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推薦一個(gè)很多小伙伴沒注意到的 Spring 官方的批處理框架。

Spring Batch 是一個(gè)輕量級(jí)但功能又十分全面的批處理框架，主要用于批處理場景比如從數(shù)據(jù)庫、文件或隊(duì)列中讀取大量記錄。不過，需要注意的是：Spring Batch 不是調(diào)度框架。商業(yè)和開源領(lǐng)域都有許多優(yōu)秀的企業(yè)調(diào)度框架比如 Quartz、XXL-JOB、Elastic-Job。它旨在與調(diào)度程序一起工作，而不是取代調(diào)度程序。

目前，Spring Batch 也已經(jīng)被收錄進(jìn)了開源項(xiàng)目 awesome-java （非常棒的 Java 開源項(xiàng)目集合）。

項(xiàng)目地址：https://github.com/CodingDocs/awesome-java

關(guān)于 Spring Batch 的詳細(xì)介紹可以參考 Spring Batch 官方文檔^[1]，入門教程可以參考下面的內(nèi)容，原文地址：https://mrbird.cc/Spring-Batch 入門.html?。

項(xiàng)目搭建

新建一個(gè) Spring Boot 項(xiàng)目，版本為 2.2.4.RELEASE，artifactId 為 spring-batch-start，項(xiàng)目結(jié)構(gòu)如下圖所示：

然后在 pom.xml 中引入 Spring Batch、MySQL 和 JDBC 依賴，引入后 pom.xml 內(nèi)容如下所示：


<project?xmlns="http://maven.apache.org/POM/4.0.0"?xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
?????????xsi:schemaLocation="http://maven.apache.org/POM/4.0.0?https://maven.apache.org/xsd/maven-4.0.0.xsd">
????<modelVersion>4.0.0modelVersion>
????<parent>
????????<groupId>org.springframework.bootgroupId>
????????<artifactId>spring-boot-starter-parentartifactId>
????????<version>2.2.5.RELEASEversion>
????????<relativePath/>?
????parent>
????<groupId>cc.mrbirdgroupId>
????<artifactId>spring-batch-startartifactId>
????<version>0.0.1-SNAPSHOTversion>
????<name>spring-batch-startname>
????<description>Demo?project?for?Spring?Bootdescription>

????<properties>
????????<java.version>1.8java.version>
????properties>

????<dependencies>
????????<dependency>
????????????<groupId>org.springframework.bootgroupId>
????????????<artifactId>spring-boot-starter-batchartifactId>
????????dependency>

????????<dependency>
????????????<groupId>mysqlgroupId>
????????????<artifactId>mysql-connector-javaartifactId>
????????dependency>
????????<dependency>
????????????<groupId>org.springframework.bootgroupId>
????????????<artifactId>spring-boot-starter-jdbcartifactId>
????????dependency>
????dependencies>

????<build>
????????<plugins>
????????????<plugin>
????????????????<groupId>org.springframework.bootgroupId>
????????????????<artifactId>spring-boot-maven-pluginartifactId>
????????????plugin>
????????plugins>
????build>
project>

在編寫代碼之前，我們先來簡單了解下 Spring Batch 的組成：

Spring Batch 里最基本的單元就是任務(wù) Job，一個(gè) Job 由若干個(gè)步驟 Step 組成。
任務(wù)啟動(dòng)器 Job Launcher 負(fù)責(zé)運(yùn)行 Job。
任務(wù)存儲(chǔ)倉庫 Job Repository 存儲(chǔ)著 Job 的執(zhí)行狀態(tài)，參數(shù)和日志等信息。Job 處理任務(wù)又可以分為三大類：

數(shù)據(jù)讀取 Item Reader
數(shù)據(jù)中間處理 Item Processor
數(shù)據(jù)輸出 Item Writer。

任務(wù)存儲(chǔ)倉庫可以是關(guān)系型數(shù)據(jù)庫 MySQL，非關(guān)系型數(shù)據(jù)庫 MongoDB 或者直接存儲(chǔ)在內(nèi)存中，本篇使用的是 MySQL 作為任務(wù)存儲(chǔ)倉庫。

新建一個(gè)名稱為 springbatch 的 MySQL 數(shù)據(jù)庫，然后導(dǎo)入 org.springframework.batch.core 目錄下的 schema-mysql.sql 文件：

導(dǎo)入后，庫表如下圖所示：

然后在項(xiàng)目的配置文件 application.yml 里添加 MySQL 相關(guān)配置：

spring:
??datasource:
????driver-class-name:?com.mysql.cj.jdbc.Driver
????url:?jdbc:mysql://127.0.0.1:3306/springbatch
????username:?root
????password:?123456

接著在 Spring Boot 的入口類上添加 @EnableBatchProcessing 注解，表示開啟 Spring Batch 批處理功能：

@SpringBootApplication
@EnableBatchProcessing
public?class?SpringBatchStartApplication?{
????public?static?void?main(String[]?args)?{
????????SpringApplication.run(SpringBatchStartApplication.class,?args);
????}
}

至此，基本框架搭建好了，下面開始配置一個(gè)簡單的任務(wù)。

編寫第一個(gè)任務(wù)

