Spring Integration Cassandra persistence workflow - cassandra

Question

I try to realize the following workflow with Spring Integration:
1) Poll REST API
2) store the POJO in Cassandra cluster
It's my first try with Spring Integration, so I'm still a bit overwhelmed about the mass of information from the reference. After some research, I could make the following work.
1) Poll REST API
2) Transform mapped POJO JSON result into a string
3) save string into file
Here's the code:
#Configuration
public class ConsulIntegrationConfig {
#InboundChannelAdapter(value = "consulHttp", poller = #Poller(maxMessagesPerPoll = "1", fixedDelay = "1000"))
public String consulAgentPoller() {
return "";
}
#Bean
public MessageChannel consulHttp() {
return MessageChannels.direct("consulHttp").get();
}
#Bean
#ServiceActivator(inputChannel = "consulHttp")
MessageHandler consulAgentHandler() {
final HttpRequestExecutingMessageHandler handler =
new HttpRequestExecutingMessageHandler("http://localhost:8500/v1/agent/self");
handler.setExpectedResponseType(AgentSelfResult.class);
handler.setOutputChannelName("consulAgentSelfChannel");
LOG.info("Created bean'consulAgentHandler'");
return handler;
}
#Bean
public MessageChannel consulAgentSelfChannel() {
return MessageChannels.direct("consulAgentSelfChannel").get();
}
#Bean
public MessageChannel consulAgentSelfFileChannel() {
return MessageChannels.direct("consulAgentSelfFileChannel").get();
}
#Bean
#ServiceActivator(inputChannel = "consulAgentSelfFileChannel")
MessageHandler consulAgentFileHandler() {
final Expression directoryExpression = new SpelExpressionParser().parseExpression("'./'");
final FileWritingMessageHandler handler = new FileWritingMessageHandler(directoryExpression);
handler.setFileNameGenerator(message -> "../../agent_self.txt");
handler.setFileExistsMode(FileExistsMode.APPEND);
handler.setCharset("UTF-8");
handler.setExpectReply(false);
return handler;
}
}
#Component
public final class ConsulAgentTransformer {
#Transformer(inputChannel = "consulAgentSelfChannel", outputChannel = "consulAgentSelfFileChannel")
public String transform(final AgentSelfResult json) throws IOException {
final String result = new StringBuilder(json.toString()).append("\n").toString();
return result;
}
This works fine!
But now, instead of writing the object to a file, I want to store it in a Cassandra cluster with spring-data-cassandra. For that, I commented out the file handler in the config file, return the POJO in transformer and created the following, :
#MessagingGateway(name = "consulCassandraGateway", defaultRequestChannel = "consulAgentSelfFileChannel")
public interface CassandraStorageService {
#Gateway(requestChannel="consulAgentSelfFileChannel")
void store(AgentSelfResult agentSelfResult);
}
#Component
public final class CassandraStorageServiceImpl implements CassandraStorageService {
#Override
public void store(AgentSelfResult agentSelfResult) {
//use spring-data-cassandra repository to store
LOG.info("Received 'AgentSelfResult': {} in Cassandra cluster...");
LOG.info("Trying to store 'AgentSelfResult' in Cassandra cluster...");
}
}
But this seems to be a wrong approach, the service method is never triggered.
So my question is, what would be a correct approach for my usecase? Do I have to implement the MessageHandler interface in my service component, and use a #ServiceActivator in my config. Or is there something missing in my current "gateway-approach"?? Or maybe there is another solution, that I'm not able to see..
Like mentioned before, I'm new to SI, so this may be a stupid question...
Nevertheless, thanks a lot in advance!

Answer 1

It's not clear how you are wiring in your CassandraStorageService bean.
The Spring Integration Cassandra Extension Project has a message-handler implementation.
The Cassandra Sink in spring-cloud-stream-modules uses it with Java configuration so you can use that as an example.

Answer 2

So I finally made it work. All I needed to do was
#Component
public final class CassandraStorageServiceImpl implements CassandraStorageService {
#ServiceActivator(inputChannel="consulAgentSelfFileChannel")
#Override
public void store(AgentSelfResult agentSelfResult) {
//use spring-data-cassandra repository to store
LOG.info("Received 'AgentSelfResult': {}...");
LOG.info("Trying to store 'AgentSelfResult' in Cassandra cluster...");
}
}
The CassandraMessageHandler and the spring-cloud-streaming seemed to be a to big overhead to my use case, and I didn't really understand yet... And with this solution, I keep control over what happens in my spring component.