spring schedule定时任务详解
spring schedule定时任务
文章目录
- spring schedule定时任务
- 一、如何使用定时任务
- 1、启动类使用@EnableScheduling注解开启定时任务
- 2、方法使用@Scheduled注解，或者实现SchedulingConfigurer接口，添加定时任务
- 二、配置定时任务多线程非阻塞运行
- 1、阻塞原因
- 2、如何解决，实现SchedulingConfigurer接口，设置任务调度器实现类
- 三、源码解析
- 1、@EnableScheduling注解启用定时任务
- 2、扫描@Scheduled、@Schedules注解
- 3、扫描SchedulingConfigurer实现类
- 4、添加定时任务到线程池
一、如何使用定时任务
1、启动类使用@EnableScheduling注解开启定时任务
@SpringBootApplication
@EnableScheduling
public class ScheduledTest {
public static void main(String[] args) {
SpringApplication.run(ScheduledTest.class);
}
}
2、方法使用@Scheduled注解，或者实现SchedulingConfigurer接口，添加定时任务
@Scheduled(cron = "0/2 * * * * ? ")
public void index1() {
log.info("定时任务1，2秒执行一次，time：" + DateTime.now() + " 线程：" + Thread.currentThread().getName());
}
@Configuration
@Component
@Slf4j
public class TestTask implements SchedulingConfigurer {
@Override
public void configureTasks(ScheduledTaskRegistrar taskRegistrar) {
taskRegistrar.addFixedDelayTask(this::index3, 1000);
}
public void index2() {
log.info("定时任务2，1秒执行一次，time：" + DateTime.now() + " 线程：" + Thread.currentThread().getName());
}
}
二、配置定时任务多线程非阻塞运行
1、阻塞原因
默认情况，定时任务使用的是单例线程执行器Executors.newSingleThreadScheduledExecutor()，所以当一个定时任务阻塞是，所有定时任务都不会执行：
public class ScheduledTaskRegistrar implements ScheduledTaskHolder, InitializingBean, DisposableBean {
@SuppressWarnings("deprecation")
protected void scheduleTasks() {
if (this.taskScheduler == null) {
this.localExecutor = Executors.newSingleThreadScheduledExecutor();
this.taskScheduler = new ConcurrentTaskScheduler(this.localExecutor);
}
if (this.triggerTasks != null) {
for (TriggerTask task : this.triggerTasks) {
addScheduledTask(scheduleTriggerTask(task));
}
}
if (this.cronTasks != null) {
for (CronTask task : this.cronTasks) {
addScheduledTask(scheduleCronTask(task));
}
}
if (this.fixedRateTasks != null) {
for (IntervalTask task : this.fixedRateTasks) {
addScheduledTask(scheduleFixedRateTask(task));
}
}
if (this.fixedDelayTasks != null) {
for (IntervalTask task : this.fixedDelayTasks) {
addScheduledTask(scheduleFixedDelayTask(task));
}
}
}
}
2、如何解决，实现SchedulingConfigurer接口，设置任务调度器实现类
使用线程池执行定时任务，ThreadPoolExecutor.AbortPolicy:丢弃任务并抛出RejectedExecutionException异常。
@Configuration
@Component
@Slf4j
public class TestTask implements SchedulingConfigurer {
@Override
public void configureTasks(ScheduledTaskRegistrar taskRegistrar) {
ThreadFactory nameThreadFactory = new ThreadFactoryBuilder().setNameFormat("scheduled-%d").build();
taskRegistrar.setScheduler(new ScheduledThreadPoolExecutor(5,
nameThreadFactory,
new ThreadPoolExecutor.AbortPolicy()));
}
}
三、源码解析
1、@EnableScheduling注解启用定时任务
打开注解，发现这里只是在引用SchedulingConfiguration.class配置
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Import(SchedulingConfiguration.class)
@Documented
public @interface EnableScheduling {
}
打开配置类，发现是在实例化ScheduledAnnotationBeanPostProcessor类
@Configuration(proxyBeanMethods = false)
@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
public class SchedulingConfiguration {
@Bean(name = TaskManagementConfigUtils.SCHEDULED_ANNOTATION_PROCESSOR_BEAN_NAME)
@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
public ScheduledAnnotationBeanPostProcessor scheduledAnnotationProcessor() {
return new ScheduledAnnotationBeanPostProcessor();
}
}
注解Bean后置处理器初始化方法是在实例化ScheduledTaskRegistrar类
public class ScheduledAnnotationBeanPostProcessor
implements ScheduledTaskHolder, MergedBeanDefinitionPostProcessor, DestructionAwareBeanPostProcessor,
Ordered, EmbeddedValueResolverAware, BeanNameAware, BeanFactoryAware, ApplicationContextAware,
SmartInitializingSingleton, ApplicationListener<ContextRefreshedEvent>, DisposableBean {
/**
* The default name of the {@link TaskScheduler} bean to pick up: {@value}.
