java – Spring Batch – 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<Step> steps) {
    SimpleAsyncTaskExecutor taskExecutor = new SimpleAsyncTaskExecutor();
    taskExecutor.setConcurrencyLimit(steps.size());         

    Flow[] flows = new Flow[steps.size()];
    for (int i = 0; i < steps.size(); i++) {
        flows[i] = new FlowBuilder<SimpleFlow>(steps.get(i).getName()).start(steps.get(i)).build();
    }           

    return new FlowBuilder<SimpleFlow>("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<String> allQueries = (List<String>) 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<Flow> 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<Step> extractData(@Value("#{jobExecutionContext[HQL]}") List<String> queries){
    List<Step> steps = new ArrayList<Step>();
    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<String> filenames = Arrays.asList("file1.txt", "file2.txt");

    @Bean
    public Job myJob() {

       List<Step> 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<Step> steps) {
        SimpleAsyncTaskExecutor taskExecutor = new SimpleAsyncTaskExecutor();
        taskExecutor.setConcurrencyLimit(steps.size());

        List<Flow> flows = steps.stream() // we have to convert the steps to a flows
            .map(step -> //
                    new FlowBuilder<Flow>("flow_" + step.getName()) //
                    .start(step) //
                    .build()) //
            .collect(Collectors.toList());

        return new FlowBuilder<SimpleFlow>("parallelStepsFlow").split(taskExecutor) //
            .add(flows.toArray(new Flow[flows.size()])) //
            .build();
    }


    // helper methods to create filereader and filewriters
    public static <T> ItemReader<T> createFileReader(Resource source, LineMapper<T> lineMapper) throws Exception {
        FlatFileItemReader<T> reader = new FlatFileItemReader<>();

        reader.setEncoding("UTF-8");
        reader.setResource(source);
        reader.setLineMapper(lineMapper);
        reader.afterPropertiesSet();

        return reader;
    }

    public static <T> ItemWriter<T> createFileWriter(Resource target, LineAggregator<T> aggregator) throws Exception {
        FlatFileItemWriter<T> writer = new FlatFileItemWriter<>();

        writer.setEncoding("UTF-8");
        writer.setResource(target);
        writer.setLineAggregator(aggregator);

        writer.afterPropertiesSet();
        return writer;
    }
}

标签：spring-java-config,java,spring,spring-batch
来源： https://codeday.me/bug/20190926/1819037.html