multi-file-input.adoc

Multi-File Input

It is a common requirement to process multiple files within a single Step. Assuming the files all have the same formatting, the MultiResourceItemReader supports this type of input for both XML and flat file processing. Consider the following files in a directory:

file-1.txt  file-2.txt  ignored.txt

file-1.txt and file-2.txt are formatted the same and, for business reasons, should be processed together. The MultiResourceItemReader can be used to read in both files by using wildcards.

Java

The following example shows how to read files with wildcards in Java:

Java Configuration

@Bean
public MultiResourceItemReader multiResourceReader() {
	return new MultiResourceItemReaderBuilder<Foo>()
					.delegate(flatFileItemReader())
					.resources(resources())
					.build();
}

XML

The following example shows how to read files with wildcards in XML:

XML Configuration

<bean id="multiResourceReader" class="org.spr...MultiResourceItemReader">
    <property name="resources" value="classpath:data/input/file-*.txt" />
    <property name="delegate" ref="flatFileItemReader" />
</bean>

The referenced delegate is a simple FlatFileItemReader. The above configuration reads input from both files, handling rollback and restart scenarios. It should be noted that, as with any ItemReader, adding extra input (in this case a file) could cause potential issues when restarting. It is recommended that batch jobs work with their own individual directories until completed successfully.

Note	Input resources are ordered by using MultiResourceItemReader#setComparator(Comparator) to make sure resource ordering is preserved between job runs in restart scenario.