Java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
{
}
}
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<p>
* 配置参数<p>
* checkSessionKey 需检查的在 Session 中保存的关键字<br/>
* redirectURL 如果用户未登录，则重定向到指定的页面，URL不包括 ContextPath<br/>
* notCheckURLList 不做检查的URL列表，以分号分开，并且 URL 中不包括 ContextPath<br/>
*/
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
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

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;
}*/
}
}