Java tutorial
/* ========================================================================== * Copyright 2002-2005 Cyclops Group Community * * Licensed under the Open Software License, Version 2.1 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://opensource.org/licenses/osl-2.1.php * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. * ========================================================================= */ package com.cyclopsgroup.waterview.utils; import java.net.URL; import java.security.MessageDigest; import java.util.LinkedList; import java.util.List; import org.apache.avalon.framework.service.ServiceManager; import org.apache.commons.codec.binary.Hex; import org.apache.commons.jelly.JellyContext; import org.apache.commons.jelly.JellyTagException; import org.apache.commons.jelly.MissingAttributeException; import org.apache.commons.jelly.Tag; import org.apache.commons.jelly.TagSupport; import org.apache.commons.jelly.XMLOutput; import org.apache.commons.lang.StringUtils; /** * Base jelly tag * * @author <a href="mailto:jiaqi.guo@gmail.com">Jiaqi Guo </a> */ public abstract class TagSupportBase extends TagSupport { private static final String DIGEST_ALGORITHM = "SHA"; private static final URL[] EMPTY_URL_ARRAY = new URL[0]; private static final String SCRIPT_RESOURCE_NAME = TagSupportBase.class.getName() + "/scriptresource"; /** * Set the resource for script * * @param resource Resource of script * @param context Context to set */ public static final void addScriptResource(URL resource, JellyContext context) { synchronized (context) { LinkedList scriptResources = (LinkedList) context.getVariable(SCRIPT_RESOURCE_NAME); if (scriptResources == null) { scriptResources = new LinkedList(); context.setVariable(SCRIPT_RESOURCE_NAME, scriptResources); } scriptResources.add(resource); } } /** * Remove last script resource * * @param resource Resource to remove * @param context Jelly context */ public static final void removeScriptResource(URL resource, JellyContext context) { synchronized (context) { LinkedList scriptResources = (LinkedList) context.getVariable(SCRIPT_RESOURCE_NAME); if (scriptResources == null) { return; } URL last = (URL) scriptResources.getLast(); if (last.sameFile(resource)) { scriptResources.removeLast(); } else { throw new IllegalStateException("The resource to remove is not the last resource"); } } } private String tagId; private String uniqueTagId; /** * Overwrite or implement method doTag() * * @see org.apache.commons.jelly.Tag#doTag(org.apache.commons.jelly.XMLOutput) */ public void doTag(XMLOutput output) throws MissingAttributeException, JellyTagException { try { processTag(output); } catch (Exception e) { JellyTagException ex = null; if (e instanceof JellyTagException) { ex = (JellyTagException) e; } else { ex = new JellyTagException(e); } URL[] scriptResources = getScriptResources(); StringBuffer sb = new StringBuffer(); for (int i = 0; i < scriptResources.length; i++) { URL url = scriptResources[i]; sb.append(">").append(url.toString()); } ex.setFileName(sb.toString()); throw ex; } } /** * Get the resource containing this script * * @return URL of script resource */ protected URL[] getScriptResources() { List scriptResources = (List) getContext().getVariable(SCRIPT_RESOURCE_NAME); if (scriptResources == null) { return EMPTY_URL_ARRAY; } return (URL[]) scriptResources.toArray(EMPTY_URL_ARRAY); } /** * Get service manager * * @return Service manager object */ protected ServiceManager getServiceManager() { return (ServiceManager) getContext().getVariable(ServiceManager.class.getName()); } /** * @return Returns the id. */ public final String getTagId() { return tagId; } /** * Get internal tag id * * @return Tag id * @throws Exception */ public synchronized String getUniqueTagId() throws Exception { if (StringUtils.isNotEmpty(uniqueTagId)) { return uniqueTagId; } if (StringUtils.isEmpty(getTagId())) { throw new IllegalArgumentException("tagId attribute is required for " + this + " to get unique ID"); } StringBuffer s = new StringBuffer(getTagId()).append('@'); URL[] scriptResources = getScriptResources(); for (int i = 0; i < scriptResources.length; i++) { URL resource = scriptResources[i]; s.append("->").append(resource); } MessageDigest digest = MessageDigest.getInstance(DIGEST_ALGORITHM); String d = new String(Hex.encodeHex(digest.digest(s.toString().getBytes()))); uniqueTagId = getTagId() + d; return uniqueTagId; } /** * process the tag * * @param output Output * @throws Exception Throw it out */ protected abstract void processTag(XMLOutput output) throws Exception; /** * Require body of a tag * * @throws JellyTagException If the body is empty, throw it out */ protected final void requireBody() throws JellyTagException { if (StringUtils.isEmpty(getBodyText())) { throw new JellyTagException("Body text is required"); } } /** * Require this tag to be inside given tag class * * @param parentTagClass Given tag class * @return Parent tag * @throws JellyTagException Throw it if requirement is not met */ protected final Tag requireInside(Class parentTagClass) throws JellyTagException { Tag parent = findAncestorWithClass(parentTagClass); if (parent == null) { throw new JellyTagException("Tag must be inside " + parentTagClass.getName()); } return parent; } /** * Require parent to be a class * * @param parentTagClass Parent class * @throws JellyTagException Throw it out if not matched * @return Parent tag */ protected final Tag requireParent(Class parentTagClass) throws JellyTagException { if (!parentTagClass.isAssignableFrom(getParent().getClass())) { throw new JellyTagException("Tag's parent must be " + parentTagClass.getName()); } return getParent(); } /** * @param id The id to set. */ public final void setTagId(String id) { this.tagId = id; } }