Listener

Listener监听器（观察者设计模式）
1.监听域对象产生和销毁
2.监听域对象存值、修改、删除

package listener;
import javax.servlet.ServletRequestAttributeEvent;
import javax.servlet.ServletRequestAttributeListener;
import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;
public class TestRequestListener implements ServletRequestListener, ServletRequestAttributeListener {
    @Override
    public void requestDestroyed(ServletRequestEvent sre) {
        System.out.println("request对象销毁了");
    }
    @Override
    public void requestInitialized(ServletRequestEvent sre) {
        System.out.println("request对象创建了");
    }
    @Override
    public void attributeAdded(ServletRequestAttributeEvent srae) {
        System.out.println("request对象添加了数据");
    }
    @Override
    public void attributeRemoved(ServletRequestAttributeEvent srae) {
        System.out.println("request对象删除了数据");
    }
    @Override
    public void attributeReplaced(ServletRequestAttributeEvent srae) {
        System.out.println("request对象修改了数据");
    }
}

<listener>
        <listener-class>listener.TestRequestListener</listener-class>
    </listener>

<listener>
        <listener-class>listener.TestSessionListener</listener-class>
    </listener>

package listener;

import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

public class TestSessionListener implements HttpSessionListener, HttpSessionAttributeListener {
    @Override
    public void sessionCreated(HttpSessionEvent se) {
        System.out.println("session对象创建了");
    }

    @Override
    public void sessionDestroyed(HttpSessionEvent se) {
        System.out.println("session对象销毁了");
    }

    @Override
    public void attributeAdded(HttpSessionBindingEvent se) {
        System.out.println("session对象添加了值");
    }

    @Override
    public void attributeRemoved(HttpSessionBindingEvent se) {
        System.out.println("session对象删除了值");
    }

    @Override
    public void attributeReplaced(HttpSessionBindingEvent se) {
        System.out.println("session对象修改了值");
    }
}

其他和request类似，但让sessiom对象销毁的方法是session.invalidate();
setMaxInactiveInterval()方法设置了最大活跃时间，不活跃不等于销毁