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.ajax.markup.html; 018 019import java.util.Optional; 020import org.apache.wicket.Component; 021 022import org.apache.wicket.ajax.AjaxEventBehavior; 023import org.apache.wicket.ajax.AjaxRequestTarget; 024import org.apache.wicket.ajax.attributes.AjaxRequestAttributes; 025import org.apache.wicket.markup.ComponentTag; 026import org.apache.wicket.markup.html.link.Link; 027import org.apache.wicket.model.IModel; 028 029/** 030 * An ajax link that will degrade to a normal request if ajax is not available or javascript is 031 * disabled. 032 * 033 * <p> 034 * If JavaScript is enabled then the registered JavaScript event 'click' handler will be used, 035 * otherwise the 'href' attribute if the markup element is an <a>, <area> or 036 * <link>. AjaxFallbackLink doesn't fallback if the markup element is none of the three above. 037 * </p> 038 * 039 * @since 1.2 040 * 041 * @author Igor Vaynberg (ivaynberg) 042 * @param <T> 043 * type of model object 044 */ 045public abstract class AjaxFallbackLink<T> extends Link<T> 046{ 047 /** */ 048 private static final long serialVersionUID = 1L; 049 050 /** 051 * Construct. 052 * 053 * @param id 054 */ 055 public AjaxFallbackLink(final String id) 056 { 057 this(id, null); 058 } 059 060 /** 061 * Construct. 062 * 063 * @param id 064 * @param model 065 */ 066 public AjaxFallbackLink(final String id, final IModel<T> model) 067 { 068 super(id, model); 069 070 } 071 072 @Override 073 protected void onInitialize() 074 { 075 super.onInitialize(); 076 add(newAjaxEventBehavior("click")); 077 } 078 079 /** 080 * @param event 081 * the name of the default event on which this link will listen to 082 * @return the ajax behavior which will be executed when the user clicks the link 083 */ 084 protected AjaxEventBehavior newAjaxEventBehavior(String event) 085 { 086 return new AjaxEventBehavior(event) 087 { 088 private static final long serialVersionUID = 1L; 089 090 @Override 091 protected void onEvent(AjaxRequestTarget target) 092 { 093 onClick(Optional.of(target)); 094 } 095 096 @Override 097 protected void updateAjaxAttributes(AjaxRequestAttributes attributes) 098 { 099 super.updateAjaxAttributes(attributes); 100 attributes.setPreventDefault(true); 101 AjaxFallbackLink.this.updateAjaxAttributes(attributes); 102 } 103 104 @Override 105 public boolean getStatelessHint(Component component) 106 { 107 return AjaxFallbackLink.this.getStatelessHint(); 108 } 109 }; 110 } 111 112 /** 113 * @param attributes 114 */ 115 protected void updateAjaxAttributes(AjaxRequestAttributes attributes) 116 { 117 } 118 119 @Override 120 public final void onClick() 121 { 122 onClick(Optional.empty()); 123 } 124 125 /** 126 * Callback for the onClick event. If ajax failed and this event was generated via a normal link 127 * the target argument will be null 128 * 129 * @param target 130 * ajax target if this linked was invoked using ajax, null otherwise 131 */ 132 public abstract void onClick(final Optional<AjaxRequestTarget> target); 133 134 /** 135 * Checks if the tag supports href: a, area or link. 136 * 137 * @param tag 138 * the component tag 139 */ 140 @Override 141 protected void onComponentTag(ComponentTag tag) 142 { 143 super.onComponentTag(tag); 144 145 String tagName = tag.getName(); 146 if (isEnabledInHierarchy() && 147 !("a".equalsIgnoreCase(tagName) || "area".equalsIgnoreCase(tagName) || "link".equalsIgnoreCase(tagName))) 148 { 149 String msg = String.format( 150 "%s must be used only with <a>, <area> or <link> markup elements. " 151 + "The fallback functionality doesn't work for other markup elements. " 152 + "Component path: %s, markup element: <%s>.", 153 AjaxFallbackLink.class.getSimpleName(), getClassRelativePath(), tagName); 154 findMarkupStream().throwMarkupException(msg); 155 } 156 } 157 158 @Override 159 protected boolean useJSEventBindingWhenNeeded() 160 { 161 // AjaxFallbackLink uses Ajax event binding. 162 return false; 163 } 164}