CODEWITHSUNDEEP
javareflection
NullVoxPopuli
NullVoxPopuli

Reputation: 65103

Java: is there a way to convert text into a class?

I have the input: "ListClients param1 param2" which splits by " " to "ListClients", "param1", "param2";

and I want to call a static method from ListClients.

So it would do ListClients.someMethodThatTakesPraams(param1, param2);

is there a way to do that in java?

Upvotes: 3

Views: 336

Answers (4)

OscarRyz
OscarRyz

Reputation: 199215

The simple hard coded way would be to create an if/else chain and invoke the right method:

String input = "ListClients param1 param2";
String [] args = input.split(" ");
switch( args.length ) { 
    case 0: 
       return ListClients.someMethod();
    case 1: 
       return ListClients.someMethod( args[0] );
    case 2: 
        return LIstClients.someMethod( args[1] );
    default: 
         return // something default         
}

While this may seem a bit antiquate, it is very safe, because you program exactly how your code should be invoked.

The other solution would involve using reflection as others mention: 

String input = "ListClients param1 param2";
String [] args = input.split(" ");
Class[] types = new Classs[ args.length ];
Object[] values = new Object[ args.lenght ];
for( int i = 0 ; i < types.lenght ; i++ ) { 
   types[i] = String.class;
   values [i] = args[i];
 }   

ListClients.class
   .getDeclaredMethod("someMethod", types )
   .invoke( null, values );

All that surrounded by a number of reflection checked exceptions.

You should consider how dynamic you need your application to be, and / if you would do something to prevent a wild call like this: "System.exit(0)" be invoked or any other sort of code injection.

Upvotes: 2

Aravind Yarram
Aravind Yarram

Reputation: 80176

Yes you can use reflection. Below is an e.g. of creating a new instance

Class<Object> fc = Class.forName("ListClients");
   Object myObj = fc.newInstance();

Here are some examples of invoking methods

Upvotes: 3

templatetypedef
templatetypedef

Reputation: 372724

Yes indeed! You can use Class.getDeclaredMethod to look up a Method object given a name and the types of the parameters. For example, to find your someMethodThatTakesParams method, you could write

Method m = ListClients.class.getDeclaredMethod("someMethodThatTakesParams", ArgType1.class, ArgType2.class);

Here, ArgType1 and ArgType2 are the types of the arguments.

Once you have the method, you can invoke it as follows:

m.invoke(null, arg1, arg2);

Where arg1 and arg2 are the parameters you want to pass. Note that the first argument to invoke is null because the method is static.

This approach omits all sorts of weirdness with exceptions you have to catch and security permissions you might have to acquire, but fortunately those aren't that hard to pick up.

Upvotes: 5

biziclop
biziclop

Reputation: 49724

Reflection will be your friend.

Upvotes: -1

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