎转载但请注明出处：http://blog.csdn.net/pistolove/article/details/49975443

最近在学习定时相关的技术。当前，几乎所有的互联网公司都会涉及定时相关的业务。比如网站首页的定时更新，内容的定时推送等等都会涉及。在找工作面试中，面试官也会问相关的问题。所以，在对定时学习和理解的基础上，简单地整理了一下学习笔记，下文主要以代码的方式展示。启动一个定时任务的流程大致为：创建Marven项目->在pom文件中引入依赖包->配置需要执行的任务和时间->启动定时器->解析配置文件->获取待处理的类和方法->启动定时任务->执行具体的任务->监听->到下一次时间到达时再次执行。详情见下方代码，希望本文对你有所帮助。

1、由于创建的是marven项目，所以需要引入包。对应的pom文件如下。

<span style="font-size:18px;">		<dependency>
			<groupId>javax.servlet</groupId>
			<artifactId>javax.servlet-api</artifactId>
			<version>3.0.1</version>
			<scope>provided</scope>
		</dependency>

		<dependency>
			<groupId>log4j</groupId>
			<artifactId>log4j</artifactId>
			<version>1.2.17</version>
		</dependency>

		<dependency>
			<groupId>org.quartz-scheduler</groupId>
			<artifactId>quartz</artifactId>
			<version>2.1.5</version>
			<scope>compile</scope>
		</dependency>
		<dependency>
			<groupId>org.apache.qpid</groupId>
			<artifactId>qpid-client</artifactId>
			<version>0.28</version>
		</dependency>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-jms</artifactId>
			<version>4.1.5.RELEASE</version>
		</dependency></span>

2、要创建定时任务，需要配置待执行的类、类中的方法、方法的执行周期。这里指定待执行的定时任务名称为searchJob，方法名称为search，定时器执行时间为10秒/次。注：配置文件中可以加入多个定时任务，自行配置。

timer.properties文件信息如下： searchJob:search:0/10 * * * * ?

3、定时任务的入口类如下所示。首先，加载配置文件，获取待执行的定时任务和时间；其次，启动定时器，然后解析配置文件，获取加载的类的和方法；最后，启动定时任务，当时间到达指定执行时，会执行相应的方法。

try {
	/*
	 * 加载定时任务
	 */
	ApplicationContext applicationContext = new ClassPathXmlApplicationContext("file:d:/conf/time-quartz.xml");

	/*
	 * 启动定时器
	 */
	SchedulerFactory schedulerFactory = new StdSchedulerFactory();
	Scheduler scheduler = schedulerFactory.getScheduler();
	scheduler.start();

	/*
	 * 启动定时任务
	 */
	for (String task : tasks) {
		String[] parm = task.split(":");
		String beanName = parm[0];
		String methodName = parm[1];
		String cron = parm[2];

		JobDataMap jobDataMap = new JobDataMap();
		jobDataMap.put("object", applicationContext.getBean(beanName));
		jobDataMap.put("methodName", methodName);
			JobDetail jobDetail = JobBuilder.newJob(JobAdapter.class).
					withIdentity(beanName, methodName).usingJobData(jobDataMap).build();

			Trigger trigger = TriggerBuilder.newTrigger().
					withIdentity(beanName, methodName).withSchedule(CronScheduleBuilder.cronSchedule(cron)).build();

			scheduler.scheduleJob(jobDetail, trigger);
		}
	} catch (Exception e) {
		log.error(e.getMessage(),e);
	}
}

4、定时任务代理

import java.lang.reflect.Method;
import org.quartz.Job;
import org.quartz.JobExecutionContext;
import org.quartz.JobExecutionException;

/**
 * 定时任务代理
 */
public class JobAdapter implements Job {

	private Object object;

	private String methodName;

	public Object getObject() {
		return this.object;
	}

	public void setObject(Object object) {
		this.object = object;
	}

	public String getMethodName() {
		return this.methodName;
	}

	public void setMethodName(String methodName) {
		this.methodName = methodName;
	}

	@Override
	public void execute(JobExecutionContext context)
			throws JobExecutionException {
		try {
			Method method = this.object.getClass().getMethod(this.methodName, new Class[0]);
			method.invoke(this.object, new Object[0]);
		} catch (Exception e) {
			throw new JobExecutionException(e.getMessage(), e);
		}
	}
}

5、定时任务

import javax.annotation.Resource;
import org.springframework.stereotype.Component;
import com.timer.modules.SearchService;

@Component("searchJob")
public class SearchJob {

	@Resource
	private SearchService searchService;

	public void search(){
		searchService.getSearhData();
	}
}

6、定时任务的实现类

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.util.ArrayList;
import java.util.List;
import org.springframework.stereotype.Service;

@Service
public class SearchService extends BaseJobService{

	public void getSearhData() {
		System.err.println("开始写入数据：");
		try {
			String filePath = System.getProperty("user.dir")
					+ "\\src\\main\\java\\com\\timer\\dto\\" + "searchDto.txt";
			File f = new File(filePath);

			if(f.exists() && f.length() > 10){
				f.delete();
				f = new File(filePath);
				f.createNewFile();
			}

			FileWriter fileWritter = new FileWriter(f.getCanonicalPath(), true);
			BufferedWriter bufferWritter = new BufferedWriter(fileWritter);

			List<String> content = getContent("http://www.baidu.com");
			bufferWritter.newLine();
			bufferWritter.newLine();
			for (String str : content) {
				bufferWritter.write(new String(str.getBytes("gb2312"),"UTF-8"));
				bufferWritter.newLine();
			}
			bufferWritter.flush();
			bufferWritter.close();
			System.err.println(content.toArray().toString());
		} catch (IOException e) {
			e.printStackTrace();
		}
		System.err.println("写入数据完成");
	}

	private List<String> getContent(String path) {
		List<String> result = new ArrayList<String>();
		StringBuffer sb = new StringBuffer();
		try {
			java.net.URL url = new java.net.URL(path);
			HttpURLConnection connection = (HttpURLConnection) url.openConnection();
			connection.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)");
			connection.connect();
			InputStream inputStream = connection.getInputStream();
			BufferedReader in = new BufferedReader(new InputStreamReader(inputStream));

			String line;
			while ((line = in.readLine()) != null) {
				result.add(line);
			}
			in.close();
		} catch (Exception e) {
			sb.append(e.toString());
			System.err.println(e);
			System.err.println("Usage:   java   HttpClient   <URL>   [<filename>]");
		}
		return result;
	}
}