servlet中的8个Listener

servlet中的8个Listener：

Xml：

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee"

    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee

    http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">

    <display-name>TestBootWeb</display-name>

    <servlet>

        <servlet-name>TestServlet4</servlet-name>

        <servlet-class>com.stono.servlet.TestServlet4</servlet-class>

        <init-param>

            <param-name>testServlet4ParamName</param-name>

            <param-value>testServlet4ParamValue</param-value>

        </init-param>

    </servlet>

    <servlet-mapping>

        <servlet-name>TestServlet4</servlet-name>

        <url-pattern>/test4.do</url-pattern>

    </servlet-mapping>

    <context-param>

        <param-name>contextParamName</param-name>

        <param-value>contextParamValue</param-value>

    </context-param>

    <welcome-file-list>

        <welcome-file>index.jsp</welcome-file>

    </welcome-file-list>

    <listener>

        <listener-class>com.stono.servlet.listeners.MyServletContextListener</listener-class>

        <listener-class>com.stono.servlet.listeners.MyServletContextAttributeListener</listener-class>

        <listener-class>com.stono.servlet.listeners.MyHttpSessionListener</listener-class>

        <listener-class>com.stono.servlet.listeners.MyHttpSessionAttributeListener</listener-class>

        <listener-class>com.stono.servlet.listeners.MyServletRequestListener</listener-class>

        <listener-class>com.stono.servlet.listeners.MyServletRequestAttributeListener</listener-class>

        <!-- 不知道这个Listener是否需要在这里面配置 -->

        <listener-class>com.stono.servlet.listeners.MyHttpSessionActivationListener</listener-class>

    </listener>

</web-app>

Listener：

package com.stono.servlet.listeners;

import javax.servlet.http.HttpSessionActivationListener;

import javax.servlet.http.HttpSessionEvent;

/* 文档中提到进行JVM迁移的时候才能激发此事件； */

public class MyHttpSessionActivationListener implements HttpSessionActivationListener {

    @Override

    public void sessionDidActivate(HttpSessionEvent arg0) {

        System.out.println("com.stono.servlet.listeners.MyHttpSessionActivationListener.sessionDidActivate(HttpSessionEvent)");

    }

    @Override

    public void sessionWillPassivate(HttpSessionEvent arg0) {

        System.out.println("com.stono.servlet.listeners.MyHttpSessionActivationListener.sessionWillPassivate(HttpSessionEvent)");

    }

}

package com.stono.servlet.listeners;

import javax.servlet.http.HttpSessionAttributeListener;

import javax.servlet.http.HttpSessionBindingEvent;

public class MyHttpSessionAttributeListener implements HttpSessionAttributeListener {

    @Override

    /* 调用session.setAttribute的时候触发事件； */

    public void attributeAdded(HttpSessionBindingEvent arg0) {

        System.out.println("com.stono.servlet.listeners.MyHttpSessionAttributeListener.attributeAdded(HttpSessionBindingEvent)");

        String name = arg0.getName();

        Object value = arg0.getValue();

        System.out.println("name:" + name + ";value:" + value);

    }

    @Override

    /* 调用session.invalidate()方法之后触发这个事件； */

    public void attributeRemoved(HttpSessionBindingEvent arg0) {

        System.out.println("com.stono.servlet.listeners.MyHttpSessionAttributeListener.attributeRemoved(HttpSessionBindingEvent)");

        String name = arg0.getName();

        Object value = arg0.getValue();

        System.out.println("name:" + name + ";value:" + value);

    }

    @Override

    /* 第二次调用session.setAttribute的时候会触发此事件，但是arg0.getValue()还是返回之前的值 */

    public void attributeReplaced(HttpSessionBindingEvent arg0) {

        System.out.println("com.stono.servlet.listeners.MyHttpSessionAttributeListener.attributeReplaced(HttpSessionBindingEvent)");

        String name = arg0.getName();

        Object value = arg0.getValue();

        System.out.println("name:" + name + ";value:" + value);

    }

}

package com.stono.servlet.listeners;

import javax.servlet.http.HttpSessionBindingEvent;

import javax.servlet.http.HttpSessionBindingListener;

public class MyHttpSessionBindingListener implements HttpSessionBindingListener {

    private String name;

    private String value;

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

    public String getValue() {

        return value;

    }

    public void setValue(String value) {

        this.value = value;

    }

    @Override

    /* 将此对象设置到session中的时候触发的事件； */

    public void valueBound(HttpSessionBindingEvent arg0) {

        System.out.println("com.stono.servlet.listeners.MyHttpSessionBindingListener.valueBound(HttpSessionBindingEvent)");