* <p>Note that the initial lookup happens by type; this is just the fallback
* in case of multiple scheduler beans found in the context.
* @since 4.2
*/
public static final String DEFAULT_TASK_SCHEDULER_BEAN_NAME = "taskScheduler";
protected final Log logger = LogFactory.getLog(getClass());
private final ScheduledTaskRegistrar registrar;
@Nullable
private Object scheduler;
private final Set<Class<?>> nonAnnotatedClasses = Collections.newSetFromMap(new ConcurrentHashMap<>(64));
private final Map<Object, Set<ScheduledTask>> scheduledTasks = new IdentityHashMap<>(16);
/**
* Create a default {@code ScheduledAnnotationBeanPostProcessor}.
*/
public ScheduledAnnotationBeanPostProcessor() {
this.registrar = new ScheduledTaskRegistrar();
}
}
2、扫描@Scheduled、@Schedules注解
ScheduledAnnotationBeanPostProcessor实现了BeanPostProcessor接口。调用postProcessAfterInitialization后置处理器扫描注解，全部转换为Scheduled后，调用processScheduled方法
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) {
if (bean instanceof AopInfrastructureBean || bean instanceof TaskScheduler ||
bean instanceof ScheduledExecutorService) {
// Ignore AOP infrastructure such as scoped proxies.
return bean;
}
Class<?> targetClass = AopProxyUtils.ultimateTargetClass(bean);
if (!this.nonAnnotatedClasses.contains(targetClass) &&
AnnotationUtils.isCandidateClass(targetClass, Arrays.asList(Scheduled.class, Schedules.class))) {
Map<Method, Set<Scheduled>> annotatedMethods = MethodIntrospector.selectMethods(targetClass,
(MethodIntrospector.MetadataLookup<Set<Scheduled>>) method -> {
Set<Scheduled> scheduledAnnotations = AnnotatedElementUtils.getMergedRepeatableAnnotations(
method, Scheduled.class, Schedules.class);
return (!scheduledAnnotations.isEmpty() ? scheduledAnnotations : null);
});
if (annotatedMethods.isEmpty()) {
this.nonAnnotatedClasses.add(targetClass);
if (logger.isTraceEnabled()) {
logger.trace("No @Scheduled annotations found on bean class: " + targetClass);
}
}
else {
// Non-empty set of methods
annotatedMethods.forEach((method, scheduledAnnotations) ->
scheduledAnnotations.forEach(scheduled -> processScheduled(scheduled, method, bean)));
if (logger.isTraceEnabled()) {
logger.trace(annotatedMethods.size() + " @Scheduled methods processed on bean '" + beanName +
"': " + annotatedMethods);
}
}
}
return bean;
}
先创建执行runnable获取延迟执行时间获取cron表达式，创建CronTask，registrar中添加任务获取固定延迟，创建FixedDelayTask，registrar中添加任务获取固定执行间隔，创建FixedRateTask，registrar中添加任务把所有任务都添加到scheduledTasks
protected void processScheduled(Scheduled scheduled, Method method, Object bean) {
try {
Runnable runnable = createRunnable(bean, method);
boolean processedSchedule = false;
String errorMessage =
"Exactly one of the 'cron', 'fixedDelay(String)', or 'fixedRate(String)' attributes is required";
Set<ScheduledTask> tasks = new LinkedHashSet<>(4);
// Determine initial delay
long initialDelay = scheduled.initialDelay();
String initialDelayString = scheduled.initialDelayString();
if (StringUtils.hasText(initialDelayString)) {
Assert.isTrue(initialDelay < 0, "Specify 'initialDelay' or 'initialDelayString', not both");
