🎃过滤器与监听器
目录
一、过滤器Filter
?作用：编码过滤和权限控制
?实现方式：继承类HttpServlet 或实现接口Filter
?配置方式：通过注解或web.xml中进行配置
?注意：web.xml中配置和注解配置里不要加“/"
1、编码过滤
案例演示：
EncodingFilter.java过滤器文件：》》》
//@WebServlet("/*")错误写法
@WebFilter(value = "*")//*代表所有
public class EncodingFilter implements Filter {
@Override
public void init(FilterConfig filterConfig) throws ServletException {
System.out.println("初始化..................");
}
@Override
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
// 强制类型转换
HttpServletRequest req=(HttpServletRequest) servletRequest;
HttpServletResponse resp=(HttpServletResponse) servletResponse;
//设置编码格式
req.setCharacterEncoding("utf-8");
resp.setContentType("text/html;charset=utf-8");
//放行
filterChain.doFilter(req,resp);
}
@Override
public void destroy() {
System.out.println("销毁................");
}
}
测试文件Servlet:>>>测试中文是否乱码
@WebServlet("/test1")
public class Servlet01 extends HttpServlet {
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String name=req.getParameter("name");
System.out.println(name);
resp.getWriter().println(name);
}
}
结果：》》》
2、权限控制
- 通过权限的控制，使得不登录无法访问其他页面以及后台信息，登录成功则转发至成功界面，否则重新转发至login.jsp登录界面。
权限控制文件PowerFilter.java:>>>
@WebFilter("*")
public class PowerFilter implements Filter {
@Override
public void init(FilterConfig filterConfig) throws ServletException {
System.out.println("初始化权限设置");
}
@Override
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
HttpServletRequest req=(HttpServletRequest) servletRequest;
HttpServletResponse resp=(HttpServletResponse) servletResponse;
//获取用户名和密码
String name=req.getParameter("uname");
String psw=req.getParameter("psw");
//判断
if(name!=null && psw!=null){
filterChain.doFilter(req,resp);
}
//获取当前uri
String uri=req.getRequestURI();
if(uri.contains("login.jsp")){
filterChain.doFilter(req,resp);
}
if(uri.contains("Login")){
filterChain.doFilter(req,resp);
}
if(uri.contains("test1")){
filterChain.doFilter(req,resp);
}
//统一拦截分配
req.getRequestDispatcher("login.jsp").forward(req,resp);
}
@Override
public void destroy() {
}
}
登录界面login.java>>>
@WebServlet("/login")
public class Login extends HttpServlet {
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String name=req.getParameter("uname");
String psw=req.getParameter("psw");
if("admin".equals(name)&& "admin".equals(psw)){
req.setAttribute("name",name);
req.setAttribute("psw",psw);
req.getRequestDispatcher("true.jsp").forward(req,resp);
}else{
req.getRequestDispatcher("login.jsp?msg=登录失败").forward(req,resp);
}
}
}
登录界面login.jsp>>>
<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>
<html>
<head>
<title>登录</title>
</head>
<body>
<h4>${param.msg}</h4>
<hr>
<form action="login" method="post">
用户名：<input type="text" name="uname">
密码：<input type="password" name="psw">
<input type="submit" value="登录">
</form>
</body>
</html>
测试结果:>>>
二、监听器
- web监听是Servlet的特俗类
案列演示：》》》监听在线人数
Linterner.java监听器：>>>
@WebListener
public class Listerner implements HttpSessionListener {
private Integer num=0;//引用数据类默认为空null
@Override
public void sessionCreated(HttpSessionEvent httpSessionEvent) {
num++; httpSessionEvent.getSession().getServletContext().setAttribute("num",num);
}
@Override
public void sessionDestroyed(HttpSessionEvent httpSessionEvent) {
num--;
httpSessionEvent.getSession().getServletContext().setAttribute("num",num);
}
}
在线显示页面：>>>
@WebServlet("/login")
public class Login extends HttpServlet {
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.setCharacterEncoding("utf-8");
resp.setContentType("text/html;charset=utf-8");
//获取key
String key= req.getParameter("key");
//判断
if(key!=null && "out".equals(key)){
req.getSession().invalidate();//销毁
return;
}
//获取最新的人数
Integer num=(Integer) req.getSession().getServletContext().getAttribute("num");
//打印出来
resp.getWriter().println("<h4>目前在线人数："+num+"</h4><a href='login?key=out'>退出</a>");
}
}
测试结果：
三、两种配置方式
1.方式一：注解
eg：很简单
@WebServlet("/login")
2.方式二：web.xml文件配置
<web-app>
<display-name>Archetype Created Web Application</display-name>
<!-- 配置filter-->
<filter>
<!-- 命名filter1-->
<filter-name>filter1</filter-name>
<!-- filter的class文件（全限定名）-->
<filter-class>EncodingFilter</filter-class>
</filter>
<!-- 映射-->
<filter-mapping>
<!-- 通过名字映射-->
<filter-name>filter1</filter-name>
<!-- 条件*所有的-->
<url-pattern>*</url-pattern>
</filter-mapping>
</web-app>