        String name2 = arg0.getName();

        Object value2 = arg0.getValue();

        Object source = arg0.getSource();

        System.out.println("name:" + name2 + ";value:" + value2 + ";source:" + source);

    }

    @Override

    /* session.invalide()的时候触发的事件； */

    public void valueUnbound(HttpSessionBindingEvent arg0) {

        System.out.println("com.stono.servlet.listeners.MyHttpSessionBindingListener.valueUnbound(HttpSessionBindingEvent)");

        String name2 = arg0.getName();

        Object value2 = arg0.getValue();

        Object source = arg0.getSource();

        System.out.println("name:" + name2 + ";value:" + value2 + ";source:" + source);

    }

}

package com.stono.servlet.listeners;

import javax.servlet.http.HttpSessionEvent;

import javax.servlet.http.HttpSessionListener;

public class MyHttpSessionListener implements HttpSessionListener {

    @Override

    /* 必须调用一下session.getAttributeNames();才可以激活这个事件； */

    public void sessionCreated(HttpSessionEvent arg0) {

        System.out.println("com.stono.servlet.listeners.MyHttpSessionListener.sessionCreated(HttpSessionEvent)");

    }

    @Override

    /* 调用session.invalidate()的时候激活这个事件； */

    public void sessionDestroyed(HttpSessionEvent arg0) {

        System.out.println("com.stono.servlet.listeners.MyHttpSessionListener.sessionDestroyed(HttpSessionEvent)");

    }

}

package com.stono.servlet.listeners;

import javax.servlet.ServletContextAttributeEvent;

import javax.servlet.ServletContextAttributeListener;

public class MyServletContextAttributeListener implements ServletContextAttributeListener {

    @Override

    /* 进行context.setAttribute的时候调用 */

    public void attributeAdded(ServletContextAttributeEvent arg0) {

        System.out.println("com.stono.servlet.listeners.MyServletContextAttributeListener.attributeAdded(ServletContextAttributeEvent)");

        String name = arg0.getName();

        Object value = arg0.getValue();

        System.out.println("name=" + name + ";value=" + value);

    }

    @Override

    /* 进行context.removeAttribute的时候调用 */

    public void attributeRemoved(ServletContextAttributeEvent arg0) {

        System.out.println("com.stono.servlet.listeners.MyServletContextAttributeListener.attributeRemoved(ServletContextAttributeEvent)");

        String name = arg0.getName();

        Object value = arg0.getValue();

        System.out.println("name=" + name + ";value=" + value);

    }

    @Override

    /* 不知何时调用? */

    public void attributeReplaced(ServletContextAttributeEvent arg0) {

        System.out.println("com.stono.servlet.listeners.MyServletContextAttributeListener.attributeReplaced(ServletContextAttributeEvent)");

    }

}

package com.stono.servlet.listeners;

import javax.servlet.ServletContextEvent;

import javax.servlet.ServletContextListener;

public class MyServletContextListener implements ServletContextListener {

    @Override

    /* tomcat自动重新Reload Context的时候会调用； */

    public void contextDestroyed(ServletContextEvent arg0) {

        String x = "com.stono.servlet.listeners.MyServletContextListener.contextDestroyed(javax.servlet.ServletContextEvent)";

        System.out.println(x);

    }

    @Override

    /* Context初始化的时候会调用； */

    public void contextInitialized(ServletContextEvent arg0) {

        String x = "com.stono.servlet.listeners.MyServletContextListener.contextInitialized(javax.servlet.ServletContextEvent)";

        System.out.println(x);

    }

}

package com.stono.servlet.listeners;

import javax.servlet.ServletRequestAttributeEvent;

import javax.servlet.ServletRequestAttributeListener;

public class MyServletRequestAttributeListener implements ServletRequestAttributeListener {

    @Override

    /* 在request.setAttribute()方法调用的时候触发； */

    public void attributeAdded(ServletRequestAttributeEvent arg0) {

        System.out.println("com.stono.servlet.listeners.MyServletRequestAttributeListener.attributeAdded(ServletRequestAttributeEvent)");

        String name = arg0.getName();

        Object value = arg0.getValue();

        System.out.println("name:" + name + ";value:" + value);

    }

    @Override

    /* 在request.removeAttribute()的时候触发； */

    public void attributeRemoved(ServletRequestAttributeEvent arg0) {

        System.out.println("com.stono.servlet.listeners.MyServletRequestAttributeListener.attributeRemoved(ServletRequestAttributeEvent)");

