五种过滤器
一、使浏览器不缓存页面的过滤器???
import javax.servlet.*;???
import javax.servlet.http.HttpServletResponse;???
import java.io.IOException;???
??
/**
* 用于的使 Browser 不缓存页面的过滤器
*/??
public class ForceNoCacheFilter implements Filter {???
??
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()???
{???
}???
??
???? public void init(FilterConfig filterConfig) throws ServletException???
{???
}???
}?
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二、检测用户是否登陆的过滤器???
??
import javax.servlet.*;???
import javax.servlet.http.HttpServletRequest;???
import javax.servlet.http.HttpServletResponse;???
import javax.servlet.http.HttpSession;???
import java.util.List;???
import java.util.ArrayList;???
import java.util.StringTokenizer;???
import java.io.IOException;???
??
/**
* 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 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);???
}???
??
public void destroy()???
{???
??? notCheckURLList.clear();???
}???
??
private boolean checkRequestURIIntNotFilterList(HttpServletRequest request)???
{???
??? String uri = request.getServletPath() + (request.getPathInfo() == null ? "" : request.getPathInfo());???
?? return notCheckURLList.contains(uri);???
}???
??
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());???
???? }???
??? }???
}???
}???
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三、字符编码的过滤器???
??
import javax.servlet.*;???
import java.io.IOException;???
??
/**
* 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 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;???
}???
??
???? public void init(FilterConfig filterConfig) throws ServletException???
{???
????????? this.filterConfig = filterConfig;???
???????? this.encoding = filterConfig.getInitParameter("encoding");???
??
}???
}???
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四、资源保护过滤器???
??
??
package catalog.view.util;???
??
import javax.servlet.Filter;???
import javax.servlet.FilterConfig;???
import javax.servlet.ServletRequest;???
import javax.servlet.ServletResponse;???
import javax.servlet.FilterChain;???
import javax.servlet.ServletException;???
import javax.servlet.http.HttpServletRequest;???
import java.io.IOException;???
import java.util.Iterator;???
import java.util.Set;???
import java.util.HashSet;???
//???
import org.apache.commons.logging.Log;???
import org.apache.commons.logging.LogFactory;???
??
/**
* This Filter class handle the security of the application.
*
* It should be configured inside the web.xml.
*
* @author Derek Y. Shen
*/??
public class SecurityFilter implements Filter {???
//the login page uri???
private static final String LOGIN_PAGE_URI = "login.jsf";???
??
//the logger object???
private Log logger = LogFactory.getLog(this.getClass());???
??
//a set of restricted resources???
private Set restrictedResources;???
??
/**
?? * Initializes the Filter.
?? */??
public void init(FilterConfig filterConfig) throws ServletException {???
? this.restrictedResources = new HashSet();???
? this.restrictedResources.add("/createProduct.jsf");???
? this.restrictedResources.add("/editProduct.jsf");???
? this.restrictedResources.add("/productList.jsf");???
}???
??
/**
?? * Standard doFilter object.
?? */??
public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)???
?? throws IOException, ServletException {???
? this.logger.debug("doFilter");???
?????
?? String contextPath = ((HttpServletRequest)req).getContextPath();???
?? String requestUri = ((HttpServletRequest)req).getRequestURI();???
?????
? this.logger.debug("contextPath = " + contextPath);???
? this.logger.debug("requestUri = " + requestUri);???
?????
? if (this.contains(requestUri, contextPath) && !this.authorize((HttpServletRequest)req)) {???
?? this.logger.debug("authorization failed");???
??? ((HttpServletRequest)req).getRequestDispatcher(LOGIN_PAGE_URI).forward(req, res);???
?? }???
? else {???
?? this.logger.debug("authorization succeeded");???
??? chain.doFilter(req, res);???
?? }???
}???
??
public void destroy() {}???
??
private boolean contains(String value, String contextPath) {???
?? Iterator ite = this.restrictedResources.iterator();???
?????
? while (ite.hasNext()) {???
??? String restrictedResource = (String)ite.next();???
??????
?? if ((contextPath + restrictedResource).equalsIgnoreCase(value)) {???
??? return true;???
??? }???
?? }???
?????
? return false;???
}???
??
private boolean authorize(HttpServletRequest req) {???
??
????????????? //处理用户登录???
?????? /* UserBean user = (UserBean)req.getSession().getAttribute(BeanNames.USER_BEAN);
??
?? if (user != null && user.getLoggedIn()) {
??? //user logged in
??? return true;
?? }
?? else {
??? return false;
?? }*/??
}???
}??
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五 利用Filter限制用户浏览权限
在一个系统中通常有多个权限的用户。不同权限用户的可以浏览不同的页面。使用Filter进行判断不仅省下了代码量，而且如果要更改的话只需要在Filter文件里动下就可以。
以下是Filter文件代码：
import java.io.IOException;???
??
import javax.servlet.Filter;???
import javax.servlet.FilterChain;???
import javax.servlet.FilterConfig;???
import javax.servlet.ServletException;???
import javax.servlet.ServletRequest;???
import javax.servlet.ServletResponse;???
import javax.servlet.http.HttpServletRequest;???
??
public class RightFilter implements Filter {???
??
??? public void destroy() {???
???????????
???? }???
??
??? 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???
???????????? }???
???????? }???
??????? //下面还可以添加其他的用户权限，省去。???
??
???? }???
??
??? public void init(FilterConfig arg0) throws ServletException {???
???????????
???? }???
??
}
<!-- 判断页面的访问权限 -->??
? <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>??
在web.xml中加入Filter的配置，如下：
<filter>??
??????? <filter-name>EncodingAndCacheflush</filter-name>??
??????? <filter-class>EncodingAndCacheflush</filter-class>??
??????? <init-param>??
??????????? <param-name>encoding</param-name>??
??????????? <param-value>UTF-8</param-value>??
??????? </init-param>??
??? </filter>??
??? <filter-mapping>??
??????? <filter-name>EncodingAndCacheflush</filter-name>??
??????? <url-pattern>/*</url-pattern>??
??? </filter-mapping>??
要传递参数的时候最好使用form进行传参，如果使用链接的话当中文字符的时候过滤器转码是不会起作用的，还有就是页面上
form的method也要设置为post，不然过滤器也起不了作用。
