注意：

1.注解后面不加分号" ；"

2.所示例的注解只是基本用法，它还有其它参数，如需要需百度下用法





路径匹配格式解释：

1.绝对文件：/test.jsp

2.相对文件：/test/*

3.类型文件：*.jsp

4.任意文件：/*



Servlet：(用于接收请求处理类：get,post等)

@WebServlet("/*") //正则，符号"/*"表示所有请求，也可以指定请求路径
@WebServlet("/url") //单页
@WebServlet(value={"/url1","/url2"}) //多页

示例：

文件名：Hello.java

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/hello") //显示声明，前端访问地址，如：localhost/hello
public class Hello extends HttpServlet { //这个类名经测试，跟前端访问无关，根据类的作用取,但必须跟文件名同名
	private static final long serialVersionUID = 1L;
 
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
	
	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		
	}

}





Filter：(过滤器，在请求类之前，先过滤信息，决定是否放行，或处理)

@WebFilter("/*") //正则，符号"/*"表示所有请求，也可以指定请求路径
@WebFilter("/url") //单页
@WebFilter(value={"/url1","url2"}) //多页

参数：拦截类型
@WebFilter(
	value = ｛"/*"｝,
	dispatcherTypes = {
		DispatcherType.REQUEST,	//请求，默认
		DispatcherType.INCLUDE,	//包含
		DispatcherType.FORWARD,	//转发
		DispatcherType.ASYNC,	//异步
		DispatcherType.ERROR})	//错误
	



示例：

文件名：HelloFilter.java

import javax.servlet.Filter;  
import javax.servlet.FilterChain;  
import javax.servlet.FilterConfig;  
import javax.servlet.ServletException;  
import javax.servlet.ServletRequest;  
import javax.servlet.ServletResponse;
import javax.servlet.DispatcherType;  
import javax.servlet.annotation.WebFilter;  
import java.io.IOException;    


@WebFilter("/*")
public class HelloFilter implements Filter {      
	
	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
		//初始化，服务器启动时执行
	}        

	@Override      
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
		//注意：ServletRequest需要转化类
		HttpServletRequest req = (HttpServletRequest)request;
		HttpServletResponse res = (HttpServletResponse)response
		
		//客户端请求 @WebFilter("/*") 指定路径时拦截
		//这里处理请求参数
		
		chain.doFilter(request, response); //没问题，执行正常请求路径类
	}       

	@Override      
	public void destroy() {
		// 销毁，服务器关闭时执行
	}  
}







Listener：（监听器，用于监听下列类事件）

ServletContext：
ServletContextListener
	初始化时：void contextInitialized(ServletContextEvent event)
   销毁时：void contextDestroyed(ServletContextEvent event)
ServletContextAttributeListener
	添加属性时：void attributeAdded(ServletContextAttributeEvent event)
	替换属性时：void attributeReplaced(ServletContextAttributeEvent event)
	删除属性时：void attributeRemoved(ServletContextAttributeEvent event)


HttpSession：
HttpSessionListener
	初始化时：void sessionCreated(HttpSessionEvent event)
	销毁时：void sessionDestroyed(HttpSessionEvent event)
HttpSessioniAttributeListener
	添加属性时：void attributeAdded(HttpSessioniAttributeEvent event)
	替换属性时：void attributeReplaced(HttpSessioniAttributeEvent event)
	删除属性时：void attributeRemoved(HttpSessioniAttributeEvent event)

ServletRequest：
ServletRequestListener
	初始化时：void requestInitialized(ServletRequestEvent event)          
	销毁时：	void requestDestroyed(ServletRequestEvent event)
ServletRequestAttributeListener
	添加属性时： void attributeAdded(ServletRequestAttributeEvent event)
	替换属性时： void attributeReplaced(ServletRequestAttributeEvent event)
	删除属性时： void attributeRemoved(ServletRequestAttributeEvent event)


HttpSessionBinding：
HttpSessionBindingListener
HttpSessionActivationListener


示例：监听ServletContextListener

package listener;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;  
import javax.servlet.ServletContextListener;  
import javax.servlet.annotation.WebListener;    

@WebListener    //监听注解   
public class myServletContextListener implements ServletContextListener {         

	@Override      
	public void contextInitialized(ServletContextEvent event) {
		// 监听到了对象的创建
		
		// 获取对象
		ServletContext servletContext = servletContextEvent.getServletContext();
		System.out.println(servletContext);
	}

	@Override
	public void contextDestroyed(ServletContextEvent event) {
		//监听到了对象的销毁
	}  
}