/*
* Copyright 2016 Nabarun Mondal
* 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 com.noga.njexl.lang.internal;
import java.lang.reflect.InvocationTargetException;
/**
* Specialized executor to get a property from an object.
* <p>Duck as in duck-typing for an interface like:
* <code>
* interface Get {
* Object get(Object key);
* }
* </code>
* </p>
* @since 2.0
*/
public final class DuckGetExecutor extends AbstractExecutor.Get {
/** The property. */
private final Object property;
/**
* Creates an instance by attempting discovery of the get method.
* @param is the introspector
* @param clazz the class to introspect
* @param identifier the property to get
*/
public DuckGetExecutor(Introspector is, Class<?> clazz, Object identifier) {
super(clazz, discover(is, clazz, identifier));
property = identifier;
}
/** {@inheritDoc} */
@Override
public Object getTargetProperty() {
return property;
}
/**
* Get the property from the object.
* @param obj the object.
* @return object.get(property)
* @throws IllegalAccessException Method is inaccessible.
* @throws InvocationTargetException Method body throws an exception.
*/
@Override
public Object execute(Object obj)
throws IllegalAccessException, InvocationTargetException {
Object[] args = {property};
return method == null ? null : method.invoke(obj, args);
}
/** {@inheritDoc} */
@Override
public Object tryExecute(Object obj, Object key) {
if (obj != null && method != null
// ensure method name matches the property name
&& property.equals(key)
&& objectClass.equals(obj.getClass())) {
try {
Object[] args = {property};
return method.invoke(obj, args);
} catch (InvocationTargetException xinvoke) {
return TRY_FAILED; // fail
} catch (IllegalAccessException xill) {
return TRY_FAILED;// fail
}
}
return TRY_FAILED;
}
/**
* Discovers a method for a {@link GetExecutor.DuckGet}.
*@param is the introspector
*@param clazz the class to find the get method from
*@param identifier the key to use as an argument to the get method
*@return the method if found, null otherwise
*/
private static java.lang.reflect.Method discover(Introspector is,
final Class<?> clazz, Object identifier) {
return is.getMethod(clazz, "get", makeArgs(identifier));
}
}