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>