JavaWeb-监听器

1.基本介绍

2.ServletContextListener

1.基本介绍

2.创建maven项目，导入依赖

    <dependency><groupId>javax.servlet</groupId><artifactId>javax.servlet-api</artifactId><version>3.1.0</version></dependency>

3.代码演示

1.实现ServletContextListener接口

package listener;import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;/*** @author 孙显圣* @version 1.0*/
public class ServletContextListener implements javax.servlet.ServletContextListener {public void contextInitialized(ServletContextEvent servletContextEvent) {ServletContext servletContext = servletContextEvent.getServletContext();System.out.println("监听到servletContext创建");}public void contextDestroyed(ServletContextEvent servletContextEvent) {ServletContext servletContext = servletContextEvent.getServletContext();System.out.println("监听到servletContext销毁 ");}
}

2.配置web.xml

  <listener><listener-class>listener.ServletContextListener</listener-class></listener>

3.结果

3.ServletContextAttributeListener监听器

1.基本介绍

2.代码实例

1.ServletContextAttributeListener.java

package listener;import javax.servlet.ServletContextAttributeEvent;/*** @author 孙显圣* @version 1.0*/
public class ServletContextAttributeListener implements javax.servlet.ServletContextAttributeListener {public void attributeAdded(ServletContextAttributeEvent servletContextAttributeEvent) {System.out.println("ServletContextAttributeListener监听到添加属性" + servletContextAttributeEvent.getName()+ servletContextAttributeEvent.getValue());}public void attributeRemoved(ServletContextAttributeEvent servletContextAttributeEvent) {System.out.println("ServletContextAttributeListener监听到删除属性" + servletContextAttributeEvent.getName()+ servletContextAttributeEvent.getValue());}public void attributeReplaced(ServletContextAttributeEvent servletContextAttributeEvent) {System.out.println("ServletContextAttributeListener监听到修改属性" + servletContextAttributeEvent.getName()+ servletContextAttributeEvent.getValue());}
}

2.配置web.xml

  <listener><listener-class>listener.ServletContextAttributeListener</listener-class></listener>

3.创建servlet演示

package servlet;import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;/*** @author 孙显圣* @version 1.0*/
@WebServlet(urlPatterns = "/modify")
public class modifyServletContextAttribute extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {ServletContext servletContext = super.getServletContext();//添加servletContext.setAttribute("name","孙显圣");//替换servletContext.setAttribute("name","李白");//删除servletContext.removeAttribute("name");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

4.结果

4.HttpSessionListener

1.基本介绍

2.代码实例

1.HttpSessionListener.java

package listener;import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionEvent;/*** @author 孙显圣* @version 1.0*/
public class HttpSessionListener implements javax.servlet.http.HttpSessionListener {public void sessionCreated(HttpSessionEvent httpSessionEvent) {HttpSession session = httpSessionEvent.getSession();System.out.println("HttpSessionListener监听到session创建id为" + session.getId());}public void sessionDestroyed(HttpSessionEvent httpSessionEvent) {HttpSession session = httpSessionEvent.getSession();System.out.println("HttpSessionListener监听到session销毁id为" + session.getId());}
}

2.配置web.xml

  <listener><listener-class>listener.HttpSessionListener</listener-class></listener>

3.创建servlet演示

package servlet;import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;/*** @author 孙显圣* @version 1.0*/
@WebServlet(urlPatterns = "/modifySession")
public class modifySession extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//创建sessionHttpSession session = req.getSession();//删除sessionsession.invalidate();}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

4.结果

5.HttpSessionAttributeListener

1.基本介绍

2.代码实例

1.HttpSessionAttributeListener.java

package listener;import javax.servlet.http.HttpSessionBindingEvent;/*** @author 孙显圣* @version 1.0*/
public class HttpSessionAttributeListener implements javax.servlet.http.HttpSessionAttributeListener {public void attributeAdded(HttpSessionBindingEvent httpSessionBindingEvent) {String name = httpSessionBindingEvent.getName();System.out.println("监听到session创建属性：" + name);}public void attributeRemoved(HttpSessionBindingEvent httpSessionBindingEvent) {String name = httpSessionBindingEvent.getName();System.out.println("监听到session删除属性：" + name);}public void attributeReplaced(HttpSessionBindingEvent httpSessionBindingEvent) {String name = httpSessionBindingEvent.getName();System.out.println("监听到session替换属性：" + name);}
}

2.配置web.xml

  <listener><listener-class>listener.HttpSessionAttributeListener</listener-class></listener>

3.创建servlet演示

package servlet;import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;/*** @author 孙显圣* @version 1.0*/
@WebServlet(urlPatterns = "/modifySessionAttribute")
public class modifySessionAttribute extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {HttpSession session = req.getSession();session.setAttribute("name","孙显圣");session.setAttribute("name","李白");session.removeAttribute("name");}
}

4.结果

6.ServletRequestListener

1.基本介绍

2.代码实例

1.ServletRequestListener.java

package listener;import javax.servlet.ServletRequest;
import javax.servlet.ServletRequestEvent;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;/*** @author 孙显圣* @version 1.0*/
public class ServletRequestListener implements javax.servlet.ServletRequestListener {public void requestDestroyed(ServletRequestEvent servletRequestEvent) {System.out.println("ServletRequestListener 监听到 request对象销毁");}public void requestInitialized(ServletRequestEvent servletRequestEvent) {System.out.println("ServletRequestListener 监听到 request对象创建");ServletRequest servletRequest = servletRequestEvent.getServletRequest();//可以向下转型为HttpServletRequest，获取更多信息System.out.println("访问ip：" + servletRequest.getRemoteAddr());System.out.println("访问资源：" + ((HttpServletRequest)servletRequest).getRequestURL());}
}

2.配置web.xml

  <listener><listener-class>listener.ServletRequestListener</listener-class></listener>

3.结果

7.其他监听器

8.监听器小结

1.创建监听器

1.基本概念

2.创建方法

1. 实现接口，进行相应操作
2. 配置web.xml（告诉tomcat）

2.ServletContextListener

3.ServletContextAttributeListener

4.HttpSessionListener

5.HttpSessionAttributeListener

6.ServletRequestListener