Java Servlet常用到的几个Filter

Java Servlet常用到的几个Filter

一、使浏览器不缓存页面的过滤器
Java代码 
public class ForceNoCacheFilter implements Filter { 
 
    public void init(FilterConfig filterConfig) throws ServletException { 
     
    } 
     
    public void doFilter(ServletRequest request, ServletResponse response, 
            FilterChain filterChain) throws IOException, ServletException { 
        ((HttpServletResponse) response).setHeader("Cache-Control", "no-cache"); 
        ((HttpServletResponse) response).setHeader("Pragma", "no-cache"); 
        ((HttpServletResponse) response).setDateHeader("Expires", -1); 
        filterChain.doFilter(request, response); 
    } 
 
    public void destroy() { 
     
    } 
 
} 
二、检测用户是否登陆的过滤器
Java代码 
/**
* 用于检测用户是否登陆的过滤器，如果未登录，则重定向到指的登录页面 配置参数 checkSessionKey 需检查的在 Session 中保存的关键字
* redirectURL 如果用户未登录，则重定向到指定的页面，URL不包括 ContextPath notCheckURLList
* 不做检查的URL列表，以分号分开，并且 URL 中不包括 ContextPath
*/ 
public class CheckLoginFilter implements Filter { 
    protected FilterConfig filterConfig = null; 
    private String redirectURL = null; 
    private List notCheckURLList = new ArrayList(); 
    private String sessionKey = null; 
    public void init(FilterConfig filterConfig) throws ServletException { 
        this.filterConfig = filterConfig; 
        redirectURL = filterConfig.getInitParameter("redirectURL"); 
        sessionKey = filterConfig.getInitParameter("checkSessionKey"); 
 
        String notCheckURLListStr = filterConfig 
                .getInitParameter("notCheckURLList"); 
 
        if (notCheckURLListStr != null) { 
            StringTokenizer st = new StringTokenizer(notCheckURLListStr, ";"); 
            notCheckURLList.clear(); 
            while (st.hasMoreTokens()) { 
                notCheckURLList.add(st.nextToken()); 
            } 
        } 
    } 
    public void doFilter(ServletRequest servletRequest, 
            ServletResponse servletResponse, FilterChain filterChain) 
            throws IOException, ServletException { 
        HttpServletRequest request = (HttpServletRequest) servletRequest; 
        HttpServletResponse response = (HttpServletResponse) servletResponse; 
 
        HttpSession session = request.getSession(); 
        if (sessionKey == null) { 
            filterChain.doFilter(request, response); 
            return; 
        } 
        if ((!checkRequestURIIntNotFilterList(request)) 
                && session.getAttribute(sessionKey) == null) { 
            response.sendRedirect(request.getContextPath() + redirectURL); 
            return; 
        } 
        filterChain.doFilter(servletRequest, servletResponse); 
    } 
    private boolean checkRequestURIIntNotFilterList(HttpServletRequest request) { 
        String uri = request.getServletPath() 
                + (request.getPathInfo() == null ? "" : request.getPathInfo()); 
        return notCheckURLList.contains(uri); 
    } 
    public void destroy() { 
        notCheckURLList.clear(); 
    } 
     
} 
三、字符编码的过滤器
Java代码 
/**
* 用于设置 HTTP 请求字符编码的过滤器，通过过滤器参数encoding指明使用何种字符编码,用于处理Html Form请求参数的中文问题
*/ 
public class CharacterEncodingFilter implements Filter { 
    protected FilterConfig filterConfig = null; 
    protected String encoding = ""; 
    public void init(FilterConfig filterConfig) throws ServletException { 
        this.filterConfig = filterConfig; 
        this.encoding = filterConfig.getInitParameter("encoding"); 
 
    } 
    public void doFilter(ServletRequest servletRequest, 
            ServletResponse servletResponse, FilterChain filterChain) 
            throws IOException, ServletException { 
        if (encoding != null) 
            servletRequest.setCharacterEncoding(encoding); 
        filterChain.doFilter(servletRequest, servletResponse); 
    } 
 
    public void destroy() { 
        filterConfig = null; 
        encoding = null; 
    } 
} 
四 利用Filter限制用户浏览权限
Java代码 
public class RightFilter implements Filter { 
 
    public void init(FilterConfig arg0) throws ServletException { 
    } 
 
    public void doFilter(ServletRequest sreq, ServletResponse sres, 
            FilterChain arg2) throws IOException, ServletException { 
        // 获取uri地址 
        HttpServletRequest request = (HttpServletRequest) sreq; 
        String uri = request.getRequestURI(); 
        String ctx = request.getContextPath(); 
        uri = uri.substring(ctx.length()); 
        // 判断admin级别网页的浏览权限 
        if (uri.startsWith("/admin")) { 
            if (request.getSession().getAttribute("admin") == null) { 
                request.setAttribute("message", "您没有这个权限"); 
                request.getRequestDispatcher("/login.jsp").forward(sreq, sres); 
                return; 
            } 
        } 
        // 判断manage级别网页的浏览权限 
        if (uri.startsWith("/manage")) { 
            // 这里省去 
        } 
    } 
 
    public void destroy() { 
    } 
} 
<!-- 判断页面的访问权限 -->
Xml代码 
<filter>   
    <filter-name>RightFilter</filter-name>   
    <filter-class>cn.itkui.filter.RightFilter</filter-class>   
</filter>   
<filter-mapping>   
    <filter-name>RightFilter</filter-name>   
    <url-pattern>/admin/*</url-pattern>   
</filter-mapping>   
<filter-mapping>   
    <filter-name>RightFilter</filter-name>   
    <url-pattern>/manage/*</url-pattern>   
</filter-mapping>