1. Filter(拦截器, 也叫过滤器)
- 作用:对客户端发出的请求进行拦截,处理后继续交给其他拦截器或服务器处理, 之后的服务端响应也同样。
- 相关接口:Filter
- 相关机制:
- 创建拦截器:先建一个实现Filter接口的类,再配置web.xml文件即可(在eclipse环境下)
package filter;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
public class MyFilter implements Filter {
@Override
public void destroy() {
// TODO Auto-generated method stub
}
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
// TODO Auto-generated method stub
System.out.println("拦截请求");
chain.doFilter(request, response);
System.out.println("拦截响应");
}
@Override
public void init(FilterConfig filterConfig) throws ServletException {
// TODO Auto-generated method stub
}
}
配置拦截器,在web.xml文件中加入以下代码
<filter>
<filter-name>填入名字(名字无所谓,与下面filter-name中的名字对应就行)</filter-name>
<filter-class>填入拦截器类(包名一起写)</filter-class>
</filter>
<filter-mapping>
<filter-name>填入同样的名字</filter-name>
<url-pattern>填入需要拦截的servlet的路径(比如:/servlet)<url-pattern>
</filter-mapping>
2.Listener(监听器)
Servlet监听器分为三大类
1、数据域对象创建和销毁监听器
2、数据域对象和属性变更监听器
3、绑定到 HttpSession 域中的某个对象的状态的事件监听器
2.1. 数据域对象创建和销毁监听器
- 作用:对数据域对象(ServletRequest,HttpSession,ServletContext)进行创建或销毁
- 相关接口: ServletRequestListener, HttpSessionListener, ServletContextListener
- 相关机制:
- 创建监听器:先建一个实现三个接口的类,再配置web.xml文件即可(在eclipse环境下)
package ContextSessionRequestListener;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
public class ContextSessionRequestListener implements ServletRequestListener, HttpSessionListener, ServletContextListener{
@Override
public void sessionCreated(HttpSessionEvent arg0) {
// TODO Auto-generated method stub
System.out.println("监听HttpSession对象,创建对象:"+arg0);
}
@Override
public void sessionDestroyed(HttpSessionEvent arg0) {
// TODO Auto-generated method stub
System.out.println("监听HttpSession对象,销毁对象:"+arg0);
}
@Override
public void requestDestroyed(ServletRequestEvent arg0) {
// TODO Auto-generated method stub
System.out.println("监听ServletRequest对象,销毁对象:"+arg0);
}
@Override
public void requestInitialized(ServletRequestEvent arg0) {
// TODO Auto-generated method stub
System.out.println("监听ServletRequest对象,创建对象:"+arg0);
}
@Override
public void contextDestroyed(ServletContextEvent arg0) {
// TODO Auto-generated method stub
System.out.println("监听ServletContext对象,销毁对象:"+arg0);
}
@Override
public void contextInitialized(ServletContextEvent arg0) {
// TODO Auto-generated method stub
System.out.println("监听ServletContext对象,创建对象:"+arg0);
}
}
配置拦截器,在web.xml文件中加入以下代码
<listener>
<listener-class>填入监听器类(包名一起写)</listener-class>
</listener>
2.2. 数据域对象和属性变更监听器
- 作用:监听数据域对象和属性发生增加,删除, 替换时的变化
attributeAdded 监听属性添加 —- 当数据范围对象没有该属性,第一次添加时调用执行
attributeRemoved 监听属性移除 —- 从一个数据范围对象删除一个已经存在属性执行
attributeReplaced 监听属性替换 —– 当一个数据范围已经存在一个属性,向数据范围添加相同名称属性触发替换方法 - 相关接口:ServletContextAttributeListener,HttpSessionAttributeListener,ServletRequestAttributeListener
- 相关机制:
- 创建监听器:建一个实现三个接口的类,在设置需要监听的属性即可(在eclipse环境下).
package ContextSessionRequestListener;
import javax.servlet.ServletContextAttributeEvent;
import javax.servlet.ServletContextAttributeListener;
import javax.servlet.ServletRequestAttributeEvent;
import javax.servlet.ServletRequestAttributeListener;
import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;
public class AttributeListener implements ServletContextAttributeListener,HttpSessionAttributeListener,ServletRequestAttributeListener {
String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public void attributeAdded(ServletRequestAttributeEvent arg0) {
// TODO Auto-generated method stub
System.out.println("在request数据域中添加属性");
}
@Override
public void attributeRemoved(ServletRequestAttributeEvent arg0) {
// TODO Auto-generated method stub
System.out.println("在request数据域中移除属性");
}
@Override
public void attributeReplaced(ServletRequestAttributeEvent arg0) {
// TODO Auto-generated method stub
System.out.println("在request数据域中替换属性");
}
@Override
public void attributeAdded(HttpSessionBindingEvent arg0) {
// TODO Auto-generated method stub
System.out.println("在Session数据域中添加属性");
}
@Override
public void attributeRemoved(HttpSessionBindingEvent arg0) {
// TODO Auto-generated method stub
System.out.println("在Session数据域中移除属性");
}
@Override
public void attributeReplaced(HttpSessionBindingEvent arg0) {
// TODO Auto-generated method stub
System.out.println("在Session数据域中替换属性");
}
@Override
public void attributeAdded(ServletContextAttributeEvent scab) {
// TODO Auto-generated method stub
System.out.println("在Context数据域中添加属性");
}
@Override
public void attributeRemoved(ServletContextAttributeEvent scab) {
// TODO Auto-generated method stub
System.out.println("在Context数据域中移除属性");
}
@Override
public void attributeReplaced(ServletContextAttributeEvent scab) {
// TODO Auto-generated method stub
System.out.println("在Context数据域中替换属性");
}
}
2.3. 绑定到 HttpSession 域中的某个对象的状态的事件监听器
- 作用:当将对象绑定或解绑到HttpSession域中或者当将对象发生钝化或活化时(即序列化或反序列化),发生监听事件。
- 相关接口:HttpSessionBindingListener(绑定/解绑),HttpSessionActivationListener, Serializable(钝化或活化).
- 相关机制:
关于绑定/解绑
关于钝化/活化 - 创建监听器:建一个实现接口的类,在设置需要监听的属性即可(在eclipse环境下).
package ContextSessionRequestListener;
import java.io.Serializable;
import javax.servlet.http.HttpSessionActivationListener;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionBindingListener;
import javax.servlet.http.HttpSessionEvent;
public class SessionListener implements HttpSessionBindingListener,HttpSessionActivationListener,Serializable{
String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public void valueBound(HttpSessionBindingEvent arg0) {
// TODO Auto-generated method stub
System.out.println("绑定HttpSession");
}
@Override
public void valueUnbound(HttpSessionBindingEvent arg0) {
// TODO Auto-generated method stub
System.out.println("解绑HttpSession");
}
@Override
public void sessionDidActivate(HttpSessionEvent arg0) {
// TODO Auto-generated method stub
System.out.println("发生钝化,存入文件中");
}
@Override
public void sessionWillPassivate(HttpSessionEvent arg0) {
// TODO Auto-generated method stub
System.out.println("发生活化, 文件读取中");
}
}