JCrontab简单入门实例 JCrontab简单入门实例详解

时间:2021-03-28 易雪寒人气:0

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创建一个JavaWeb项目

1、首先要下载JCrontab的相关jar包，Jcrontab-2.0-RC0.jar。放到lib文件夹下。

2、在src下新建文件jcrontab.properties如下：

#crontab.xml

文件的目录，这个是作业调度规则
org.jcrontab.data.file =E:/EclipseWorkspace/ADemo/WebContent/WEB-INF/crontab.xml
#sax解析驱动类型
org.xml.sax.driver=org.apache.xerces.parsers.SAXParser
#datasource文件类型
org.jcrontab.data.datasource=org.jcrontab.data.XMLSource

3、在WEB-INF下新建文件crontab.xml

<?xml version="1.0" encoding="utf-8"?>
<crontab>
<crontabentry id="2014">
<seconds>0,5,10,15,20,25,30,35,40,45,50,55</seconds>
<minutes>*</minutes>
<hours>*</hours>
<daysofmonth>*</daysofmonth>
<months>*</months>
<daysofweek>*</daysofweek>
<years>*</years>
<bussinesdays>true</bussinesdays>
<startDate></startDate>
<endDate></endDate>
<class>xu.crontab.Crontab1</class>
<method>run</method>
<parameters></parameters>
<description></description>
</crontabentry>
</crontab>

以上属性自己百度一下，<seconds>0,5,10,15,20,25,30,35,40,45,50,55</seconds>这个是秒数是5的倍数就调用作业

4、web.xml配置如下

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
id="WebApp_ID" version="3.1">
<display-name>ADemo</display-name>
 
<servlet>
<servlet-name>LoadOnStartupServlet</servlet-name>
<servlet-class>xu.crontab.LoadCrontabServlet</servlet-class>
<init-param>
<param-name>PROPERTIES_FILE</param-name>
<!--此处路径是绝对路径 -->
<param-value>E:\EclipseWorkspace\ADemo\src\jcrontab.properties</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>LoadOnStartupServlet</servlet-name>
<url-pattern>/Startup</url-pattern>
</servlet-mapping>
</web-app>

5、在xu.crontab包下新建两个java文件（文件位置见最上的截图）【其他java文件不用理会】

LoadCrontabServlet.java

package xu.crontab;
 
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Enumeration;
import java.util.Properties;
 
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
 
import org.jcrontab.Crontab;
import org.jcrontab.log.Log;
 
public class LoadCrontabServlet extends HttpServlet {
 
/**
 *
 */
private static final long serialVersionUID = 1L;
private Crontab cron = null;
 
public void init(ServletConfig config) throws ServletException {
super.init(config);
 
try {
System.out.print("Working?...");
process();
System.out.println("OK");
} catch (Exception e) {
throw new ServletException(e);
}
}
 
protected InputStream createPropertiesStream(String name) throws IOException {
return new FileInputStream(name);
}
 
public void process() {
 
String propz = "jcrontab.properties";
 
String props = getServletConfig().getInitParameter("PROPERTIES_FILE");
if (props == null) {
props = propz;
}
 
Properties propObj = new Properties();
try {
InputStream input = createPropertiesStream(props);
propObj.load(input);
} catch (IOException ioe) {
ioe.printStackTrace();
}
ServletConfig c = getServletConfig();
Enumeration keys = c.getInitParameterNames();
while (keys.hasMoreElements()) {
String key = (String) keys.nextElement();
propObj.setProperty(key, c.getInitParameter(key));
}
 
cron = Crontab.getInstance();
 
try {
ShutdownHook();
cron.init(propObj);
} catch (Exception e) {
Log.error(e.toString(), e);
}
}
 
 
public void ShutdownHook() throws Exception {
Runtime.getRuntime().addShutdownHook(new Thread() {
public void run() {
doStop();
}
});
}
 
public void destroy() {
doStop();
}
 
public void doStop() {
Log.info("Shutting down...");
cron.uninit(100);
Log.info("Stoped");
}
}

Crontab1.java

package xu.crontab;
 
import java.util.Date;
 
public class Crontab1 {
  public static void run(String[] args) {
    System.out.println(new Date()+"-----> hello world!!!");
  }
}

启动tomcat后即可看到作业每隔5秒就调用一下，希望你们顺利。

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