在 cc.mrbird.batch 目錄下新建 job 包，然后在該包下新建一個(gè) FirstJobDemo 類，代碼如下所示：

@Component
public?class?FirstJobDemo?{

????@Autowired
????private?JobBuilderFactory?jobBuilderFactory;
????@Autowired
????private?StepBuilderFactory?stepBuilderFactory;

????@Bean
????public?Job?firstJob()?{
????????return?jobBuilderFactory.get("firstJob")
????????????????.start(step())
????????????????.build();
????}

????private?Step?step()?{
????????return?stepBuilderFactory.get("step")
????????????????.tasklet((contribution,?chunkContext)?->?{
????????????????????System.out.println("執(zhí)行步驟....");
????????????????????return?RepeatStatus.FINISHED;
????????????????}).build();
????}
}

上面代碼中，我們注入了JobBuilderFactory任務(wù)創(chuàng)建工廠和StepBuilderFactory步驟創(chuàng)建工廠，分別用于創(chuàng)建任務(wù) Job 和步驟 Step。JobBuilderFactory的get方法用于創(chuàng)建一個(gè)指定名稱的任務(wù)，start方法指定任務(wù)的開始步驟，步驟通過StepBuilderFactory構(gòu)建。

步驟 Step 由若干個(gè)小任務(wù) Tasklet 組成，所以我們通過tasklet方法創(chuàng)建。tasklet方法接收一個(gè)Tasklet類型參數(shù)，Tasklet是一個(gè)函數(shù)是接口，源碼如下：

public?interface?Tasklet?{
????@Nullable
????RepeatStatus?execute(StepContribution?contribution,?ChunkContext?chunkContext)?throws?Exception;
}

所以我們可以使用 lambda 表達(dá)式創(chuàng)建一個(gè)匿名實(shí)現(xiàn)：

(contribution,?chunkContext)?->?{
????System.out.println("執(zhí)行步驟....");
????return?RepeatStatus.FINISHED;
}

該匿名實(shí)現(xiàn)必須返回一個(gè)明確的執(zhí)行狀態(tài)，這里返回RepeatStatus.FINISHED表示該小任務(wù)執(zhí)行成功，正常結(jié)束。

此外，需要注意的是，我們配置的任務(wù) Job 必須注冊到 Spring IOC 容器中，并且任務(wù)的名稱和步驟的名稱組成唯一。比如上面的例子，我們的任務(wù)名稱為 firstJob，步驟的名稱為 step，如果存在別的任務(wù)和步驟組合也叫這個(gè)名稱的話，則會(huì)執(zhí)行失敗。

啟動(dòng)項(xiàng)目，控制臺(tái)打印日志如下：

...
2020-03-06?11:01:11.785??INFO?17324?---?[???????????main]?o.s.b.c.l.support.SimpleJobLauncher??????:?Job:?[SimpleJob:?[name=firstJob]]?launched?with?the?following?parameters:?[{}]
2020-03-06?11:01:11.846??INFO?17324?---?[???????????main]?o.s.batch.core.job.SimpleStepHandler?????:?Executing?step:?[step]
執(zhí)行步驟....
2020-03-06?11:01:11.886??INFO?17324?---?[???????????main]?o.s.batch.core.step.AbstractStep?????????:?Step:?[step]?executed?in?40ms
2020-03-06?11:01:11.909??INFO?17324?---?[???????????main]?o.s.b.c.l.support.SimpleJobLauncher??????:?Job:?[SimpleJob:?[name=firstJob]]?completed?with?the?following?parameters:?[{}]?and?the?following?status:?[COMPLETED]?in?101ms

可以看到，任務(wù)成功執(zhí)行了，數(shù)據(jù)庫的庫表也將記錄相關(guān)運(yùn)行日志。

重新啟動(dòng)項(xiàng)目，控制臺(tái)并不會(huì)再次打印出任務(wù)執(zhí)行日志，因?yàn)?Job 名稱和 Step 名稱組成唯一，執(zhí)行完的不可重復(fù)的任務(wù)，不會(huì)再次執(zhí)行。

多步驟任務(wù)

一個(gè)復(fù)雜的任務(wù)一般包含多個(gè)步驟，下面舉個(gè)多步驟任務(wù)的例子。在 job 包下新建MultiStepJobDemo類：

@Component
public?class?MultiStepJobDemo?{

????@Autowired
????private?JobBuilderFactory?jobBuilderFactory;
????@Autowired
????private?StepBuilderFactory?stepBuilderFactory;

????@Bean
????public?Job?multiStepJob()?{
????????return?jobBuilderFactory.get("multiStepJob")
????????????????.start(step1())
????????????????.next(step2())
????????????????.next(step3())
????????????????.build();
????}

????private?Step?step1()?{
????????return?stepBuilderFactory.get("step1")
????????????????.tasklet((stepContribution,?chunkContext)?->?{
????????????????????System.out.println("執(zhí)行步驟一操作。。。");
????????????????????return?RepeatStatus.FINISHED;
????????????????}).build();
????}

