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.renderStrategy; 018 019import org.apache.wicket.Component; 020import org.apache.wicket.MarkupContainer; 021import org.apache.wicket.markup.html.internal.HtmlHeaderContainer; 022import org.apache.wicket.markup.html.internal.HtmlHeaderContainer.HeaderStreamState; 023import org.apache.wicket.util.lang.Args; 024import org.apache.wicket.util.visit.IVisit; 025 026/** 027 * This a header render strategy implements a child->parent->root sequence, which is inverse to how 028 * it was until Wicket 1.5. It now allows parent containers to replace child contributions, since 029 * their contribution is added to the markup after the child ones (see <a 030 * href="https://issues.apache.org/jira/browse/WICKET-2693">WICKET-2693</a>). 031 * 032 * Please note that irrespective of the render strategy, if the same header content (e.g. CSS file) 033 * gets added twice to the header, only the first will be rendered and the 2nd will be skipped. 034 * 035 * @author Juergen Donnerstag 036 */ 037public class ChildFirstHeaderRenderStrategy extends AbstractHeaderRenderStrategy 038{ 039 /** 040 * Construct. 041 */ 042 public ChildFirstHeaderRenderStrategy() 043 { 044 } 045 046 @Override 047 public void renderHeader(final HtmlHeaderContainer headerContainer, 048 HeaderStreamState headerStreamState, final Component rootComponent) 049 { 050 Args.notNull(headerContainer, "headerContainer"); 051 Args.notNull(rootComponent, "rootComponent"); 052 053 // First the application level headers 054 renderApplicationLevelHeaders(headerContainer); 055 056 // Then its child hierarchy 057 renderChildHeaders(headerContainer, rootComponent); 058 059 // Then the root component's headers 060 renderRootComponent(headerContainer, headerStreamState, rootComponent); 061 } 062 063 /** 064 * Render the child hierarchy headers. 065 * 066 * @param headerContainer 067 * @param rootComponent 068 */ 069 @Override 070 protected void renderChildHeaders(final HtmlHeaderContainer headerContainer, 071 final Component rootComponent) 072 { 073 Args.notNull(headerContainer, "headerContainer"); 074 Args.notNull(rootComponent, "rootComponent"); 075 076 if (rootComponent instanceof MarkupContainer) 077 { 078 new DeepChildFirstVisitor() 079 { 080 @Override 081 public void component(final Component component, final IVisit<Void> visit) 082 { 083 if (component != rootComponent) 084 { 085 component.internalRenderHead(headerContainer); 086 } 087 } 088 089 @Override 090 public boolean preCheck(Component component) 091 { 092 return component.isVisibleInHierarchy(); 093 } 094 }.visit(rootComponent); 095 } 096 } 097}