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[Java教程]JSP之应用Servlet过滤器进行身份验证


1、Servlet过滤器的作用描述
(1)在HttpServletRequest到达Servlet 之前,拦截客户的HttpServletRequest。
根据需要检查HttpServletRequest,也可以修改HttpServletRequest头和数据。
(2)在HttpServletResponse 到达客户端之前,拦截HttpServletResponse。
根据需要检查HttpServletResponse,可以修改HttpServletResponse头和数据。

2、应用Servlet过滤器进行身份验证

假设网站根目录下的login1.htm、longin1.jsp用于用户登录,而chap08目录下的文件需要用户登录后才能访问。

(1)编写Servlet过滤器

@WebFilter("/FilterStation")
public class FilterStation extends HttpServlet implements Filter {
private FilterConfig filterConfig;
public FilterStation() {
super();
}

public void destroy() {
}

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
HttpSession session=((HttpServletRequest)request).getSession();
response.setCharacterEncoding("gb2312");
if(session.getAttribute("me")==null){
PrintWriter out=response.getWriter();
out.print("<script>alert('请登录!');location.href='../login1.htm'</script>");
}
else{
// pass the request along the filter chain
chain.doFilter(request, response);
}
}

public void init(FilterConfig fConfig) throws ServletException {
// TODO Auto-generated method stub
this.filterConfig=fConfig;
}

}

(2)配置web.

<filter>
<filter-name>filterstation</filter-name>
<filter-class>zhou.FilterStation</filter-class>
</filter>

<filter-mapping>
<filter-name>filterstation</filter-name>
<url-pattern>/chap08/*</url-pattern>
</filter-mapping>

(3)login1.htm代码

<html>
<head>
<title>用户登录</title>
</head>
<body>
<form method="POST" action="login1.jsp">
<p>用户名:<input type="text" name="user" size="18"></p>
<p>密码:<input type="text" name="pass" size="20"></p>
<p><input type="submit" value="提交" name="ok">
<input type="reset" value="重置" name="cancel"></p>
</form>
</body>
</html>

(4)login1.jsp代码

<%@ page contentType="text/html;charset=GB2312" %>
<html>
<head><title>Session 应用演示</title></head>
<%
if (request.getParameter("user")!=null && request.getParameter("pass")!=null)
{
String strName=request.getParameter("user");
String strPass=request.getParameter("pass");
if (strName.equals("admin") && strPass.equals("admin"))
{
session.setAttribute("login","OK");
session.setAttribute("me",strName);
response.sendRedirect("chap08/welcome.jsp");

}
else
{
out.print("<script>alert('用户名或密码错误');location.href='login1.htm'</script>");
}
}
%>
</html>