if (this.embeddedValueResolver != null) {
initialDelayString = this.embeddedValueResolver.resolveStringValue(initialDelayString);
}
if (StringUtils.hasLength(initialDelayString)) {
try {
initialDelay = parseDelayAsLong(initialDelayString);
}
catch (RuntimeException ex) {
throw new IllegalArgumentException(
"Invalid initialDelayString value \\"" + initialDelayString + "\\" - cannot parse into long");
}
}
}
// Check cron expression
String cron = scheduled.cron();
if (StringUtils.hasText(cron)) {
String zone = scheduled.zone();
if (this.embeddedValueResolver != null) {
cron = this.embeddedValueResolver.resolveStringValue(cron);
zone = this.embeddedValueResolver.resolveStringValue(zone);
}
if (StringUtils.hasLength(cron)) {
Assert.isTrue(initialDelay == -1, "'initialDelay' not supported for cron triggers");
processedSchedule = true;
if (!Scheduled.CRON_DISABLED.equals(cron)) {
TimeZone timeZone;
if (StringUtils.hasText(zone)) {
timeZone = StringUtils.parseTimeZoneString(zone);
}
else {
timeZone = TimeZone.getDefault();
}
tasks.add(this.registrar.scheduleCronTask(new CronTask(runnable, new CronTrigger(cron, timeZone))));
}
}
}
// At this point we don't need to differentiate between initial delay set or not anymore
if (initialDelay < 0) {
initialDelay = 0;
}
// Check fixed delay
long fixedDelay = scheduled.fixedDelay();
if (fixedDelay >= 0) {
Assert.isTrue(!processedSchedule, errorMessage);
processedSchedule = true;
tasks.add(this.registrar.scheduleFixedDelayTask(new FixedDelayTask(runnable, fixedDelay, initialDelay)));
}
String fixedDelayString = scheduled.fixedDelayString();
if (StringUtils.hasText(fixedDelayString)) {
if (this.embeddedValueResolver != null) {
fixedDelayString = this.embeddedValueResolver.resolveStringValue(fixedDelayString);
}
if (StringUtils.hasLength(fixedDelayString)) {
Assert.isTrue(!processedSchedule, errorMessage);
processedSchedule = true;
try {
fixedDelay = parseDelayAsLong(fixedDelayString);
}
catch (RuntimeException ex) {
throw new IllegalArgumentException(
"Invalid fixedDelayString value \\"" + fixedDelayString + "\\" - cannot parse into long");
}
tasks.add(this.registrar.scheduleFixedDelayTask(new FixedDelayTask(runnable, fixedDelay, initialDelay)));
}
}
// Check fixed rate
long fixedRate = scheduled.fixedRate();
if (fixedRate >= 0) {
Assert.isTrue(!processedSchedule, errorMessage);
processedSchedule = true;
tasks.add(this.registrar.scheduleFixedRateTask(new FixedRateTask(runnable, fixedRate, initialDelay)));
}
String fixedRateString = scheduled.fixedRateString();
if (StringUtils.hasText(fixedRateString)) {
if (this.embeddedValueResolver != null) {
fixedRateString = this.embeddedValueResolver.resolveStringValue(fixedRateString);
}
if (StringUtils.hasLength(fixedRateString)) {
Assert.isTrue(!processedSchedule, errorMessage);
processedSchedule = true;
try {
fixedRate = parseDelayAsLong(fixedRateString);
}
catch (RuntimeException ex) {
throw new IllegalArgumentException(
"Invalid fixedRateString value \\"" + fixedRateString + "\\" - cannot parse into long");