????private?Step?step2()?{
????????return?stepBuilderFactory.get("step2")
????????????????.tasklet((stepContribution,?chunkContext)?->?{
????????????????????System.out.println("執(zhí)行步驟二操作。。。");
????????????????????return?RepeatStatus.FINISHED;
????????????????}).build();
????}

????private?Step?step3()?{
????????return?stepBuilderFactory.get("step3")
????????????????.tasklet((stepContribution,?chunkContext)?->?{
????????????????????System.out.println("執(zhí)行步驟三操作。。。");
????????????????????return?RepeatStatus.FINISHED;
????????????????}).build();
????}
}

上面代碼中，我們通過step1()、step2()和step3()三個(gè)方法創(chuàng)建了三個(gè)步驟。Job 里要使用這些步驟，只需要通過JobBuilderFactory的start方法指定第一個(gè)步驟，然后通過next方法不斷地指定下一個(gè)步驟即可。

啟動(dòng)項(xiàng)目，控制臺(tái)打印日志如下：

2020-03-06?13:52:52.188??INFO?18472?---?[???????????main]?o.s.b.c.l.support.SimpleJobLauncher??????:?Job:?[SimpleJob:?[name=multiStepJob]]?launched?with?the?following?parameters:?[{}]
2020-03-06?13:52:52.222??INFO?18472?---?[???????????main]?o.s.batch.core.job.SimpleStepHandler?????:?Executing?step:?[step1]
執(zhí)行步驟一操作。。。
2020-03-06?13:52:52.251??INFO?18472?---?[???????????main]?o.s.batch.core.step.AbstractStep?????????:?Step:?[step1]?executed?in?29ms
2020-03-06?13:52:52.292??INFO?18472?---?[???????????main]?o.s.batch.core.job.SimpleStepHandler?????:?Executing?step:?[step2]
執(zhí)行步驟二操作。。。
2020-03-06?13:52:52.323??INFO?18472?---?[???????????main]?o.s.batch.core.step.AbstractStep?????????:?Step:?[step2]?executed?in?30ms
2020-03-06?13:52:52.375??INFO?18472?---?[???????????main]?o.s.batch.core.job.SimpleStepHandler?????:?Executing?step:?[step3]
執(zhí)行步驟三操作。。。
2020-03-06?13:52:52.405??INFO?18472?---?[???????????main]?o.s.batch.core.step.AbstractStep?????????:?Step:?[step3]?executed?in?29ms
2020-03-06?13:52:52.428??INFO?18472?---?[???????????main]?o.s.b.c.l.support.SimpleJobLauncher??????:?Job:?[SimpleJob:?[name=multiStepJob]]?completed?with?the?following?parameters:?[{}]?and?the?following?status:?[COMPLETED]?in?231ms

三個(gè)步驟依次執(zhí)行成功。

多個(gè)步驟在執(zhí)行過程中也可以通過上一個(gè)步驟的執(zhí)行狀態(tài)來決定是否執(zhí)行下一個(gè)步驟，修改上面的代碼：

@Component
public?class?MultiStepJobDemo?{

????@Autowired
????private?JobBuilderFactory?jobBuilderFactory;
????@Autowired
????private?StepBuilderFactory?stepBuilderFactory;

????@Bean
????public?Job?multiStepJob()?{
????????return?jobBuilderFactory.get("multiStepJob2")
????????????????.start(step1())
????????????????.on(ExitStatus.COMPLETED.getExitCode()).to(step2())
????????????????.from(step2())
????????????????.on(ExitStatus.COMPLETED.getExitCode()).to(step3())
????????????????.from(step3()).end()
????????????????.build();
????}

????private?Step?step1()?{
????????return?stepBuilderFactory.get("step1")
????????????????.tasklet((stepContribution,?chunkContext)?->?{
????????????????????System.out.println("執(zhí)行步驟一操作。。。");
????????????????????return?RepeatStatus.FINISHED;
????????????????}).build();
????}

????private?Step?step2()?{
????????return?stepBuilderFactory.get("step2")
????????????????.tasklet((stepContribution,?chunkContext)?->?{
????????????????????System.out.println("執(zhí)行步驟二操作。。。");
????????????????????return?RepeatStatus.FINISHED;
????????????????}).build();
????}

????private?Step?step3()?{
????????return?stepBuilderFactory.get("step3")
????????????????.tasklet((stepContribution,?chunkContext)?->?{
????????????????????System.out.println("執(zhí)行步驟三操作。。。");
????????????????????return?RepeatStatus.FINISHED;
????????????????}).build();
????}
}

multiStepJob()方法的含義是：multiStepJob2 任務(wù)先執(zhí)行 step1，當(dāng) step1 狀態(tài)為完成時(shí)，接著執(zhí)行 step2，當(dāng) step2 的狀態(tài)為完成時(shí)，接著執(zhí)行 step3。ExitStatus.COMPLETED常量表示任務(wù)順利執(zhí)行完畢，正常退出，該類還包含以下幾種退出狀態(tài)：

public?class?ExitStatus?implements?Serializable,?Comparable<ExitStatus>?{

????/**
?????*?Convenient?constant?value?representing?unknown?state?-?assumed?not
?????*?continuable.
?????*/
????public?static?final?ExitStatus?UNKNOWN?=?new?ExitStatus("UNKNOWN");

