我如何知道在Spring批处理步骤开始时要处理的块/项的总数？

import org.springframework.batch.core.JobExecution;
import org.springframework.batch.core.JobParameter;
import org.springframework.batch.core.JobParameters;
import org.springframework.batch.core.StepExecution;
import org.springframework.batch.core.listener.StepExecutionListenerSupport;

import java.util.Map;

public class MyStepExecutionListener extends StepExecutionListenerSupport {

    @Override
    public void beforeStep(StepExecution stepExecution) {
        JobExecution jobExecution = stepExecution.getJobExecution();
        JobParameters jobParameters = jobExecution.getJobParameters();
        Map<String, JobParameter> parameters = jobParameters.getParameters();

        // 获取要处理的块/项的总数
        long totalItems = parameters.get("totalItems").getValue();

        // 在Job的执行上下文中存储要处理的块/项的总数
        jobExecution.getExecutionContext().put("totalItems", totalItems);
    }
}