001/* 002 * Shredzone Commons 003 * 004 * Copyright (C) 2012 Richard "Shred" Körber 005 * http://commons.shredzone.org 006 * 007 * This program is free software: you can redistribute it and/or modify 008 * it under the terms of the GNU Library General Public License as 009 * published by the Free Software Foundation, either version 3 of the 010 * License, or (at your option) any later version. 011 * 012 * This program is distributed in the hope that it will be useful, 013 * but WITHOUT ANY WARRANTY; without even the implied warranty of 014 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 015 * GNU General Public License for more details. 016 * 017 * You should have received a copy of the GNU Library General Public License 018 * along with this program. If not, see <http://www.gnu.org/licenses/>. 019 */ 020package org.shredzone.commons.taglib.proxy; 021 022import java.util.Enumeration; 023 024import javax.annotation.Nonnull; 025import javax.servlet.jsp.JspContext; 026import javax.servlet.jsp.PageContext; 027import javax.servlet.jsp.tagext.JspTag; 028 029import org.springframework.beans.factory.BeanFactory; 030import org.springframework.web.servlet.FrameworkServlet; 031 032/** 033 * An abstract TagProxy implementation that offers all basic methods. 034 * 035 * @param <T> 036 * Type of the {@link JspTag} this proxy delegates to 037 * @author Richard "Shred" Körber 038 */ 039public abstract class AbstractTagProxy<T extends JspTag> implements JspTag, ProxiedTag<T> { 040 041 public static final String TAGPROXY_BEANFACTORY_CACHE = AbstractTagProxy.class + ".beanFactory"; 042 043 private T tagImpl; 044 045 protected abstract String getBeanName(); 046 047 /** 048 * Creates a new instance of the implementing target bean. 049 * 050 * @param jspContext 051 * {@link JspContext} 052 */ 053 @SuppressWarnings("unchecked") 054 protected void initTargetBean(@Nonnull JspContext jspContext) { 055 BeanFactory bf = getBeanFactory(jspContext); 056 057 String beanName = getBeanName(); 058 if (!bf.isPrototype(beanName)) { 059 throw new IllegalStateException("Bean " + beanName + " must be prototype scoped!"); 060 } 061 062 tagImpl = (T) bf.getBean(beanName); 063 } 064 065 /** 066 * Gets the {@link BeanFactory} from the given {@link JspContext}. The default 067 * implementation automagically finds a {@link BeanFactory} that was previously set by 068 * a {@link FrameworkServlet}. The result is cached. 069 * 070 * @param jspContext 071 * {@link JspContext} to be used 072 * @return {@link BeanFactory} found 073 */ 074 @SuppressWarnings("unchecked") 075 protected @Nonnull BeanFactory getBeanFactory(@Nonnull JspContext jspContext) { 076 Object bfCache = jspContext.getAttribute(TAGPROXY_BEANFACTORY_CACHE, PageContext.APPLICATION_SCOPE); 077 if (bfCache != null && bfCache instanceof BeanFactory) { 078 return (BeanFactory) bfCache; 079 } 080 081 Enumeration<String> en = jspContext.getAttributeNamesInScope(PageContext.APPLICATION_SCOPE); 082 while (en.hasMoreElements()) { 083 String attribute = en.nextElement(); 084 if (attribute.startsWith(FrameworkServlet.SERVLET_CONTEXT_PREFIX)) { 085 Object bf = jspContext.getAttribute(attribute, PageContext.APPLICATION_SCOPE); 086 if (bf != null && bf instanceof BeanFactory) { 087 BeanFactory bfBean = (BeanFactory) bf; 088 jspContext.setAttribute(TAGPROXY_BEANFACTORY_CACHE, bfBean, PageContext.APPLICATION_SCOPE); 089 return bfBean; 090 } 091 } 092 } 093 094 throw new IllegalStateException("Could not find a BeanFactory. Use a FrameworkServlet or @BeanFactoryReference."); 095 } 096 097 @Override 098 public T getTargetBean() { 099 return tagImpl; 100 } 101 102}