講授Javax.servlet.Filter使用總結例子
阿新 • • 發佈：2019-02-16
今天給同學們講解SpringMVC，很多同學們反應對Servlet過濾器、監聽了解甚少，所以現場給大家分享了一個小例子，然大家學習掌握一下；
1、登入頁面
<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>login pages</title> </head> <body> <form action="login" method="post"> <input name="userName" type="text" /> <input name="userPwd" type="password" /> <input type="submit" value="submit" /> </form> </body> </html>
2、請求Servlet
3、登入成功頁面package springdemo01; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class LoginServlet extends HttpServlet { @Override public void init() throws ServletException { // TODO Auto-generated method stub super.init(); } /** * 當view發生請求時，進入該Servlet，然後呼叫Dao進行持久化使用者.... */ @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { resp.setCharacterEncoding("utf-8"); String userName = req.getParameter("userName"); String userPwd = req.getParameter("userPwd"); if("huayongsheng".equals(userName) && "123456".equals(userPwd)){ resp.sendRedirect("main.jsp"); req.getSession().setAttribute("userName", userName); }else{ resp.getWriter().print("<script>alert('登入失敗了');window.history.back(-1);</script>"); } } @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doPost(req, resp); } }
<%@ page language="java" contentType="text/html; charset=utf-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title>歡迎您的登入</title> </head> <body>歡迎您的登入... </body> </html>
4、web.xml配置
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<servlet>
<servlet-name>LoadServlet</servlet-name>
<servlet-class>springdemo01.LoadServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>LoadServlet</servlet-name>
<url-pattern>/load</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>LoginServlet</servlet-name>
<servlet-class>springdemo01.LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>LoginServlet</servlet-name>
<url-pattern>/login</url-pattern>
</servlet-mapping>
<filter>
<filter-name>loginFilter</filter-name>
<filter-class>springdemo01.LoginFilter</filter-class>
<init-param>
<param-name>excludedPages</param-name>
<param-value>/login,login.jsp</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>loginFilter</filter-name>
<!-- 過濾所有的請求 -->
<url-pattern>/*</url-pattern>
</filter-mapping>
<welcome-file-list>
<welcome-file>login.jsp</welcome-file>
</welcome-file-list>
</web-app>
package springdemo01;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
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.HttpSession;
public class LoginFilter implements Filter {
private String excludedPagesString;
private List<String> excludedPagesList;
public void init(FilterConfig filterConfig) throws ServletException {
// TODO Auto-generated method stub
System.out.println("過濾器====init");
excludedPagesString = filterConfig.getInitParameter("excludedPages");
if(!"".equals(excludedPagesString)){
String[] arr = excludedPagesString.split(",");
excludedPagesList = Arrays.asList(arr);
}
}
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
// TODO Auto-generated method stub
response.setCharacterEncoding("utf-8");
System.out.println("過濾器====doFilter");
//請求的Url路徑
boolean flag = false;//是否在排除過濾的url當中
String requestUrl = ((HttpServletRequest) request).getRequestURI();
for (String string : excludedPagesList) {
if(requestUrl.contains(string)){
flag = true;
break;
}
}
HttpSession session = ((HttpServletRequest)request).getSession();
if(flag ||( session.getAttribute("userName") != null && !"".equals(session.getAttribute("userName")))){
chain.doFilter(request,response);//放行。讓其走到下個鏈或目標資源中
}else{
response.getWriter().print("<script>alert('過濾器過濾了,無許可權訪問');window.locaiton.href='login.jsp';</script>");
}
}
public void destroy() {
// TODO Auto-generated method stub
System.out.println("過濾器====destroy");
}
}
6、Filter執行流程如下圖
OK，將例子放入eclipse即可執行；
1、當部署專案之後，啟動Tomcat；此時控制檯列印：“過濾器====init”；說明在啟動Tomcat容器時，過濾器已經執行init方法；
2、當開啟http://127.0.0.1/springdemo01/login.jsp時，錄入使用者名稱huayongsheng、密碼123456；可以正常登入；
此時已經控制檯列印""過濾器====doFilter"；因為在web.xml配置了
<filter>
<filter-name>loginFilter</filter-name>
<filter-class>springdemo01.LoginFilter</filter-class>
<init-param>
<param-name>excludedPages</param-name>
<param-value>/login,login.jsp</param-value><!--排除此處的請求，允許你訪問的jsp與servlet；否則無法顯示登入介面>
</init-param>
</filter>
<filter-mapping>
<filter-name>loginFilter</filter-name>
<!-- 過濾所有的請求 -->
<url-pattern>/*</url-pattern>
</filter-mapping>