????/**
?????*?Convenient?constant?value?representing?continuable?state?where?processing
?????*?is?still?taking?place,?so?no?further?action?is?required.?Used?for
?????*?asynchronous?execution?scenarios?where?the?processing?is?happening?in
?????*?another?thread?or?process?and?the?caller?is?not?required?to?wait?for?the
?????*?result.
?????*/
????public?static?final?ExitStatus?EXECUTING?=?new?ExitStatus("EXECUTING");

????/**
?????*?Convenient?constant?value?representing?finished?processing.
?????*/
????public?static?final?ExitStatus?COMPLETED?=?new?ExitStatus("COMPLETED");

????/**
?????*?Convenient?constant?value?representing?job?that?did?no?processing?(e.g.
?????*?because?it?was?already?complete).
?????*/
????public?static?final?ExitStatus?NOOP?=?new?ExitStatus("NOOP");

????/**
?????*?Convenient?constant?value?representing?finished?processing?with?an?error.
?????*/
????public?static?final?ExitStatus?FAILED?=?new?ExitStatus("FAILED");

????/**
?????*?Convenient?constant?value?representing?finished?processing?with
?????*?interrupted?status.
?????*/
????public?static?final?ExitStatus?STOPPED?=?new?ExitStatus("STOPPED");

????...
}

啟動(dòng)項(xiàng)目，控制臺(tái)日志打印如下：

2020-03-06?14:21:49.384??INFO?18745?---?[???????????main]?o.s.b.c.l.support.SimpleJobLauncher??????:?Job:?[FlowJob:?[name=multiStepJob2]]?launched?with?the?following?parameters:?[{}]
2020-03-06?14:21:49.427??INFO?18745?---?[???????????main]?o.s.batch.core.job.SimpleStepHandler?????:?Executing?step:?[step1]
執(zhí)行步驟一操作。。。
2020-03-06?14:21:49.456??INFO?18745?---?[???????????main]?o.s.batch.core.step.AbstractStep?????????:?Step:?[step1]?executed?in?29ms
2020-03-06?14:21:49.501??INFO?18745?---?[???????????main]?o.s.batch.core.job.SimpleStepHandler?????:?Executing?step:?[step2]
執(zhí)行步驟二操作。。。
2020-03-06?14:21:49.527??INFO?18745?---?[???????????main]?o.s.batch.core.step.AbstractStep?????????:?Step:?[step2]?executed?in?26ms
2020-03-06?14:21:49.576??INFO?18745?---?[???????????main]?o.s.batch.core.job.SimpleStepHandler?????:?Executing?step:?[step3]
執(zhí)行步驟三操作。。。
2020-03-06?14:21:49.604??INFO?18745?---?[???????????main]?o.s.batch.core.step.AbstractStep?????????:?Step:?[step3]?executed?in?28ms
2020-03-06?14:21:49.629??INFO?18745?---?[???????????main]?o.s.b.c.l.support.SimpleJobLauncher??????:?Job:?[FlowJob:?[name=multiStepJob2]]?completed?with?the?following?parameters:?[{}]?and?the?following?status:?[COMPLETED]?in?238ms

Flow 的用法

Flow 的作用就是可以將多個(gè)步驟 Step 組合在一起然后再組裝到任務(wù) Job 中。舉個(gè) Flow 的例子，在 job 包下新建FlowJobDemo類：

@Component
public?class?FlowJobDemo?{

????@Autowired
????private?JobBuilderFactory?jobBuilderFactory;
????@Autowired
????private?StepBuilderFactory?stepBuilderFactory;

????@Bean
????public?Job?flowJob()?{
????????return?jobBuilderFactory.get("flowJob")
????????????????.start(flow())
????????????????.next(step3())
????????????????.end()
????????????????.build();
????}

????private?Step?step1()?{
????????return?stepBuilderFactory.get("step1")
????????????????.tasklet((stepContribution,?chunkContext)?->?{
????????????????????System.out.println("執(zhí)行步驟一操作。。。");
????????????????????return?RepeatStatus.FINISHED;
????????????????}).build();
????}

????private?Step?step2()?{
????????return?stepBuilderFactory.get("step2")
????????????????.tasklet((stepContribution,?chunkContext)?->?{
????????????????????System.out.println("執(zhí)行步驟二操作。。。");
????????????????????return?RepeatStatus.FINISHED;
????????????????}).build();
????}

????private?Step?step3()?{
????????return?stepBuilderFactory.get("step3")
????????????????.tasklet((stepContribution,?chunkContext)?->?{
????????????????????System.out.println("執(zhí)行步驟三操作。。。");
????????????????????return?RepeatStatus.FINISHED;
????????????????}).build();
????}

????//?創(chuàng)建一個(gè)flow對(duì)象，包含若干個(gè)step
????private?Flow?flow()?{
????????return?new?FlowBuilder("flow")
????????????????.start(step1())
????????????????.next(step2())
????????????????.build();
????}
}

