Tomcat监听器

# Tomcat监听器

- Servlet监听器用于监听一些重要事件的发生，监听器对象可以在事情发生前、发生后可以做一些必要的处理

- 通过实现Servlet API提供的Listense接口，可以在监听正在执行的某一个程序，并且根据程序的需求做出适当的响应

- 监听作用域对象的创建和销毁以及属性的相关配置，可以添加一些公共的属性配置，做逻辑判断

- 也可以通过Log4j来做日志的记录等等

## ServletRequest监听对象

- 需要是实现的接口与重写方法

- servletRequestListener：监听request对象的创建和销毁

- public void requestDestroyed(ServletRequestEvent servletRequestEvent) request对象被销毁的时候添加的逻辑代码

- public void requestInitialized(ServletRequestEvent servletRequestEvent) request对象被初始化的时候添加的逻辑代码

- ServletRequestAttributeListener：监听request作用域属性的添加，删除和修改

- public void attributeAdded(ServletRequestAttributeEvent servletRequestAttributeEvent) :request作用域属性被添加的时候的逻辑代码

- public void attributeRemoved(ServletRequestAttributeEvent servletRequestAttributeEvent) :request作用域属性被删除的时候的逻辑代码

- public void attributeReplaced(ServletRequestAttributeEvent servletRequestAttributeEvent) :request作用域属性被修改的时候的逻辑代码

```java

package com.shanlei.listense;

import javax.servlet.*;

import java.util.Date;

/**

* @author: shanlei

* @version: 1.0

*/

public class Mylistense implements ServletRequestListener, ServletRequestAttributeListener {

@Override

public void requestDestroyed(ServletRequestEvent servletRequestEvent) {

System.out.println("request对象被销毁--:"+new Date());

}

@Override

public void requestInitialized(ServletRequestEvent servletRequestEvent) {

System.out.println("request对象被初始化---:"+new Date());

}

@Override

public void attributeAdded(ServletRequestAttributeEvent servletRequestAttributeEvent) {

System.out.println("request对象属性被添加---："+new Date());

System.out.println(servletRequestAttributeEvent.getName());

System.out.println(servletRequestAttributeEvent.getValue());

}

@Override

public void attributeRemoved(ServletRequestAttributeEvent servletRequestAttributeEvent) {

System.out.println("request对象属性被删除---："+new Date());

}

@Override

public void attributeReplaced(ServletRequestAttributeEvent servletRequestAttributeEvent) {

System.out.println("request对象属性被修改---："+new Date());

}

}

```

## ServletContext监听对象

- 需要是实现的接口与重写方法

- ServletContextListener：监听servletContext对象的创建和销毁

- public void contextDestroyed(ServletContextEvent servletContextEvent) servletContext对象被销毁的时候添加的逻辑代码

- public void contextInitialized(ServletContextEvent servletContextEvent) servletContext对象被初始化的时候添加的逻辑代码

- ServletContextAttributeListener：监听servletContext作用域属性的添加，删除和修改

- public void attributeAdded(ServletContextAttributeEvent servletContextAttributeEvent) :servletContext作用域属性被添加的时候的逻辑代码

- public void attributeRemoved(ServletContextAttributeEvent servletContextAttributeEvent) :servletContext作用域属性被删除的时候的逻辑代码

- public void attributeReplaced(ServletContextAttributeEvent servletContextAttributeEvent) :servletContext作用域属性被修改的时候的逻辑代码

```java

package com.shanlei.listense;

import javax.servlet.*;

import java.util.Date;

/**

* @author: shanlei

* @version: 1.0

*/

public class Mylistense implements ServletContextListener, ServletContextAttributeListener {

@Override

public void attributeAdded(ServletContextAttributeEvent servletContextAttributeEvent) {

System.out.println("ervletContext对象属性被添加---："+new Date());

System.out.println(servletContextAttributeEvent.getName());

System.out.println(servletContextAttributeEvent.getValue());

}

@Override

public void attributeRemoved(ServletContextAttributeEvent servletContextAttributeEvent) {

System.out.println("servletContext对象属性被删除---："+new Date());

System.out.println(servletContextAttributeEvent.getName());

System.out.println(servletContextAttributeEvent.getValue());

}

@Override

public void attributeReplaced(ServletContextAttributeEvent servletContextAttributeEvent) {

System.out.println("servletContext对象属性被修改---："+new Date());

System.out.println(servletContextAttributeEvent.getName());

System.out.println(servletContextAttributeEvent.getValue());

}

@Override

public void contextInitialized(ServletContextEvent servletContextEvent) {

System.out.println("servletContext对象被初始化--:"+new Date());

}

@Override

public void contextDestroyed(ServletContextEvent servletContextEvent) {

System.out.println("servletContext对象被销毁--:"+new Date());

}

}

```

## HttpSession监听对象

- 需要是实现的接口与重写方法

- HttpSessionListener：监听session的创建与销毁

- public void sessionCreated(HttpSessionEvent httpSessionEvent) session对象被创建的时候添加的逻辑代码

- public void sessionDestroyed(HttpSessionEvent httpSessionEvent) session对象被销毁的时候添加的逻辑代码

- HttpSessionAttributeListener：监听session的属性的添加、删除与修改

- public void attributeAdded(HttpSessionBindingEvent httpSessionBindingEvent) :session添加属性的时候添加的逻辑代码

- public void attributeRemoved(HttpSessionBindingEvent httpSessionBindingEvent) :session添加属性的时候删除的逻辑代码

- public void attributeReplaced(HttpSessionBindingEvent httpSessionBindingEvent) :session添加属性的时候修改的逻辑代码

- HttpSessionActivationListenser是在session被持久化后当被重新读取到内存中的时候使用的监听器，一般不使用

- HttpSessionBindingListener绑定监听器，需要另外创建对象才能实现监听，所以也一般不使用

```java

package com.shanlei.listense;

import javax.servlet.http.HttpSessionAttributeListener;

import javax.servlet.http.HttpSessionBindingEvent;

import javax.servlet.http.HttpSessionEvent;

import javax.servlet.http.HttpSessionListener;

/**

* @author: shanlei

* @version: 1.0

*/

public class SessionListense implements HttpSessionListener, HttpSessionAttributeListener {

@Override

public void sessionCreated(HttpSessionEvent httpSessionEvent) {

System.out.println("session对象被创建");

}

@Override

public void sessionDestroyed(HttpSessionEvent httpSessionEvent) {

System.out.println("session对象被销毁");

}

@Override

public void attributeAdded(HttpSessionBindingEvent httpSessionBindingEvent) {

System.out.println("session添加属性");

System.out.println(httpSessionBindingEvent.getName());

System.out.println(httpSessionBindingEvent.getValue());

}

@Override

public void attributeRemoved(HttpSessionBindingEvent httpSessionBindingEvent) {

System.out.println("session删除属性");

System.out.println(httpSessionBindingEvent.getName());

System.out.println(httpSessionBindingEvent.getValue());

}

@Override

public void attributeReplaced(HttpSessionBindingEvent httpSessionBindingEvent) {

System.out.println("session修改属性");

System.out.println(httpSessionBindingEvent.getName());

System.out.println(httpSessionBindingEvent.getValue());

}

}

```