001/*
002 * Copyright 2002-2017 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.core;
018
019import java.lang.reflect.Constructor;
020import java.lang.reflect.Method;
021import java.util.LinkedList;
022import java.util.List;
023
024import org.springframework.lang.Nullable;
025
026/**
027 * {@link ParameterNameDiscoverer} implementation that tries several discoverer
028 * delegates in succession. Those added first in the {@code addDiscoverer} method
029 * have highest priority. If one returns {@code null}, the next will be tried.
030 *
031 * <p>The default behavior is to return {@code null} if no discoverer matches.
032 *
033 * @author Rod Johnson
034 * @author Juergen Hoeller
035 * @since 2.0
036 */
037public class PrioritizedParameterNameDiscoverer implements ParameterNameDiscoverer {
038
039        private final List<ParameterNameDiscoverer> parameterNameDiscoverers = new LinkedList<>();
040
041
042        /**
043         * Add a further {@link ParameterNameDiscoverer} delegate to the list of
044         * discoverers that this {@code PrioritizedParameterNameDiscoverer} checks.
045         */
046        public void addDiscoverer(ParameterNameDiscoverer pnd) {
047                this.parameterNameDiscoverers.add(pnd);
048        }
049
050
051        @Override
052        @Nullable
053        public String[] getParameterNames(Method method) {
054                for (ParameterNameDiscoverer pnd : this.parameterNameDiscoverers) {
055                        String[] result = pnd.getParameterNames(method);
056                        if (result != null) {
057                                return result;
058                        }
059                }
060                return null;
061        }
062
063        @Override
064        @Nullable
065        public String[] getParameterNames(Constructor<?> ctor) {
066                for (ParameterNameDiscoverer pnd : this.parameterNameDiscoverers) {
067                        String[] result = pnd.getParameterNames(ctor);
068                        if (result != null) {
069                                return result;
070                        }
071                }
072                return null;
073        }
074
075}