}
tasks.add(this.registrar.scheduleFixedRateTask(new FixedRateTask(runnable, fixedRate, initialDelay)));
}
}
// Check whether we had any attribute set
Assert.isTrue(processedSchedule, errorMessage);
// Finally register the scheduled tasks
synchronized (this.scheduledTasks) {
Set<ScheduledTask> regTasks = this.scheduledTasksputeIfAbsent(bean, key -> new LinkedHashSet<>(4));
regTasks.addAll(tasks);
}
}
catch (IllegalArgumentException ex) {
throw new IllegalStateException(
"Encountered invalid @Scheduled method '" + method.getName() + "': " + ex.getMessage());
}
}
3、扫描SchedulingConfigurer实现类
ScheduledAnnotationBeanPostProcessor实现了ApplicationListener接口，当工程启动好后调用onApplicationEvent方法，执行finishRegistration方式。扫描所有的SchedulingConfigurer实现类，调用configureTasks回调函数添加定时任务。调用registrar 的afterPropertiesSet方法。
@Override
public void onApplicationEvent(ContextRefreshedEvent event) {
if (event.getApplicationContext() == this.applicationContext) {
// Running in an ApplicationContext -> register tasks this late...
// giving other ContextRefreshedEvent listeners a chance to perform
// their work at the same time (e.g. Spring Batch's job registration).
finishRegistration();
}
}
private void finishRegistration() {
if (this.scheduler != null) {
this.registrar.setScheduler(this.scheduler);
}
if (this.beanFactory instanceof ListableBeanFactory) {
Map<String, SchedulingConfigurer> beans =
((ListableBeanFactory) this.beanFactory).getBeansOfType(SchedulingConfigurer.class);
List<SchedulingConfigurer> configurers = new ArrayList<>(beans.values());
AnnotationAwareOrderComparator.sort(configurers);
for (SchedulingConfigurer configurer : configurers) {
configurer.configureTasks(this.registrar);
}
}
if (this.registrar.hasTasks() && this.registrar.getScheduler() == null) {
Assert.state(this.beanFactory != null, "BeanFactory must be set to find scheduler by type");
try {
// Search for TaskScheduler bean...
this.registrar.setTaskScheduler(resolveSchedulerBean(this.beanFactory, TaskScheduler.class, false));
}
catch (NoUniqueBeanDefinitionException ex) {
if (logger.isTraceEnabled()) {
logger.trace("Could not find unique TaskScheduler bean - attempting to resolve by name: " +
ex.getMessage());
}
try {
this.registrar.setTaskScheduler(resolveSchedulerBean(this.beanFactory, TaskScheduler.class, true));
}
catch (NoSuchBeanDefinitionException ex2) {
if (logger.isInfoEnabled()) {
logger.info("More than one TaskScheduler bean exists within the context, and " +
"none is named 'taskScheduler'. Mark one of them as primary or name it 'taskScheduler' " +
"(possibly as an alias); or implement the SchedulingConfigurer interface and call " +
"ScheduledTaskRegistrar#setScheduler explicitly within the configureTasks() callback: " +
ex.getBeanNamesFound());
}
}
}
catch (NoSuchBeanDefinitionException ex) {
if (logger.isTraceEnabled()) {
logger.trace("Could not find default TaskScheduler bean - attempting to find ScheduledExecutorService: " +
ex.getMessage());
}
// Search for ScheduledExecutorService bean next...
