从StaxWriterCallback访问执行上下文

Question

我正在实现一个作业，该作业将从数据库加载数据并将结果写入xml文件。xml文件将有一个基于存储在执行上下文中的一些属性的头。因此，我想访问执行上下文。我已经在其他beans在这项工作中做到了这一点，但我不知道如何从我的StaxWriterCallback内访问执行上下文。

在工作中，我的作家目前被实现为:

@Bean(name = "writer")
@StepScope
public StaxEventItemWriter<Data> writer(@Value("#{jobParameters['path']}") String path) {

StaxEventItemWriter<Data> itemWriter = new StaxEventItemWriter<Data>();
itemWriter.setVersion("1.0");
itemWriter.setEncoding("UTF-8");
itemWriter.setStandalone(false);

itemWriter.setHeaderCallback(headerCallback());
itemWriter.setFooterCallback(new CustomXMLFooterCallback());

itemWriter.setMarshaller(new XStreamMarshaller());

FileSystemResource file = new FileSystemResource(path + "test.xml");
itemWriter.setResource(file);

return itemWriter;
}

报头回调实现为:

@Component
public class CustomXMLHeaderCallback implements StaxWriterCallback {

private StepExecution stepExecution;
@BeforeStep
public void beforeStep(StepExecution stepExecution) {
this.stepExecution = stepExecution;
}
@Override
public void write(XMLEventWriter writer) throws IOException {

String currentFile = stepExecution.getExecutionContext().getString("currentFile");
try {
XMLEventFactory eventFactory = XMLEventFactory.newInstance();
XMLEvent end = eventFactory.createDTD("n");
XMLEvent tab = eventFactory.createDTD("t");
writer.add(eventFactory.createStartElement("", "", "file"));
writer.add(eventFactory.createCharacters(currentFile.substring(19, 31)));
writer.add(eventFactory.createEndElement("", "", "file"));
writer.add(end);
} catch (Exception e) {
e.printStackTrace();
}
}
}

头回调被添加到批处理作业中:

@Bean
@StepScope
public CustomXMLHeaderCallback headerCallback() {
return new CustomXMLHeaderCallback();
}

不幸的是，我得到以下错误:

