Web开发五个有用的过滤器（转）

声明：本文所有代码纯属转载，原文请参考：http://wwwdd2315.blog.163.com/blog/static/66661889201110150206606/

一、使浏览器不缓存页面的过滤器??
Java代码

Java代码?
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 {???????
??? }???????
}??????

?
二、检测用户是否登陆的过滤器??
Java代码

Java代码?
???
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());???????
??????????? }???????
??????? }???????
??? }???????
}??????
?

???
三、字符编码的过滤器??
Java代码

Java代码?
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");???????
??? }???????
}??????


四、资源保护过滤器??
?
? Java代码

Java代码?
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;???
??????? }?
??? }???????
}?????


五 利用Filter限制用户浏览权限
Java代码
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：??
?

Java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")) {???????????
??????? }???????
??????? //下面还可以添加其他的用户权限，省去。???????
??????
???? }???????
??????
???? public void init(FilterConfig arg0) throws ServletException {???????????
???? }???????
??????
}???



Xml代码
<!-- 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>???

<!-- 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：
Xml代码
<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>???
<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

?