Servlet监听器

所有事件都继承自 java.util.Event

分成三类：application范围、session范围和request范围

• 监听器接口和注册

  • javax.servlet.ServletContextListener: 响应 ServletContext生命周期事件，Context创建之后，关闭之前会被调用
  • javax.servlet.ServletContextAttributeListener: 响应Context范围的属性 增删替换
  • javax.servlet.http.HttpSessionListener: 响应session创建 超时 失效事件
  • javax.servlet.http.HttpSessionAttributeListener:
  • javax.servlet.http.HttpSessionActivationListener: 响应session失效 激活事件
  • javax.servlet.http.HttpSessionBindingListener: 响应HttpSession中有 添加 删除 值时
  • javax.servlet.ServletRequestListener: 响应ServletRequest的创建or删除
  • javax.servlet.ServletRequestAttributeListener:
  • javax.servlet.AsyncListener: 异步操作监听器

• Servlet3.0 - 3.1 两种方法实现

  • @WebListenerpublic class ListenerClass implements ListenerInterface{}

  •             
             
              fully-qualified listener class 
             
            

• javax.servlet.ServletContextListener

  • public interface ServletContextListener extends EventListener {    void contextInitialized(ServletContextEvent var1);    void contextDestroyed(ServletContextEvent var1);}//监听器方法入参类型public class ServletContextEvent extends EventObject {    private static final long serialVersionUID = 1L;    public ServletContextEvent(ServletContext source) {        super(source);    }    public ServletContext ServletContextEvent() {        return (ServletContext)super.getSource();    }}

  • 通过入参ServletContextEvent中的ServletContextEvent()可以获取应用上下文获取数据

  • 对ServletContext创建和销毁做出反应

• javax.servlet.ServletContextAttributeListener

  • public interface ServletContextAttributeListener extends EventListener {    void attributeAdded(ServletContextAttributeEvent var1);    void attributeRemoved(ServletContextAttributeEvent var1);    void attributeReplaced(ServletContextAttributeEvent var1);}//监听器方法入参类型public class ServletContextAttributeEvent extends ServletContextEvent {    private static final long serialVersionUID = 1L;    private final String name;    private final Object value;    public ServletContextAttributeEvent(ServletContext source, String name, Object value) {        super(source);        this.name = name;        this.value = value;    }    public String getName() {        return this.name;    }    public Object getValue() {        return this.value;    }}

• javax.servlet.http.HttpSessionListener

  • public interface HttpSessionListener extends EventListener {    void sessionCreated(HttpSessionEvent var1);    void sessionDestroyed(HttpSessionEvent var1);}//监听器方法入参类型public class HttpSessionEvent extends EventObject {    private static final long serialVersionUID = 1L;    public HttpSessionEvent(HttpSession source) {        super(source);    }    public HttpSession getSession() {        return (HttpSession)super.getSource();    }}

• javax.servlet.http.HttpSessionActivationListener

  • public interface HttpSessionAttributeListener extends EventListener {    void attributeAdded(HttpSessionBindingEvent var1);    void attributeRemoved(HttpSessionBindingEvent var1);    void attributeReplaced(HttpSessionBindingEvent var1);}//监听器方法入参类型public class HttpSessionBindingEvent extends HttpSessionEvent {    private static final long serialVersionUID = 1L;    private final String name;    private final Object value;    public HttpSessionBindingEvent(HttpSession session, String name) {        super(session);        this.name = name;        this.value = null;    }    public HttpSessionBindingEvent(HttpSession session, String name, Object value) {        super(session);        this.name = name;        this.value = value;    }    public HttpSession getSession() {        return super.getSession();    }    public String getName() {        return this.name;    }    public Object getValue() {        return this.value;    }}

  • HttpSessionBindingEvent extends HttpSessionEvent 所以 在HttpSessionBindingEvent 也能够拿到HttpSession对象

• javax.servlet.http.HttpSessionActivationListener

  在分布式环境下，会用多个容器来进行负载均衡，有可能需要将session保存起来，在容器之间传递，ex一个容器内存不足，会将很少用到的对象转存刀其他容器上，这时候就会通知HttpSessionActivationListener
  • public interface HttpSessionActivationListener extends EventListener {    //钝化    void sessionWillPassivate(HttpSessionEvent var1);    //活化    void sessionDidActivate(HttpSessionEvent var1); }

• javax.servlet.http.HttpSessionBindingListener

  • public interface HttpSessionBindingListener extends EventListener {    void valueBound(HttpSessionBindingEvent var1);    void valueUnbound(HttpSessionBindingEvent var1);}

• javax.servlet.ServletRequestListener

  • public interface ServletRequestListener extends EventListener {    void requestDestroyed(ServletRequestEvent var1);    void requestInitialized(ServletRequestEvent var1);}//监听器方法入参类型public class ServletRequestEvent extends EventObject {    private static final long serialVersionUID = 1L;    private final transient ServletRequest request;    public ServletRequestEvent(ServletContext sc, ServletRequest request) {        super(sc);        this.request = request;    }    public ServletRequest getServletRequest() {        return this.request;    }    public ServletContext getServletContext() {        return (ServletContext)super.getSource();    }}

• javax.servlet.ServletRequestAttributeListener

  • public interface ServletRequestAttributeListener extends EventListener {    void attributeAdded(ServletRequestAttributeEvent var1);    void attributeRemoved(ServletRequestAttributeEvent var1);    void attributeReplaced(ServletRequestAttributeEvent var1);}