Servlet过滤器

Servlet过滤器大全

一、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HtmlForm请求参数的中文问题
*/
public class CharacterEncodingFilter
implements Filter
{
protectedFilterConfigfilterConfig=null;
protectedStringencoding="";

publicvoiddoFilter(ServletRequestservletRequest,ServletResponseservletResponse,FilterChainfilterChain)throwsIOException,ServletException
{
if(encoding!=null)
servletRequest.setCharacterEncoding(encoding);
filterChain.doFilter(servletRequest,servletResponse);
}

publicvoiddestroy()
{
filterConfig=null;
encoding=null;
}

publicvoidinit(FilterConfigfilterConfig)throwsServletException
{
this.filterConfig=filterConfig;
this.encoding=filterConfig.getInitParameter("encoding");

}
}

二、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 {

publicvoiddoFilter(ServletRequestrequest,ServletResponseresponse,FilterChainfilterChain)throwsIOException,ServletException
{
((HttpServletResponse)response).setHeader("Cache-Control","no-cache");
((HttpServletResponse)response).setHeader("Pragma","no-cache");
((HttpServletResponse)response).setDateHeader("Expires",-1);
filterChain.doFilter(request,response);
}

publicvoiddestroy(){
}

publicvoidinit(FilterConfigfilterConfig)throwsServletException{
}
}

三、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
{
protectedFilterConfigfilterConfig=null;
privateStringredirectURL=null;
privateListnotCheckURLList=newArrayList();
privateStringsessionKey=null;

publicvoiddoFilter(ServletRequestservletRequest,ServletResponseservletResponse,FilterChainfilterChain)throwsIOException,ServletException
{
HttpServletRequestrequest=(HttpServletRequest)servletRequest;
HttpServletResponseresponse=(HttpServletResponse)servletResponse;

HttpSessionsession=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);
}

publicvoiddestroy()
{
notCheckURLList.clear();
}

privatebooleancheckRequestURIIntNotFilterList(HttpServletRequestrequest)
{
Stringuri=request.getServletPath()+(request.getPathInfo()==null?"":request.getPathInfo());
returnnotCheckURLList.contains(uri);
}

publicvoidinit(FilterConfigfilterConfig)throwsServletException
{
this.filterConfig=filterConfig;
redirectURL=filterConfig.getInitParameter("redirectURL");
sessionKey=filterConfig.getInitParameter("checkSessionKey");

StringnotCheckURLListStr=filterConfig.getInitParameter("notCheckURLList");

if(notCheckURLListStr!=null)
{
StringTokenizerst=newStringTokenizer(notCheckURLListStr,";");
notCheckURLList.clear();
while(st.hasMoreTokens())
{
notCheckURLList.add(st.nextToken());
}
}
}
}

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;

/***/ /**
*ThisFilterclasshandlethesecurityoftheapplication.
*
*Itshouldbeconfiguredinsidetheweb.xml.
*
*@authorDerekY.Shen
*/
public class SecurityFilter implements Filter {
//theloginpageuri
privatestaticfinalStringLOGIN_PAGE_URI="login.jsf";

//theloggerobject
privateLoglogger=LogFactory.getLog(this.getClass());

//asetofrestrictedresources
privateSetrestrictedResources;

/***//**
*InitializestheFilter.
*/
publicvoidinit(FilterConfigfilterConfig)throwsServletException{
this.restrictedResources=newHashSet();
this.restrictedResources.add("/createProduct.jsf");
this.restrictedResources.add("/editProduct.jsf");
this.restrictedResources.add("/productList.jsf");
}

/***//**
*StandarddoFilterobject.
*/
publicvoiddoFilter(ServletRequestreq,ServletResponseres,FilterChainchain)
throwsIOException,ServletException{
this.logger.debug("doFilter");

StringcontextPath=((HttpServletRequest)req).getContextPath();
StringrequestUri=((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("authorizationfailed");
((HttpServletRequest)req).getRequestDispatcher(LOGIN_PAGE_URI).forward(req,res);
}
else{
this.logger.debug("authorizationsucceeded");
chain.doFilter(req,res);
}
}

publicvoiddestroy(){}

privatebooleancontains(Stringvalue,StringcontextPath){
Iteratorite=this.restrictedResources.iterator();

while(ite.hasNext()){
StringrestrictedResource=(String)ite.next();

if((contextPath+restrictedResource).equalsIgnoreCase(value)){
returntrue;
}
}

returnfalse;
}

privatebooleanauthorize(HttpServletRequestreq){

//处理用户登录
/**//*UserBeanuser=(UserBean)req.getSession().getAttribute(BeanNames.USER_BEAN);

if(user!=null&&user.getLoggedIn()){
//userloggedin
returntrue;
}
else{
returnfalse;
}*/
}
}

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 {

publicvoiddestroy(){

}

publicvoiddoFilter(ServletRequestsreq,ServletResponsesres,FilterChainarg2)throwsIOException,ServletException{
//获取uri地址
HttpServletRequestrequest=(HttpServletRequest)sreq;
Stringuri=request.getRequestURI();
Stringctx=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(FilterConfigarg0) 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。