filter(过滤器)和listener(监听器)的生命周期
老实说
生命周期要是说成作用的时间范围我会理解的更好
filter
package com.javaweb.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;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public abstract class HttpFilter implements Filter {
private FilterConfig filterConfig;
@Override
public void destroy() {
}
@Override
public void doFilter(ServletRequest servletrequest, ServletResponse servletresponse, FilterChain filterchain)
throws IOException, ServletException {
HttpServletRequest request=(HttpServletRequest)servletrequest;
HttpServletResponse response=(HttpServletResponse)servletresponse;
doFilter(request,response,filterchain);
}
public abstract void doFilter(HttpServletRequest request, HttpServletResponse response, FilterChain filterchain)
throws IOException, ServletException ;
@Override
public void init(FilterConfig filterconfig) throws ServletException {
this.filterConfig=filterconfig;
init();
}
public FilterConfig getFilterConfig() {
return filterConfig;
}
public void init() throws ServletException{
}
}
package com.javaweb.login;
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;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class LoginFilter extends HttpFilter {
public void destroy() {
// TODO Auto-generated method stub
System.out.println("离开LoginFilter");
}
public void init() throws ServletException {
// TODO Auto-generated method stub
System.out.println("初始化LoginFilter 只会出现一次!");
}
public void doFilter(HttpServletRequest request, HttpServletResponse response, FilterChain filterchain)
throws IOException, ServletException {
System.out.println("进入LoginFilter");
filterchain.doFilter(request, response);//放行
System.out.println("离开LoginFilter");
}
}
listener
package com.javaweb.listener;
import javax.servlet.ServletRequestAttributeEvent;
import javax.servlet.ServletRequestAttributeListener;
import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;
public class MyHttpRequestListener implements ServletRequestListener,ServletRequestAttributeListener {
@Override
public void requestDestroyed(ServletRequestEvent servletrequestevent) {
System.out.println("requestDestroyed...");
}
@Override
public void requestInitialized(ServletRequestEvent servletrequestevent) {
System.out.println("requestInitialized...");
}
@Override
public void attributeAdded(ServletRequestAttributeEvent servletrequestattributeevent) {
// TODO Auto-generated method stub
}
@Override
public void attributeRemoved(ServletRequestAttributeEvent servletrequestattributeevent) {
// TODO Auto-generated method stub
}
@Override
public void attributeReplaced(ServletRequestAttributeEvent servletrequestattributeevent) {
// TODO Auto-generated method stub
}
}
servlet
package com.javaweb.login;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class LoginServlet extends HttpServlet {
private static final long serialVersionUID = -6820554522964310475L;
private String userName;
private String password;
public void init(){
userName=getServletConfig().getInitParameter("username");
password=getServletConfig().getInitParameter("password");
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String username=req.getParameter("username");
String pwd=req.getParameter("password");
if(username!=null && !"".equals(username) && pwd!=null && !"".equals(pwd)){
if(userName.equals(username) && password.equals(pwd)){
HttpSession session=req.getSession();
session.setAttribute("username", username);
session.setAttribute("password", pwd);
resp.sendRedirect(req.getContextPath()+"/login.jsp");
}else{
resp.sendRedirect(req.getContextPath()+"/index.jsp");
}
}
}
}
filiter在服务器第一次加载时就运行一次init
而监听器每一次request请求就会运行一次init
但在响应时
监听器先得到响应
过滤器后得到响应
(在实际中,是并发执行,只是过滤器慢一点)
过滤器的过滤顺序是按web.xml里
那个先注册哪个先过滤的