InvokeParentRule improvement

[Pablo Lalloni]

Here's a small improvement to InvokeParentRule that allows it to invoke
methods with more than 1 argument on the target object.

It takes the last n objects from the stack and use them to find and
invoke a method.

You can specify n with the "args" attribute.

Should I add it to JIRA besides posting it here?

-- 
Pablo I. Lalloni 
Tel�fono +54 (11) 4347-3177 
Proyecto Pampa
Direcci�n Inform�tica Tributaria
AFIP

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//  Copyright 2004 The Apache Software Foundation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package org.apache.hivemind.schema.rules;

import java.lang.reflect.Method;

import org.apache.hivemind.ApplicationRuntimeException;
import org.apache.hivemind.Element;
import org.apache.hivemind.schema.SchemaProcessor;

/**
 * Rule used to connect a child object to its parent by invoking a method on the
 * parent, passing the child. The child object is the top object on the stack
 * and the parent object is the next object down on the stack. Created from the
 * <code>&lt;invoke-parent&gt;</code> element. Generally, this is the last
 * rule in a sequence of rules.
 * 
 * @author Howard Lewis Ship
 */
public class InvokeParentRule extends BaseRule {

	private String _methodName;

	private int _depth = 1;

	private int _args = 1;

	public InvokeParentRule() {

	}

	public InvokeParentRule(String methodName) {
		_methodName = methodName;
	}

	/**
	 * Invokes the named method on the parent object (using reflection).
	 */
	public void begin(SchemaProcessor processor, Element element) {
		Object parent = processor.peek(_depth);

		Object[] params = buildParams(processor, _args);

		try {
			findMethod(parent, _methodName, classes(params)).invoke(parent, params);
		} catch (Exception ex) {
			throw new ApplicationRuntimeException(RulesMessages.errorInvokingMethod(_methodName, parent, getLocation(), ex),
				getLocation(), ex);
		}
	}

	/**
	 * @param params
	 * @return
	 */
	private Class[] classes(Object[] params) {
		Class[] classes = new Class[params.length];
		for (int i = 0; i < params.length; i++) {
			classes[i] = params[i].getClass();
		}
		return classes;
	}

	/**
	 * 
	 */
	private Object[] buildParams(SchemaProcessor processor, int args) {
		Object[] params = new Object[args];
		for (int i = 0; i < args; i++) {
			params[i] = processor.peek(args - i - 1);
		}
		return params;
	}

	public String getMethodName() {
		return _methodName;
	}

	public void setMethodName(String string) {
		_methodName = string;
	}

	/**
	 * Sets the depth of the parent object. The default is 1.
	 */
	public void setDepth(int i) {
		_depth = i;
	}

	/**
	 * Searches for the *first* public method the has the right name, and takes
	 * a single parameter that is compatible with the parameter type.
	 * 
	 * @throws NoSuchMethodException
	 *             if a method can't be found
	 */
	private Method findMethod(Object target, String name, Class[] parameterTypes) throws NoSuchMethodException {
		Method[] methods = target.getClass().getMethods();

		I : for (int i = 0; i < methods.length; i++) {
			Method m = methods[i];

			if (m.getParameterTypes().length != parameterTypes.length) continue;

			if (!m.getName().equals(name)) continue;

			for (int j = 0; j < parameterTypes.length; j++) {
				if (m.getParameterTypes()[j].isAssignableFrom(parameterTypes[j])) continue I;
			}

			return m;

		}

		throw new NoSuchMethodException(name);
	}

	public int getArgs() {
		return _args;
	}

	public void setArgs(int args) {
		_args = args;
	}

}

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