Java web过滤器验证登录（避免未经登录进入主页）

今天用ssh2写了个简单的系统，发现了一个问题，我这系统必须先登录成功才能进入主页，但我在浏览器里直接输入主页地址，发现也能进入，这个肯定不好，毫无安全性可言，后经查资料发现需要登录过滤器，就试了下，发现果然可以避免未经登录即可进入主页的危险，下面是我整理出的详细步骤：

1.首先写一个权限过滤filter类,实现Filter接口

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 implements Filter {

@Override
public void init(FilterConfig filterConfig) throws ServletException {
// TODO Auto-generated method stub

}

@Override
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
// 获得在下面代码中要用的request,response,session对象
HttpServletRequest servletRequest = (HttpServletRequest) request;
HttpServletResponse servletResponse = (HttpServletResponse) response;
HttpSession session = servletRequest.getSession();

// 获得用户请求的URI
String path = servletRequest.getRequestURI();
//System.out.println(path);

// 从session里取员工工号信息
String empId = (String) session.getAttribute("empId");

/*创建类Constants.java，里面写的是无需过滤的页面
for (int i = 0; i < Constants.NoFilter_Pages.length; i++) {

if (path.indexOf(Constants.NoFilter_Pages[i]) > -1) {
chain.doFilter(servletRequest, servletResponse);
return;
}
}*/

// 登陆页面无需过滤
if(path.indexOf("/login.jsp") > -1) {
chain.doFilter(servletRequest, servletResponse);
return;
}

// 判断如果没有取到员工信息,就跳转到登陆页面
if (empId == null || "".equals(empId)) {
// 跳转到登陆页面
servletResponse.sendRedirect("/JingXing_OA/login.jsp");
} else {
// 已经登陆,继续此次请求
chain.doFilter(request, response);
}

}

@Override
public void destroy() {
// TODO Auto-generated method stub

}
}2.然后在web.xml里配置需要登陆权限验证的JSP文件:
     a.如果是某个具体的JSP文件(如a.jsp)需要登陆验证
<!-- 配置登陆过滤器 -->
<filter>
<filter-name>login</filter-name>
<filter-class>com.jingxing.oa.filter.LoginFilter</filter-class>
</filter>

<filter-mapping>
<filter-name>login</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping> 
  b.如果是某一个目录(如a/目录)整个目录下的文件都需要登陆验证:

<!-- 配置登陆过滤器 -->
<filter>
<filter-name>login</filter-name>
<filter-class>com.jingxing.oa.filter.LoginFilter</filter-class>
</filter>

<filter-mapping>
<filter-name>login</filter-name>
<url-pattern>/a/*</url-pattern>
</filter-mapping>