上面代碼中，我們通過FlowBuilder將 step1 和 step2 組合在一起，創(chuàng)建了一個(gè)名為 flow 的 Flow，然后再將其賦給任務(wù) Job。使用 Flow 和 Step 構(gòu)建 Job 的區(qū)別是，Job 流程中包含 Flow 類型的時(shí)候需要在build()方法前調(diào)用end()方法。

啟動(dòng)程序，控制臺(tái)日志打印如下：

2020-03-06?14:36:42.621??INFO?18865?---?[???????????main]?o.s.b.c.l.support.SimpleJobLauncher??????:?Job:?[FlowJob:?[name=flowJob]]?launched?with?the?following?parameters:?[{}]
2020-03-06?14:36:42.667??INFO?18865?---?[???????????main]?o.s.batch.core.job.SimpleStepHandler?????:?Executing?step:?[step1]
執(zhí)行步驟一操作。。。
2020-03-06?14:36:42.697??INFO?18865?---?[???????????main]?o.s.batch.core.step.AbstractStep?????????:?Step:?[step1]?executed?in?30ms
2020-03-06?14:36:42.744??INFO?18865?---?[???????????main]?o.s.batch.core.job.SimpleStepHandler?????:?Executing?step:?[step2]
執(zhí)行步驟二操作。。。
2020-03-06?14:36:42.771??INFO?18865?---?[???????????main]?o.s.batch.core.step.AbstractStep?????????:?Step:?[step2]?executed?in?27ms
2020-03-06?14:36:42.824??INFO?18865?---?[???????????main]?o.s.batch.core.job.SimpleStepHandler?????:?Executing?step:?[step3]
執(zhí)行步驟三操作。。。
2020-03-06?14:36:42.850??INFO?18865?---?[???????????main]?o.s.batch.core.step.AbstractStep?????????:?Step:?[step3]?executed?in?25ms
2020-03-06?14:36:42.874??INFO?18865?---?[???????????main]?o.s.b.c.l.support.SimpleJobLauncher??????:?Job:?[FlowJob:?[name=flowJob]]?completed?with?the?following?parameters:?[{}]?and?the?following?status:?[COMPLETED]?in?245ms

并行執(zhí)行

任務(wù)中的步驟除了可以串行執(zhí)行（一個(gè)接著一個(gè)執(zhí)行）外，還可以并行執(zhí)行，并行執(zhí)行在特定的業(yè)務(wù)需求下可以提供任務(wù)執(zhí)行效率。

將任務(wù)并行化只需兩個(gè)簡單步驟：

將步驟 Step 轉(zhuǎn)換為 Flow；
任務(wù) Job 中指定并行 Flow。

舉個(gè)例子，在 job 包下新建SplitJobDemo類：

@Component
public?class?SplitJobDemo?{

????@Autowired
????private?JobBuilderFactory?jobBuilderFactory;
????@Autowired
????private?StepBuilderFactory?stepBuilderFactory;

????@Bean
????public?Job?splitJob()?{
????????return?jobBuilderFactory.get("splitJob")
????????????????.start(flow1())
????????????????.split(new?SimpleAsyncTaskExecutor()).add(flow2())
????????????????.end()
????????????????.build();

????}

????private?Step?step1()?{
????????return?stepBuilderFactory.get("step1")
????????????????.tasklet((stepContribution,?chunkContext)?->?{
????????????????????System.out.println("執(zhí)行步驟一操作。。。");
????????????????????return?RepeatStatus.FINISHED;
????????????????}).build();
????}

????private?Step?step2()?{
????????return?stepBuilderFactory.get("step2")
????????????????.tasklet((stepContribution,?chunkContext)?->?{
????????????????????System.out.println("執(zhí)行步驟二操作。。。");
????????????????????return?RepeatStatus.FINISHED;
????????????????}).build();
????}

????private?Step?step3()?{
????????return?stepBuilderFactory.get("step3")
????????????????.tasklet((stepContribution,?chunkContext)?->?{
????????????????????System.out.println("執(zhí)行步驟三操作。。。");
????????????????????return?RepeatStatus.FINISHED;
????????????????}).build();
????}

????private?Flow?flow1()?{
????????return?new?FlowBuilder("flow1")
????????????????.start(step1())
????????????????.next(step2())
????????????????.build();
????}

????private?Flow?flow2()?{
????????return?new?FlowBuilder("flow2")
????????????????.start(step3())
????????????????.build();
????}
}

上面例子中，我們創(chuàng)建了兩個(gè) Flow：flow1（包含 step1 和 step2）和 flow2（包含 step3）。然后通過JobBuilderFactory的split方法，指定一個(gè)異步執(zhí)行器，將 flow1 和 flow2 異步執(zhí)行（也就是并行）。

