Decorator Example

An example of circuit breakers and performance monitors using the decorator pattern.

Introduction

The tools that are included in the jrugged core library allow anyone to wrap a method call that they are making with a some interesting additional functionality. The two pieces of additional functionality, circuit breakers and performance monitors, are shown in a code snippet below.

It should also be noted that it is possible to wrap a method call in more than one piece of additional functionality. This allows programmers to choose to use both a CircuitBreaker and a PerformanceMonitor on the same method call.

Details

This is an example of wrapping a backend call in a circuit breaker.

public class MySystem {
.........
       //This is the method I want to decorate
     public BackEndData processArgument(final String myArg) {
          final BackEndService theBackend = backend;

          try {
               return cBreaker.invoke(new Callable< BackEndData >() {
                    public BackEndData call() throws Exception {
                         return theBackend.processArgument(myArg);
                    }
               });
          } catch (RuntimeException re) {
               throw re;
          } catch (Exception e) {
               throw new RuntimeException("wrapped", e);
          }
     }
}

This is an example of wrapping a backend call in a performance monitor. You should note that the performance monitor decoration looks nearly identical to the circuit breaker decoration.

public class MySystem {
.........
     //This is the method I want to decorate
     public BackEndData processArgument(final String myArg) {
          final BackEndService theBackend = backend;

          try {
               return perfMonitor.invoke(new Callable< BackEndData >() {
                    public BackEndData call() throws Exception {
                          return theBackend.processArgument(myArg);
                    }
               });
          } catch (RuntimeException re) {
               throw re;
          } catch (Exception e) {
               throw new RuntimeException("wrapped", e);
          }
     }
}