/*
 * Copyright 2002-2017 the original author or authors.
 *
 * 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.springframework.core;

import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.util.LinkedList;
import java.util.List;

import org.springframework.lang.Nullable;

ParameterNameDiscoverer implementation that tries several discoverer delegates in succession. Those added first in the addDiscoverer method have highest priority. If one returns null, the next will be tried. 
The default behavior is to return null if no discoverer matches. 
Author:
Rod Johnson, Juergen Hoeller
Since:
2.0/**
 * {@link ParameterNameDiscoverer} implementation that tries several discoverer
 * delegates in succession. Those added first in the {@code addDiscoverer} method
 * have highest priority. If one returns {@code null}, the next will be tried.
 *
 * <p>The default behavior is to return {@code null} if no discoverer matches.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @since 2.0
 */
public class PrioritizedParameterNameDiscoverer implements ParameterNameDiscoverer {

	private final List<ParameterNameDiscoverer> parameterNameDiscoverers = new LinkedList<>();


	
Add a further ParameterNameDiscoverer delegate to the list of discoverers that this PrioritizedParameterNameDiscoverer checks. /**
	 * Add a further {@link ParameterNameDiscoverer} delegate to the list of
	 * discoverers that this {@code PrioritizedParameterNameDiscoverer} checks.
	 */
	public void addDiscoverer(ParameterNameDiscoverer pnd) {
		this.parameterNameDiscoverers.add(pnd);
	}


	@Override
	@Nullable
	public String[] getParameterNames(Method method) {
		for (ParameterNameDiscoverer pnd : this.parameterNameDiscoverers) {
			String[] result = pnd.getParameterNames(method);
			if (result != null) {
				return result;
			}
		}
		return null;
	}

	@Override
	@Nullable
	public String[] getParameterNames(Constructor<?> ctor) {
		for (ParameterNameDiscoverer pnd : this.parameterNameDiscoverers) {
			String[] result = pnd.getParameterNames(ctor);
			if (result != null) {
				return result;
			}
		}
		return null;
	}

}