啟動(dòng)項(xiàng)目，控制臺(tái)日志打印如下：

2020-03-06?15:25:43.602??INFO?19449?---?[???????????main]?o.s.b.c.l.support.SimpleJobLauncher??????:?Job:?[FlowJob:?[name=splitJob]]?launched?with?the?following?parameters:?[{}]
2020-03-06?15:25:43.643??INFO?19449?---?[cTaskExecutor-1]?o.s.batch.core.job.SimpleStepHandler?????:?Executing?step:?[step3]
2020-03-06?15:25:43.650??INFO?19449?---?[cTaskExecutor-2]?o.s.batch.core.job.SimpleStepHandler?????:?Executing?step:?[step1]
執(zhí)行步驟三操作。。。
執(zhí)行步驟一操作。。。
2020-03-06?15:25:43.673??INFO?19449?---?[cTaskExecutor-2]?o.s.batch.core.step.AbstractStep?????????:?Step:?[step1]?executed?in?23ms
2020-03-06?15:25:43.674??INFO?19449?---?[cTaskExecutor-1]?o.s.batch.core.step.AbstractStep?????????:?Step:?[step3]?executed?in?31ms
2020-03-06?15:25:43.714??INFO?19449?---?[cTaskExecutor-2]?o.s.batch.core.job.SimpleStepHandler?????:?Executing?step:?[step2]
執(zhí)行步驟二操作。。。
2020-03-06?15:25:43.738??INFO?19449?---?[cTaskExecutor-2]?o.s.batch.core.step.AbstractStep?????????:?Step:?[step2]?executed?in?24ms
2020-03-06?15:25:43.758??INFO?19449?---?[???????????main]?o.s.b.c.l.support.SimpleJobLauncher??????:?Job:?[FlowJob:?[name=splitJob]]?completed?with?the?following?parameters:?[{}]?and?the?following?status:?[COMPLETED]?in?146ms

可以看到 step3 并沒有在 step2 后才執(zhí)行，說明步驟已經(jīng)是并行化的（開啟并行化后，并行的步驟執(zhí)行順序并不能 100%確定，因?yàn)榫€程調(diào)度具有不確定性）。

任務(wù)決策器

決策器的作用就是可以指定程序在不同的情況下運(yùn)行不同的任務(wù)流程，比如今天是周末，則讓任務(wù)執(zhí)行 step1 和 step2，如果是工作日，則之心 step1 和 step3。

使用決策器前，我們需要自定義一個(gè)決策器的實(shí)現(xiàn)。在 cc.mrbird.batch 包下新建 decider 包，然后創(chuàng)建MyDecider類，實(shí)現(xiàn)JobExecutionDecider接口：

@Component
public?class?MyDecider?implements?JobExecutionDecider?{
????@Override
????public?FlowExecutionStatus?decide(JobExecution?jobExecution,?StepExecution?stepExecution)?{
????????LocalDate?now?=?LocalDate.now();
????????DayOfWeek?dayOfWeek?=?now.getDayOfWeek();

????????if?(dayOfWeek?==?DayOfWeek.SATURDAY?||?dayOfWeek?==?DayOfWeek.SUNDAY)?{
????????????return?new?FlowExecutionStatus("weekend");
????????}?else?{
????????????return?new?FlowExecutionStatus("workingDay");
????????}
????}
}

MyDecider實(shí)現(xiàn)JobExecutionDecider接口的decide方法，該方法返回FlowExecutionStatus。上面的邏輯是：判斷今天是否是周末，如果是，返回FlowExecutionStatus("weekend")狀態(tài)，否則返回FlowExecutionStatus("workingDay")狀態(tài)。

下面演示如何在任務(wù) Job 里使用決策器。在 job 包下新建DeciderJobDemo：

@Component
public?class?DeciderJobDemo?{

????@Autowired
????private?JobBuilderFactory?jobBuilderFactory;
????@Autowired
????private?StepBuilderFactory?stepBuilderFactory;
????@Autowired
????private?MyDecider?myDecider;

????@Bean
????public?Job?deciderJob()?{
????????return?jobBuilderFactory.get("deciderJob")
????????????????.start(step1())
????????????????.next(myDecider)
????????????????.from(myDecider).on("weekend").to(step2())
????????????????.from(myDecider).on("workingDay").to(step3())
????????????????.from(step3()).on("*").to(step4())
????????????????.end()
????????????????.build();
????}

????private?Step?step1()?{
????????return?stepBuilderFactory.get("step1")
????????????????.tasklet((stepContribution,?chunkContext)?->?{
????????????????????System.out.println("執(zhí)行步驟一操作。。。");
????????????????????return?RepeatStatus.FINISHED;
????????????????}).build();
????}

????private?Step?step2()?{
????????return?stepBuilderFactory.get("step2")
????????????????.tasklet((stepContribution,?chunkContext)?->?{
????????????????????System.out.println("執(zhí)行步驟二操作。。。");
????????????????????return?RepeatStatus.FINISHED;
????????????????}).build();
????}

????private?Step?step3()?{
????????return?stepBuilderFactory.get("step3")
????????????????.tasklet((stepContribution,?chunkContext)?->?{
????????????????????System.out.println("執(zhí)行步驟三操作。。。");
????????????????????return?RepeatStatus.FINISHED;
????????????????}).build();
????}


????private?Step?step4()?{
????????return?stepBuilderFactory.get("step4")
????????????????.tasklet((stepContribution,?chunkContext)?->?{
????????????????????System.out.println("執(zhí)行步驟四操作。。。");
????????????????????return?RepeatStatus.FINISHED;
????????????????}).build();
????}

