001/* -*- mode: Java; c-basic-offset: 2; indent-tabs-mode: nil; coding: utf-8-unix -*- 002 * 003 * Copyright © 2020 microBean™. 004 * 005 * Licensed under the Apache License, Version 2.0 (the "License"); 006 * you may not use this file except in compliance with the License. 007 * You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or 014 * implied. See the License for the specific language governing 015 * permissions and limitations under the License. 016 */ 017package org.microbean.settings.converter; 018 019import java.lang.reflect.Array; 020import java.lang.reflect.ParameterizedType; 021import java.lang.reflect.Type; 022 023import java.util.Collection; 024import java.util.Objects; 025 026import java.util.function.Function; 027 028import java.util.regex.Pattern; 029 030import javax.enterprise.inject.Vetoed; 031 032import org.microbean.settings.Converter; 033import org.microbean.settings.Value; 034 035/** 036 * An abstract class that can serve as the base class for 037 * implementations of, but which deliberately does not itself 038 * implement, the {@link Converter} interface. 039 * 040 * @author <a href="https://about.me/lairdnelson" 041 * target="_parent">Laird Nelson</a> 042 * 043 * @see Converter 044 * 045 * @see #convert(Value) 046 */ 047@Vetoed 048public abstract class ArrayConverter<T> { 049 050 051 /* 052 * Static fields. 053 */ 054 055 056 private static final long serialVersionUID = 1L; 057 058 059 /* 060 * Instance fields. 061 */ 062 063 064 private final Class<?> arrayComponentType; 065 066 private final Converter<? extends Collection<? extends T>> collectionConverter; 067 068 069 /* 070 * Constructors. 071 */ 072 073 074 /** 075 * Creates a new {@link ArrayConverter}. 076 * 077 * @param collectionConverter a {@link Converter} that returns 078 * {@link Collection}s whose elements are of the appropriate type 079 * from its {@link Converter#convert(Value)} method; must not be 080 * {@code null} 081 * 082 * @exception NullPointerException if {@code collectionConverter} is 083 * {@code null} 084 * 085 * @see #convert(Value) 086 */ 087 protected ArrayConverter(final Converter<? extends Collection<? extends T>> collectionConverter) { 088 super(); 089 Type genericSuperclass = this.getClass(); 090 while (genericSuperclass instanceof Class) { 091 genericSuperclass = ((Class<?>)genericSuperclass).getGenericSuperclass(); 092 } 093 assert genericSuperclass instanceof ParameterizedType : "Unexpected genericSuperclass: " + genericSuperclass; 094 final ParameterizedType genericSupertype = (ParameterizedType)genericSuperclass; 095 final Type[] actualTypeArguments = genericSupertype.getActualTypeArguments(); 096 assert actualTypeArguments != null; 097 assert actualTypeArguments.length == 1; 098 final Type firstTypeArgument = actualTypeArguments[0]; 099 assert firstTypeArgument instanceof Class; 100 this.arrayComponentType = (Class<?>)firstTypeArgument; 101 this.collectionConverter = Objects.requireNonNull(collectionConverter); 102 } 103 104 105 /* 106 * Instance methods. 107 */ 108 109 110 /** 111 * Converts the supplied {@link Value} into an appropriately-typed 112 * array and returns the result. 113 * 114 * @param value the {@link Value} to convert; may be {@code null} 115 * 116 * @return an appropriately-typed array, or {@code null} 117 * 118 * @nullability This method does and its overrides are permitted to 119 * return {@code null}. 120 * 121 * @idempotency No guarantees are made about the idempotency of this 122 * method or its overrides. 123 * 124 * @threadsafety This method is and its overrides must be safe for 125 * concurrent use by multiple threads. 126 * 127 * @see Converter#convert(Value) 128 */ 129 public T[] convert(final Value value) { 130 final Collection<? extends T> collection = this.collectionConverter.convert(value); 131 final T[] returnValue; 132 if (collection == null) { 133 returnValue = null; 134 } else { 135 @SuppressWarnings("unchecked") 136 final T[] targetArray = (T[])Array.newInstance(this.arrayComponentType, collection.size()); 137 returnValue = collection.toArray(targetArray); 138 } 139 return returnValue; 140 } 141 142}