java中使用Filter控制用户登录权限具体实例
作者：
学jsp这么长时间，做的项目也有七八个了，可所有的项目都是用户登录就直接跳转到其拥有权限的页面，或者显示可访问页面的链接。使用这种方式来幼稚地控制访问权限。从来没有想过如果我没有登录，直接输入地址也可以直接访问用户的页面的。
在jsp中权限的控制是通过Filter过滤器来实现的，所有的开发框架中都集成有Filter，如果不适用开发框架则有如下实现方法：
LoginFilter.java
public class LoginFilter implements Filter {
private String permitUrls[] = null;
private String gotoUrl = null;
public void destroy() {
// TODO Auto-generated method stub
permitUrls = null;
gotoUrl = null;
}
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
// TODO Auto-generated method stub
HttpServletRequest res=(HttpServletRequest) request;
HttpServletResponse resp=(HttpServletResponse)response;
if(!isPermitUrl(request)){
if(filterCurrUrl(request)){
System.out.println("--->请登录");
resp.sendRedirect(res.getContextPath()+gotoUrl);
return;
}
}
System.out.println("--->允许访问");
chain.doFilter(request, response);
}
public boolean filterCurrUrl(ServletRequest request){
boolean filter=false;
HttpServletRequest res=(HttpServletRequest) request;
User user =(User) res.getSession().getAttribute("user");
if(null==user)
filter=true;
return filter;
}
public boolean isPermitUrl(ServletRequest request) {
boolean isPermit = false;
String currentUrl = currentUrl(request);
if (permitUrls != null && permitUrls.length > 0) {
for (int i = 0; i < permitUrls.length; i++) {
if (permitUrls[i].equals(currentUrl)) {
isPermit = true;
break;
}
}
}
return isPermit;
}
//请求地址
public String currentUrl(ServletRequest request) {
HttpServletRequest res = (HttpServletRequest) request;
String task = request.getParameter("task");
String path = res.getContextPath();
String uri = res.getRequestURI();
if (task != null) {// uri格式 xx/ser
uri = uri.substring(path.length(), uri.length()) + "?" + "task="
+ task;
} else {
uri = uri.substring(path.length(), uri.length());
}
System.out.println("当前请求地址:" + uri);
return uri;
}
public void init(FilterConfig filterConfig) throws ServletException {
// TODO Auto-generated method stub
String permitUrls = filterConfig.getInitParameter("permitUrls");
String gotoUrl = filterConfig.getInitParameter("gotoUrl");
this.gotoUrl = gotoUrl;
if (permitUrls != null && permitUrls.length() > 0) {
this.permitUrls = permitUrls.split(",");
}
}
}
Web.xml
<filter>
<filter-name>loginFilter</filter-name>
<filter-class>filter.LoginFilter</filter-class>
<init-param>
<param-name>ignore</param-name>
<param-value>false</param-value>
</init-param>
<init-param>
<param-name>permitUrls</param-name>
<param-value>/,/servlet/Loginservlet?task=login,/public.jsp,/login.jsp</param-value>
</init-param>
<init-param>
<param-name>gotoUrl</param-name>
<param-value>/login.jsp</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>loginFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
这短代码主要实现了用户登录的过滤，权限过滤原理相同。只需要把判断用户是否登录换成是否有权限就可以了！