上面代碼中，我們注入了自定義決策器MyDecider，然后在jobDecider()方法里使用了該決策器：

@Bean
public?Job?deciderJob()?{
????return?jobBuilderFactory.get("deciderJob")
????????????.start(step1())
????????????.next(myDecider)
????????????.from(myDecider).on("weekend").to(step2())
????????????.from(myDecider).on("workingDay").to(step3())
????????????.from(step3()).on("*").to(step4())
????????????.end()
????????????.build();
}

這段代碼的含義是：任務(wù) deciderJob 首先執(zhí)行 step1，然后指定自定義決策器，如果決策器返回 weekend，那么執(zhí)行 step2，如果決策器返回 workingDay，那么執(zhí)行 step3。如果執(zhí)行了 step3，那么無論 step3 的結(jié)果是什么，都將執(zhí)行 step4。

啟動(dòng)項(xiàng)目，控制臺(tái)輸出如下所示：

2020-03-06?16:09:10.541??INFO?19873?---?[???????????main]?o.s.b.c.l.support.SimpleJobLauncher??????:?Job:?[FlowJob:?[name=deciderJob]]?launched?with?the?following?parameters:?[{}]
2020-03-06?16:09:10.609??INFO?19873?---?[???????????main]?o.s.batch.core.job.SimpleStepHandler?????:?Executing?step:?[step1]
執(zhí)行步驟一操作。。。
2020-03-06?16:09:10.641??INFO?19873?---?[???????????main]?o.s.batch.core.step.AbstractStep?????????:?Step:?[step1]?executed?in?32ms
2020-03-06?16:09:10.692??INFO?19873?---?[???????????main]?o.s.batch.core.job.SimpleStepHandler?????:?Executing?step:?[step3]
執(zhí)行步驟三操作。。。
2020-03-06?16:09:10.723??INFO?19873?---?[???????????main]?o.s.batch.core.step.AbstractStep?????????:?Step:?[step3]?executed?in?31ms
2020-03-06?16:09:10.769??INFO?19873?---?[???????????main]?o.s.batch.core.job.SimpleStepHandler?????:?Executing?step:?[step4]
執(zhí)行步驟四操作。。。
2020-03-06?16:09:10.797??INFO?19873?---?[???????????main]?o.s.batch.core.step.AbstractStep?????????:?Step:?[step4]?executed?in?27ms
2020-03-06?16:09:10.818??INFO?19873?---?[???????????main]?o.s.b.c.l.support.SimpleJobLauncher??????:?Job:?[FlowJob:?[name=deciderJob]]?completed?with?the?following?parameters:?[{}]?and?the?following?status:?[COMPLETED]?in?256ms

因?yàn)榻裉焓?2020 年 03 月 06 日星期五，是工作日，所以任務(wù)執(zhí)行了 step1、step3 和 step4。

任務(wù)嵌套

任務(wù) Job 除了可以由 Step 或者 Flow 構(gòu)成外，我們還可以將多個(gè)任務(wù) Job 轉(zhuǎn)換為特殊的 Step，然后再賦給另一個(gè)任務(wù) Job，這就是任務(wù)的嵌套。

舉個(gè)例子，在 job 包下新建NestedJobDemo類：

@Component
public?class?NestedJobDemo?{

????@Autowired
????private?JobBuilderFactory?jobBuilderFactory;
????@Autowired
????private?StepBuilderFactory?stepBuilderFactory;
????@Autowired
????private?JobLauncher?jobLauncher;
????@Autowired
????private?JobRepository?jobRepository;
????@Autowired
????private?PlatformTransactionManager?platformTransactionManager;

????//?父任務(wù)
????@Bean
????public?Job?parentJob()?{
????????return?jobBuilderFactory.get("parentJob")
????????????????.start(childJobOneStep())
????????????????.next(childJobTwoStep())
????????????????.build();
????}


????//?將任務(wù)轉(zhuǎn)換為特殊的步驟
????private?Step?childJobOneStep()?{
????????return?new?JobStepBuilder(new?StepBuilder("childJobOneStep"))
????????????????.job(childJobOne())
????????????????.launcher(jobLauncher)
????????????????.repository(jobRepository)
????????????????.transactionManager(platformTransactionManager)
????????????????.build();
????}

????//?將任務(wù)轉(zhuǎn)換為特殊的步驟
????private?Step?childJobTwoStep()?{
????????return?new?JobStepBuilder(new?StepBuilder("childJobTwoStep"))
????????????????.job(childJobTwo())
????????????????.launcher(jobLauncher)
????????????????.repository(jobRepository)
????????????????.transactionManager(platformTransactionManager)
????????????????.build();
????}

????//?子任務(wù)一
????private?Job?childJobOne()?{
????????return?jobBuilderFactory.get("childJobOne")
????????????????.start(
????????????????????stepBuilderFactory.get("childJobOneStep")
????????????????????????????.tasklet((stepContribution,?chunkContext)?->?{
????????????????????????????????System.out.println("子任務(wù)一執(zhí)行步驟。。。");
????????????????????????????????return?RepeatStatus.FINISHED;
????????????????????????????}).build()
????????????????).build();
????}