java.lang.NullPointerException: Cannot invoke "org.springframework.batch.core.StepExecution.getExecutionContext()" because "this.stepExecution" is null
at com.test.xml.callback.CustomXMLHeaderCallback.write(CustomXMLHeaderCallback.java:39) ~[classes/:na]
at com.test.xml.callback.CustomXMLHeaderCallback$$FastClassBySpringCGLIB$$e0795ecb.invoke(<generated>) ~[classes/:na]
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218) ~[spring-core-5.3.3.jar:5.3.3]
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:779) ~[spring-aop-5.3.3.jar:5.3.3]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) ~[spring-aop-5.3.3.jar:5.3.3]
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:750) ~[spring-aop-5.3.3.jar:5.3.3]
at org.springframework.aop.support.DelegatingIntroductionInterceptor.doProceed(DelegatingIntroductionInterceptor.java:137) ~[spring-aop-5.3.3.jar:5.3.3]
at org.springframework.aop.support.DelegatingIntroductionInterceptor.invoke(DelegatingIntroductionInterceptor.java:124) ~[spring-aop-5.3.3.jar:5.3.3]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.3.jar:5.3.3]
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:750) ~[spring-aop-5.3.3.jar:5.3.3]
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:692) ~[spring-aop-5.3.3.jar:5.3.3]
at com.test.xml.callback.CustomXMLHeaderCallback$$EnhancerBySpringCGLIB$$e9083311.write(<generated>) ~[classes/:na]
at org.springframework.batch.item.xml.StaxEventItemWriter.open(StaxEventItemWriter.java:447) ~[spring-batch-infrastructure-4.3.1.jar:4.3.1]
at org.springframework.batch.item.xml.StaxEventItemWriter$$FastClassBySpringCGLIB$$d105dd1.invoke(<generated>) ~[spring-batch-infrastructure-4.3.1.jar:4.3.1]
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218) ~[spring-core-5.3.3.jar:5.3.3]
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:779) ~[spring-aop-5.3.3.jar:5.3.3]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) ~[spring-aop-5.3.3.jar:5.3.3]
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:750) ~[spring-aop-5.3.3.jar:5.3.3]
at org.springframework.aop.support.DelegatingIntroductionInterceptor.doProceed(DelegatingIntroductionInterceptor.java:137) ~[spring-aop-5.3.3.jar:5.3.3]
at org.springframework.aop.support.DelegatingIntroductionInterceptor.invoke(DelegatingIntroductionInterceptor.java:124) ~[spring-aop-5.3.3.jar:5.3.3]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.3.jar:5.3.3]
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:750) ~[spring-aop-5.3.3.jar:5.3.3]
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:692) ~[spring-aop-5.3.3.jar:5.3.3]
at org.springframework.batch.item.xml.StaxEventItemWriter$$EnhancerBySpringCGLIB$$599f2f97.open(<generated>) ~[spring-batch-infrastructure-4.3.1.jar:4.3.1]
at org.springframework.batch.item.support.CompositeItemStream.open(CompositeItemStream.java:104) ~[spring-batch-infrastructure-4.3.1.jar:4.3.1]
at org.springframework.batch.core.step.tasklet.TaskletStep.open(TaskletStep.java:311) ~[spring-batch-core-4.3.1.jar:4.3.1]
at org.springframework.batch.core.step.AbstractStep.execute(AbstractStep.java:205) ~[spring-batch-core-4.3.1.jar:4.3.1]
at org.springframework.batch.core.job.SimpleStepHandler.handleStep(SimpleStepHandler.java:148) ~[spring-batch-core-4.3.1.jar:4.3.1]
at org.springframework.batch.core.job.AbstractJob.handleStep(AbstractJob.java:411) ~[spring-batch-core-4.3.1.jar:4.3.1]
at org.springframework.batch.core.job.SimpleJob.doExecute(SimpleJob.java:136) ~[spring-batch-core-4.3.1.jar:4.3.1]
at org.springframework.batch.core.job.AbstractJob.execute(AbstractJob.java:320) ~[spring-batch-core-4.3.1.jar:4.3.1]
at org.springframework.batch.core.launch.support.SimpleJobLauncher$1.run(SimpleJobLauncher.java:147) ~[spring-batch-core-4.3.1.jar:4.3.1]
at org.springframework.core.task.SyncTaskExecutor.execute(SyncTaskExecutor.java:50) ~[spring-core-5.3.3.jar:5.3.3]
at org.springframework.batch.core.launch.support.SimpleJobLauncher.run(SimpleJobLauncher.java:140) ~[spring-batch-core-4.3.1.jar:4.3.1]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
at java.base/java.lang.reflect.Method.invoke(Method.java:564) ~[na:na]
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:344) ~[spring-aop-5.3.3.jar:5.3.3]
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:198) ~[spring-aop-5.3.3.jar:5.3.3]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) ~[spring-aop-5.3.3.jar:5.3.3]
at org.springframework.batch.core.configuration.annotation.SimpleBatchConfiguration$PassthruAdvice.invoke(SimpleBatchConfiguration.java:128) ~[spring-batch-core-4.3.1.jar:4.3.1]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.3.jar:5.3.3]
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:215) ~[spring-aop-5.3.3.jar:5.3.3]
at com.sun.proxy.$Proxy62.run(Unknown Source) ~[na:na]
at org.springframework.boot.autoconfigure.batch.JobLauncherApplicationRunner.execute(JobLauncherApplicationRunner.java:199) ~[spring-boot-autoconfigure-2.4.2.jar:2.4.2]
at org.springframework.boot.autoconfigure.batch.JobLauncherApplicationRunner.executeLocalJobs(JobLauncherApplicationRunner.java:173) ~[spring-boot-autoconfigure-2.4.2.jar:2.4.2]
at org.springframework.boot.autoconfigure.batch.JobLauncherApplicationRunner.launchJobFromProperties(JobLauncherApplicationRunner.java:160) ~[spring-boot-autoconfigure-2.4.2.jar:2.4.2]
at org.springframework.boot.autoconfigure.batch.JobLauncherApplicationRunner.run(JobLauncherApplicationRunner.java:155) ~[spring-boot-autoconfigure-2.4.2.jar:2.4.2]
at org.springframework.boot.autoconfigure.batch.JobLauncherApplicationRunner.run(JobLauncherApplicationRunner.java:150) ~[spring-boot-autoconfigure-2.4.2.jar:2.4.2]
at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:795) ~[spring-boot-2.4.2.jar:2.4.2]
at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:785) ~[spring-boot-2.4.2.jar:2.4.2]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:333) ~[spring-boot-2.4.2.jar:2.4.2]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1311) ~[spring-boot-2.4.2.jar:2.4.2]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1300) ~[spring-boot-2.4.2.jar:2.4.2]
at com.test.main(MainOutboundDatins.java:18) ~[classes/:na]

Answer 1

如果您希望在CustomXMLHeaderCallback中的步骤之前调用beforeStep方法，则需要使用步骤构建器的listener方法之一将该组件注册为步骤中的侦听器。这在这里的文档中有解释:拦截步骤执行。

否则，您可以使用@Value:

注入步骤执行。

@Value("#{StepExecution}")
private StepExecution stepExecution;

第三个选项是从步骤执行上下文中注入所需的属性:

// define your header as follows:
public class CustomXMLHeaderCallback implements StaxWriterCallback {
private String currentFile;
public CustomXMLHeaderCallback(String currentFile) {
this.currentFile = currentFile;
}
@Override
public void write(XMLEventWriter writer) throws IOException {
// use this.currentFile as needed here
}

}
// decalre your bean as follows:
@Bean
@StepScope
public CustomXMLHeaderCallback headerCallback(@Value("#{stepExecutionContext['currentFile']}") String currentFile) {
return new CustomXMLHeaderCallback(currentFile);
}

我推荐第三个选项，因为它只注入所需的属性，而不是整个步骤执行对象。