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Spring Batch的核心概念
如下图,JobLancher启动job,一个job包含若干step,每个step又包含一个ItemReader(读数据),ItemProcessor(处理数据),和ItemWriter(输出数据),job的元数据和运行状态则存储在JobRepository中。
Spring batch主要有以下部分组成
- JobRepository 用来注册job的容器
- JobLauncher 用来启动Job的接口
- Job 实际执行的任务,包含一个或多个Step
- Step step包含ItemReader、ItemProcessor和ItemWriter
- ItemReader 用来读取数据的接口
- ItemProcessor 用来处理数据的接口
- ItemWriter 用来输出数据的接口
以上Spring Batch的主要组成部分只需要注册成Spring的Bean即可。若想开启批处理的支持还需在配置类上使用@EnableBatchProcessing,在Spring Batch中提供了大量的ItemReader和ItemWriter的实现,用来读取不同的数据来源,数据的处理和校验都要通过ItemProcessor接口实现来完成。
Job运行时概念
Job的一次完整运行称为一个JobInstance,由JobParameter区分(Spring认为相同的Job不应该多次运行),即如果JobParameter相同则为同一个Job,而一次运行如果中途失败或者抛异常,再次运行仍为一个JobInstance,而其中的每次运行称为一个JobExecution。执行一个step称为StepExecution
关系如下:
Job 1->n JobInstance 1->n JobExecution 1->n StepExecution
JobExecution和StepExecution各包含一个ExecutionContext,其中存储了key-value对,可以用来存储运行状态。
框架实践
下面这个例子实现的是:从变量中读取3个字符串全转化大写并输出到控制台,加了一个监听,当任务完成时输出一个字符串到控制台,通过web端来调用。
版本说明:
- spring-boot:2.0.1.RELEASE
- spring-batch-4.0.1.RELEASE(Spring-Boot 2.0.1就是依赖的此版本)
POM文件:
4.0.0 com.javainuse springboot-batch 0.0.1 jar SpringBatch Spring Batch-Spring Boot org.springframework.boot spring-boot-starter-parent 2.0.1.RELEASE UTF-8 UTF-8 1.8 org.springframework.boot spring-boot-starter org.springframework.boot spring-boot-starter-web com.h2database h2 org.springframework.boot spring-boot-devtools true org.springframework.boot spring-boot-starter-test test org.springframework.boot spring-boot-starter-batch org.springframework.boot spring-boot-maven-plugin
Item Reader
读取:从数组中读取3个字符串
package com.javainuse.step;import org.springframework.batch.item.ItemReader;import org.springframework.batch.item.NonTransientResourceException;import org.springframework.batch.item.ParseException;import org.springframework.batch.item.UnexpectedInputException;public class Reader implements ItemReader{ private String[] messages = { "javainuse.com", "Welcome to Spring Batch Example", "We use H2 Database for this example" }; private int count = 0; @Override public String read() throws Exception, UnexpectedInputException, ParseException, NonTransientResourceException { if (count < messages.length) { return messages[count++]; } else { count = 0; } return null; } }
Item Processor
处理:将字符串转为大写
package com.javainuse.step;import org.springframework.batch.item.ItemProcessor;public class Processor implements ItemProcessor{ @Override public String process(String data) throws Exception { return data.toUpperCase(); } }
Item Writer
输出:把转为大写的字符串输出到控制台
package com.javainuse.step;import java.util.List;import org.springframework.batch.item.ItemWriter;public class Writer implements ItemWriter{ @Override public void write(List messages) throws Exception { for (String msg : messages) { System.out.println("Writing the data " + msg); } } }
Listener
监听:任务成功完成后往控制台输出一行字符串
package com.javainuse.listener;import org.springframework.batch.core.BatchStatus;import org.springframework.batch.core.JobExecution;import org.springframework.batch.core.listener.JobExecutionListenerSupport;public class JobCompletionListener extends JobExecutionListenerSupport { @Override public void afterJob(JobExecution jobExecution) { if (jobExecution.getStatus() == BatchStatus.COMPLETED) { System.out.println("BATCH JOB COMPLETED SUCCESSFULLY"); } } }
Config
Spring Boot配置
package com.javainuse.config;import org.springframework.batch.core.Job;import org.springframework.batch.core.JobExecutionListener;import org.springframework.batch.core.Step;import org.springframework.batch.core.configuration.annotation.JobBuilderFactory;import org.springframework.batch.core.configuration.annotation.StepBuilderFactory;import org.springframework.batch.core.launch.support.RunIdIncrementer;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import com.javainuse.listener.JobCompletionListener;import com.javainuse.step.Processor;import com.javainuse.step.Reader;import com.javainuse.step.Writer;@Configurationpublic class BatchConfig { @Autowired public JobBuilderFactory jobBuilderFactory; @Autowired public StepBuilderFactory stepBuilderFactory; @Bean public Job processJob() { return jobBuilderFactory.get("processJob") .incrementer(new RunIdIncrementer()).listener(listener()) .flow(orderStep1()).end().build(); } @Bean public Step orderStep1() { return stepBuilderFactory.get("orderStep1").chunk(1) .reader(new Reader()).processor(new Processor()) .writer(new Writer()).build(); } @Bean public JobExecutionListener listener() { return new JobCompletionListener(); } }
Controller
控制器:配置web路由,访问/invokejob来调用任务
package com.javainuse.controller; import org.springframework.batch.core.Job;import org.springframework.batch.core.JobParameters;import org.springframework.batch.core.JobParametersBuilder;import org.springframework.batch.core.launch.JobLauncher;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RestController; @RestControllerpublic class JobInvokerController { @Autowired JobLauncher jobLauncher; @Autowired Job processJob; @RequestMapping("/invokejob") public String handle() throws Exception { JobParameters jobParameters = new JobParametersBuilder().addLong("time", System.currentTimeMillis()) .toJobParameters(); jobLauncher.run(processJob, jobParameters); return "Batch job has been invoked"; }}
application.properties
配置:Spring Batch在加载的时候job默认都会执行,把spring.batch.job.enabled
置为false,即把job设置成不可用,应用便会根据jobLauncher.run来执行。下面2行是数据库的配置,不配置也可以,使用的嵌入式数据库h2。
spring.batch.job.enabled=falsespring.datasource.url=jdbc:h2:file:./DBspring.jpa.properties.hibernate.hbm2ddl.auto=update
Application
Spring Boot入口类:加注解@EnableBatchProcessing
package com.javainuse;import org.springframework.batch.core.configuration.annotation.EnableBatchProcessing;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplication@EnableBatchProcessingpublic class SpringBatchApplication { public static void main(String[] args) { SpringApplication.run(SpringBatchApplication.class, args); }}
进阶
方案一:spring boot上构建spring batch远程分区Step
方案二:spring batch进阶-基于RabbitMQ远程分区Step
参考:
查了十几个帖子总结,如有侵权请联系作者。
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