Question regarding decoupled Factory
Hello Java Experts!
I'm rather new to patterns and I tried to make a Factory of some kind that can return Commands of various types (create, find, update, delete) and of different families (different cases).
The code below works but I would like to hear from you experts what you think of it. Can I go with this design? I specify the Factories and Commands in .properties files.
T.I.A.
/Karl
****************************************************************************************
CLIENT
[...]
CommandFactory cf = CommandFactory.getFactory("casetwo");
Command c = cf.getCommand("update");
System.out.println(c.class.getName());
[...]
Gives the output
[...].command.UpdateCaseTwoCommand
And that's what I want; a command of "update" type from the "casetwo" factory...
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public abstract class CommandFactory {
private static Hashtable factories;
Hashtable commands = new Hashtable();
static {
try {
factories = classProperties(CommandFactory.class);//<-- ?
}
catch (Exception ex) {
throw new RuntimeException(ex);
}
}
public CommandFactory(Class c) throws FactoryException {
try {
commands = classProperties(c);
}
catch (Exception ex) {
throw new FactoryException(ex);
}
}
public static CommandFactory getFactory(String factory) throws FactoryException {
return (CommandFactory) factories.get(factory);
}
private static Hashtable classProperties(Class c) throws ClassNotFoundException, InstantiationException, IllegalAccessException, IOException {
String classname = c.getName();
String prefix = classname.substring(classname.lastIndexOf(".") + 1);
String suffix = "properties";
Properties propsfile = new Properties();
propsfile.load(c.getResourceAsStream(prefix + "." + suffix));
Hashtable properties = new Hashtable();
Map.Entry entry = null;
for (Iterator i = propsfile.entrySet().iterator(); i.hasNext(); ) {
entry = (Map.Entry) i.next();
properties.put( (String) entry.getKey(), ObjectCreator.createObject( (String) entry.getValue()));
}
return properties;
}
public abstract Command getCommand(String action) throws FactoryException;
}
****************************************************************************************
public class CaseOneCommandFactory extends CommandFactory {
public CaseOneCommandFactory() throws FactoryException {
super(CaseOneCommandFactory.class); //<-- ?
}
public Command getCommand(String action) throws FactoryException {
return (Command) commands.get(action);
}
}
****************************************************************************************
And the property file for the factory...
"CommandFactory.properties"
caseone=[...].factory.CaseOneCommandFactory
casetwo=[...].factory.CaseTwoCommandFactory
casethree=[...].factory.CaseThreeCommandFactory
casefour=[...].factory.CaseFourCommandFactory
And one command property file for each factory (four of them)
"CaseOneCommandFactory.properties"
create=[...].command.CreateCaseOneCommand
find=[...].command.FindCaseOneCommand
update=[...].command.UpdateCaseOneCommand
delete=[...].command.DeleteCaseOneCommand
"CaseTwoCommandFactory.properties"
create=[...].command.CreateCaseTwoCommand
find=[...].command.FindCaseTwoCommand
update=[...].command.UpdateCaseTwoCommand
delete=[...].command.DeleteCaseTwoCommand
and so on...
