防止用户直接访问url

这是个过滤器的内容，

[java]
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest req = (HttpServletRequest) request;
HttpServletResponse resp = (HttpServletResponse) response;
String conString = "";
conString = req.getHeader("REFERER");//获取父url--如果不是直接输入的话就是先前的访问过来的页面，要是用户输入了，这个父url是不存在的
if("".equals(conString) || null==conString){ //判断如果上一个目录为空的话，说明是用户直接输入url访问的
String servletPath = req.getServletPath();//当前请求url，去掉几个可以直接访问的页面
if(servletPath.contains("index.jsp") || servletPath.contains("admin/login.jsp")){ //跳过index.jsp和登陆Login.jsp
chain.doFilter(request, response);
} else {
resp.sendRedirect("/ejuornal/index.jsp");//跳回首页
}
} else {
chain.doFilter(request, response);
}
}

public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest req = (HttpServletRequest) request;
HttpServletResponse resp = (HttpServletResponse) response;
String conString = "";
conString = req.getHeader("REFERER");//获取父url--如果不是直接输入的话就是先前的访问过来的页面，要是用户输入了，这个父url是不存在的
if("".equals(conString) || null==conString){ //判断如果上一个目录为空的话，说明是用户直接输入url访问的
String servletPath = req.getServletPath();//当前请求url，去掉几个可以直接访问的页面
if(servletPath.contains("index.jsp") || servletPath.contains("admin/login.jsp")){ //跳过index.jsp和登陆Login.jsp
chain.doFilter(request, response);
} else {
resp.sendRedirect("/ejuornal/index.jsp");//跳回首页
}
} else {
chain.doFilter(request, response);
}
}下面是过滤器的配置文件

[html]
< ?xml version="1.0" encoding="UTF-8"?>
< web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5">
<display-name></display-name>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
<filter>
<filter-name>FilterPages</filter-name>
<filter-class>com.ejuornal.filter.FilterPages</filter-class>
</filter>
<filter-mapping>
<filter-name>FilterPages</filter-name>
<url-pattern>*.jsp</url-pattern>
</filter-mapping>
< /web-app>

<?xml version="1.0" encoding="UTF-8"?>
< web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5">
<display-name></display-name>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
<filter>
<filter-name>FilterPages</filter-name>
<filter-class>com.ejuornal.filter.FilterPages</filter-class>
</filter>
<filter-mapping>
<filter-name>FilterPages</filter-name>
<url-pattern>*.jsp</url-pattern>
</filter-mapping>
< /web-app>这时候再去直接输入url时就会在跳回首页。

但是有两个需要注意的问题，过滤器中的chain.doFilter(request, response);的使用------------错误如下：

[html]
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest req = (HttpServletRequest) request;
HttpServletResponse resp = (HttpServletResponse) response;
String conString = "";
conString = req.getHeader("REFERER");//获取父url
if("".equals(conString) || null==conString){
String servletPath = req.getServletPath();//当前请求url
if(servletPath.contains("index.jsp") || servletPath.contains("admin/login.jsp")){
chain.doFilter(request, response);
}else {
resp.sendRedirect("/ejuornal/index.jsp");
}
}
<SPAN style="COLOR: #ff0000">chain.doFilter(request, response);</SPAN>
}

public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest req = (HttpServletRequest) request;
HttpServletResponse resp = (HttpServletResponse) response;
String conString = "";
conString = req.getHeader("REFERER");//获取父url
if("".equals(conString) || null==conString){
String servletPath = req.getServletPath();//当前请求url
if(servletPath.contains("index.jsp") || servletPath.contains("admin/login.jsp")){
chain.doFilter(request, response);
}else {
resp.sendRedirect("/ejuornal/index.jsp");
}
}
chain.doFilter(request, response);
}
如果这样放的话会如下图的效果：

有两个页面重合在一起，原因是：有两个chain.doFilter(request, response);的执行导致的。

也就是说咩执行一次chain.doFilter(request, response);就是一个请求的执行。