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filter servlet java

filter过滤器主要使用于前台向后台传递数据是的过滤操作。程度很简单就不说明了，直接给几个已经写好的代码：
一、使浏览器不缓存页面的过滤器

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

1.import javax.servlet.*;
2.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

1.import javax.servlet.*;
2.import java.io.IOException;
3.
4./**
5. * 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
6. */
7.public class CharacterEncodingFilter
8. implements Filter
9.{
10. protected FilterConfig filterConfig = null;
11. protected String encoding = "";
12.
13. public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException
14. {
15. if(encoding != null)
16. servletRequest.setCharacterEncoding(encoding);
17. filterChain.doFilter(servletRequest, servletResponse);
18. }
19.
20. public void destroy()
21. {
22. filterConfig = null;
23. encoding = null;
24. }
25.
26. public void init(FilterConfig filterConfig) throws ServletException
27. {
28. this.filterConfig = filterConfig;
29. this.encoding = filterConfig.getInitParameter("encoding");
30.
31. }
32.}
四、记录用户的访问操作器

代码：
package com.qwserv.itm.pfl.log.svr;

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 java.text.SimpleDateFormat;
import javax.servlet.http.HttpServletRequest;
import com.qwserv.itm.api.pfl.sm.vo.Person;
import java.sql.*;
import com.qwserv.itm.api.ServiceAccess;
import com.qwserv.itm.util.toolkit.DebugUtil;

public class ObserveFilter implements Filter {
 protected static DebugUtil log = DebugUtil.getInstances("pfl-log", ObserveFilter.class);
 public void destroy() {
 }

 public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException,
 ServletException {
 //记录用户的访问操作
 HttpServletRequest request1 = (HttpServletRequest)request;
 StringBuffer url = request1.getRequestURL();

 //对url进行过滤，如果是js/css/image则不进行处理
 if (judgeFile(url.toString())){
 String operTime = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").
 format(new java.util.Date());
 String hostIp = request.getRemoteAddr();
 String sessionId = request1.getRequestedSessionId();
 String userId = "";
 Person person = (Person)request1.getSession().getAttribute("userObj");
 if (null != person && null != person.getUser()){
 userId = person.getUser().getId();
 }
 String queryString = request1.getQueryString();
 if (null != queryString) {
 url.append('?');
 url.append(queryString);
 }

 //保存到数据库中
 saveToDb(userId,hostIp,sessionId,url.toString(),operTime,"");
 }
 // Pass control on to the next filter
 chain.doFilter(request, response);
 }

 public void init(FilterConfig filterConfig) throws ServletException {
 }

 public boolean judgeFile(String url){
 if (url.endsWith(".gif") || url.endsWith(".jpg") || url.endsWith(".png")
 || url.endsWith(".bmp") || url.endsWith(".css") || url.endsWith(".js")
 || url.endsWith(".jsx")){
 return false;
 } else {
 return true;
 }
 }

 public int saveToDb(String userId, String hostIp,String sessionId,String url,
 String operTime,String desc){
 //将报表任务数据保存到数据库中
 Connection conn = null;
 Statement st = null;

 try {

 //构造sql表达式，将数据插入数据库
 conn = ServiceAccess.getSystemSupportService().getDefaultConnection();
 st = conn.createStatement();
 String sql = "insert into LOG_OBSERVE_HISTORY(USERID,URL,Detail,SessionID,HostName,StartDate) values('"+
 userId + "','" + url + "','" + desc + "','" + sessionId
 + "','" + hostIp + "','" + operTime + "')";
 if (ServiceAccess.getSystemSupportService().getConnectionType(conn)==ServiceAccess.getSystemSupportService().JCA_TYPE_ORACLE){
 sql = "insert into LOG_OBSERVE_HISTORY(Id,USERID,URL,Detail,SessionID,HostName,StartDate) values(LOG_OBSERVE_SEQ.nextval,'"+
 userId + "','" + url + "','" + desc + "','" + sessionId
 + "','" + hostIp + "',TO_DATE('" + operTime
 + "','YYYY-MM-DD HH24:MI:SS'))";
 }
 st.executeUpdate(sql);
 } catch (Exception e) {
 e.printStackTrace();
 log.error("--------------------The url String is:" + url + "-------------------------------");
 return 1; //表示操作失败
 } finally {
 if (null != st)
 {
 try{
 st.close();
 }
 catch(Exception e)
 {
 e.printStackTrace();
 }

 st = null;
 }

 if (conn != null) {
 try {
 conn.close();
 } catch (Exception e) {
 e.printStackTrace();
 }
 conn = null;
 }
 }

 return 0; //表示操作成功
 }
}

 <filter>
 <filter-name>ObserveFilter</filter-name>
 <filter-class>com.qwserv.itm.pfl.log.svr.ObserveFilter</filter-class>
 </filter>
 <filter-mapping>
 <filter-name>ObserveFilter</filter-name>
 <url-pattern>/*</url-pattern>
 </filter-mapping>

五.Filter防止用户访问一些未被授权的资源

1.package
com.drp.util.filter;

•
•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;
•import javax.servlet.http.HttpServletResponse;
•import javax.servlet.http.HttpSession;
•
•public class AuthFilter implements Filter {
•
• public void destroy() {
•
• }
•
• public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse,
• FilterChain filterChain) throws IOException, ServletException {//1,doFilter方法的第一个参数为ServletRequest对象。此对象给过滤器提供了对进入的信息（包括表单数据、cookie和HTTP请求头）的完全访问。第二个参数为ServletResponse，通常在简单的过滤器中忽略此参数。最后一个参数为FilterChain，此参数用来调用servlet或JSP页。
•
• HttpServletRequest request = (HttpServletRequest)servletRequest;//;//如果处理HTTP请求，并且需要访问诸如getHeader或getCookies等在ServletRequest中无法得到的方法，就要把此request对象构造成HttpServletRequest
• HttpServletResponse response = (HttpServletResponse)servletResponse。
•
•
• String currentURL = request.getRequestURI();//取得根目录所对应的绝对路径:
•
•
• String targetURL = currentURL.substring(currentURL.indexOf("/", 1), currentURL.length()); //截取到当前文件名用于比较
•
• HttpSession session = request.getSession(false);
•
• if (!"/login.jsp".equals(targetURL)) {//判断当前页是否是重定向以后的登录页面页面，如果是就不做session的判断，防止出现死循环
• if (session == null || session.getAttribute("user") == null) {//*用户登录以后需手动添加session
• System.out.println("request.getContextPath()=" + request.getContextPath());
• response.sendRedirect(request.getContextPath() + "/login.jsp");//如果session为空表示用户没有登录就重定向到login.jsp页面
• return;
• }
• }
• //加入filter链继续向下执行
• filterChain.doFilter(request, response);//.调用FilterChain对象的doFilter方法。Filter接口的doFilter方法取一个FilterChain对象作为它的一个参数。在调用此对象的doFilter方法时，激活下一个相关的过滤器。如果没有另一个过滤器与servlet或JSP页面关联，则servlet或JSP页面被激活。
•
• }
•
• public void init(FilterConfig filterConfig) throws ServletException {
•
• }
•}
<filter>
 <filter-name>AuthFilter</filter-name>
 <filter-class>com.drp.util.filter.AuthFilter</filter-class>
</filter>

<filter-mapping>
 <filter-name>AuthFilter</filter-name>
 <url-pattern>*.jsp</url-pattern>//表示对所有jsp文件有效
</filter-mapping>

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