Dispatching SOAP function calls

Question

I'm receiving a certain string value over the network and I need to call a function based on that value.

So this is more or less what I have at the moment:

String methodName = soapObj.getMethodName();

switch(methodName) {
    case "getTemperature":
        getDeviceTemp();
        break;
    case "getBrightness":
        getScreenBrightness();
        break;
    ...
}

And.. there are about 60 to 70 methods supported like that.

What's the most elegant way of handling above situation without using reflection? (The app is moderately constrained performance-wise).

Answer 1

I would suggest to:

• Define an interface with a method that will be called inside every case, e.g.

  public interface ServiceMethod {
      public void execute();
  }
  

• Create a map that will contain contain instances of ServiceMethod findable by the a String key, e.g.:

  Map<String, ServiceMethod> serviceMethodMap = new HashMap<>();
  

• Fill up the serviceMethodMap map with ServiceMethod instances (this is to avoid the switch), e.g.:

  serviceMethodMap.put("getTemperature", new ServiceMethod() {
      public void execute() {
          getDeviceTemp();
      });
  serviceMethodMap.put("getBrightness", new ServiceMethod() {
      public void execute() {
          getBrightness();
      });   
  

• Finally replace the switch with:

  final ServiceMethod serviceMethod = serviceMethodMap.get(methodName);
  if(serviceMethod != null) {
      serviceMethod.execute();
  }
  

---

Update 2/18/2015, added Java 8 support

• Define an interface with a method that will be called inside every case, e.g.

  @FunctionalInterface
  public interface ServiceMethod {
      public void execute();
  }
  

• Create a map that will contain contain instances of ServiceMethod findable by the a String key, e.g.:

  Map<String, ServiceMethod> serviceMethodMap = new HashMap<>();
  

• Fill up the serviceMethodMap map with ServiceMethod instances (this is to avoid the switch), e.g.:

  serviceMethodMap.put("getTemperature", () -> getDeviceTemp());
  serviceMethodMap.put("getBrightness", () -> getBrightness());
  

• Finally replace the switch with:

  final ServiceMethod serviceMethod = serviceMethodMap.get(methodName);
  if(serviceMethod != null) {
      serviceMethod.execute();
  }
  

Answer 2

The easiest way is to create an interface for your function, for instance:

public interface ParameterGetter
{
    int getValue()
}

Then have a Map<String, ParameterGetter> in which you would pair keys with implementations of ParameterGetter. If no entry exists, of course, the method call is wrong.

While this is easy, however, it is not practical. Many frameworks, including light ones, include annotation systems which will do the job automatically for you -- you should try and find one, and use it.

There is also another solution -- since this is JDK 7 you are using, you'll have it: ServiceLoader.

It also requires that you implement an interface, but using this, you can load your method implementations easily. This is what I use in one of my projects, and it works quite well; the only trouble with it is you need to create a file in META-INF/services, but it's a trouble you only have to do once for each method you create; or if you use Maven, there is a plugin to generate it for you.

Answer 3

Why don't you use reflection (I know the drawbacks) but there is trade of, rename all your methods to exact same as the service would return String and execute the method with 2 lines of code.

Method m = Class.forName(MyClass.class.getName()).getDeclaredMethod(methodName);
m.invoke(null);