定时任务迁移到SnailJob的优化历程

1. 今天同事在对接我基于elasticJob二次开发的snailJob时，说需要把每个定时任务都要实现SimpleJob接口，感觉很麻烦，希望直接指定其方法，减少对接的成本
2. Quart初始化总结：
   2.1 初始化scheduler
   2.2 将Job和触发器添加到scheduler中
   （1）Job对应于scheduler的jobDetail属性
   （2）触发器对应于scheduler的trigger属性
3. Quart调用定时任务方法总结
   3.1 在JobDetail中指定Quart的Job，Quart调度时会触发Job的execute
   3.2 Job#execute触发器JobDataMap中指定类和方法

1. Spring集成Quart入口：

2. SchedulerFactoryBean实现InitializingBean接口，故在afterPropertiesSet方法时会初始化Scheduler实例

   	public void afterPropertiesSet() throws Exception {
   		// 初始化scheduler 
   		this.scheduler = prepareScheduler(prepareSchedulerFactory());
   		try {
   		         ..........
   		         //注册定时任务
   				registerJobsAndTriggers();
   		}
   	}
   

   2.1 SchedulerFactoryBean继承SchedulerAccessor，其triggers属性中包含所有的定时任务，在registerJobsAndTriggers方法中将trigger加入到Sheduler

3. 将trigger加入到Sheduler(SchedulerAccessor#addTriggerToScheduler)

   	private boolean addTriggerToScheduler(Trigger trigger) throws SchedulerException {
   		//从trigger中取出jobDetail
   		JobDetail jobDetail = (JobDetail) trigger.getJobDataMap().remove("jobDetail");
   		if (jobDetail != null && this.jobDetails != null && !this.jobDetails.contains(jobDetail) &&
   					(this.overwriteExistingJobs || getScheduler().getJobDetail(jobDetail.getKey()) == null)) {
   			    //将trigger加入到Sheduler	
   				getScheduler().scheduleJob(jobDetail, trigger);
   				this.jobDetails.add(jobDetail);
   		}
   	}
   

   3.1 首先看一下，配置trigger长啥样？见下方
   （1） trigger主要配置定时任务的job以及触发器，那Quart怎样触发Job方法？

1. Job配置如下
   1.1 主要配置了Job所在的类以及对应的方法
   1.2 MethodInvokingJobDetailFactoryBean继承ArgumentConvertingMethodInvoker（继承MethodInvoker）

   
   		
   			
   		
   		
   			run
   		
   
   

2. MethodInvokingJobDetailFactoryBean实现FactoryBean，在getObject时返回JobDetail
   2.1 在其afterPropertiesSet方法时初始化jobDetail

   public void afterPropertiesSet() throws ClassNotFoundException, NoSuchMethodException {
   	// 初始化methodInvoker的methodObject属性
   	prepare();
   	
   	// Consider the concurrent flag to choose between stateful and stateless job.(默认为MethodInvokingJob)
   	Class jobClass = (this.concurrent ? MethodInvokingJob.class : StatefulMethodInvokingJob.class);
   	
   	// Build JobDetail instance.
   	JobDetailImpl jdi = new JobDetailImpl();
   	jdi.setName(name != null ? name : toString());
   	jdi.setGroup(this.group);
   	// MethodInvokingJob通过QuartzJobBean实现Quart的Job
   	jdi.setJobClass((Class) jobClass);
   	jdi.setDurability(true);
   	// 重点：最终会在JobRunShell时，将MethodInvokingJobDetailFactoryBean设置到MethodInvokingJob的methodInvoker属性
   	jdi.getJobDataMap().put("methodInvoker", this);
   	this.jobDetail = jdi;
   }
   

   3.2 MethodInvoker#prepare分析

   public void prepare() throws ClassNotFoundException, NoSuchMethodException {
   	//用户设置的定时任务类
   	Class targetClass = getTargetClass();
   	//设置的定时任务方法
   	String targetMethod = getTargetMethod();
   	// 用户设置的定时任务方法参数
   	Object[] arguments = getArguments();
   	Class[] argTypes = new Class[arguments.length];
   	for (int i = 0; i < arguments.length; ++i) {
   		argTypes[i] = (arguments[i] != null ? arguments[i].getClass() : Object.class);
   	}
   	
   	try {
   		this.methodObject = targetClass.getMethod(targetMethod, argTypes);
   	}
   }
   

3. MethodInvokingJobDetailFactoryBean$MethodInvokingJob#executeInternal执行任务

   protected void executeInternal(JobExecutionContext context) throws JobExecutionException {
   	try {
   		//this.methodInvoker.invoke()调用指定任务方法
   		context.setResult(this.methodInvoker.invoke());
   	}catch (InvocationTargetException ex) {
   		.....
   }
   

   3.1 MethodInvoker#invoke分析

   public Object invoke() throws InvocationTargetException, IllegalAccessException {
   	// In the static case, target will simply be {@code null}.
   	Object targetObject = getTargetObject();
   	Method preparedMethod = getPreparedMethod();
   	if (targetObject == null && !Modifier.isStatic(preparedMethod.getModifiers())) {
   		throw new IllegalArgumentException("Target method must not be non-static without a target");
   	}
   	ReflectionUtils.makeAccessible(preparedMethod);
   	return preparedMethod.invoke(targetObject, getArguments());
   }
   

1. SnailJob是基于elatiscJob的代码改造出来的公司内部调度框架
2. SnailJob创建JobDetail代码示例

   private JobDetail createJobDetail() {
        JobDetail result = JobBuilder.newJob(LiteJob.class).withIdentity(getJobConfig().getJobName()).build();
        result.getJobDataMap().put(JOB_EXECUTOR_DATA_MAP_KEY, jobExecutor);
        return result;
    }
   

3. Quart调度触发任务的调用栈
   

1. 在执行任务时，多了一层判断，如果是spring方式的定时任务，则直接反射调用其指定的方法
   1.1 直接加if判断，感觉不优雅（后期优化，哈哈哈）

if(snailJob instanceof JobDetailImpl){
	  JobDataMap jobDataMap = ((JobDetailImpl) snailJob).getJobDataMap();
      MethodInvokingJobDetailFactoryBean methodInvoker = (MethodInvokingJobDetailFactoryBean) jobDataMap.get("methodInvoker");
      methodInvoker.invoke();
  }else{
      ((SimpleJob)snailJob).execute(shardingContexts.createShardingContext(item));
  }