作者:青石路
cnblogs.com/youzhibing/p/10024558.html
java定時任務調度的實現方式
Timer
這個相信大家都有用過,我也用過,但用的不多;
特點是:簡單易用,但由於所有任務都是由同一個線程來調度,因此所有任務都是串行執行的,同一時間只能有一個任務在執行,前一個任務的延遲或異常都將會影響到之後的任務;能實現簡單的定時任務,稍微複雜點(或要求高一些)的定時任務卻不好實現。
ScheduledExecutor
這個我相信大家也都用過,而且用的比Timer多;正是鑑於Timer的缺陷,Java 5推出了基於線程池設計的ScheduledExecutor;
特點:每一個被調度的任務都會由線程池中一個線程去執行,因此任務是併發執行的,相互之間不會受到干擾。需要注意的是,只有當任務的執行時間到來時,ScheduedExecutor 才會真正啟動一個線程,其餘時間 ScheduledExecutor 都是在輪詢任務的狀態。
雖然用ScheduledExecutor和Calendar能夠實現複雜任務調度,但實現起來還是比較麻煩,對開發還是不夠友善。
Spring Scheduler
spring對任務調度的實現支持,可以指定任務的執行時間,但對任務隊列和線程池的管控較弱;一般集成於項目中,小任務很方便。
JCronTab
JCronTab則是一款完全按照crontab語法編寫的java任務調度工具。
特點:
- 可指定任務的執行時間;
- 提供完全按照Unix的UNIX-POSIX crontab的格式來規定時間;
- 支持多種任務調度的持久化方法,包括普通文件、數據庫以及 XML 文件進行持久化;
- JCronTab內置了發郵件功能,可以將任務執行結果方便地發送給需要被通知的人;
- 設計和部署是高性能並可擴展。
Quartz
本文主角,請往下看
當然還有XXL-JOB、Elastic-Job、Saturn等等
quartz相關概念
- Scheduler:調度器,進行任務調度;quartz的大腦
- Job:業務job,亦可稱業務組件;定時任務的具體執行業務需要實現此接口,調度器會調用此接口的execute方法完成我們的定時業務
- JobDetail:用來定義業務Job的實例,我們可以稱之為quartz job,很多時候我們談到的job指的是JobDetail
- Trigger:觸發器,用來定義一個指定的Job何時被執行
- JobBuilder:Job構建器,用來定義或創建JobDetail的實例;JobDetail限定了只能是Job的實例
- TriggerBuilder:觸發器構建器,用來定義或創建觸發器的實例
具體為什麼要分這麼細,大家可以去查閱下相關資料,你會發現很多東西。
工程實現
pom.xml
application.xml
這樣,quartz就配置好了,應用裡面直接用即可
JobController.java
JobServiceImpl.java
主要就是以上文件,詳情請查看spring-boot-quartz
https://gitee.com/youzhibing/spring-boot-2.0.3/tree/master/spring-boot-quartz
工程裡面數據源用的druid,springboot默認也會將該數據源應用到quartz,如果想給quartz單獨配置數據源,可配合@QuartzDataSource來實現
最終效果如下
trigger狀態
org.quartz.impl.jdbcjobstore.Constants中存放了一些列的常量,源代碼如下
<code>/*
* All content copyright Terracotta, Inc., unless otherwise indicated. All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy
* of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
*/
package org.quartz.impl.jdbcjobstore;
/**
* <p>
* This interface can be implemented by any <code>{@link
* org.quartz.impl.jdbcjobstore.DriverDelegate}</code>
* class that needs to use the constants contained herein.
* </p>
*
* @author <a href="mailto:[email protected]">Jeffrey Wescott</a>
* @author James House
*/
public interface Constants {
/*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* Constants.
*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
// Table names
String TABLE_JOB_DETAILS = "JOB_DETAILS";
String TABLE_TRIGGERS = "TRIGGERS";
String TABLE_SIMPLE_TRIGGERS = "SIMPLE_TRIGGERS";
String TABLE_CRON_TRIGGERS = "CRON_TRIGGERS";
String TABLE_BLOB_TRIGGERS = "BLOB_TRIGGERS";
String TABLE_FIRED_TRIGGERS = "FIRED_TRIGGERS";
String TABLE_CALENDARS = "CALENDARS";
String TABLE_PAUSED_TRIGGERS = "PAUSED_TRIGGER_GRPS";
String TABLE_LOCKS = "LOCKS";
String TABLE_SCHEDULER_STATE = "SCHEDULER_STATE";
// TABLE_JOB_DETAILS columns names
String COL_SCHEDULER_NAME = "SCHED_NAME";
String COL_JOB_NAME = "JOB_NAME";
String COL_JOB_GROUP = "JOB_GROUP";
String COL_IS_DURABLE = "IS_DURABLE";
String COL_IS_VOLATILE = "IS_VOLATILE";
String COL_IS_NONCONCURRENT = "IS_NONCONCURRENT";
String COL_IS_UPDATE_DATA = "IS_UPDATE_DATA";
String COL_REQUESTS_RECOVERY = "REQUESTS_RECOVERY";
String COL_JOB_DATAMAP = "JOB_DATA";
String COL_JOB_CLASS = "JOB_CLASS_NAME";
String COL_DESCRIPTION = "DESCRIPTION";
// TABLE_TRIGGERS columns names
String COL_TRIGGER_NAME = "TRIGGER_NAME";
String COL_TRIGGER_GROUP = "TRIGGER_GROUP";
String COL_NEXT_FIRE_TIME = "NEXT_FIRE_TIME";
