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/*
 * Copyright 2002-2007 the original author or authors.
 *
 * Licensed 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.
 */

package org.springframework.web.servlet;

import java.util.Enumeration;
import java.util.HashSet;
import java.util.Set;

import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.BeanWrapper;
import org.springframework.beans.BeanWrapperImpl;
import org.springframework.beans.BeansException;
import org.springframework.beans.MutablePropertyValues;
import org.springframework.beans.PropertyValue;
import org.springframework.beans.PropertyValues;
import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceEditor;
import org.springframework.core.io.ResourceLoader;
import org.springframework.util.StringUtils;
import org.springframework.web.context.support.ServletContextResourceLoader;

/**
 * Simple extension of {@link javax.servlet.http.HttpServlet} which treats
 * its config parameters (init-param entries within the
 * servlet tag in web.xml) as bean properties.
 *
 * 

A handy superclass for any type of servlet. Type conversion of config * parameters is automatic, with the corresponding setter method getting * invoked with the converted value. It is also possible for subclasses to * specify required properties. Parameters without matching bean property * setter will simply be ignored. * *

This servlet leaves request handling to subclasses, inheriting the default * behavior of HttpServlet (doGet, doPost, etc). * *

This generic servlet base class has no dependency on the Spring * {@link org.springframework.context.ApplicationContext} concept. Simple * servlets usually don't load their own context but rather access service * beans from the Spring root application context, accessible via the * filter's {@link #getServletContext() ServletContext} (see * {@link org.springframework.web.context.support.WebApplicationContextUtils}). * *

The {@link FrameworkServlet} class is a more specific servlet base * class which loads its own application context. FrameworkServlet serves * as direct base class of Spring's full-fledged {@link DispatcherServlet}. * * @author Rod Johnson * @author Juergen Hoeller * @see #addRequiredProperty * @see #initServletBean * @see #doGet * @see #doPost */ public abstract class HttpServletBean extends HttpServlet { /** Logger available to subclasses */ protected final Log logger = LogFactory.getLog(getClass()); /** * Set of required properties (Strings) that must be supplied as * config parameters to this servlet. */ private final Set requiredProperties = new HashSet(); /** * Subclasses can invoke this method to specify that this property * (which must match a JavaBean property they expose) is mandatory, * and must be supplied as a config parameter. This should be called * from the constructor of a subclass. *

This method is only relevant in case of traditional initialization * driven by a ServletConfig instance. * @param property name of the required property */ protected final void addRequiredProperty(String property) { this.requiredProperties.add(property); } /** * Map config parameters onto bean properties of this servlet, and * invoke subclass initialization. * @throws ServletException if bean properties are invalid (or required * properties are missing), or if subclass initialization fails. */ public final void init() throws ServletException { if (logger.isDebugEnabled()) { logger.debug("Initializing servlet '" + getServletName() + "'"); } // Set bean properties from init parameters. try { PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties); BeanWrapper bw = new BeanWrapperImpl(this); ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext()); bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader)); initBeanWrapper(bw); bw.setPropertyValues(pvs, true); } catch (BeansException ex) { logger.error("Failed to set bean properties on servlet '" + getServletName() + "'", ex); throw ex; } // Let subclasses do whatever initialization they like. initServletBean(); if (logger.isDebugEnabled()) { logger.debug("Servlet '" + getServletName() + "' configured successfully"); } } /** * Initialize the BeanWrapper for this HttpServletBean, * possibly with custom editors. *

This default implementation is empty. * @param bw the BeanWrapper to initialize * @throws BeansException if thrown by BeanWrapper methods * @see org.springframework.beans.BeanWrapper#registerCustomEditor */ protected void initBeanWrapper(BeanWrapper bw) throws BeansException { } /** * Overridden method that simply returns null when no * ServletConfig set yet. * @see #getServletConfig() */ public final String getServletName() { return (getServletConfig() != null ? getServletConfig().getServletName() : null); } /** * Overridden method that simply returns null when no * ServletConfig set yet. * @see #getServletConfig() */ public final ServletContext getServletContext() { return (getServletConfig() != null ? getServletConfig().getServletContext() : null); } /** * Subclasses may override this to perform custom initialization. * All bean properties of this servlet will have been set before this * method is invoked. *

This default implementation is empty. * @throws ServletException if subclass initialization fails */ protected void initServletBean() throws ServletException { } /** * PropertyValues implementation created from ServletConfig init parameters. */ private static class ServletConfigPropertyValues extends MutablePropertyValues { /** * Create new ServletConfigPropertyValues. * @param config ServletConfig we'll use to take PropertyValues from * @param requiredProperties set of property names we need, where * we can't accept default values * @throws ServletException if any required properties are missing */ public ServletConfigPropertyValues(ServletConfig config, Set requiredProperties) throws ServletException { Set missingProps = (requiredProperties != null && !requiredProperties.isEmpty()) ? new HashSet(requiredProperties) : null; Enumeration en = config.getInitParameterNames(); while (en.hasMoreElements()) { String property = (String) en.nextElement(); Object value = config.getInitParameter(property); addPropertyValue(new PropertyValue(property, value)); if (missingProps != null) { missingProps.remove(property); } } // Fail if we are still missing properties. if (missingProps != null && missingProps.size() > 0) { throw new ServletException( "Initialization from ServletConfig for servlet '" + config.getServletName() + "' failed; the following required properties were missing: " + StringUtils.collectionToDelimitedString(missingProps, ", ")); } } } }





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