Spring Integration: Custom Splitter with Header Enrichment - spring

Question

Is it possible to have an implementation of a message splitter that can return an Iterator AND add custom header information?
For instance if I have the following class
public class CsvFileToIteratorSplitter extends AbstractMessageSplitter {
#Override
protected Object splitMessage(Message<?> message) {
Object payload = message.getPayload();
Assert.isInstanceOf(File.class, payload, "Expected java.io.File in the message payload");
try {
InputStream source = new FileInputStream((File) payload);
BufferedReader reader = new BufferedReader(new InputStreamReader(source));
String header = reader.lines().findFirst().orElse(null);
return MessageBuilder.withPayload(reader.lines().iterator())
.setHeaderIfAbsent("HEADER", header)
.build();
} catch (IOException e) {
throw new UncheckedIOException(e);
}
}
}
Then I can add to the header but the payload is actually an instance of Iterator and the split fails
If I modify so that the class is now
public class CsvFileToIteratorSplitter extends AbstractMessageSplitter {
#Override
protected Object splitMessage(Message<?> message) {
log.debug("{}", message.toString());
Object payload = message.getPayload();
Assert.isInstanceOf(File.class, payload, "Expected java.io.File in the message payload");
try {
InputStream source = new FileInputStream((File) payload);
BufferedReader reader = new BufferedReader(new InputStreamReader(source));
return reader.lines().iterator();
} catch (IOException e) {
throw new UncheckedIOException(e);
}
}
}
The split works but I lose the header info.
Is there any way to have a functioning split with the ability to add to the header?

Answer 1

You should return an Iterator<MessageBuilder<String>> ...
#SpringBootApplication
public class So44604817Application {
public static void main(String[] args) {
ConfigurableApplicationContext context = SpringApplication.run(So44604817Application.class, args);
context.getBean("in", MessageChannel.class).send(new GenericMessage<>(new File("/tmp/foo.txt")));
context.close();
}
#Bean
#Splitter(inputChannel = "in")
public MySplitter splitter() {
MySplitter splitter = new MySplitter();
splitter.setOutputChannelName("out");
return splitter;
}
#Bean
public MessageChannel out() {
return new MessageChannel() {
#Override
public boolean send(Message<?> message) {
return send(message, -1);
}
#Override
public boolean send(Message<?> message, long timeout) {
System.out.println(message);
return true;
}
};
}
public static class MySplitter extends AbstractMessageSplitter {
#SuppressWarnings("resource")
#Override
protected Object splitMessage(Message<?> message) {
Object payload = message.getPayload();
Assert.isInstanceOf(File.class, payload, "Expected java.io.File in the message payload");
try {
InputStream source = new FileInputStream((File) payload);
final BufferedReader reader = new BufferedReader(new InputStreamReader(source));
final String header = reader.lines().findFirst().orElse(null);
final Iterator<String> iterator = reader.lines().iterator();
Iterator<MessageBuilder<String>> builderIterator = new Iterator<MessageBuilder<String>>() {
private String next;
#Override
public boolean hasNext() {
if (this.next != null) { // handle multiple hasNext() calls.
return true;
}
if (!iterator.hasNext()) {
try {
reader.close();
}
catch (IOException e) {
e.printStackTrace();
}
return false;
}
else {
this.next = iterator.next();
// Handle empty last line
if (next.length() == 0 && !iterator.hasNext()) {
try {
reader.close();
}
catch (IOException e) {
e.printStackTrace();
}
return false;
}
return true;
}
}
#Override
public MessageBuilder<String> next() {
String line = this.next;
this.next = null;
return MessageBuilder
.withPayload(line).setHeaderIfAbsent("HEADER", header);
}
};
return builderIterator;
}
catch (IOException e) {
throw new UncheckedIOException(e);
}
}
}
}
Note that your skip(1) is incorrect, since the first line has already been consumed from the reader.
With file:
FOO,BAR
foo,bar
baz.qux
result:
GenericMessage [payload=foo,bar, headers={sequenceNumber=1, HEADER=FOO,BAR, correlationId=42ce2e1f-5337-1f75-d4fe-0d7f366f76f1, id=94e98261-fd49-b4d0-f6a0-3181b27f145b, sequenceSize=0, timestamp=1497713691192}]
GenericMessage [payload=baz.qux, headers={sequenceNumber=2, HEADER=FOO,BAR, correlationId=42ce2e1f-5337-1f75-d4fe-0d7f366f76f1, id=c0b1edd6-adb9-3857-cb7c-70f603f376bc, sequenceSize=0, timestamp=1497713691192}]
JIRA Issue INT-4297 to add this functionality to FileSplitter.