Spring Batch: org.springframework.batch.item.ReaderNotOpenException: Reader must be open before it can be read

Question

I read SO related questions but the solutions don\'t work for me.

I get the org.springframework.batch.item.ReaderNotOpenException: Reader must be open before i

Answer 1

I think you should increase your chunk size in processPlayerStats() step bean class, i.e from chunk(10) to chunk(100/more may be).

Answer 2

Same problem here. Changing return type of my reader to the real implementation and adding to the reader

implements ItemStream

Did the trick for me

Answer 3

The method I defined is like below:

    @Bean
    @StepScope
    public ItemReader<BP> BPReader(){
       
        JdbcCursorItemReader<BP> itemReader = new JdbcCursorItemReader<BP>();
        ...
        return itemReader;
    }

The type I defined in the method is ItemReader which is an interface, the return type is JdbcCursorItemReader which is a sub-class of it. By changing the return type defination to JdbcCursorItemReader solved my problem

Answer 4

It is because ItemReader don't have the open method, using hte StepScope will create a proxy class based on the return type. It is also ok to return ItemStreamReader

Answer 5

I have fixed it by:

reader.open(new ExecutionContext());

Answer 6

Since you put the reader in StepScope, the bean return type should be the implementing type FlatFileItemReader:

@Bean
@StepScope
public FlatFileItemReader<Player> reader(@Value("#{jobParameters[inputZipfile]}") String inputZipfile) {
            ...
            return reader;
}

If you specify the interface, the Spring proxy only has access to the methods and annotations specified on the interface ItemReader and is missing important annotations. There is also a warning (with a typo) in the logs:

2015-05-07 10:40:22,733 WARN  [main] org.springframework.batch.item.ItemReader is an interface.  The implementing class will not be queried for annotation based listener configurations.  If using @StepScope on a @Bean method, be sure to return the implementing class so listner annotations can be used.
2015-05-07 10:40:22,748 WARN  [main] org.springframework.batch.item.ItemReader is an interface.  The implementing class will not be queried for annotation based listener configurations.  If using @StepScope on a @Bean method, be sure to return the implementing class so listner annotations can be used. 

Currently the Spring Boot Batch example is also returning the ItemReader, so I guess other people will struggle with the same issues.