java - Spring批处理FlatFileItemWriter从Object写为csv

问题描述

我正在使用 Spring 批处理并有一个 ItemWriter，如下所示：

public class MyItemWriter implements ItemWriter<Fixing> {

    private final FlatFileItemWriter<Fixing> writer;
    private final FileSystemResource resource;

    public MyItemWriter () {
        this.writer = new FlatFileItemWriter<>();
        this.resource = new FileSystemResource("target/output-teste.txt");
    }


    @Override
    public void write(List<? extends Fixing> items) throws Exception {

        this.writer.setResource(new FileSystemResource(resource.getFile()));
        this.writer.setLineAggregator(new PassThroughLineAggregator<>());
        this.writer.afterPropertiesSet();
        this.writer.open(new ExecutionContext());
        this.writer.write(items);
    }

    @AfterWrite
    private void close() {
        this.writer.close();
    }
}

当我运行我的春季批处理作业时，这些项目被写入文件：

Fixing{id='123456', source='TEST', startDate=null, endDate=null}
Fixing{id='1234567', source='TEST', startDate=null, endDate=null}
Fixing{id='1234568', source='TEST', startDate=null, endDate=null}

1 /我怎样才能只写数据，以便值以逗号分隔，并且它为空，它不被写入。所以目标文件应该是这样的：

123456,TEST
1234567,TEST
1234568,TEST

2 / 其次，我遇到了一个问题，只有当我退出 spring boot 应用程序时，我才能看到文件被创建。我想要的是，一旦它处理了所有项目并写入，该文件就可以在不关闭 Spring Boot 应用程序的情况下使用。

标签： javaspringspring-bootspring-batch

解决方案

有多个选项可以写入 csv 文件。关于第二个问题 writer flush 将解决问题。

https://howtodoinjava.com/spring-batch/flatfileitemwriter-write-to-csv-file/

我们更喜欢将 OpenCSV 与 Spring Batch 一起使用，因为我们正在获得更快的速度和对大文件示例片段的控制，如下所示

class DocumentWriter implements ItemWriter<BaseDTO>, Closeable {

       private static final Logger LOG = LoggerFactory.getLogger(StatementWriter.class);

       private  ColumnPositionMappingStrategy<Statement> strategy ;

       private static final String[] columns = new String[] { "csvcolumn1", "csvcolumn2", "csvcolumn3",

                                    "csvcolumn4", "csvcolumn5", "csvcolumn6", "csvcolumn7"};

       private BufferedWriter writer;
       private StatefulBeanToCsv<Statement> beanToCsv;
       public DocumentWriter() throws Exception {

                      strategy = new ColumnPositionMappingStrategy<Statement>();

                     strategy.setType(Statement.class);

                      strategy.setColumnMapping(columns);

                      filename = env.getProperty("globys.statement.cdf.path")+"-"+processCount+".dat";

                      File cdf = new File(filename);

               if(cdf.exists()){

                   writer = Files.newBufferedWriter(Paths.get(filename), StandardCharsets.UTF_8,StandardOpenOption.APPEND);

               }else{

                   writer = Files.newBufferedWriter(Paths.get(filename), StandardCharsets.UTF_8,StandardOpenOption.CREATE_NEW);

               }

               beanToCsv = new StatefulBeanToCsvBuilder<Statement>(writer).withQuotechar(CSVWriter.NO_QUOTE_CHARACTER)

                       .withMappingStrategy(strategy).withSeparator(',').build();

       }

       @Override

       public void write(List<? extends BaseDTO> items) throws Exception {

                      List<Statement> settlementList = new ArrayList<Statement>();

                      for (int i = 0; i < items.size(); i++) {

                                    BaseDTO baseDTO = items.get(i);

                                    settlementList.addAll(baseDTO.getStatementList());

                      }

                      beanToCsv.write(settlementList);

                      writer.flush();

       }

       @PreDestroy

       @Override

       public void close() throws IOException {

                      writer.close();

       }

}

java - Spring批处理FlatFileItemWriter从Object写为csv

问题描述

解决方案

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