Java tutorial
package org.apache.velocity.tools; /* * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance * with the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * 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. */ import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.util.HashMap; import java.util.Map; import org.apache.commons.beanutils.PropertyUtils; import org.apache.velocity.tools.ClassUtils; import org.apache.velocity.tools.config.SkipSetters; /** * Manages data needed to create instances of a tool. New instances * are returned for every call to create(obj). * * @author Nathan Bubna * @author <a href="mailto:henning@schmiedehausen.org">Henning P. Schmiedehausen</a> * @version $Id: ToolInfo.java 511959 2007-02-26 19:24:39Z nbubna $ */ public class ToolInfo implements java.io.Serializable { private static final long serialVersionUID = -8145087882015742757L; public static final String CONFIGURE_METHOD_NAME = "configure"; private String key; private Class clazz; private boolean restrictToIsExact; private String restrictTo; private Map<String, Object> properties; private Boolean skipSetters; private transient Method configure = null; /** * Creates a new instance using the minimum required info * necessary for a tool. */ public ToolInfo(String key, Class clazz) { setKey(key); setClass(clazz); } /*********************** Mutators *************************/ public void setKey(String key) { this.key = key; if (this.key == null) { throw new NullPointerException("Key cannot be null"); } } /** * Tries to create an instance of the specified Class, then looks for a * configure(Map<String,Object>) method. * * @param clazz the java.lang.Class of the tool */ public void setClass(Class clazz) { if (clazz == null) { throw new NullPointerException("Tool class must not be null"); } this.clazz = clazz; //NOTE: we used to check here that we could get an instance of // the tool class, but that's been moved to ToolConfiguration // in order to fail as earlier as possible. most people won't // manually create ToolInfo. if they do and we can't get an // instance, they should be capable of figuring out what happened } /** * @param path the full or partial request path restriction of the tool */ public void restrictTo(String path) { if (path != null && !path.startsWith("/")) { path = "/" + path; } if (path == null || path.equals("*")) { // match all paths restrictToIsExact = false; this.restrictTo = null; } else if (path.endsWith("*")) { // match some paths restrictToIsExact = false; this.restrictTo = path.substring(0, path.length() - 1); } else { // match one path restrictToIsExact = true; this.restrictTo = path; } } public void setSkipSetters(boolean cfgOnly) { this.skipSetters = cfgOnly; } /** * Adds a map of properties from a parent scope to the properties * for this tool. Only new properties will be added; any that * are already set for this tool will be ignored. */ public void addProperties(Map<String, Object> parentProps) { // only add those new properties for which we // do not already have a value. first prop set wins. Map<String, Object> properties = getProps(); for (Map.Entry<String, Object> prop : parentProps.entrySet()) { if (!properties.containsKey(prop.getKey())) { properties.put(prop.getKey(), prop.getValue()); } } } /** * Puts a new property for this tool. */ public Object putProperty(String name, Object value) { return getProps().put(name, value); } protected synchronized Map<String, Object> getProps() { if (properties == null) { properties = new HashMap<String, Object>(); } return properties; } /*********************** Accessors *************************/ public String getKey() { return key; } public String getClassname() { return clazz.getName(); } public Class getToolClass() { return clazz; } public Map<String, Object> getProperties() { return getProps(); } public boolean hasConfigure() { return (getConfigure() != null); } public boolean isSkipSetters() { if (skipSetters == null) { skipSetters = (clazz.getAnnotation(SkipSetters.class) != null); } return skipSetters; } /** * @param path the path of a template requesting this tool * @return <code>true</code> if the specified * request path matches the restrictions of this tool. * If there is no request path restriction for this tool, * it will always return <code>true</code>. */ public boolean hasPermission(String path) { if (this.restrictTo == null) { return true; } else if (restrictToIsExact) { return this.restrictTo.equals(path); } else if (path != null) { return path.startsWith(this.restrictTo); } return false; } /*********************** create() *************************/ /** * Returns a new instance of the tool. If the tool * has an configure(Map) method, the new instance * will be initialized using the given properties combined with * whatever "constant" properties have been put into this * ToolInfo. */ public Object create(Map<String, Object> dynamicProperties) { /* Get the tool instance */ Object tool = newInstance(); /* put configured props into the combo last, since dynamic properties will almost always be conventions and we need to let configuration win out */ Map<String, Object> props; if (properties == null) { props = dynamicProperties; } else { props = combine(dynamicProperties, properties); } // perform the actual configuration of the new tool configure(tool, props); return tool; } /*********************** protected methods *************************/ /** * Actually performs configuration of the newly instantiated tool * using the combined final set of configuration properties. First, * if the class lacks the {@link SkipSetters} annotation, then any * specific setters matching the configuration keys are called, then * the general configure(Map) method (if any) is called. */ protected void configure(Object tool, Map<String, Object> configuration) { if (!isSkipSetters() && configuration != null) { try { // look for specific setters for (Map.Entry<String, Object> conf : configuration.entrySet()) { setProperty(tool, conf.getKey(), conf.getValue()); } } catch (RuntimeException re) { throw re; } catch (Exception e) { // convert to a runtime exception, and re-throw throw new RuntimeException(e); } } if (hasConfigure()) { invoke(getConfigure(), tool, configuration); } } protected Method getConfigure() { if (this.configure == null) { // search for a configure(Map params) method in the class try { this.configure = ClassUtils.findMethod(clazz, CONFIGURE_METHOD_NAME, new Class[] { Map.class }); } catch (SecurityException se) { // fail early, rather than wait until String msg = "Unable to gain access to '" + CONFIGURE_METHOD_NAME + "(Map)'" + " method for '" + clazz.getName() + "' under the current security manager." + " This tool cannot be properly configured for use."; throw new IllegalStateException(msg, se); } } return this.configure; } /* TODO? if we have performance issues with copyProperties, look at possibly finding and caching these common setters setContext(VelocityContext) setVelocityEngine(VelocityEngine) setLog(Log) setLocale(Locale) these four are tricky since we may not want servlet deps here setRequest(ServletRequest) setSession(HttpSession) setResponse(ServletResponse) setServletContext(ServletContext) */ protected Object newInstance() { try { return clazz.newInstance(); } /* we shouldn't get either of these exceptions here because * we already got an instance of this class during setClass(). * but to be safe, let's catch them and re-throw as RuntimeExceptions */ catch (IllegalAccessException iae) { String message = "Unable to instantiate instance of \"" + getClassname() + "\""; throw new IllegalStateException(message, iae); } catch (InstantiationException ie) { String message = "Exception while instantiating instance of \"" + getClassname() + "\""; throw new IllegalStateException(message, ie); } } protected void invoke(Method method, Object tool, Object param) { try { // call the setup method on the instance method.invoke(tool, new Object[] { param }); } catch (IllegalAccessException iae) { String msg = "Unable to invoke " + method + " on " + tool; // restricting access to this method by this class ist verboten throw new IllegalStateException(msg, iae); } catch (InvocationTargetException ite) { String msg = "Exception when invoking " + method + " on " + tool; // convert to a runtime exception, and re-throw throw new RuntimeException(msg, ite.getCause()); } } protected void setProperty(Object tool, String name, Object value) throws Exception { if (PropertyUtils.isWriteable(tool, name)) { //TODO? support property conversion here? // heavy-handed way is BeanUtils.copyProperty(...) PropertyUtils.setProperty(tool, name, value); } } //TODO? move to Utils? protected Map<String, Object> combine(Map<String, Object>... maps) { Map<String, Object> combined = new HashMap<String, Object>(); for (Map<String, Object> map : maps) { if (map != null) { combined.putAll(map); } } return combined; } }