001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. 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 implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.wicket.markup.html.form; 018 019import org.danekja.java.util.function.serializable.SerializableFunction; 020 021/** 022 * Renders one choice. Separates the 'id' values used for internal representation from 'display 023 * values' which are the values shown to the user of components that use this renderer. 024 * <p> 025 * Usage: 026 * 027 * <pre> 028 * new DropDownChoice<User>("users", new Model<User>(selectedUser), listOfUsers, 029 * new LambdaChoiceRenderer<User>(User::getName)) 030 * </pre> 031 * <p> 032 * creates a DropDownChoice of users and the display value will be looked up by function 033 * (User::getName) and the id the index of the object in the ListOfUsers 034 * </p> 035 * <p> 036 * 037 * <pre> 038 * new DropDownChoice<User>("users", new Model<User>(selectedUser), listOfUsers, 039 * new LambdaChoiceRenderer<User>(User::getName, User::getId)) 040 * </pre> 041 * <p> 042 * creates a DropDownChoice of users and the display value will be looked up by function 043 * (User::getName) and the id will be looked up by the function (User::getId) 044 * </p> 045 * 046 * @param <T> The model object type 047 */ 048public class LambdaChoiceRenderer<T> implements IChoiceRenderer<T> { 049 private static final long serialVersionUID = 1L; 050 051 /** 052 * function for getting the display value. 053 */ 054 private final SerializableFunction<T, ?> displayExpression; 055 056 /** 057 * function for getting the id. 058 */ 059 private final SerializableFunction<T, ?> idExpression; 060 061 /** 062 * Constructor. 063 * <p> 064 * When you use this constructor, the display value will be determined by calling 065 * toString() on the list object, and the id will be based on the list index. the id value will 066 * be the index 067 */ 068 public LambdaChoiceRenderer() { 069 this(null); 070 } 071 072 /** 073 * Constructor. 074 * <p> 075 * When you use this constructor, the display value will be determined by executing 076 * the given function on the list object, and the id will be based on the list index. 077 * The display value will be calculated by the given function 078 * 079 * @param displayExpression A function to get the display value 080 */ 081 public LambdaChoiceRenderer(SerializableFunction<T, ?> displayExpression) { 082 this(displayExpression, null); 083 } 084 085 /** 086 * Constructor. 087 * <p> 088 * When you use this constructor, both the id and the display value will be 089 * determined by executing the given functions on the list object. 090 * 091 * @param displayExpression A function to get the display value 092 * @param idExpression A function to get the id value 093 */ 094 public LambdaChoiceRenderer(SerializableFunction<T, ?> displayExpression, SerializableFunction<T, ?> idExpression) { 095 this.displayExpression = displayExpression; 096 this.idExpression = idExpression; 097 } 098 099 @Override 100 public Object getDisplayValue(T object) { 101 Object returnValue = object; 102 if ((displayExpression != null) && (object != null)) { 103 returnValue = displayExpression.apply(object); 104 } 105 106 if (returnValue == null) { 107 return ""; 108 } 109 110 return returnValue; 111 } 112 113 @Override 114 public String getIdValue(T object, int index) { 115 if (idExpression == null) { 116 return Integer.toString(index); 117 } 118 119 if (object == null) { 120 return ""; 121 } 122 123 Object returnValue = idExpression.apply(object); 124 if (returnValue == null) { 125 return ""; 126 } 127 128 return returnValue.toString(); 129 } 130}