1. 我们可以在web.xml中配置filter来对指定的URL进行过滤，进行一些特殊操作如权限验证等。

SessionFilter

com.xm.chris.SessionFilter

SessionFilter

/resources/*

public class SessionFilter implementsFilter {private static final String CONTENT_TYPE = "text/html; charset=UTF-8";private FilterConfig _filterConfig = null;public void init(FilterConfig filterConfig) throwsServletException {

_filterConfig=filterConfig;

}public voiddestroy() {

_filterConfig= null;

}public voiddoFilter(ServletRequest request, ServletResponse response,

FilterChain chain)throwsIOException,

ServletException {

HttpServletRequest rq=(HttpServletRequest) request;

HttpSession httpSession=rq.getSession();

Long userId= (Long) httpSession.getAttribute("userId");if (userId == null) {

response.setContentType(CONTENT_TYPE);

PrintWriter out=response.getWriter();

out.println("");

out.println("

Error");

out.println("

");

out.println("

错误.

");

out.println("");

out.close();

}else{

chain.doFilter(request, response);

}

}

}

这时所有请求了contextPath/resources/*路径的request都会被SessionFilter验证是否登录。

2. 但是我们有一些特定的url不想验证登录，想要直接能够访问，怎么办呢？

这时可以配置一个参数，告诉Filter哪些url不想验证。

SecurityFilter

com.oracle.ccsc.jcs.sx.filter.SecurityFilter

excludedPages

/xm/portal/notice

然后在Filter中就可以根据参数判断是否需要过滤。

public class SecurityFilter implementsFilter {private static final String CONTENT_TYPE = "text/html; charset=UTF-8";private FilterConfig _filterConfig = null;privateString excludedPages;privateString[] excludedPageArray;public void init(FilterConfig filterConfig) throwsServletException {

_filterConfig=filterConfig;

excludedPages= filterConfig.getInitParameter("excludedPages");if(StringUtils.isNotEmpty(excludedPages)) {

excludedPageArray= excludedPages.split(",");

}

}public voiddestroy() {

_filterConfig= null;

}public voiddoFilter(ServletRequest request, ServletResponse response,

FilterChain chain)throwsIOException,

ServletException {

HttpServletRequest rq=(HttpServletRequest) request;boolean isExcludedPage = false;for (String page : excludedPageArray) { //判断是否在过滤url之外if(rq.getPathInfo().equals(page)) {

isExcludedPage= true;break;

}

}if (isExcludedPage) { //在过滤url之外

chain.doFilter(request, response);

}else { //不在过滤url之外，判断登录

HttpSession httpSession =rq.getSession();

Long userId= (Long) httpSession.getAttribute("userId");if (userId == null) {

response.setContentType(CONTENT_TYPE);

PrintWriter out=response.getWriter();

out.println("");

out.println("

Error");

out.println("

");

out.println("

错误.

");

out.println("");

out.close();

}else{

chain.doFilter(request, response);

}

}

}

}

3. 关于用Servlet获取URL地址。

在HttpServletRequest类里，有以下六个取URL的函数

getContextPath 取得项目名

getServletPath 取得Servlet名

getPathInfo 取得Servlet后的URL名，不包括URL参数

getRequestURL 取得不包括参数的URL

getRequestURI 取得不包括参数的URI，即去掉协议和服务器名的URL

具体如下图：

相对应的函数的值如下：

getContextPath：/ServletTest

getServletPath：/main

getPathInfo：/index/testpage/test

getRequestURL：http://localhost:8080/ServletTest/main/index/testpage/test

getRequestURI：/ServletTest/main/index/testpage/test