java–SpringBatch–循环读取器/处理器/写入器步骤

回答

根据接受的答案代码,对该代码的以下调整对我有用：

// helper method to create a split flow out of a List of steps
private static Flow createParallelFlow(List steps) {
SimpleAsyncTaskExecutor taskExecutor = new SimpleAsyncTaskExecutor();
taskExecutor.setConcurrencyLimit(steps.size());
Flow[] flows = new Flow[steps.size()];
for (int i = 0; i flows[i] = new FlowBuilder(steps.get(i).getName()).start(steps.get(i)).build();
}
return new FlowBuilder("parallelStepsFlow")
.split(taskExecutor)
.add(flows)
.build();
}


编辑

我已经将问题更新为正确循环的版本,但是随着应用程序的扩展,能够并行处理很重要,而且我仍然不知道如何在运行时动态地使用javaconfig …

精炼问题：如何在运行时动态创建一个读取器 – 处理器 – 写入器,例如5个不同的情况(5个查询意味着现在配置的循环为5)？

我的LoopDecider看起来像这样：

public class LoopDecider implements JobExecutionDecider {
private static final Logger LOG = LoggerFactory.getLogger(LoopDecider.class);
private static final String COMPLETED = "COMPLETED";
private static final String COnTINUE= "CONTINUE";
private static final String ALL = "queries";
private static final String COUNT = "count";
private int currentQuery;
private int limit;
@SuppressWarnings("unchecked")
@Override
public FlowExecutionStatus decide(JobExecution jobExecution, StepExecution stepExecution) {
List allQueries = (List) jobExecution.getExecutionContext().get(ALL);
this.limit = allQueries.size();
jobExecution.getExecutionContext().put(COUNT, currentQuery);
if (++currentQuery >= limit) {
return new FlowExecutionStatus(COMPLETED);
} else {
LOG.info("Looping for query: " + allQueries.get(currentQuery - 1));
return new FlowExecutionStatus(CONTINUE);
}
}
}


基于查询列表(HQL查询),我想要每个查询的读取器 – 处理器 – 编写器.我当前的配置如下所示：

工作

@Bean
public Job subsetJob() throws Exception {
LoopDecider loopDecider = new LoopDecider();
FlowBuilder flowBuilder = new FlowBuilder<>(FLOW_NAME);
Flow flow = flowBuilder
.start(createHQL())
.next(extractData())
.next(loopDecider)
.on("CONTINUE")
.to(extractData())
.from(loopDecider)
.on("COMPLETED")
.end()
.build();
return jobBuilderFactory.get("subsetJob")
.start(flow)
.end()
.build();
}


步

public Step extractData(){
return stepBuilderFactory.get("extractData")
.chunk(100_000)
.reader(reader())
.processor(processor())
.writer(writer())
.build();
}


读者

public HibernateCursorItemReader reader(){
CustomHibernateCursorItemReader reader = new CustomHibernateCursorItemReader();
reader.setSessionFactory(HibernateUtil.getSessionFactory());
reader.setUseStatelessSession(false);
return reader;
}


处理器

public DynamicRecordProcessor processor(){
return new DynamicRecordProcessor();
}


作家

public FlatFileItemWriter writer(){
CustomFlatFileItemWriter writer = new CustomFlatFileItemWriter();
writer.setLineAggregator(new DelimitedLineAggregator(){{
setDelimiter(TARGET_DELIMITER);
setFieldExtractor(new PassThroughFieldExtractor());
}}
);
return writer;
}


目前,该过程适用于单个查询.但是,我实际上有一个查询列表.

我最初的想法是循环步骤并将步骤传递给查询列表,并为每个查询读取 – 进程 – 写入.这对于并行分块也是理想的选择.

但是,当我将查询列表作为参数添加到extractData步骤时,对于每个查询,我创建一个步骤,返回一个步骤列表,而不是预期的单个步骤.工作开始抱怨它需要一步而不是一系列步骤.