????//?子任務(wù)二
????private?Job?childJobTwo()?{
????????return?jobBuilderFactory.get("childJobTwo")
????????????????.start(
????????????????????stepBuilderFactory.get("childJobTwoStep")
????????????????????????????.tasklet((stepContribution,?chunkContext)?->?{
????????????????????????????????System.out.println("子任務(wù)二執(zhí)行步驟。。。");
????????????????????????????????return?RepeatStatus.FINISHED;
????????????????????????????}).build()
????????????????).build();
????}
}

上面代碼中，我們通過childJobOne()和childJobTwo()方法創(chuàng)建了兩個(gè)任務(wù) Job，這里沒什么好說的，前面都介紹過。關(guān)鍵在于childJobOneStep()方法和childJobTwoStep()方法。在childJobOneStep()方法中，我們通過JobStepBuilder構(gòu)建了一個(gè)名稱為childJobOneStep的 Step，顧名思義，它是一個(gè)任務(wù)型 Step 的構(gòu)造工廠，可以將任務(wù)轉(zhuǎn)換為“特殊”的步驟。在構(gòu)建過程中，我們還需要傳入任務(wù)執(zhí)行器 JobLauncher、任務(wù)倉庫 JobRepository 和事務(wù)管理器 PlatformTransactionManager。

將任務(wù)轉(zhuǎn)換為特殊的步驟后，將其賦給父任務(wù) parentJob 即可，流程和前面介紹的一致。

配置好后，啟動(dòng)項(xiàng)目，控制臺(tái)輸出如下所示：

2020-03-06?16:58:39.771??INFO?21588?---?[???????????main]?o.s.b.c.l.support.SimpleJobLauncher??????:?Job:?[SimpleJob:?[name=parentJob]]?launched?with?the?following?parameters:?[{}]
2020-03-06?16:58:39.812??INFO?21588?---?[???????????main]?o.s.batch.core.job.SimpleStepHandler?????:?Executing?step:?[childJobOneStep]
2020-03-06?16:58:39.866??INFO?21588?---?[???????????main]?o.s.b.c.l.support.SimpleJobLauncher??????:?Job:?[SimpleJob:?[name=childJobOne]]?launched?with?the?following?parameters:?[{}]
2020-03-06?16:58:39.908??INFO?21588?---?[???????????main]?o.s.batch.core.job.SimpleStepHandler?????:?Executing?step:?[childJobOneStep]
子任務(wù)一執(zhí)行步驟。。。
2020-03-06?16:58:39.940??INFO?21588?---?[???????????main]?o.s.batch.core.step.AbstractStep?????????:?Step:?[childJobOneStep]?executed?in?32ms
2020-03-06?16:58:39.960??INFO?21588?---?[???????????main]?o.s.b.c.l.support.SimpleJobLauncher??????:?Job:?[SimpleJob:?[name=childJobOne]]?completed?with?the?following?parameters:?[{}]?and?the?following?status:?[COMPLETED]?in?86ms
2020-03-06?16:58:39.983??INFO?21588?---?[???????????main]?o.s.batch.core.step.AbstractStep?????????:?Step:?[childJobOneStep]?executed?in?171ms
2020-03-06?16:58:40.019??INFO?21588?---?[???????????main]?o.s.batch.core.job.SimpleStepHandler?????:?Executing?step:?[childJobTwoStep]
2020-03-06?16:58:40.067??INFO?21588?---?[???????????main]?o.s.b.c.l.support.SimpleJobLauncher??????:?Job:?[SimpleJob:?[name=childJobTwo]]?launched?with?the?following?parameters:?[{}]
2020-03-06?16:58:40.102??INFO?21588?---?[???????????main]?o.s.batch.core.job.SimpleStepHandler?????:?Executing?step:?[childJobTwoStep]
子任務(wù)二執(zhí)行步驟。。。
2020-03-06?16:58:40.130??INFO?21588?---?[???????????main]?o.s.batch.core.step.AbstractStep?????????:?Step:?[childJobTwoStep]?executed?in?28ms
2020-03-06?16:58:40.152??INFO?21588?---?[???????????main]?o.s.b.c.l.support.SimpleJobLauncher??????:?Job:?[SimpleJob:?[name=childJobTwo]]?completed?with?the?following?parameters:?[{}]?and?the?following?status:?[COMPLETED]?in?75ms
2020-03-06?16:58:40.157??INFO?21588?---?[???????????main]?o.s.batch.core.step.AbstractStep?????????:?Step:?[childJobTwoStep]?executed?in?138ms
2020-03-06?16:58:40.177??INFO?21588?---?[???????????main]?o.s.b.c.l.support.SimpleJobLauncher??????:?Job:?[SimpleJob:?[name=parentJob]]?completed?with?the?following?parameters:?[{}]?and?the?following?status:?[COMPLETED]?in?398ms

本節(jié)源碼鏈接：https://github.com/wuyouzhuguli/SpringAll/tree/master/67.spring-batch-start。

參考資料

[1]

Spring Batch 官方文檔: https://docs.spring.io/spring-batch/docs/4.3.x/reference/html/spring-batch-intro.html#spring-batch-intro

[2]

https://mrbird.cc/Spring-Batch 入門.html: https://mrbird.cc/Spring-Batch入門.html

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