Add continueAsNew mechanism to cadence java sample

Author: chopincode

src/main/java/com/uber/cadence/samples/spring/workflows/impl/SignalWorkflowImpl.java

@@ -3,6 +3,7 @@
 import com.uber.cadence.samples.spring.models.SampleMessage;
 import com.uber.cadence.samples.spring.workflows.SignalWorkflow;
 import com.uber.cadence.workflow.Workflow;
+import java.util.Optional;
 import org.slf4j.Logger;
 
 public class SignalWorkflowImpl implements SignalWorkflow {
@@ -22,6 +23,16 @@ public void getGreeting(SampleMessage sampleMessage) {
       if (!this.greetingMsg.isEmpty()) {
         logger.info(++count + ": " + this.greetingMsg + "!");
         this.greetingMsg = "";
+
+        // A workflow execution cannot receive infinite number of signals due to history limit
+        // By default 10000 is MaximumSignalsPerExecution which can be configured by DynamicConfig of Cadence cluster.
+        // But it's recommended to do continueAsNew after receiving certain number of signals.
+        // in production, use a number <1000.
+        if (count == 3) {
+          Workflow.continueAsNew(
+              Optional.of("SignalWorkflow::getGreeting"), Optional.empty(), sampleMessage);
+          return;
+        }
       }
     }