Servlet过滤器大全

最新推荐文章于 2024-08-08 05:03:31 发布

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文章标签：

#java #web.xml

本文详细介绍了如何使用过滤器在Web应用中实现字符编码过滤、浏览器不缓存页面、检测用户登录状态、资源保护以及限制用户权限等功能。通过配置和实现特定的过滤器，开发者可以有效地管理Web应用的访问权限和资源安全性。

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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");

}

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

{

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

{

}

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

{

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());

}

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;

}*/

}

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

{

}

< 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-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

http://maqianli.iteye.com/blog/290423