/*
* Copyright 2012-2017 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.boot.web.servlet;
import java.util.Collections;
import java.util.EventListener;
import java.util.HashSet;
import java.util.Set;
import javax.servlet.ServletContext;
import javax.servlet.ServletContextAttributeListener;
import javax.servlet.ServletContextListener;
import javax.servlet.ServletException;
import javax.servlet.ServletRequestAttributeListener;
import javax.servlet.ServletRequestListener;
import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionListener;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
/**
* A {@link ServletContextInitializer} to register {@link EventListener}s in a Servlet
* 3.0+ container. Similar to the {@link ServletContext#addListener(EventListener)
* registration} features provided by {@link ServletContext} but with a Spring Bean
* friendly design.
*
* This bean can be used to register the following types of listener:
* <ul>
* <li>{@link ServletContextAttributeListener}</li>
* <li>{@link ServletRequestListener}</li>
* <li>{@link ServletRequestAttributeListener}</li>
* <li>{@link HttpSessionAttributeListener}</li>
* <li>{@link HttpSessionListener}</li>
* <li>{@link ServletContextListener}</li>
* </ul>
*
* @param <T> the type of listener
* @author Dave Syer
* @author Phillip Webb
* @since 1.4.0
*/
public class ServletListenerRegistrationBean<T extends EventListener>
extends RegistrationBean {
private static final Log logger = LogFactory
.getLog(ServletListenerRegistrationBean.class);
private static final Set<Class<?>> SUPPORTED_TYPES;
static {
Set<Class<?>> types = new HashSet<>();
types.add(ServletContextAttributeListener.class);
types.add(ServletRequestListener.class);
types.add(ServletRequestAttributeListener.class);
types.add(HttpSessionAttributeListener.class);
types.add(HttpSessionListener.class);
types.add(ServletContextListener.class);
SUPPORTED_TYPES = Collections.unmodifiableSet(types);
}
private T listener;
/**
* Create a new {@link ServletListenerRegistrationBean} instance.
*/
public ServletListenerRegistrationBean() {
}
/**
* Create a new {@link ServletListenerRegistrationBean} instance.
* @param listener the listener to register
*/
public ServletListenerRegistrationBean(T listener) {
Assert.notNull(listener, "Listener must not be null");
Assert.isTrue(isSupportedType(listener), "Listener is not of a supported type");
this.listener = listener;
}
/**
* Set the listener that will be registered.
* @param listener the listener to register
*/
public void setListener(T listener) {
Assert.notNull(listener, "Listener must not be null");
Assert.isTrue(isSupportedType(listener), "Listener is not of a supported type");
this.listener = listener;
}
@Override
public void onStartup(ServletContext servletContext) throws ServletException {
if (!isEnabled()) {
logger.info("Listener " + this.listener + " was not registered (disabled)");
return;
}
try {
servletContext.addListener(this.listener);
}
catch (RuntimeException ex) {
throw new IllegalStateException(
"Failed to add listener '" + this.listener + "' to servlet context",
ex);
}
}
public T getListener() {
return this.listener;
}
/**
* Returns {@code true} if the specified listener is one of the supported types.
* @param listener the listener to test
* @return if the listener is of a supported type
*/
public static boolean isSupportedType(EventListener listener) {
for (Class<?> type : SUPPORTED_TYPES) {
if (ClassUtils.isAssignableValue(type, listener)) {
return true;
}
}
return false;
}
/**
* Return the supported types for this registration.
* @return the supported types
*/
public static Set<Class<?>> getSupportedTypes() {
return SUPPORTED_TYPES;
}
}