Maps, objects
I'm a complete newbie to Java but have coded in C++ and VB for years. I have to code against a 3rd party's api. They use maps to transfer data:
Map input = new HashMap();
input.put("Action","CreateApplication");
I then call a function that passes that map through a bunch of stuff and eventually another piece of Java gets it back.
On the other side of things, I need to pull out the action and do something based on it:
action = (String)input.get("Action");
output = new HashMap();
if (action.equals("CreateApplication")){
output = createApplication(input,out);
}
else if(action.equals("CreateUser")){
}
//etc. for all functionality I need
else{
throw new UnknownAuthenticationTypeException("Unknown action type:" + action);
}
This code works perfectly fine, but YUCK! I'm dependent on getting those two strings to be exactly the same.
An enum would work nicely with a switch, but I don't quite know how to do that. And it seems that the map needs objects so I can't just define integers to represent the strings.
There's got to be a better way to do this!
TIA,
Candi
[1201 byte] By [
Candia] at [2007-10-1 1:32:22]
My approach would be to define constants to be used for the valid actions in the map, and only add/remove those constant values.
public final static String CREATE_APPLICATION = "CreateApplication";
input.put("Action", CREATE_APPLICATION);
That will help a little with having to match up strings.
I would do the same with the key as well ie define constant ACTION="Action"
and have input.put(ACTION, CREATE_APPLICATION);
You don't HAVE to put a String object into the hashmap.
You can always use Integer objects (java.lang.Integer) in maps, so you CAN pass in a number if you so wish .
int actionValue = ((Integer)input.get("Action")).intValue();
That will give you something you can switch on.
You can even code your own custom object to store in there.
eg
public class MyAction{
// action constants
public final static int CREATE_APPLICATION = 1;
public final static int DELETE_APPLICATION = 2;
...
private actionId;
public getActionId(){
return actionId;
}
}
action = (MyAction)input.get("Action");
switch (action.getActionId()){
case MyAction.CREATE_APPLICATION:
output = createApplication(input, out);
break;
case MyAction.DELETE_APPLICATION:
...
}
Hope this helps some,
evnafets
Consider using polymorphism.public interface Action {
public Object execute();
}
public class CreateApplication implements Action {
public Object execute() {return blah;}
}
public class CreateUser implements Action {
public Object execute() {return blah;}
}
Then, in the calling method:Action action = (Action) input.get("Action");
Object o = action.execute();
> This code works perfectly fine, but YUCK! I'm dependent on getting those two strings to be exactly the same.
This is the same as C++ and most other langauges. You have to lookup what you put in.
If you want to avoid repeating you code use a constant just as you would in C++
public static final String ACTION = "Action"
You shouldn't try good programming practice out the window just because you have a different language.
