Camel: How to retain aggregation result when exception occurs? - apache-camel

Question

I have a route which multicast to 2 places. If a exception occurs when calling 1 of the place, I'm not able to retain the aggregation result. Inside the processor of the onException, the Map which I created during aggregating is not there. Im using camel 2.25.
onException(RuntimeException.class)
.process(new Processor() {
#Override
public void process(Exchange exchange) throws Exception {
Map<String, String> results = exchange.getProperty(SimpleAggregationStrategy.RESULTS, Map.class);
System.out.println(results);
}
});
from(DIRECT_FIRST)
.log("First route")
.setBody(constant("FIRST TEXT"));
from(DIRECT_SECOND)
.log("Second route")
.setBody(constant("SECOND TEXT"))
.throwException(new RuntimeException("Dummy Exception"));
from(DIRECT_ENTRY)
.multicast().stopOnException().aggregationStrategy(new AggregationStrategy() {
public static final String RESULTS = "RESULTS";
#Override
public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
System.out.println("INSIDE SimpleAggregationStrategy !!!!!!!!!!!!!!!!");
Map<String, String> results;
if (oldExchange != null) {
results = oldExchange.getProperty(RESULTS, Map.class);
} else {
results = new HashMap<>();
}
results.put(newExchange.getIn().getBody(String.class), newExchange.getIn().getBody(String.class));
return newExchange;
}
})
.to(DIRECT_FIRST, DIRECT_SECOND);

Answer 1

I assume that the aggregator aborts processing due to stopOnException() and therefore does not return the (incomplete) result.
You could try to put the aggregation strategy into a context managed bean and make the Map an instance variable that is accessible through a getter method.
In case of an exception you could try to get the incomplete Map from the bean. But I have no idea if it still holds the data or if it is emptied when the processing is aborted.

Answer 2

The solution is simpler than I thought. We only need to create a exchangeProperty before the multicast step. Then that exchange property can store the aggregation results even in the case of exception while doing multicast
onException(RuntimeException.class)
.process(new Processor() {
#Override
public void process(Exchange exchange) throws Exception {
Map<String, String> results = exchange.getProperty("RESULTS", Map.class);
System.out.println(results);
}
});
from(DIRECT_FIRST)
.log("First route")
.setBody(constant("FIRST TEXT"));
from(DIRECT_SECOND)
.log("Second route")
.setBody(constant("SECOND TEXT"))
.throwException(new RuntimeException("Dummy Exception"));
from(DIRECT_ENTRY)
.process(exch -> {
exch.setProperty("RESULTS", new HashMap<String, String>())
})
.multicast().stopOnException().aggregationStrategy(new AggregationStrategy() {
public static final String RESULTS = "RESULTS";
#Override
public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
Map<String, String> results;
if (oldExchange != null) {
results = oldExchange.getProperty(RESULTS, Map.class);
} else {
results = new HashMap<>();
}
results.put(newExchange.getIn().getBody(String.class), newExchange.getIn().getBody(String.class));
return newExchange;
}
})
.to(DIRECT_FIRST, DIRECT_SECOND);