增加方式如下：web.xml中加入
<listener>
<listener-class>org.springframework.web.util.IntrospectorCleanupListener</listener-class>
</listener>
org.springframework.web.util.IntrospectorCleanupListener源代码中对其的解释如下：
在Web应用程序关闭时IntrospectorCleanupListener将会刷新JDK的JavaBeans的Introspector缓存。在你的web.xml中注册这个listener来确保Web应用程序的类加载器以及其加载的类正确的释放资源。
如果JavaBeans的Introspector已被用来分析应用程序类，系统级的Introspector缓存将持有这些类的一个硬引用。因此，这些类和Web应用程序的类加载器在Web应用程序关闭时将不会被垃圾收集器回收！而IntrospectorCleanupListener则会对其进行适当的清理，已使其能够被垃圾收集器回收。
不幸的是，唯一能够清理Introspector的方法是刷新整个Introspector缓存，没有其他办法来确切指定应用程序所引用的类。这将删除所有其他应用程序在服务器的缓存的Introspector结果。
请注意，在使用Spring内部的bean机制时，不需要使用此监听器，因为Spring自己的introspection results cache将会立即刷新被分析过的JavaBeans Introspector cache，而仅仅会在应用程序自己的ClassLoader里面持有一个cache。虽然Spring本身不产生泄漏，注意，即使在Spring框架的类本身驻留在一个“共同”类加载器（如系统的ClassLoader）的情况下，也仍然应该使用使用IntrospectorCleanupListener。在这种情况下，这个IntrospectorCleanupListener将会妥善清理Spring的introspection cache。
应用程序类，几乎不需要直接使用JavaBeans Introspector，所以，通常都不是Introspector resource造成内存泄露。相反，许多库和框架，不清理Introspector，例如： Struts和Quartz。
需要注意的是一个简单Introspector泄漏将会导致整个Web应用程序的类加载器不会被回收！这样做的结果，将会是在web应用程序关闭时，该应用程序所有的静态类资源（比如：单实例对象）都没有得到释放。而导致内存泄露的根本原因其实并不是这些未被回收的类！
IntrospectorCleanupListener应该注册为web.xml中的第一个Listener，在任何其他Listener之前注册，比如在Spring's ContextLoaderListener注册之前，才能确保IntrospectorCleanupListener在Web应用的生命周期适当时机生效。
下面是源码
/*
* Copyright 2002-2012 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.util;
import java.beans.Introspector;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import org.springframework.beans.CachedIntrospectionResults;
/**
* Listener that flushes the JDK's {@link java.beans.Introspector JavaBeans Introspector}
* cache on web app shutdown. Register this listener in your {@code web.xml} to
* guarantee proper release of the web application class loader and its loaded classes.
*
* <p><b>If the JavaBeans Introspector has been used to analyze application classes,
* the system-level Introspector cache will hold a hard reference to those classes.
* Consequently, those classes and the web application class loader will not be
* garbage-collected on web app shutdown!</b> This listener performs proper cleanup,
* to allow for garbage collection to take effect.
*
* <p>Unfortunately, the only way to clean up the Introspector is to flush
* the entire cache, as there is no way to specifically determine the
* application's classes referenced there. This will remove cached
* introspection results for all other applications in the server too.
*
* <p>Note that this listener is <i>not</i> necessary when using Spring's beans
* infrastructure within the application, as Spring's own introspection results
* cache will immediately flush an analyzed class from the JavaBeans Introspector
* cache and only hold a cache within the application's own ClassLoader.
*
* <b>Although Spring itself does not create JDK Introspector leaks, note that this
* listener should nevertheless be used in scenarios where the Spring framework classes
* themselves reside in a 'common' ClassLoader (such as the system ClassLoader).</b>
* In such a scenario, this listener will properly clean up Spring's introspection cache.
*
* <p>Application classes hardly ever need to use the JavaBeans Introspector
* directly, so are normally not the cause of Introspector resource leaks.
* Rather, many libraries and frameworks do not clean up the Introspector:
* e.g. Struts and Quartz.
*
* <p>Note that a single such Introspector leak will cause the entire web
* app class loader to not get garbage collected! This has the consequence that
* you will see all the application's static class resources (like singletons)
* around after web app shutdown, which is not the fault of those classes!
*
* <p><b>This listener should be registered as the first one in {@code web.xml},
* before any application listeners such as Spring's ContextLoaderListener.</b>
* This allows the listener to take full effect at the right time of the lifecycle.
*
* @author Juergen Hoeller
* @since 1.1
* @see java.beans.Introspector#flushCaches()
* @see org.springframework.beans.CachedIntrospectionResults#acceptClassLoader
* @see org.springframework.beans.CachedIntrospectionResults#clearClassLoader
*/
public class IntrospectorCleanupListener implements ServletContextListener {
public void contextInitialized(ServletContextEvent event) {
CachedIntrospectionResults.acceptClassLoader(Thread.currentThread().getContextClassLoader());
}
public void contextDestroyed(ServletContextEvent event) {
CachedIntrospectionResults.clearClassLoader(Thread.currentThread().getContextClassLoader());
Introspector.flushCaches();
}
}
注意：quartz默认开启的时候就会启动很多线程