Spring Scheduled + Redis 实现分布式定时器（一）
1、需要了解的技术点：
1.1、Redis的命令：SETNX,EXPIRE;
1.2、
Spring的Scheduled定时器注解，触发器，任务，调度器；
1.3、
Spring的applicationContext上下文对象，自定义注解，java反射机制；
2、思路：
2.1、创建一个自定义注解，参数：cron（时间格式）；
2.2、创建一个@
Component组件，用来实现自定义注解的功能，
2.2.1、实现
ApplicationContextAware
接口，用来获取spring的ApplicationContext上下文对象；
2.2.2、
实现
BeanPostProcessor接口，用来获取自定义注解所对应的方法；
2
.2.3、实现
SchedulingConfigurer
接口，用来创建定时器任务；
2.2.4、创建一个实现Runabel接口的类，用来反射自定义注解所对应的方法和抢占redis的锁；
2.2.5、创建一个实现
Trigger接口的
触发器对象，用来获取下一次执行任务的时间，以便给redis设置锁的生存时间；
2.3、程序执行流程：
2.3.1、给需要加定时器的方法加上自定义注解
2.3.2、程序启动，获取spring上下文对象；
2.3.3、扫描自定义注解所对应的方法；
2.3.4、根据每个自定义注解的信息创建对应触发器和任务；
2.3.5、调度器触发任务时，先去抢占锁，再根据情况判断本实例是否要执行任务；
3、代码分解：
3.1、创建自定义注解；
@Target({ElementType.METHOD, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface KyScheduled {
/**
* A cron-like expression, extending the usual UN*X definition to include
* triggers on the second as well as minute, hour, day of month, month
* and day of week. e.g. {@code "0 * * * * MON-FRI"} means once per minute on
* weekdays (at the top of the minute - the 0th second).
* @return an expression that can be parsed to a cron schedule
*/
String cron() default "";
}public class KyScheduledExecution {
public class KyTask {
private KyScheduled kyScheduled;
private Method kyMethod;
public KyScheduled getKyScheduled() {
return kyScheduled;
}
public void setKyScheduled(KyScheduled kyScheduled) {
this.kyScheduled = kyScheduled;
}
public Method getKyMethod() {
return kyMethod;
}
public void setKyMethod(Method kyMethod) {
this.kyMethod = kyMethod;
}
}
}
3.3、实现
ApplicationContextAware接口，获取spring上下文对象；
原因：如果单纯使用java的反射机制，当定时器任务使用
@Autowired
注解时，会获取不到bean实例，所以要实现
ApplicationContextAware接口
；
@Component
public class KyScheduledExecution implements ApplicationContextAware {
private ApplicationContext applicationContext;
@Override
public void setApplicationContext(ApplicationContext context) throws BeansException {
this.applicationContext = context;
}
private Object getBean(Class classname) {
try {
return this.applicationContext.getBean(classname);
} catch (Exception e) {
log.error(e);
return "";
}
}
}
3.4、实现BeanPostProcessor接口，获取自定义注解信息；
@Component
public class KyScheduledExecution implements BeanPostProcessor {
private Log log = LogFactory.getLog(getClass());
//记录任务集合
private List kyTaskList = new ArrayList<>();
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
return bean;
}
/**
* 获取所有自定义注解，并记录注解和方法的信息
* @param bean bean
* @param beanName beanName
* @return Object
* @throws BeansException BeansException
*/
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
Method[] methods = ReflectionUtils.getAllDeclaredMethods(bean.getClass());
if (methods != null) {
for (Method method : methods) {
KyScheduled annotation = AnnotationUtils.findAnnotation(method, KyScheduled.class);
if (annotation != null && !"".equals(annotation.cron())) {
KyTask at = new KyTask();
at.setKyScheduled(annotation);
at.setKyMethod(method);
kyTaskList.add(at);
}
}
}
return bean;
}
} public class KyScheduledExecution{
private Log log = LogFactory.getLog(getClass());
@Value("${spring.redis.host}")
private String redisHost;
@Value("${spring.redis.port}")
private int redisPort;
private Jedis jedis;
//记录任务集合
private List kyTaskList = new ArrayList<>();
private ApplicationContext applicationContext;
/**
* 创建redis客户端
*/
private void createRedisClient() {
if (jedis == null) {
jedis = new Jedis(redisHost, redisPort);
}
}
/**
* 获取分布式锁
*
* @param lockName 锁名称
* @param second 加锁时间（秒）
* @return 如果获取到锁，则返回lockId值，否则为null
*/
private String setnxLock(String lockName, int second) {
synchronized (this) {
//生成随机的Value值
String lockId = UUID.randomUUID().toString();
//抢占锁
Long lock = this.jedis.setnx(lockName, lockId);
if (lock == 1) {
//拿到Lock，设置超时时间
this.jedis.expire(lockName, second - 1);
return lockId;
}
}
return null;
}
} public class KyTrigger implements Trigger, Serializable {
private String cron;
private boolean syncLock;
public KyTrigger(KyScheduled kyScheduled){
if(kyScheduled.cron() != null && !"".equals(kyScheduled.cron())) {
this.cron = kyScheduled.cron();
}
this.syncLock = kyScheduled.synclock();
}
public boolean getSyncLock(){
return this.syncLock;
}
public String getCron() {
return cron;
}
public void setCron(String cron) {
if(cron != null && !"".equals(cron)) {
this.cron = cron;
}
}
@Override
public Date nextExecutionTime(TriggerContext triggerContext) {
CronTrigger cronTrigger = new CronTrigger(this.cron);
return cronTrigger.nextExecutionTime(triggerContext);
}
}public class KyScheduledExecution{
private Log log = LogFactory.getLog(getClass());
/**
* 任务对象
*/
public class Job implements Runnable {
private Method method;
private String lockName;
private Object invokeMethod;
private Trigger trigger;
public String getLockName() {
return lockName;
}
Job(Method m, Trigger t) {
this.trigger = t;
this.invokeMethod = getBean(m.getDeclaringClass());//获取bean实例
this.lockName = m.getDeclaringClass().getName() + "." + m.getName();//构造LockName
this.method = m;
}
@Override
public void run() {
//获取下次执行时间（秒）
long nextTime = (this.trigger.nextExecutionTime(new SimpleTriggerContext()).getTime() - new Date().getTime()) / 1000;
//抢占分布式锁
String result = setnxLock(this.lockName, (int) nextTime);
if (result != null && !"".equals(result)) {
try {
//执行自定义注解的方法
this.method.invoke(this.invokeMethod);
} catch (IllegalAccessException | InvocationTargetException e) {
e.printStackTrace();
log.error(e);
}
}
}
}
}
3.7、
在
KyScheduledExecution
类中
实现
SchedulingConfigurer接口；
@Component
public class KyScheduledExecution implements SchedulingConfigurer{
private Log log = LogFactory.getLog(getClass());
/**
* 配置定时器
*
* @param taskRegistrar ScheduledTaskRegistrar
*/
@Override
public void configureTasks(ScheduledTaskRegistrar taskRegistrar) {
if (taskRegistrar != null) {
for (KyTask kt : kyTaskList) {
Method method = kt.getKyMethod();
//创建触发器
KyTrigger trigger = new KyTrigger(kt.getKyScheduled());
//创建任务
Job job = new Job(method, trigger);
//将任务加入调度器中
taskRegistrar.addTriggerTask(job, trigger);
}
}
}
}
代码分解完毕，以上为所有代码！！！