本文研究的主要是Java中filter过滤器的相关用法,具体实现代码如下。
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
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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
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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
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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、记录用户的访问操作器
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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 } } |
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< 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
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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 { } } |
html
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< 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 > |
总结
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原文链接:https://www.cnblogs.com/go4mi/p/5509879.html