另一个想法是创建一个自定义MultiHibernateCursorItemReader与MultiItemResourceReader具有相同的想法,但我真的在寻找一个更开箱即用的解决方案.

@Bean
public List extractData(@Value("#{jobExecutionContext[HQL]}") List queries){
List steps = new ArrayList();
for (String query : queries) {
steps.add(stepBuilderFactory.get("extractData")
.chunk(100_000)
.reader(reader(query))
.processor(processor())
.writer(writer(query))
.build());
}
return steps;
}


题
如何循环步骤并将其集成到作业中？

解决方法:

不要将您的步骤,读者,处理器和作者实例化为Spring-Beans.没有必要这样做.只有你的作业实例必须是一个Spring Bean.

因此,只需从步骤,读取器,编写器和处理器创建者方法中删除@Bean和@StepScope配置,并在需要时将其实例化.

只有一个catch,你必须手动调用afterPropertiesSet().例如.：

// @Bean -> delete
// @StepScope -> delete
public FlatFileItemWriter writer(@Value("#{jobExecutionContext[fileName]}") String fileName){
FlatFileItemWriter writer = new FlatFileItemWriter();
writer.setResource(new FileSystemResource(new File(TARGET_LOCATION + fileName + TARGET_FILE_EXTENSION)));
writer.setLineAggregator(new DelimitedLineAggregator(){{
setDelimiter(TARGET_DELIMITER);
setFieldExtractor(new PassThroughFieldExtractor());
}}
);
// ------- ADD!!
writer.afterPropertiesSet();
return writer;
}


这样,您的步骤,读取器,编写器实例将自动“步长”,因为您明确地为每个步骤实例化它们.

如果我的回答不够明确,请告诉我.然后我会添加一个更详细的例子.

编辑

一个简单的例子：

@Configuration
public class MyJobConfiguration {
@Autowired
private JobBuilderFactory jobBuilderFactory;
@Autowired
private StepBuilderFactory stepBuilderFactory;
List filenames = Arrays.asList("file1.txt", "file2.txt");
@Bean
public Job myJob() {
List steps = filenames.stream().map(name -> createStep(filename));
return jobBuilderFactory.get("subsetJob")
.start(createParallelFlow(steps));
.end()
.build();
}
// helper method to create a step
private Step createStep(String filename) {
{
return stepBuilderFactory.get("convertStepFor" + filename); // !!! Stepname has to be unique
.chunk(100_000)
.reader(createFileReader(new FileSystemResource(new File(filename)), new YourInputLineMapper()));
.processor(new YourConversionProcessor());
.writer(createFileWriter(new FileSystemResource(new File("converted_"+filename)), new YourOutputLineAggregator()));
.build();
}
// helper method to create a split flow out of a List of steps
private static Flow createParallelFlow(List steps) {
SimpleAsyncTaskExecutor taskExecutor = new SimpleAsyncTaskExecutor();
taskExecutor.setConcurrencyLimit(steps.size());
List flows = steps.stream() // we have to convert the steps to a flows
.map(step -> // new FlowBuilder("flow_" + step.getName()) // .start(step) // .build()) //
.collect(Collectors.toList());
return new FlowBuilder("parallelStepsFlow").split(taskExecutor) //
.add(flows.toArray(new Flow[flows.size()])) //
.build();
}
// helper methods to create filereader and filewriters
public static ItemReader createFileReader(Resource source, LineMapper lineMapper) throws Exception {
FlatFileItemReader reader = new FlatFileItemReader<>();
reader.setEncoding("UTF-8");
reader.setResource(source);
reader.setLineMapper(lineMapper);
reader.afterPropertiesSet();
return reader;
}
public static ItemWriter createFileWriter(Resource target, LineAggregator aggregator) throws Exception {
FlatFileItemWriter writer = new FlatFileItemWriter<>();
writer.setEncoding("UTF-8");
writer.setResource(target);
writer.setLineAggregator(aggregator);
writer.afterPropertiesSet();
return writer;
}
}