try {
this.registrar.setScheduler(resolveSchedulerBean(this.beanFactory, ScheduledExecutorService.class, false));
}
catch (NoUniqueBeanDefinitionException ex2) {
if (logger.isTraceEnabled()) {
logger.trace("Could not find unique ScheduledExecutorService bean - attempting to resolve by name: " +
ex2.getMessage());
}
try {
this.registrar.setScheduler(resolveSchedulerBean(this.beanFactory, ScheduledExecutorService.class, true));
}
catch (NoSuchBeanDefinitionException ex3) {
if (logger.isInfoEnabled()) {
logger.info("More than one ScheduledExecutorService bean exists within the context, and " +
"none is named 'taskScheduler'. Mark one of them as primary or name it 'taskScheduler' " +
"(possibly as an alias); or implement the SchedulingConfigurer interface and call " +
"ScheduledTaskRegistrar#setScheduler explicitly within the configureTasks() callback: " +
ex2.getBeanNamesFound());
}
}
}
catch (NoSuchBeanDefinitionException ex2) {
if (logger.isTraceEnabled()) {
logger.trace("Could not find default ScheduledExecutorService bean - falling back to default: " +
ex2.getMessage());
}
// Giving up -> falling back to default scheduler within the registrar...
logger.info("No TaskScheduler/ScheduledExecutorService bean found for scheduled processing");
}
}
}
this.registrar.afterPropertiesSet();
}
4、添加定时任务到线程池
afterPropertiesSet实际是在调用scheduleTasks方法安排任务判断任务执行器是否存在，如果不存在则使用Executors.newSingleThreadScheduledExecutor()判断triggerTasks、cronTasks、fixedRateTasks、fixedDelayTasks是否存在，如果存在则addScheduledTask(scheduleTriggerTask(task))添加到taskScheduler，然后添加到scheduledTasks
@Override
public void afterPropertiesSet() {
scheduleTasks();
}
/**
* Schedule all registered tasks against the underlying
* {@linkplain #setTaskScheduler(TaskScheduler) task scheduler}.
*/
@SuppressWarnings("deprecation")
protected void scheduleTasks() {
if (this.taskScheduler == null) {
this.localExecutor = Executors.newSingleThreadScheduledExecutor();
this.taskScheduler = new ConcurrentTaskScheduler(this.localExecutor);
}
if (this.triggerTasks != null) {
for (TriggerTask task : this.triggerTasks) {
addScheduledTask(scheduleTriggerTask(task));
}
}
if (this.cronTasks != null) {
for (CronTask task : this.cronTasks) {
addScheduledTask(scheduleCronTask(task));
}
}
if (this.fixedRateTasks != null) {
for (IntervalTask task : this.fixedRateTasks) {
addScheduledTask(scheduleFixedRateTask(task));
}
}
if (this.fixedDelayTasks != null) {
for (IntervalTask task : this.fixedDelayTasks) {
addScheduledTask(scheduleFixedDelayTask(task));
}
}
}
用triggerTasks进行分析，其他任务类似：
首先从未解决的任务里面获取并移除当前任务如果为空，则创建新的任务；从scheduleTasks()方法进来的时候已经存在任务如果存在任务执行器，则调用方法taskScheduler.schedule安排任务，并返回一个future执行结果
@Nullable
public ScheduledTask scheduleTriggerTask(TriggerTask task) {
ScheduledTask scheduledTask = this.unresolvedTasks.remove(task);
boolean newTask = false;
if (scheduledTask == null) {
scheduledTask = new ScheduledTask(task);
newTask = true;
}
if (this.taskScheduler != null) {
scheduledTask.future = this.taskScheduler.schedule(task.getRunnable(), task.getTrigger());
}
else {
addTriggerTask(task);
this.unresolvedTasks.put(task, scheduledTask);
}
return (newTask ? scheduledTask : null);
}
private void addScheduledTask(@Nullable ScheduledTask task) {
if (task != null) {
this.scheduledTasks.add(task);
}
}
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