/*
* Copyright 2002-2008 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.BeansException;
import org.springframework.beans.MutablePropertyValues;
import org.springframework.beans.PropertyAccessorFactory;
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 (<code>init-param</code> entries within the
* <code>servlet</code> tag in <code>web.xml</code>) as bean properties.
*
* <p>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.
*
* <p>This servlet leaves request handling to subclasses, inheriting the default
* behavior of HttpServlet (<code>doGet</code>, <code>doPost</code>, etc).
*
* <p>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}).
*
* <p>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.
* <p>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 = PropertyAccessorFactory.forBeanPropertyAccess(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.
* <p>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 <code>null</code> when no
* ServletConfig set yet.
* @see #getServletConfig()
*/
public final String getServletName() {
return (getServletConfig() != null ? getServletConfig().getServletName() : null);
}
/**
* Overridden method that simply returns <code>null</code> 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.
* <p>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, ", "));
}
}
}
}