/***
* Copyright (c) 2009 Caelum - www.caelum.com.br/opensource
* All rights reserved.
*
* 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 br.com.caelum.vraptor.eval;
import java.lang.reflect.Array;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import net.vidageek.mirror.dsl.Mirror;
import br.com.caelum.vraptor.VRaptorException;
/**
* Evaluates expressions in order to access values.
*
* @author guilherme silveira
*
*/
public class Evaluator {
public Object get(Object root, String path) {
if (root == null) {
return null;
}
String[] paths = path.split("[\\]\\.]");
Object current = root;
for (int i = 1; i < paths.length; i++) {
try {
current = navigate(current, paths[i]);
} catch (Exception e) {
throw new VRaptorException("Unable to evaluate expression " + path, e);
}
if (current == null) {
return "";
}
}
return current;
}
private Object navigate(Object current, String path) {
int index = path.indexOf("[");
int position = -1;
if (index != -1) {
position = Integer.parseInt(path.substring(index + 1));
path = path.substring(0, index);
}
Object instance = new Mirror().on(current).invoke().getterFor(path);
if (index != -1) {
instance = access(instance, position);
}
return instance;
}
@SuppressWarnings("unchecked")
private Object access(Object current, int position) {
if (current.getClass().isArray()) {
return Array.get(current, position);
} else if (List.class.isAssignableFrom(current.getClass())) {
return ((List) current).get(position);
} else if (Collection.class.isAssignableFrom(current.getClass())) {
Iterator it = ((Collection) current).iterator();
for (int i = 0; i < position; i++) {
it.next();
}
return it.next();
}
throw new VRaptorException("Unable to access position of a" + current.getClass().getName() + ".");
}
}