Java定时任务的实现

在使用Elasticsearch时，发现做了增删改查后，数据需要定时更新。于是就自己写了一个简易的定时器（不过并没有应用到项目中，因为主流框架中都有集成，但是我并不喜欢cron表达式）。以下是定时器的实现以及测试代码：

1.定义Timer注解

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * @author caojianyu
 * @create 2019-12-26 11:20
 * @mail [email protected]
 */
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Timer {
	public String hour() default "0";
    public String minutes() default "0";
    public String seconds() default "0";
}

2.定义时间转换常量值

/**
 * @author caojianyu
 * @create 2020-01-15 19:01
 * @mail [email protected]
 *
 */
public final class TimeConstant {
	public static final Long HOUR_TRANSLATE = 3600000L;
	public static final Long MINUTES_TRANSLATE = 60000L;
	public static final Long SECONDS_TRANSLATE = 1000L;
}

3.将时间转换为秒的方法

import com.yuanma.timer.constant.TimeConstant;

/**
 * @author caojianyu
 * @create 2020-01-15 19:01
 * @mail [email protected]
 *
 */
public class Transform {

	private static final Long ZERO = 0L;

	public static Long getTimeInterval(Long hour, Long minutes, Long seconds) {
		Long timeInterval = 0L;
		if (ZERO.equals(hour) && ZERO.equals(minutes) && ZERO.equals(seconds)) {
			throw new NullPointerException("定时器时间间隔未设置");
		}

		if (!ZERO.equals(hour) && ZERO.equals(minutes) && ZERO.equals(seconds)) {
			timeInterval = hour * TimeConstant.HOUR_TRANSLATE;
		} else if (ZERO.equals(hour) && !ZERO.equals(minutes) && ZERO.equals(seconds)) {
			timeInterval = minutes * TimeConstant.MINUTES_TRANSLATE;
		} else if (ZERO.equals(hour) && ZERO.equals(minutes) && !ZERO.equals(seconds)) {
			timeInterval = seconds * 1000L;
		} else if (!ZERO.equals(hour) && !ZERO.equals(minutes) && ZERO.equals(seconds)) {
			timeInterval = hour * TimeConstant.HOUR_TRANSLATE + minutes * TimeConstant.MINUTES_TRANSLATE;
		} else if (!ZERO.equals(hour) && ZERO.equals(minutes) && !ZERO.equals(seconds)) {
			timeInterval = hour * TimeConstant.HOUR_TRANSLATE + seconds * TimeConstant.SECONDS_TRANSLATE;
		} else if (ZERO.equals(hour) && !ZERO.equals(minutes) && !ZERO.equals(seconds)) {
			timeInterval = minutes * TimeConstant.MINUTES_TRANSLATE + seconds * TimeConstant.SECONDS_TRANSLATE;
		} else {
			timeInterval = hour * TimeConstant.HOUR_TRANSLATE + minutes * TimeConstant.MINUTES_TRANSLATE
					+ seconds * TimeConstant.SECONDS_TRANSLATE;
		}

		return timeInterval;
	}

}

4.执行定时任务的方法

import java.lang.reflect.*;

/**
 * @author caojianyu
 * @create 2019-12-26 11:20
 * @mail [email protected]
 * 
 */
public class Processor {

	public static void process(Class<?> clazz) {

		Runnable runnable = new Runnable() {
			public void run() {
				boolean isTrue = false;
				isTrue = clazz.isAnnotationPresent(Timer.class);
				if (isTrue) {

					Timer getAnnotation = clazz.getAnnotation(Timer.class);

					Long hour = Long.parseLong(getAnnotation.hour());
					Long minutes = Long.parseLong(getAnnotation.minutes());
					Long seconds = Long.parseLong(getAnnotation.seconds());

					Long timeInterval = Transform.getTimeInterval(hour, minutes, seconds);
					while (true) {
						for (Method method : clazz.getDeclaredMethods()) {
							Constructor<?> con;
							try {
								con = clazz.getConstructor();
								method.invoke(con.newInstance());
							} catch (NoSuchMethodException | SecurityException e) {
								e.printStackTrace();
							} catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException
									| InstantiationException e) {
								e.printStackTrace();
							}
						}

						try {
							Thread.sleep(timeInterval);
						} catch (InterruptedException e) {
							e.printStackTrace();
						}
					}
				}
			}
		};
		new Thread(runnable).start();
	}
}

5.基本框架也就搭好了，接下来创建一个测试类用于测试

使用时，在需要定时执行任务的类上加一个@Timer注解，并指定时间间隔参数（也就是注解定义的那几个参数）——共有三个参数：hour小时，minutes分钟，seconds秒。

@Timer(seconds = "2")
public class Test {
	public void print() {
		System.out.println("测试方法正在定时运行...");
	}
}

6.再创建一个主函数测试

public class TestTimer {
	public static void main(String[] args) {
		Processor.process(Test.class);
	}
}

我设置的为两秒，所以是每两秒种运行一次，如果小时和分钟有设置值，则会叠加。使用可直接打成jar包引用到项目中。以下是运行结果：

测试方法正在定时运行…
测试方法正在定时运行…
测试方法正在定时运行…