        String name = arg0.getName();

        Object value = arg0.getValue();

        System.out.println("name:" + name + ";value:" + value);

    }

    @Override

    /* 在第二次调用request.setAttribute()的时候触发此方法； */

    public void attributeReplaced(ServletRequestAttributeEvent arg0) {

        System.out.println("com.stono.servlet.listeners.MyServletRequestAttributeListener.attributeReplaced(ServletRequestAttributeEvent)");

        String name = arg0.getName();

        Object value = arg0.getValue();

        System.out.println("name:" + name + ";value:" + value);

    }

}

package com.stono.servlet.listeners;

import java.util.Enumeration;

import javax.servlet.ServletRequestEvent;

import javax.servlet.ServletRequestListener;

public class MyServletRequestListener implements ServletRequestListener {

    @Override

    /* 请求结束之后调用这个事件 */

    public void requestDestroyed(ServletRequestEvent arg0) {

        System.out.println("com.stono.servlet.listeners.MyServletRequestListener.requestDestroyed(ServletRequestEvent)");

    }

    @Override

    /* 请求到来的时候调用这个事件 */

    public void requestInitialized(ServletRequestEvent arg0) {

        System.out.println("com.stono.servlet.listeners.MyServletRequestListener.requestInitialized(ServletRequestEvent)");

        Enumeration<String> names = arg0.getServletRequest().getParameterNames();

        while(names.hasMoreElements()){

            System.out.println(names.nextElement());

        }

    }

}

Servlet：

package com.stono.servlet;

import java.io.IOException;

import java.io.PrintWriter;

import java.util.Enumeration;

import javax.servlet.ServletContext;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

import com.stono.servlet.listeners.MyHttpSessionActivationListener;

import com.stono.servlet.listeners.MyHttpSessionBindingListener;

public class TestServlet4 extends HttpServlet {

    private static final long serialVersionUID = 1L;

    @Override

    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        ServletContext context = req.getServletContext();

        Enumeration<String> names = getServletConfig().getInitParameterNames();

        Enumeration<String> names2 = context.getInitParameterNames();

        System.out.println("javax.servlet.ServletConfig.getInitParameterNames()");

        while (names.hasMoreElements()) {

            System.out.println(names.nextElement());

        }

        System.out.println("javax.servlet.ServletContext.getInitParameterNames()");

        while (names2.hasMoreElements()) {

            System.out.println(names2.nextElement());

        }

        context.setAttribute("contextSetAttributeFromSevlet4Name", "contextSetAttributeFromSevlet4Value");

        context.setAttribute("contextParamName", "contextSetAttributeFromSevlet4Value2");

        context.removeAttribute("contextParamName");

        HttpSession session = req.getSession();

        // session.getAttributeNames();

        session.setAttribute("sessionAttrInTestServlet4", "sessionAttrInTestServlet4");

        try {

            // Servlet中可以使用这样的方式进行sleep，一个Servlet只有一个实例，多个线程；

            Thread.sleep(3000);

        } catch (InterruptedException e) {

            e.printStackTrace();

        }

        session.setAttribute("sessionAttrInTestServlet4", "sessionAttrInTestServlet4_2");

        session.invalidate();

        try {

            Thread.sleep(4000);

        } catch (Exception e) {

            e.printStackTrace();

        }

        System.out.println("just before request.setAttribute");

        req.setAttribute("a", "a");

        System.out.println("just after request.setAttribute");

        try {

            Thread.sleep(2000);

        } catch (Exception e) {

            e.printStackTrace();

        }

        req.setAttribute("a", "a2");

        System.out.println("just after request.setAttribute second time");

        try {

            Thread.sleep(2000);

        } catch (Exception e) {

            e.printStackTrace();

        }

        req.removeAttribute("a");

        System.out.println("just after request.removeAttribute");

        session = req.getSession();

        MyHttpSessionBindingListener obj = new MyHttpSessionBindingListener();

        session.setAttribute("obj", obj);

        obj.setName("namename");

        obj.setValue("valuevalue");

        System.out.println("set session object second time");

        session.setAttribute("obj", obj);

        session.invalidate();

        System.out.println("MyHttpSessionActivationListener testing...");

        MyHttpSessionActivationListener activationListener = new MyHttpSessionActivationListener();

        session = req.getSession();

        session.setAttribute("activation", activationListener);

        PrintWriter writer = resp.getWriter();

        writer.println("this is from TestServlet4");

    }

}