String COL_PREV_FIRE_TIME = "PREV_FIRE_TIME";
String COL_TRIGGER_STATE = "TRIGGER_STATE";
String COL_TRIGGER_TYPE = "TRIGGER_TYPE";
String COL_START_TIME = "START_TIME";
String COL_END_TIME = "END_TIME";
String COL_PRIORITY = "PRIORITY";
String COL_MISFIRE_INSTRUCTION = "MISFIRE_INSTR";
String ALIAS_COL_NEXT_FIRE_TIME = "ALIAS_NXT_FR_TM";
// TABLE_SIMPLE_TRIGGERS columns names
String COL_REPEAT_COUNT = "REPEAT_COUNT";
String COL_REPEAT_INTERVAL = "REPEAT_INTERVAL";
String COL_TIMES_TRIGGERED = "TIMES_TRIGGERED";
// TABLE_CRON_TRIGGERS columns names
String COL_CRON_EXPRESSION = "CRON_EXPRESSION";
// TABLE_BLOB_TRIGGERS columns names
String COL_BLOB = "BLOB_DATA";
String COL_TIME_ZONE_ID = "TIME_ZONE_ID";
// TABLE_FIRED_TRIGGERS columns names
String COL_INSTANCE_NAME = "INSTANCE_NAME";
String COL_FIRED_TIME = "FIRED_TIME";
String COL_SCHED_TIME = "SCHED_TIME";
String COL_ENTRY_ID = "ENTRY_ID";
String COL_ENTRY_STATE = "STATE";
// TABLE_CALENDARS columns names
String COL_CALENDAR_NAME = "CALENDAR_NAME";
String COL_CALENDAR = "CALENDAR";
// TABLE_LOCKS columns names
String COL_LOCK_NAME = "LOCK_NAME";
// TABLE_LOCKS columns names
String COL_LAST_CHECKIN_TIME = "LAST_CHECKIN_TIME";
String COL_CHECKIN_INTERVAL = "CHECKIN_INTERVAL";
// MISC CONSTANTS
String DEFAULT_TABLE_PREFIX = "QRTZ_";
// STATES
String STATE_WAITING = "WAITING";
String STATE_ACQUIRED = "ACQUIRED";
String STATE_EXECUTING = "EXECUTING";
String STATE_COMPLETE = "COMPLETE";
String STATE_BLOCKED = "BLOCKED";
String STATE_ERROR = "ERROR";
String STATE_PAUSED = "PAUSED";
String STATE_PAUSED_BLOCKED = "PAUSED_BLOCKED";
String STATE_DELETED = "DELETED";
/**
* @deprecated Whether a trigger has misfired is no longer a state, but
* rather now identified dynamically by whether the trigger's next fire
* time is more than the misfire threshold time in the past.
*/
String STATE_MISFIRED = "MISFIRED";
String ALL_GROUPS_PAUSED = "_$_ALL_GROUPS_PAUSED_$_";
// TRIGGER TYPES
/** Simple Trigger type. */
String TTYPE_SIMPLE = "SIMPLE";
/** Cron Trigger type. */
String TTYPE_CRON = "CRON";
/** Calendar Interval Trigger type. */
String TTYPE_CAL_INT = "CAL_INT";
/** Daily Time Interval Trigger type. */
String TTYPE_DAILY_TIME_INT = "DAILY_I";
/** A general blob Trigger type. */
String TTYPE_BLOB = "BLOB";
}
// EOF/<code>
裡面有quartz的表名、各個表包含的列名、trigger狀態、trigger類型等內容。
狀態包括
- WAITING:等待中
- ACQUIRED:將觸發,此時還未到trigger真正的觸發時刻
- EXECUTING:觸發,亦可理解成執行中,trigger真正的觸發時刻
- COMPLETE:完成,不再觸發
- BLOCKED:受阻,不允許併發執行job時會出現(@DisallowConcurrentExecution)
- ERROR:出錯
- PAUSED:暫停中
- PAUSED_BLOCKED:暫停受阻,不允許併發執行job時會出現(@DisallowConcurrentExecution)
- DELETED:已刪除
- MISFIRED:觸發失敗,已棄用,有另外的替代方式
狀態變化流程圖如下所示
trigger的初始狀態是WAITING,處於WAITING狀態的trigger等待被觸發。調度線程會不停地掃triggers表,根據NEXT_FIRE_TIME提前拉取即將觸發的trigger,如果這個trigger被該調度線程拉取到,它的狀態就會變為ACQUIRED。
因為是提前拉取trigger,並未到達trigger真正的觸發時刻,所以調度線程會等到真正觸發的時刻,再將trigger狀態由ACQUIRED改為EXECUTING。如果這個trigger不再執行,就將狀態改為COMPLETE,否則為WAITING,開始新的週期。如果這個週期中的任何環節拋出異常,trigger的狀態會變成ERROR。如果手動暫停這個trigger,狀態會變成PAUSED。
總結
Quartz作為一個開源的作業調度框架,提供了巨大的靈活性而不犧牲簡單性。我們能夠用它來為執行一個作業而創建簡單的或複雜的調度。它有很多特徵,如:數據庫、集群、插件、JavaMail支持,EJB作業預構建,支持cron-like表達式等等;
springboot集成quartz非常簡單,最簡單的情況下只需要引入依賴我們就可以享受quartz提供的功能,springboot默認會幫我們配置好quartz;當然我們也可以自定義配置來實現quartz的定製;
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