java-如何在Spring-Batch中使用ItemReader跳过行？

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我有一个自定义项目阅读器,可将行从文本文件转换为我的实体：

public class EntityItemReader extends AbstractItemStreamItemReader<MyEntity> {
    @Override
    public MyEntity read() {
       String line = delegate.read();
       //analyze line and skip by condition
       //line.split
       //create entity with line values
    }
}

这类似于FlatFileItemReader.

然后,已读取的MyEntity将由JdbcItemReader保留到数据库中.

问题：有时我的行包含应跳过的值.

但是,当我只是在阅读器的read()方法内返回null时,不仅将跳过此项目,而且将完全终止读取,并且将跳过所有其他行.因为空元素是所有spring-reader的“信号”,所以要读取的文件已完成.

因此：如果无法返回null,我该怎么办才能按阅读器内部的条件跳过特定行？因为根据读者的本性,我被迫在此处返回一个对象.

解决方法:

我认为过滤某些行的好习惯是不使用阅读器,而是使用处理器(当您要过滤行时,可以在其中返回null).

请参阅http://docs.spring.io/spring-batch/trunk/reference/html/readersAndWriters.html：

6.3.2 Filtering Records

One typical use for an item processor is to filter out records before they are passed to the ItemWriter. Filtering is an action distinct from skipping; skipping indicates that a record is invalid whereas filtering simply indicates that a record should not be written.

For example, consider a batch job that reads a file containing three different types of records: records to insert, records to update, and records to delete. If record deletion is not supported by the system, then we would not want to send any “delete” records to the ItemWriter. But, since these records are not actually bad records, we would want to filter them out, rather than skip. As a result, the ItemWriter would receive only “insert” and “update” records.

To filter a record, one simply returns “null” from the ItemProcessor. The framework will detect that the result is “null” and avoid adding that item to the list of records delivered to the ItemWriter. As usual, an exception thrown from the ItemProcessor will result in a skip.

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