Java中filter用法完整代碼示例

2024-07-13 10:17:29

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本文研究的主要是Java中filter過濾器的相關用法，具體實現代碼如下。

filter過濾器主要使用于前臺向后臺傳遞數據是的過濾操作。程度很簡單就不說明了，直接給幾個已經寫好的代碼：

一、使瀏覽器不緩存頁面的過濾器

java/149022.html">java;">import javax.servlet.*;import javax.servlet.http.HttpServletResponse;import java.io.IOException;/** * 用于的使 Browser 不緩存頁面的過濾器 */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、檢測用戶是否登陸的過濾器

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、字符編碼的過濾器

import javax.servlet.*;import java.io.IOException;/**  * 用于設置 HTTP 請求字符編碼的過濾器，通過過濾器參數encoding指明使用何種字符編碼,用于處理Html Form請求參數的中文問題  */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、記錄用戶的訪問操作器

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 {		//記錄用戶的訪問操作		HttpServletRequest request1 = (HttpServletRequest)request;		StringBuffer url = request1.getRequestURL();		//對url進行過濾，如果是js/css/image則不進行處理		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);			}			//保存到數據庫中			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){		//將報表任務數據保存到數據庫中		Connection conn = null;		Statement st = null;		try {			//構造sql表達式，將數據插入數據庫			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;			//表示操作失敗		}		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防止用戶訪問一些未被授權的資源

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方法的第一個參數為ServletRequest對象。此對象給過濾器提供了對進入的信息（包括表單數據、cookie和HTTP請求頭）的完全訪問。第二個參數為ServletResponse，通常在簡單的過濾器中忽略此參數。最后一個參數為FilterChain，此參數用來調用servlet或JSP頁。  		HttpServletRequest request = (HttpServletRequest)servletRequest;		//;//如果處理HTTP請求，并且需要訪問諸如getHeader或getCookies等在ServletRequest中無法得到的方法，就要把此request對象構造成HttpServletRequest  		HttpServletResponse response = (HttpServletResponse)servletResponse。  		        String currentURL = request.getRequestURI();		//取得根目錄所對應的絕對路徑:  		String targetURL = currentURL.substring(currentURL.indexOf("/", 1), currentURL.length());		//截取到當前文件名用于比較  		HttpSession session = request.getSession(false);		if (!"/login.jsp".equals(targetURL)) {			//判斷當前頁是否是重定向以后的登錄頁面頁面，如果是就不做session的判斷，防止出現死循環  			if (session == null || session.getAttribute("user") == null) {				//*用戶登錄以后需手動添加session  				System.out.println("request.getContextPath()=" + request.getContextPath());				response.sendRedirect(request.getContextPath() + "/login.jsp");				//如果session為空表示用戶沒有登錄就重定向到login.jsp頁面  				return;			}		}		//加入filter鏈繼續向下執行  		filterChain.doFilter(request, response);		//.調用FilterChain對象的doFilter方法。Filter接口的doFilter方法取一個FilterChain對象作為它的一個參數。在調用此對象的doFilter方法時，激活下一個相關的過濾器。如果沒有另一個過濾器與servlet或JSP頁面關聯，則servlet或JSP頁面被激活。	}	public void init(FilterConfig filterConfig) throws ServletException {	}}

html

<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>//表示對所有jsp文件有效</filter-mapping>

總結

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