Commandpublic class Command extends Object implements ActionListener, InvocationHandler| This class represents a Method, the list of arguments to be passed
to that method, and the object on which the method is to be invoked.
The invoke() method invokes the method. The actionPerformed() method
does the same thing, allowing this class to implement ActionListener
and be used to respond to ActionEvents generated in a GUI or elsewhere.
The static parse() method parses a string representation of a method
and its arguments. |
| Fields Summary |
|---|
| Method | m | | Object | target | | Object[] | args | | static final Object[] | nullargs |
| Constructors Summary |
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public Command(Object target, Method m)This constructor creates a Command object for a no-arg method
this(target, m, nullargs);
| public Command(Object target, Method m, Object[] args)This constructor creates a Command object for a method that takes the
specified array of arguments. Note that the parse() method provides
another way to create a Command object
this.target = target;
this.m = m;
if (args == null) args = nullargs;
this.args = args;
| public Command(Object target, String methodName, Object[] args)This construct specifies the method to call by name. It looks for a
method of the target object with the specified name and specified number
of arguments. It does not attempt to verify the types of the arguments,
since wrapper object (Integer, Boolean, etc) in the args[] array could
represent reference or primitive arguments.
this.target = target;
if (args == null) args = nullargs;
this.args = args;
Method[] methods = target.getClass().getMethods();
for(int i = 0; i < methods.length; i++) {
Method m = methods[i];
if (m.getParameterTypes().length == args.length &&
m.getName().equals(methodName)) {
this.m = m;
break;
}
}
// If we didn't find a method, throw an exceptoin
if (this.m == null)
throw new IllegalArgumentException("Unknown method " + methodName);
|
| Methods Summary |
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| public void | actionPerformed(java.awt.event.ActionEvent e)This method implements the ActionListener interface. It is like
invoke() except that it catches the exceptions thrown by that method
and rethrows them as an unchecked RuntimeException
try {
invoke(); // Call the invoke method
}
catch (InvocationTargetException ex) { // But convert to unchecked
throw new RuntimeException(ex); // exceptions. Note that we
} // chain to the original
catch (IllegalAccessException ex) { // exception.
throw new RuntimeException(ex);
}
| | public void | invoke()Invoke the Command by calling the method on its target, and passing
the arguments. See also actionPerformed() which does not throw the
checked exceptions that this method does.
m.invoke(target, args); // Use reflection to invoke the method
| | public java.lang.Object | invoke(java.lang.Object p, java.lang.reflect.Method m, java.lang.Object[] a)This method implements the InvocationHandler interface, so that a
Command object can be used with Proxy objects. Note that it simply
calls the no-argument invoke() method, ignoring its arguments and
returning null. This means that it is only useful for proxying
interfaces that define a single no-arg void method.
invoke();
return null;
| | public static je3.reflect.Command | parse(java.lang.Object target, java.lang.String text)This static method creates a Command using the specified target object,
and the specified string. The string should contain method name
followed by an optional parenthesized comma-separated argument list and
a semicolon. The arguments may be boolean, integer or double literals,
or double-quoted strings. The parser is lenient about missing commas,
semicolons and quotes, but throws an IOException if it cannot parse the
string.
String methodname; // The name of the method
ArrayList args = new ArrayList(); // Hold arguments as we parse them.
ArrayList types = new ArrayList(); // Hold argument types.
Tokenizer t = new CharSequenceTokenizer(text);
t.skipSpaces(true).tokenizeWords(true).tokenizeNumbers(true);
t.quotes("\"'", "\"'");
if (t.next() != Tokenizer.WORD)
throw new IOException("Missing method name for command");
methodname = t.tokenText();
t.next();
if (t.tokenType() == '(") {
t.next();
for(;;) { // Loop through all arguments
int c = t.tokenType();
if (c == ')") {
// Consume closing paren
t.next();
break; // and break out of list
}
if (c == Tokenizer.WORD) {
String word = t.tokenText();
if (word.equals("true")) {
args.add(Boolean.TRUE);
types.add(boolean.class);
}
else if (word.equals("false")) {
args.add(Boolean.FALSE);
types.add(boolean.class);
}
else { // Treat unquoted identifiers as strings...
args.add(word);
types.add(String.class);
}
}
else if (c == '"") { // double-quoted string
args.add(t.tokenText());
types.add(String.class);
}
else if (c == '\'") { // single-quoted character
args.add(new Character(t.tokenText().charAt(0)));
types.add(char.class);
}
else if (c == Tokenizer.NUMBER) { // An integer
args.add(new Integer(Integer.parseInt(t.tokenText())));
types.add(int.class);
}
else { // Anything else is a syntax error
throw new IOException("Unexpected token " + t.tokenText() +
" in argument list of " +
methodname + "().");
}
// Consume the token we just parse, and then consume an
// optional comma.
if (t.next() == ',") t.next();
}
}
// Consume optional semicolon after method name or argument list
if (t.tokenType() == ';") t.next();
// We've parsed the argument list.
// Next, convert the lists of argument values and types to arrays
Object[] argValues = args.toArray();
Class[] argtypes = (Class[])types.toArray(new Class[argValues.length]);
// At this point, we've got a method name, and arrays of argument
// values and types. Use reflection on the class of the target object
// to find a method with the given name and argument types. Throw
// an exception if we can't find the named method.
Method method;
try { method = target.getClass().getMethod(methodname, argtypes); }
catch (Exception e) {
throw new IOException("No such method found, or wrong argument " +
"types: " + methodname);
}
// Finally, create and return a Command object, using the target object
// passed to this method, the Method object we obtained above, and
// the array of argument values we parsed from the string.
return new Command(target, method, argValues);
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