/* * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you 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.ambari.server.collections; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.lang.reflect.Type; import java.util.Collections; import java.util.Map; import java.util.Objects; import org.apache.ambari.server.collections.functors.PredicateClassFactory; import org.apache.commons.lang.StringUtils; import com.google.common.reflect.TypeToken; import com.google.gson.Gson; /** * PredicateUtils is a utility class providing methods to help perform tasks on {@link Predicate}s. */ public class PredicateUtils { private static final Type PARSED_TYPE = new TypeToken<Map<String, Object>>() { }.getType(); /** * Safely serializes the specified {@link Predicate} to a {@link Map} * * @param predicate the {@link Predicate} to process * @return a {@link Map} or null of the supplied predicate is null */ public static Map<String, Object> toMap(Predicate predicate) { return (predicate == null) ? null : predicate.toMap(); } /** * Builds a {@link Predicate} from a {@link Map} * * @param map a map containing the details of the predicate to create. * @return a {@link Predicate} */ public static Predicate fromMap(Map<?, ?> map) { Predicate predicate = null; if ((map != null) && !map.isEmpty()) { if (map.size() == 1) { Map.Entry<?, ?> entry = map.entrySet().iterator().next(); String name = Objects.toString(entry.getKey()); Class<? extends Predicate> predicateClass = PredicateClassFactory.getPredicateClass(name); if (predicateClass == null) { throw new IllegalArgumentException(String.format("Unexpected predicate name - %s", name)); } else { try { // Dynamically locate and invoke the static toMap method for the named Predicate // implementation using reflection Method method = predicateClass.getMethod("fromMap", Map.class); if (method == null) { throw new UnsupportedOperationException(String.format("Cannot translate data to a %s - %s", predicateClass.getName(), "Failed to find toMap method")); } else { predicate = (Predicate) method.invoke(null, Collections.singletonMap(name, entry.getValue())); } } catch (NoSuchMethodException | InvocationTargetException | IllegalAccessException e) { throw new UnsupportedOperationException(String.format("Cannot translate data to a %s - %s", predicateClass.getName(), e.getLocalizedMessage()), e); } } } else { throw new IllegalArgumentException(String.format("Too many map entries have been encountered - %d", map.size())); } } return predicate; } /** * Safely serializes the specified {@link Predicate} to a JSON-formatted {@link String} * * @param predicate the {@link Predicate} to process * @return a {@link String} or null of the supplied predicate is null */ public static String toJSON(Predicate predicate) { return (predicate == null) ? null : predicate.toJSON(); } /** * Builds a {@link Predicate} from a JSON-formatted {@link String} * * @param json a string containing the details of the predicate to create. * @return a {@link Predicate} * @see #fromMap(Map) */ public static Predicate fromJSON(String json) { Map<String, Object> map = new Gson().fromJson(json, PARSED_TYPE); return (StringUtils.isEmpty(json) ? null : fromMap(map)); } }